Underfloor Heating & Solar Panel

YourAverageJoe

Has anyone got a heating system whereby an array of solar panels feeds a buffer tank which then is used for underfloor heating, allbeit with a boiler boosting the heat if required.

Also, if you are using underfloor on only an oil boiler, is a bufer tank necessary.

Mike2006

Joe,

I have that arrangement.

I have 3 inputs to the Thermal Store:
1. Solar - Evacuated Tubes 20m2
2. Solid Fuel Room Sealed Stove with 10kW Back Boiler
3. Condensing Oil Boiler

DHW is produced through heat exchange coils which are also loacted in the thermal store.

Mike.

castlewarren

Hi Mike2006

I am in the process of putting in a similar system and I am trying to source the thermal store at the moment. Do you mind me asking the make and where you got it?

Thanks

JuniorB

Mike2006 - will have same system as that.
How is it working out? All relative I know, but are you going through much oil? Any idea if the solar is doing much of a job in the depths of winter?

Cheers

Mike2006

At the moment it is difficult to say because it is summer and I am not moved in yet but preliminary results look good.

The solar can take the the tank from 40 to 60 DegC in a few hours on an average day...

The big thing here are the controls. I have added lots of controls to the system myself to make it operate as efficiently as I can.

Im will try to explain how it works:

Inputs: Solar, Back Boiler, Cond Oil Boiler.
Solar: I have set it up to circulate once the temp of collectors is 6Deg or more than the thermal store.
Back Boiler: No control here. It is on when it is on and gives heat to the thermal store.
Oil: Only comes on in certain situations.

Temperature in the tank will always be between 50 DegC and 70 DegC.
I have set up some controls as follows using solar controller, pipe stats and relays etc..

1. 2nd available relay output on Solar Controller is used to control Oil Boiler. i.e. when the tank drops to 50 DegC, pull in boiler until tank is at 70 DegC.
but
2. Only if the Solar is not circulating. i.e. let the solar give all of its free energy to the store before using oil to get it up to temp.

This ensures that the oil only kicks in when really necessary...

Q. What if the rate of cooling is too much so that the solar can not hold the temp and it keeps falling (ie, UFH on and running a bath or showers etc..).
A. Pipe stat and relay tell the boiler to over-ride the solar controller if the temp drops below 50 and fire up the boiler until 58 DegC even if the solar is running.

Q:I have no heat dump so I had to make an allowance for what if I am avaw on holidays and the store gets up to over 90DegC and I am not there.
A: Another stat will over-ride 2 room stats in this case (both large areas) and run the UFH in those zones until the tank is back down to 50DegC. This will only ever happen if I am away for long periods of time because the solar would not get the store up to 90 DegC under any normal living circumstances.

Hope I have not confused the situation too much here.


I ran plenty of extra spare cables when installing each component because I knew that as I learn to live with the system, I will need to make extra control modifications that I may not have thought about yet..


I cannot name the thermal store supplier because of boards rules but if you PM me I can reply with it...

Mike.

JuniorB

Thanks for the detailed response Mike.
We'll be installing ours in next couple of months.
Very interested in the control aspect and ensuring that all runs as efficiently as possible. Our plumber has installed a fair few so hopefully he'll be up to speed.

Mike2006

Don't count on your plumber knowing anything about the controls required. Most likely he will just know how to connect up all the plumbing.

It will be up to your electrician to install and commission the controls and you will need to sit down with him and tell him what you want the system to be able to do and then he will design the controls around this.

This should be done sooner rather than later. You will also find out at this stage exactly how smart or not your electrician is...

Mike.

bryaner

Mike2006 wrote: »

At the moment it is difficult to say because it is summer and I am not moved in yet but preliminary results look good.

The solar can take the the tank from 40 to 60 DegC in a few hours on an average day...

The big thing here are the controls. I have added lots of controls to the system myself to make it operate as efficiently as I can.

Im will try to explain how it works:

Inputs: Solar, Back Boiler, Cond Oil Boiler.
Solar: I have set it up to circulate once the temp of collectors is 6Deg or more than the thermal store.
Back Boiler: No control here. It is on when it is on and gives heat to the thermal store.
Oil: Only comes on in certain situations.

Temperature in the tank will always be between 50 DegC and 70 DegC.
I have set up some controls as follows using solar controller, pipe stats and relays etc..

1. 2nd available relay output on Solar Controller is used to control Oil Boiler. i.e. when the tank drops to 50 DegC, pull in boiler until tank is at 70 DegC.
but
2. Only if the Solar is not circulating. i.e. let the solar give all of its free energy to the store before using oil to get it up to temp.

This ensures that the oil only kicks in when really necessary...

