Underfloor Heating & Solar Panel

Toys Out Of The Pram

Do-more wrote: »

@Toys It's better to have the boiler within the thermal envelope of the house as any heat losses from the boiler i.e. heating the air rather than the water, will still end up contributing to heating the house rather than going completely to waste in the garage.

Insulation is only one part of the equation, air tightness is the other equally important factor.

I know from practical experience that it is easier to keep my present house warm when it is -10C outside and no wind than it is in windy weather at +2C. The place is well insulated but leaks like a sieve, so in windy weather the heat is literally blown out of the house.

You really should pay close attention to air tightness measures and then have some form of controlled ventilation preferably with heat recovery. It will have a very significant effect on the heat losses from the house.

The other significant factor you should be looking at is to eliminate any cold bridges from the building.

Ok i can live with the boiler out in the garage as it will keep a little heat in it. for potential classic car been stored so with that im happy enough.

As for your air tightness argument it makes good sense so it will move up on the priority list and i need to start my homework on the cold bridges

Cheers

pache

CotBC wrote: »

Since I was involved in this thread over a year ago, and got some good information from Mike, I figured it might be of interest to provide an update on how my own system is performing.

The background is that that we moved into our new build at the start of December 2010, so just over the 1 year mark at this point. House is 306m2 (3,300 sq ft), timber frame, UFH on ground and first floors, 250mm wall insulation (0.18 nominal u-value), 150mm floor insulation (0.15 nominal u-value), 400mm attic insulation (600mm in one annex (I had some extra rolls!), triple glazed windows (0.9 average u-value). Heating system comprising of a 750l buffer tank with 5 coils (2 x solar, 2 x DHW (1 preheat and 1 final heat) + 1 for back boiler), 2 solar panels (6m2 aperature area), 15kW insert fire with back boiler (2/3 to boiler, 1/3 to room), MHRV and an oil boiler.
Heatmiser stats in all rooms with a central LCD control panel (so useful!), a Horstman timer controller for the recirculation loop and the towel rails, and an M type controller for the heat inputs to the buffer tank. Tank is located in the garage with about a 10m run back to the house.
I don't have the air tightness test repeated yet, nor the BER rating so can't give figures for those.
House has a significant amount of North and East facing glass (the price I pay for maximising the sea views!), has a 5 person household and is heated for 24/7 occupancy.

Heating systems basically operate in line with what Mike has advocated many times on this thread.

Buffer tank inputs are all controlled by the M controller, with the oil boiler only being called on when the tank temperature drops below a preset level and then only when time lockouts are not in effect. The reason for including time lockouts was because I found during the summer that there were often cases when the tank temp would drop just below the trigger temp in the morning (after showers, etc.), and thus switch on an oil burn, where, if it had waited for an hour or so, the solar panels would be providing the necessary heat input. There are many ways to facilitate such an interlock, but the M controller has the timer function available as part of each function block, so it was an easy and effective option for me.
On a related topic, I did invest in a VBus to LAN adapter, so that I can log the system performance on a computer. Once I had put in the time to get my excel file automated, it only takes a couple of minutes to copy and paste the daily text file into excel and see the system performance for the day. By allowing me to monitor the system performance over extended periods of time and adjusting settings accordingly, that piece of kit has easily paid for itself in the first year in terms of oil saved! The dedicated datalogger is the other option there, but I was trying to keep the costs down at that stage. The other advantage of the LAN adapter is that I have the program backed up on the computer and I can make any changes from there which is certainly easier than trying to navigate through the menus on the controller. It also makes it easy to have separate programs, so it looks like I will have a Summer and a Winter program (mainly just the timer lockout previously referred to which is not in place for the winter months, and a slightly different trigger temp for the boiler).
Note that it is better to set a static IP address on the router for the LAN adapter just to simplify things.

So, getting back to how things have been going!
Bottom line is that I filled the 1,100l oil tank in November 2010 before we moved in, and it lasted until November 2011 when I had to put in 919 litres to fill it again. That was despite the fact that we burned through over a third of the tank in the first 6 weeks due to a combination of the house drying out, UFH settings not optimised, very cold weather and not least because the electrician had wired it up wrong so that it was short cycling constantly. After I re-wired the boiler control by inserting an aux. relay which is switched by the M controller, it only operates as required by the temperature in the upper section of the buffer tank. The only reason for using an external relay for the oil boiler was because the potential max load conditions of everything being switched were getting uncomfortably close to the max rating for the controller, so better safe than sorry.
A side benefit of having the M controller switching it is that I can see from the data log how long and how often the oil boiler runs each day.
This winter the oil consumption maxed at just under 50l per week during the cold spell in December, which was higher than I would have expected, but it is keeping house temperatures at levels for 24/7 occupancy, and in fact some of the preset temperatures were higher than they needed to be and have been dialled back since then. At the moment it's averaging around 30l per week consumption, and that's with very dull weather so the solar input is negligible most of the time.