Q. What if the rate of cooling is too much so that the solar can not hold the temp and it keeps falling (ie, UFH on and running a bath or showers etc..).
A. Pipe stat and relay tell the boiler to over-ride the solar controller if the temp drops below 50 and fire up the boiler until 58 DegC even if the solar is running.

Q:I have no heat dump so I had to make an allowance for what if I am avaw on holidays and the store gets up to over 90DegC and I am not there.
A: Another stat will over-ride 2 room stats in this case (both large areas) and run the UFH in those zones until the tank is back down to 50DegC. This will only ever happen if I am away for long periods of time because the solar would not get the store up to 90 DegC under any normal living circumstances.

Hope I have not confused the situation too much here.


I ran plenty of extra spare cables when installing each component because I knew that as I learn to live with the system, I will need to make extra control modifications that I may not have thought about yet..


I cannot name the thermal store supplier because of boards rules but if you PM me I can reply with it...

Mike.

Wow that is some system, I'm jealous

JuniorB

Mike2006 wrote: »

Don't count on your plumber knowing anything about the controls required. Most likely he will just know how to connect up all the plumbing.

It will be up to your electrician to install and commission the controls and you will need to sit down with him and tell him what you want the system to be able to do and then he will design the controls around this.

This should be done sooner rather than later. You will also find out at this stage exactly how smart or not your electrician is...

Mike.

Sound Mike ... will do.
Have been onto the supplier of the Thermal Store previously so must get cracking on all that again as well.. Plumber has been very helpful so far in directing me to his suppliers for HRV, Solar etc with any queries I have.

Mike2006

No bother...
Any questions along the way, just drop me a PM.

Mike.

moan 77

mike iam in same position soon could you please pm with details please and any advice many many tanks.

Dugsy

Mike, would appreciate if you could PM me details as well.

tails_naf

Hi Mike,

Nice system - I was shooting for similar.

I actually purchased a small plc (about 100 quid) to do the extra control for me - essentially replaces the relays you have in yours. the device is actually called a programmable relay. It comes with up to 8 built in time-clocks, date (for summer winter settings) - but requires a bit of programming (which I happen to like !)

I was wondering what you thought of the following setup:
I have separate DHW and CH buffer, both connected to solar and condensing oil boiler.

1) solar controller heats the DHW as a primary. If DHW gets up to temp, it switches to heating the CH buffer for under-floor. If that also gets too hot, it auto turns on a dump load (heated towel rads - but I like your idea of using the UFH too!)

2) if solar cannot get DHW up to temp by 2pm, in a given day the oil boiler kicks in. Gives solar a chance to do its job. I kind of prefer your idea of using the 50C of the tank here instead to turn on the boiler.

3) if UFH is calling for heat, and buffer tank is below 40C, heat it up to 60C via boiler (could be timed for 2 heating periods, etc.

That's more or less what I have, I'd appreciate any comments on how to make this better!!

Mike2006

Well,

I actually have a PLC as well but am doing lighting/interlock controls with that. Decided to keep it awy from the central heating system just in case something went wrong with it and I lost my central heating while I was waiting for a card/processor or something...
Must have a PM offline with you on that too...

Heating system:

1. Towel Rail dump is just as good as UFH. Essentially, you are just looking to dump heat, doesn't matter how this happens really... To be honest, with just the solar running, it is unlikely to happen all that often anyway...

2. Personally, I prefer to use temperature based on/off conditions rather than time because you are measuring the process variable directly rather than just going on time... I often see that the solar is only coming into its own by about 3pm or so if the tank is almost up to temp and the solar is 'charging' because it cannot contribute.. Then at about 3pm it can contribute and it gives it a great blast.. If you have your boiler brought in just before this, that contribution temp for the solar has been increased again and you may not get the benefit...

3. In my system the buffer tank should never get below 50 DegC (48 ish) so I would need to fully understand on what that water is doing (heating coils or just for UFH water) to see what your requirements are...


The only thing that I would look at is the timing of on/off conditions as opposed to temp based on/off.... The only place I would possibly have a timer is a run-on timer on the boiler circulating pump if you have a long run from the boiler to the tank.

I toyed with the idea of 2 tanks (CH and DHW). Its a really good system. Did you go for a tank-in-tank system or 2 separate tanks??
In the end I just decided to go with the 1 tank and hope that the specification of the tank does not lead to inefficiency when I just need DWH and no CH for long periods... I think it should be ok..

Once my plumbers leave the house, I fully intend on insulating every pipe in the hot-press to a high level. I am going to lagg it and then tape it up with alu tape much the same as you would see in a plant room. Insulate manual valves etc... to minimise heat loss locally.
Plumbers are just going to clean down all pipe-work using wire wool and I will do the lagging. Again, it requires a bit of patience and the attention to detail that only the owner/end user can provide!!