It's important to note that we do light the fire most evenings, and that does give a nice amount of warm air into the building. Even with only the theoretical 5kW being transferred to the room (5.5m x 4.5m), it is a very warm room after a 4 or 5 hour burn ("cozy" for the wife, too hot for me!). The HRV does it's bit to distribute the heat by pushing it out the door of the room, but unless I maxed the fan speed, there is no way there would be sufficient air transfer to handle the heat load. For reference, increasing the fan speed on the HRV does make it audible upstairs when anywhere close to the ceiling inlets/outlets (it's located in the attic). The temperature in the room will drop a couple of degrees over night, but it will still be the warmest room in the house in the morning (door left open over-night). We bought 10 cubic meters of firewood last summer and it looks like we will go through most of it. That is more than is strictly necessary, but we like the "comfort factor" of having the fire lighting, and the fact that it is a renewable fuel makes it worth the effort for us. I cannot stress enough how important it is to get dry seasoned wood for burning. After we moved in we got a load locally which was supposed to be seasoned, but the reality was that it was far too green and would have needed another year to dry out properly. The result is that it did not burn hot enough in the stove and caused a lot of tar build up under the boiler with the resulting drop in efficiency and the soot builds up on the glass door at a frustratingly rapid rate. Last summer we bought timber that was 2 years cut, but we had to pay a premium for it, and it is increasingly difficult to get. These were large blocks (400mm length), which have the added benefit that 2 or 3 of those keep the fire going for a good long burn without having to keep checking on it. If you are seriously looking at the stove option, you will need to factor in the construction of a timber shelter large enough to allow buying the timber a year in advance so that it's properly seasoned before burning ... aim for <20% moisture. On that subject, I did get a moisture meter for approx. EUR20 after our initial experience, which showed that the original timber had moisture levels in the high thirties and some of it well over 40%.

The back boiler input to the buffer tank is a bit of a mixed bag! One negative with my arrangement where we have the buffer tank in the garage, is that the pipes from the back boiler have quite a long run to the tank. That would not have been much of an issue except for the fact that the manufacturers specified that ONLY copper piping could be used, so despite lagging those pipes as much as we could, there is still significant heat loss on the transfer to the tank. Originally, the system was setup having a standard pipe stat by the boiler which switched on the circulation pump when the back boiler water temp hit 60C and switched off when it dropped below 40C. After monitoring the way that was performing for a while (by monitoring the tank temperatures), I changed out the pipe stat and replaced it with a PT1000 sensor and again used the M controller to take over these functions. Program was setup to use a DeltaT trigger mechanism instead of fixed temperatures, with the circulation pump being switched on when the back boiler temperature is 15C higher than the middle of the buffer tank and off again when the temp difference drops to 5C (coil for back boiler is in the bottom section of the buffer tank). This allows it to automatically compensate for the initial high heat losses until the pipes heat up, and then keep the system running at good efficiency levels. Over the course of an evening, it will generally raise the temp at the very bottom of the tank by about 5C and the middle of the tank by 10C to 15C (that's heating approx 500l of water).

Finally, on the sizing of the buffer tank. This is one I don't have any good answer on. As I mentioned we went with a 750l tank based on the recommendation of the supplier. I tend to think of it as a 500l tank on the bottom and 250l on top ... there is a baffle in the middle to help with the stratification. I did put in 4 x PT1000 sensors for monitoring the tank performance and I can say that the stratification or layering of the temperatures does work very well. A typical Winter situation would be to have the bottom of the tank at 20C, the next sensor at 45C (top of the bottom section), the next sensor at 50C (bottom of the top section) and the top of the tank at 60C ... hope that makes sense! You will see some mixing at the mid levels during an oil burn, but it quickly settles down again.
One thing I did find last summer is that 2 or more consecutive long sunny days causes problems as the tank reaches max capacity and we do not use anything near enough hot water to take sufficient heat from the tank to compensate for the solar input. On the plus side, the 6m2 solar tubes I got can very effectively heat 750l of water when the sun is shining ... we just can't use that much and have no further storage. While I am on the solar subject, I will say that I found trying to select the solar tubes a very frustrating experience ... it is challenging to say the least to try to cut through the sales blurb and to get the relevant data from all the suppliers to make a realistic data driven comparison.
I am going to have to include a heat dump mechanism before this summer, which unfortunately will probably be a water flush. I did some trials last year by turning on the heated towel rails, but they did not take anything near enough heat out of the tank. The other downside with using the towel rails was that the last thing I wanted to do was add any more heat to the house, as we struggled last summer to keep the temperatures low enough in the house ... that on a very dull and relatively cold summer. Don't underestimate the potential for solar loading in rooms if you have large south facing glazed areas (we did not have curtains hanging on the relevant windows at the time), and be sure to disable the heat recovery function on the MHRV during the summer months!
So for the tank size, you will get any number of opinions on this but for me it's a trade off between having a big enough buffer during the summer to take the solar input vs. not having a huge (expensive) body of water to have to heat during the winter months. Therein lies the challenge...