I will drop you a PM over the next couple of days re: PLC controls in the house...

Mike.

CotBC

Hi Mike,
Thanks for the information above. Looks like you are a month or more ahead of me at this stage, but I have gone for the same system (Solar, Back Boiler and Oil), and am now looking at the options for the Thermal Store and control of the system. I also looked at the 2 tank option, but based on budget and an effort to simplify the set up, I am also going with a thermal store / heat bank, and going to rely on the stratification within the tank to provide the DHW via a coil at the top of the cylinder.

One question I am struggling with at the moment is the actual size of the tank. It’s easy enough to come up with a max DHW load condition, but I am waiting for my plumber to come back to me with the flow rates and the expected temperature drops for the UFH loops (UFH on both floors, 8 zones on ground floor, and 5 zones on first floor + towel heaters + re-circulation loop due to the fact that the cylinder will be in the garage). Did you come up with any good method for the size calculation ?

Also, as with the other requests, can you PM me the model you went with, or confirm if it is “dressed in the Cork colours ” ?

I would also be very interested in the control setup you used, as I am also going with a tank temperature driven system to ensure that the oil usage is minimised (and to ensure that the boiler operates in condensing mode and that there is no short cycling happening).

Thanks for any help,
Tim

Mike2006

Tim,

Yes, my tank is dressed in the Cork colours alright...

I got the company who supplied it to size it for me and I ended up with a 1000L tank.

If you know how much UFH piping you were supplied you can calculate the capacity of your UFH system. For mine, I was supplied 2000metres of UFH pipe and 10 metres contains 1 litre of water so whole capacity is 200litres...

Full details of my controls are above within this thread. Rather than typing them all out again, take a look and if you have any particular question just drop me a PM or whatever...


Mike.

CotBC

Mike,
Thanks for the tip on the UFH pipe length – should have thought of that !

Specific question about the controls was the type of pipe stat and relays you used and how you linked these together – will send PM as it is difficult to get details without mentioning brand names.

Also, was your back boiler suitable for connection to a pressurised system ?

Tim.

Mike2006

Re: back boiler:

The back boiler loop is pressurised (sealed) so it had 2 pressure safety valves on the loop. 1 local to the back boiler and another at the tank.

L driver

Hello,
Sorry to jump on board, but would this system work well in a very well insulated house. I like the idea of mains pressure throughout the house without a booster pump. Also with external plate heat exchanger and ufh could the thermal store be ran at a lower temp say ~55c. Could an inline instantaneous electric heater be used for days that the solar doesn't bring the store up to temp, but there is no need to start up the boiler for 1shower or to wash the dishes? Great work on the controls btw

galwaytt

L driver wrote: »

Hello,
Sorry to jump on board, but would this system work well in a very well insulated house. I like the idea of mains pressure throughout the house without a booster pump. Also with external plate heat exchanger and ufh could the thermal store be ran at a lower temp say ~55c. Could an inline instantaneous electric heater be used for days that the solar doesn't bring the store up to temp, but there is no need to start up the boiler for 1shower or to wash the dishes? Great work on the controls btw

Well, I have 3 x solar panels, LPG boiler and 1000l buffer, and DH&C is on a Wilo pressure pump. Mains would be useless imho, and, but having to add pumped/elec showers, you're only complicating it. Put in a pressure pump (it's tiny), pressure regulator, and use whatever mixers/taps/showers that take your fancy. Simpler, imho.

I keep my buffer at 57 deg, tbh, to avoid cracking of lime issues at higher temps - we have really, really hard water around here.

Solar more than contributes - only on the worst days is it's contribution small. On anything remotely bright, it's not inconsiderable.

L driver

Hello,
Galwaytt have you a separate dhw cylinder off the store so? Don't know why I asked that:o It must be a very efficient with the store running at 57c. What controls have you

galwaytt

L driver wrote: »

Hello,
Galwaytt have you a separate dhw cylinder off the store so? Don't know why I asked that:o It must be a very efficient with the store running at 57c. What controls have you

No, no separate DHW cylinder: my DHW is supplied by the volume of the DHW coil within the cylinder.

Tbh, by control's are basic, and I'm planning to re-do them in the new year. Currently there is a room stat in each room, and a Horstmsann 37xl 3-channel timer on the heating itself.
Channel 1 - boiler to buffer - on 24/7, keeps the temp of the buffer at 57deg with no effort. It is effectively 'self-regulating', as the boiler is also very close - about 1m ! - so no big dead leg or losses.
Channel 2 - UFH for GF, basement, garage
Channel 3 - UFH for FF

Now, in reality, the clock, whilst a good one, isn't ideal. What I'm changing to is individial digital stat's with 7-day timers, in lieu of the existing ones, and setting 'step-back' temps for periods of no/low use.

L driver

I'm thinking of doing the same with the boiler beside the ts, but thinking of using bottled gas for the first year and see how it goes. No mains gas here and Iknow bottled gas is expensive but I might be able to add on a small wood burner and the cost of the gas bulk tank will go towards that. The wood will compensate for the size of my ST at this time of year.
Do you need 7 day stats in every room? will your ch pump be on/off alot? How did you size the thermal store
Sorry for all the questions, hoping to get it right first time

galwaytt

I've no piped gas either - I have a 1t tank in the garden. Bottled cost would rob you afaik - much more expensive than a tank. You don't buy the tank anyhoo, so there is no cost - where are you getting the cost from ? Mine is leased - €100 p.a. or something, and they do annual inspection, maintenance and even paint it every few years ! Basically -I'm a lazy git

I use LPG because it's a fully modulating heat source, which suits UFH well.

You don't NEED 7-day stat's in each room, but imho, it does make sense - unless you have some sort of central plcc's which has full zone control to the same extent.

Using a clock - or time - to dictate heat makes no sense to me now. Far better to use temperature as the first control, and to refine it by time/room use. Doing it the other way around is less efficient.

By doing this, the system is 'on', or maybe we should say 'live' all the time, true, but if the room isn't calling for heat, the pumps won't run anyway - which is what you want.

I didn't size my thermal store, and I wouldn't. Let the installer do that - that's what he's getting paid for - design & fit. Otherwise you'll be the guy everyone will look at if there's an issue. Ditto for combining different systems: one system, one 'guy', one responsibility. Otherwise it's a mish-mash and it WILL go wrong (damhik....... )

Since I had the big mechanicals re-worked lately, house is much, much better.

wclarke20

Mike2006 wrote: »

At the moment it is difficult to say because it is summer and I am not moved in yet but preliminary results look good.

Hi Mike, I’d be interested to hear how your system held up in the tough winter we had?
Any problems or suggestions for somebody installing a similar system?

Appreciate it, thanks!

Mike2006

Well,

I moved in October 1st 2010 and since then I have the living area stats set at 19.5DegC and the bedroom stats set at 18.5DegC and the UFH is on 24/7, (i.e. it is self controlled through the stats and not time controlled).

So far I have used about 1100 litres of oil. Prob a little bit more than I would have initially anticipated but looking at the bad weather we had and the fact that the house was always nice and warm and 24/7 hot water as well.

When the summer/bright weather comes in now I will use significantly less oil because the 20sqm of solar tubes will come into play so I may get away with 1000l more for the remainder of the year.

House size is 3600 sq ft, 2 storey with ufh both upstairs and downstairs.

Mike.

wclarke20

Interesting, 1100 litres is a lot in a few months but then again the temperature was particularly cold. Had you the stove on much?
So with possibly just over 2000 litres oil used for the year and cost of any solid fuel for the stove, heating and DHW costs would be around the €1300 mark?
For a house of that size, I would guess that’s ok?

Mike2006

I have only lit the stove 3 or 4 times since we moved in because the room it is in was not fully finished etc...

I am hoping that the coldest 4 months which are now over (hopefully) have been covered by the 1st tank of oil so the warmer 8 months should be covered by the 2nd tank and solar contribution.

Year 2 should be better again because the house will have fully 'dried out' etc..


Mike..

JuniorB

Have a similar set up as Mike. Hosue only 3100 sq ft. Buffer tank set to 55 degrees. Stats in every room. Set to 18-20 degrees.
Moved in last week in Nov. Heat was on since start of Nov.
Just ordered my 3rd .... yes 3rd 1000 ltrs of oil 5 mins ago :mad:
Plumber due on site tomorrow and he'll have a fair few questions to answer!

Dempo1

JuniorB wrote: »

Mike2006 - will have same system as that.
How is it working out? All relative I know, but are you going through much oil? Any idea if the solar is doing much of a job in the depths of winter?

Cheers

Hi Mike,

Just came across this thread, have been intrigued about underfloor heating until I heard my neighbor screaming at the top of his voice over the winter. Basically he had this system installed after a major renovation and he is regretting the day ever since. His system has drank oil over the winter despite having the system on a constant and very low temperature.