OK- that was longer than I had planned - apologies if I went off on too many tangents.
Anyway, for those of you starting out in all of this - Good Luck!
I'm not sure if any of the above actually helps or just confuses the situation more, but it's my 2 cents worth based on my own experience.

BR,
Tim

Hi tim,can i just say i have only read your post now and have to say what a post!!!
One question i have is you mention you used an "m controller",can you give details of this on the site or pm me ,
cheers and thanks

CotBC

Hi Pache, Glad to hear that the post may have been of some help.
As for the "M Controller", I actually thought that if you Googled it you would get the required hits, but having just tried it I see that it is very much not the case, so I will PM you shortly.

pache

Thanks CotBC,pm recived.
Once again hats off to you for the post and what you have achived

llatsni

I'm not really sorry to dig up this brilliant, informative thread! I'm about to venture down a similar route to some of the posters and just had to say thanks for taking the time to write such detailed experiences. Thanks!

@CotBC, I would also appreciate some info on actual products and suppliers via PM if possible.

engineermike

hi,
Have been reading the thread, and lots of very helpful advice for home owners moving to renewable & good heat retention structures.

Some thing to add to the advice, solar controllers - data devices hooked to your homes LAN (local area network) - or indeed full control devices that can control all heating / hotwater - and which zones are on when you come home -
These will require a Static IP address, your router from Eircom or other provider comes with a dynamic IP address - that will change if the power to the router is interrupted, and control / data readings will be lost.

To get a static IP address - contact your phone / broadband provider and request a change to static IP, eircom have a small one off fee to change to the Static IP - however it doesn't require a call out or a change of your modem equipment.
Also quite useful once set up if you want IP cctv camera watching your house!
rgds,
Mike f:)

llatsni

Mike, that only applies if you want to have control (of any network enabled device) from outside of the house. If you only require static IP's internally you can configure it yourself for free.

rayfitzharris

llatsni wrote: »

Mike, that only applies if you want to have control (of any network enabled device) from outside of the house. If you only require static IP's internally you can configure it yourself for free.

Hi, just to add you can use a service like dyndns.org to give your router a hostname like mike.dyndns.org all you need then is a client running on a machine on your network that will update the ip address everytime it changes. Some routers can even do this for you. (anything that can run dd-wrt for sure) Again only needed if you want to connect to a service from outside your house.

CotBC

llatsni wrote: »

@CotBC, I would also appreciate some info on actual products and suppliers via PM if possible.

@llatsni ... anything in particular you are interested in? It's a long list of products, but I'll help out where I can

psychhead

Hi Mike, wonder if you could PM me the details of your system. Been looking at UFL in our new extension, we have rads in the old part of the extension. A company told me we couldnt use a back boiler stove with UFL, oil burner and rads. Would be great to get your input, as ideally we would also love to add solar. Thanks.

hunter1715

Hi Tim,
I read your and others excellent posts on this topic and am extremely interested in what you had to say. I'm currently in the design stage of building a A3 rated house and was considering a similar system as you and other contributors described. I'm currently try to decide wheather or not to install two cylinders or one thermal store.
I want to connect a oil boiler, thermal solar panels 8m2 (part L req for me) and two stoves with back boilers. I was initially considering a direct 300L cylinder for the solar&main pressure Hot water plus boiler input and a second indirect buffer tank of around 500L for space heating with stove and boiler inputs.

I love to know how your and ours systems are work several years on and what you would do differently if anything.

I would also interested for some details on the M Controller, I search google and couldn't find the system you described. Perhaps you would kindly PM me.

Regards, Richard

fclauson

hunter1715 wrote: »

Hi Tim,
I read your and others excellent posts on this topic and am extremely interested in what you had to say. I'm currently in the design stage of building a A3 rated house and was considering a similar system as you and other contributors described. I'm currently try to decide wheather or not to install two cylinders or one thermal store.
I want to connect a oil boiler, thermal solar panels 8m2 (part L req for me) and two stoves with back boilers. I was initially considering a direct 300L cylinder for the solar&main pressure Hot water plus boiler input and a second indirect buffer tank of around 500L for space heating with stove and boiler inputs.

I love to know how your and ours systems are work several years on and what you would do differently if anything.

I would also interested for some details on the M Controller, I search google and couldn't find the system you described. Perhaps you would kindly PM me.

Regards, Richard

suggest you do the return-on-investment calc

if you insulate right you will need very little heating (my heating is €150/year)

its then just hot water you need to cater for