I was led to believe underfloor systems were economical to run but clearly this is not my neighbors experience

JuniorB

JuniorB wrote: »

Have a similar set up as Mike. Hosue only 3100 sq ft. Buffer tank set to 55 degrees. Stats in every room. Set to 18-20 degrees.
Moved in last week in Nov. Heat was on since start of Nov.
Just ordered my 3rd .... yes 3rd 1000 ltrs of oil 5 mins ago :mad:
Plumber due on site tomorrow and he'll have a fair few questions to answer!

Only 3100 sq ft, whats the insulation like?
Do you have a mixer valve between the buffer and the UFH?
Having the buffer set to only 55c means that the boiler is probably short cycling the efficiency goes down a lot if the boiler is "drip feeding" heat into the buffer.

Dempo1

Dempo1 wrote: »

Hi Mike,

Just came across this thread, have been intrigued about underfloor heating until I heard my neighbor screaming at the top of his voice over the winter. Basically he had this system installed after a major renovation and he is regretting the day ever since. His system has drank oil over the winter despite having the system on a constant and very low temperature.

I was led to believe underfloor systems were economical to run but clearly this is not my neighbors experience

I have an oil boiler and UFH, solid fuel boiler (only fired once every few days, it provides about 5% of the hot water)
Useage so far this winter 800 litre fill in september, 500 litre fill two weeks ago, house 180m2, high levels of insulation plus MHRV.

I found it works best if you set it on for a few hours a day, my on times are 06:00 - 09:00 & 16:00 - 20:00

wclarke20

JuniorB wrote: »

Have a similar set up as Mike. Hosue only 3100 sq ft. Buffer tank set to 55 degrees. Stats in every room. Set to 18-20 degrees.
Moved in last week in Nov. Heat was on since start of Nov.
Just ordered my 3rd .... yes 3rd 1000 ltrs of oil 5 mins ago :mad:
Plumber due on site tomorrow and he'll have a fair few questions to answer!

3rd fill!! , that’s crazy. Why do you think that is? Mike mentioned the house drying out etc but 3 fills is a bit much?

Wonder how an air source heat pump replacing the oil boiler would work out instead?

Dempo1

wclarke20 wrote: »

3rd fill!! , that’s crazy. Why do you think that is? Mike mentioned the house drying out etc but 3 fills is a bit much?

Wonder how an air source heat pump replacing the oil boiler would work out instead?

Mother of god, that sounds really costly to run, no wonder my neighbour is having panic attacks!

paddy147

Can solar panels be installed and then the hot water used in some way to heat the rads in the house,just to take the chill out fo the air?

is this possible?

galwaytt

Dempo1 wrote: »

Hi Mike,

Just came across this thread, have been intrigued about underfloor heating until I heard my neighbor screaming at the top of his voice over the winter. Basically he had this system installed after a major renovation and he is regretting the day ever since. His system has drank oil over the winter despite having the system on a constant and very low temperature.

I was led to believe underfloor systems were economical to run but clearly this is not my neighbors experience

The issue is not UFH in the above, I'd say, but more the quality of the installation and/or set up.

Consider: if your house has a heat load of, say, 50kW sq/m, then whether you deliver that energy by UFH or rads is irrelevant, and the running costs should be nigh-on the same.

That it isn't leads me to believe your neighbour is losing his heat to.....the foundations, the walls........or the system is poorly set up..........or the actuall running of it is set up funny (on/off/on/off etc)

I've had UFH since 1993, and I'd never go back.

JuniorB

The plumber was out the weekend. He's installed 10 or more of the same set up in the last couple of years. He agrees there's an issue!
He's coming back today with his electical guy to have a look at the setup. The electrics were done by the builder's electrician on instuction from the plumber/supplier.

House is well insulated. Air tightness test result of 2.5. MHRV commissioned in last few weeks. Stats set to 18/20 generally. UFH downstairs/Alu-rads upstairs.

Looked back through my central stat controller - gives me logging info for last month. On average the kitchen/living room underfloor heating have been on for 10 hr per week. Bedrooms have been 28/30 - they have rads, set by stat to come on 2 hrs each day both morning and night if required. Have a store room and sun room that have been on for 50 hrs per week:eek:. Very small areas though.
3 rooms in house not being used/not finished so stats/heat have been off in them for last 2 months.

Did a bit of investigating the weekend.
Have 2 stats in the buffer tank - one 1/3 way up - the other 2/3 way up or so.
Oil boiler was off (due to no oil!). 600 ltr Buffer tank was at 17/19 degrees on Fri night. Lit a good fire and within a couple of hrs that brought it up to 26/31 degrees or so. (not sure if back boiler is configured/functioing correctly either but will sort that when the oil is sorted!)
Checked at 9am Sat morning - 29/30. Happy enough the tank is retaining heat anyway.
Turned off all stats in house. Fired up the boiler. The buffer didn't 'call' for any heat. Have a timer connected to buffer that can be set for hot water. Turned that on and the tank called for heat from the boiler. Took 50/60 mins for water to get up to 55 dgrees. I assume this is normal enough.

Turned on some stats. Boiler kept firing. Left on for half an hour or so. Intermitently turned stats on/off for rest of day. Boiler fired every time they were on - didn't seem to matter what temp the buffer was at.

Will wait and see what the plumber and his buddy find today. Will be happy enough if it's a 'configuration' issue and not a 'structural' issue

My understanding with ref to solar - solar will only contribute to the heat in the buffer when the temp goes above that off the tank. So if the tank is 40 degrees and the solar is 30 degrees then there will be no benefit.
Sayng that my solar collector was up to 30 degrees on saturday with not much sign of the sun so might not be too long before it's contributing.

JuniorB

Ref the 55 degrees setting on the buffer. It was 65 until a month or so ago. Plumber explained that it was only up to 65 to provide hot water at that temp. Underfloor needed 30 degree and rads 40 degress as far as I can remember. So turned it down to 55. Think he should have reduced down the 'lower' stat too but not sure if he did. This may have caused some knock on issues but it hasn't been set that long so can't see it being fully to blame. We'll see !

JuniorB

Update: 'bottom' stat should have been reduced to 45 degrees when he reduced the 'top' stat to 55. Condenser boiler was set too low as well and was cycling away to it's heart's content!
Will reset them this week and I'll monitor the oil usage for a few weeks. Prob wont really know unless we get another cold snap. I wont be wishing for that!

galwaytt

JuniorB wrote: »

600 ltr Buffer tank was at 17/19 degrees on Fri night. Lit a good fire and within a couple of hrs that brought it up to 26/31 degrees or so. (not sure if back boiler is configured/functioing correctly either but will sort that when the oil is sorted!)
Checked at 9am Sat morning - 29/30. Happy enough the tank is retaining heat anyway.
Turned off all stats in house. Fired up the boiler. The buffer didn't 'call' for any heat. Have a timer connected to buffer that can be set for hot water. Turned that on and the tank called for heat from the boiler. Took 50/60 mins for water to get up to 55 dgrees. I assume this is normal enough.

I'm glad someone has identified that something is indeed wrong : it certainly seems to.

My 0.02.
Your buffer should never be that low (17/19 degrees). It should be kept at a constant temp all the time, irrespective of weather or demand. It's purpose is to keep a 'pot' (sic) of energy to hand, at all times, for you to draw on, whether for floor's, dhw etc etc. The job's of your input sources is to keep it there, and which one does it - solar or dhw, is dictated by their ability to deliver (solar during the day, say, boiler at other times.....)

For this reason, get rid of the clock for your dhw - you're effectively running the boiler flat out, to heat the buffer, to heat your DHW, when you should only be drawing off a small qty of heated DHW, and letting your boiler 'top up' the system. It is a contradiction to have a temp-sensitive system, governed by time. IMHO, anyhoo.

Not sure about your tank, but a good quality modern tank, topped to proper design temp (say, 60 degrees), should, in the absence of drawoff, lose only......1 degree (?) over 24hrs...

JuniorB

Thanks for your reply GalwayTT.
It was at 17 degrees because the oil had ran out !!

Mike2006

Sorry Folks, just back online now....

In my opinion, if you do not have A-rated insulation levels then stay away from UFH. The heat needs to be reatined and the only way to do that is through high level of insulation.

Controls are very important as well and you need to understand exactly how your system works before you make any adjustments etc... Your electrician should spend an hour or 2 explaining every element of your system to you. For example, if you turn up the temp on your buffer stat to say 70 DegC and your boiler is only set to 65 DegC then the boiler will be 'called for' 24/7 and you will use 1000litres of oil pretty quickly. So you need to understand your system.
I have UFH both upstairs and downstairs. Already, I have made changes to my system and one potential big saving I can make is to change my stats upstairs to 24/7 controlled stats. I have a 35mm screed upstairs and this reacts to temp changes within an hour which I didn't expect so I could make a significant saving by timing my stats as opposed to having them maintain a temp upstairs all day and night.
This would not work downstairs because I have a 75mm screed and this would take a lot longer to 'charge' and react so it is more economical to leave it run 24/7.
I did not fully understand this before I built but now I do. Hindsight and all that.. Plus, I thought my stats were time programmable but it turns out that they are not, so I will have to change them 1 by 1 as I see fit...

Mike.

galwaytt

Mike2006 wrote: »

Sorry Folks, just back online now....

In my opinion, if you do not have A-rated insulation levels then stay away from UFH. The heat needs to be reatined and the only way to do that is through high level of insulation.

Controls are very important as well and you need to understand exactly how your system works before you make any adjustments etc... Your electrician should spend an hour or 2 explaining every element of your system to you. For example, if you turn up the temp on your buffer stat to say 70 DegC and your boiler is only set to 65 DegC then the boiler will be 'called for' 24/7 and you will use 1000litres of oil pretty quickly. So you need to understand your system.
I have UFH both upstairs and downstairs. Already, I have made changes to my system and one potential big saving I can make is to change my stats upstairs to 24/7 controlled stats. I have a 35mm screed upstairs and this reacts to temp changes within an hour which I didn't expect so I could make a significant saving by timing my stats as opposed to having them maintain a temp upstairs all day and night.
This would not work downstairs because I have a 75mm screed and this would take a lot longer to 'charge' and react so it is more economical to leave it run 24/7.
I did not fully understand this before I built but now I do. Hindsight and all that.. Plus, I thought my stats were time programmable but it turns out that they are not, so I will have to change them 1 by 1 as I see fit...

Mike.

In general all good, but don't nail your colours to 'A-rating' - that's a bit too vague. Yes, by all means insulate the wazoo out of it, but ratings and u-values are being tossed around like confetti tbh - there's more to it than that.

For instance, a friend of mine lives in a B1 rated house with UFH, and it runs very well. U-value of the wall is 0.26, airtightness is 3.25. It's because other issues come into play.

Regarding the controls and individual prorgrammable stats: + 1000

I have to re-do mine(analogue), now: which ones did you use, btw ?

Mike2006

Agreed, re A rating. I was just trying to get the point across about insulate, insulate, insulate...

I used Henco stuff. I upgraded from the analogue stat to the Digital stat but I didn't read enough of the small print. I saw day/night mode etc... and incorrectly deduced that there was time control on it, but there wasn't. You have to manually press a button to change modes which is no good for me. So I will upgrade once I find a suitable replacement.

Mike.

fclauson

Don't want to ask a dumb question - but have you also check for an oil leak.

Had this on a system a few years ago - very slow oil weap rather than leak - detected it by the very strong smell

Worth checking that are you are actually burning all you pay for.

Rayzor1

Hi all,Just wondering if anyone can help.I've just had installed underfloor heating to a new build on ground floor and first floor.Total 4500sq ft.I have heatmiser electronic stats in all rooms and have them set to 20C now so as to dry out the house.The house is well insulated,I have the condenser boiler in the garage along with my 500Litre buffer tank which is also heated by 60 solar tubes.The solars are set by there controller to activate when the temperature is 6C above the bottom stat in buffer tank.My problem is that since installing the system about 3wks ago I've used 600 litres of oil:(.The boiler seems to be running for 1min then idle for 1min then fires again.At present its only running from the limit stat thats on the boiler and as soon as the temperature drops a hair in the buffer it fires up again.because it's always on the solars aren't getting a chance to work unless I turn off the boiler which I had to do as I ran out of oil.Can anyone advise on the placement of high/low limit stats and what temperatures to have all set to as it's madness to say the least at present.surely the boiler shouldn't run like that as it seems uneconomical.Its the first underfloor heating system my electrician has wired so its new to him but the crowd that supplied it to me keep trying to fob me off by saying use a timer for the oil boiler,Any suggestions would be greatly appreciated.

Cheers,

Ray

You need a pair of stats on the tank, one near the bottom and one near the top.
They are wired so they only fire the boiler when both are below the preset temperature, the boiler stays on until they both exceed the preset temperature.
Now when hot water is drawn from the buffer the botton stat will drop below it's preset temperature but the boiler doesn't fire until the top one trips.
Doing this means that the boiler has a single long burn then stops until the contents of the buffer have been used.

Mike2006

It sounds to me like your UFH pump/s is/are calling the boiler.
i.e. every time a stat calls for heat in any room, the boiler starts.

For a 4500 sq ft house, a 500 litre buffer sounds small. You will probably have about 300 litres of water in your UFH loop so your buffer would be drained of 40 degree water pretty quickly in that instance. This will cause your boiler to cycle more regularly as well.

Get the controls looked at quickly. You can use the temp probe from your solar controller to pull in the boiler instead of having to use 2 stats and it will be more accurate as well. There should be a spare relay output on your solar controller which your electrician should be able to configure.

Mike.

Rayzor1

thanks for input lads.yes the buffer did seem to drop temp pretty quick when all the zones were looking for heat.my room stats have 4 programmable time settings per 24hr period so when I have house dried out I plan to reduce temp in certain rooms which should mean they won't call for heat as often as I'll increase there heat to suit when timed boiler is firing.I was thinking of running boiler for about 2/3 hours in the morning set about an hour before we get up to heat house to say 20C then have it stop till about 4pm and continue to run till about 8 or 9pm.This I hope should limit oil consumption and provide heat and hot water when required most.The solars should stop the tank getting cold as on bad days now they're getting about 25/30C.The way the system is set up is when any stat calls for heat it sends a signal to the garage to turn on pump at boiler.Its only when buffer tank drops temp that the boiler kicks in.Another problem I have is that if the boiler is off and the house calls for heat it sends across water which could be cold and further reduce heat of floor.:(
Can you recommend where to get these high limit and low limit stats.I have 3 places on buffer to put them top,middle and bottom.At present the top and bottom are being used from my solar controller.I have a spare relay on the solar controller which I'll read up on and see how I can incorporate it into system.can you tell me the temp I should have all the stats at in buffer/boiler etc.the underfloor provider said I should have the buffer heated to 70C while the plumber said 55C.the plumber said the mixing valve at the manifolds for underfloor should be set to 45C so as to heat the floor quickly.I think once I get these items sorted it should be ok,You'd think all this info should be with instructions of underfloor instead of trying to figure it out yourself.

Mike2006

Rayzor...

Your problem is with your electrician. He did not/does not understand how the system is supposed to work so he has wired it up stupidly....

Firstly, with UFH, you really should leave it run 24/7. But you will need to set up correctly before you do this, otherwise you will not be able to keep oil in the tank...

To try to explain this from first principles, it is the heated water in the buffer that heats the UFH loop, therefore when a stat calls for heat, it is the UFH pump associated with that loop/manifold that should be called for, not the central heating/boiler pump. This needs to be changed.

It is the temperature in the buffer that calls for the boiler to fire (not a stat or UFH pump). You have 2 options here:
1. Install 2 stats on your tank. 1 to fire the boiler when the temp drops and the 2nd to stop the boiler once the temperature in the buffer has reached its setpoint.
2. Use the existing temperature sensor which is already in the dry pocket of your buffer and wired back to the solar controller. This is done by using the spare relay output on the solar controller. Set up the relay to energise at whatever temp you want to fire the boiler at (say 50 DegC) and de-energise when the temp in the buffer gets to the desired temp (say 65 DegC). Switch a live to the boiler through this relay and now you are sorted.

I have my blend valve at my manifold set at 38DegC. I would think that 45 is a bit hot, especially if you are drying out floors... I am open to correction on this though...

I heat my buffer tank to 65Degc. The tank is rated for 110 DegC so I will see during the summer how well my solar performs...

If you are turning your boiler on and off based on time and your stats call for heat when your buffer is 'cold' then the water going through the UFH loop could potentially cool down the house..

If you have your boiler on 24/7 controls, this is not an issue (until you run out of oil..). If you wish to remain on timed based running of heating, then you would need to interlock your UFH pumps to the temperature in the tank. This can be done easily enough, but it is a solution to a problem that should not be an issue if you were running your system correctly.

Print out sections of this post and give it to your electrician. If he understands what I am on about then he will be able to make the mods required to make this work. If he doesn't, get rid of him...
It is all simple stuff so he should be able to do it....

Mike.

Rayzor1

Thanks for all your help mike,You certainly know your stuff.I have a 50mm hemi hydrate screed which is supposed to be controlled like radiators as in quick response times so thats why plumber said set manifolds to 45C.Your right of course about initial heat as too much straight away can crack the screed.I hope to use the timed boiler fire up just so as to limit oil burned unneccessarily when not at home.By setting my stats during the day when oil is not firing to a lower temp it should stop the house calling for heat during the day and sending across cold water(I hope):).I'll do this for night time also.The UFloor heating supplier had said to wire heating pump in garage to underfloor controller above the mainifolds(I have 3 manifolds)so when the stats called for heat the heat pump would come on and send hot water over through heating loop in buffer.The boiler at present directly heats buffer but obviously is over working with start stop motion.The pump at the manifolds always seems to be on but then maybe the stats are not satisfied.(I must turn off all stats and see if manifold pump stops:rolleyes:.what way do you suggest the heat pump is wired.Should it be controlled by stat in buffer so when The buffer hits just say min 40C the heat pump kicks in sending over warm water but if it not at 40C it knocks off and in turn doesn't send across cold water which could cool down slab.The manifold pump could still probably kick in and just pump existing water around the open zones.Plenty of food for thought!! Plumber is back later so I'll see what he says and I might try the heating supplier and run it by them.Thanks again.