A query re a stove connected to a triple-coil cylinder

Cerbera

I posted another thread a while back about an issue where my stove was "stealing" the heat from my cylinder

http://www.boards.ie/vbulletin/showthread.php?t=2056695256

and the plumbers solution was to fit a NRV in the pipe from the stove to the cylinder.

As per the other thread the advice was that this is bad practice and I've asked the plumber to come back but despite several appointments being made he still hasn't shown.

I have been lighting the stove the last 2 nights and discovered another issue ..... there is a pump between the stove and the cylinder as well as the NRV (they are not in series but in parallel) and a stat brings the pump on and forces the water through the cylinder, apparently to try to force it to heat the water in the cylinder quicker or something like that.

Anyhow it doesn't really work.

The stat has to be set down to 40*C to get the pump to start and even when the stove cools the pump stays running because the hot water circulating from inside the coil in the cylinder keeps the pipe above 40*C.

Obviously this system needs to be fu(ked out and replaced with the "correct" pipework and I'm probably going to have to get some other plumber to sort it.

What I need to know is what EXACTLY needs to be done to get the pipework between the stove and the cylinder to work properly ?????

The cylinder is a triple coil.

There is solar, oil and stove connected to it.

The pipe run to the cylinder from the stove is quiet short, about 1.5m

The stove will "steal" heat from the cylinder if the pipework is just straight in and out.

How does it need to be done?

Anyone got a diagram / pic they can post?

What else do you need to know to help me ?????

shane0007

If you search my posts I have posted here the correct pipe layout for this, without the solar coil but still the same.

It sounds like the system is totally wrong and needs re-piping. Make sure you get somebody who knows what to do as many systems of this sort are incorrect. Without seeing the installation it is very difficult to diagnose the issues.

shane0007

If you can't find it, pm me with your email address and I will send it on to you.

Cerbera

shane0007 wrote: »

Without seeing the installation it is very difficult to diagnose the issues.

I appreciate that.


Yeah it does seem like there is something done wrong.

I did actually reckon I was getting one the best companies to do the installation and wanted it to be right, they came highly recommended and any time I came across them on jobs they did seem to be doing top quality work.

At least if they'd come back and make an attempt to get it sorted I'd be happy but the broken promises and no-shows have p!ssed me right off at this stage.


I'll have a search through your posts.

shane0007

It seems you have followed the correct path in getting them in the first place. It may cost you significantly or little to correct the issue so rather than paying for it twice, I would write to them, explaining the issues, highlighting the let downs and broken promises and point out that although you do not wish to go down the legal route, their constant broken appointments and inability to correct the problem may lead you down the legal route.

Also speak to the person who recommended them to you.

Cerbera

I can't fault the workmanship / neatness / etc and it's just the one little issue with the stove that is a causing the issue.

The problem is that I'm being ignored ..... :mad:

And realistically there's no piont in going legal over it (the solicitor isn't great with stoves ).

shane0007

I meant the threat of it usually suffices. Having neatly installed pipework that is not fit for purpose defeats the purpse of having them installed in the first instance. I was just mentioning that if you are being ignored, then write to them with the mention of legal, then this would usually do the trick.

Cerbera

Yeah, fu(k it I might have no choice but give them a fright.

The boss man was actually in the yard yesterday dropping off the SEAI forms and met her-indoors and mumbled something about knowing we have a problem with something and he'd call back later as he was in a hurry.

She reckoned he couldn't get out of the place quick enough and got the impression we weren't likely to see him again.

Jaysu I'd love to be able to name-and-shame them on here (don't worry mods, I won't) just so others could be warned.

shane0007

If you have recieved grant assistance from SEAI, then you most definitely have another angle of attack. You can either contact the SEAI and inform them you have issues with the installation. They will send out an independent assessor FOC and enforce the contractor to return and correct the discrepancies that they find.

First off I would write the letter I described above but also mention you will report the issue to the SEAI. If they do a lot of grant assisted work, they will not want SEAI on their back as they will receive penalty points and/or be struck off their list.

AverageJoe82

sounds like you need to inject the return pipe pasted the return outlet on the cylinder, and always making sure that the pump is on the return and before the injector, ive installed 100's of solid fuel systems and have never had any problem come back due the the installation ive done

shane0007

AverageJoe82 wrote: »

sounds like you need to inject the return pipe pasted the return outlet on the cylinder, and always making sure that the pump is on the return and before the injector, ive installed 100's of solid fuel systems and have never had any problem come back due the the installation ive done

I am sure Cerbera would not know how to install an injector tee and the point here is does the installation company know how to either. If they responded to Cerbera, I am sure the question could be asked but playing ostrich usually smells of an incompetent installer.

If it was my hard earned money given to them, by now I would be playing hard ball after giving them every opportunity to return and correct their incompetence. Fair enough if they made a genuine mistake, but they received payment and the installation is not fit for purpose and are ignoring the issue.

Cappry

Hi folks:
I too had similar problems with the stove stealing cylinder hot water. This problem was anticipated during the build (in 2007) so we placed an analogue room stat adjacent to the stove, to automatically activate and deactivate the stove pump. It did successfully activate the stove to cyclinder pump, but unfortunately the fire would be gone out 3-6 hours before it would turn off again. I put this down to residual heat from the stove which is inset to a brace which also held residual heat. We then bypassed the stat at the stove and placed a pipe mounted stat before the tank, which I now manually turn on and off. Its a pain and potentially dangerous should I forget one day.

If I can add to this thread.
I have a triple coil 260 ltr cylinder. Currently fed by 22kw monster stove & condensing boiler, with future plans for solar thermal panels (not done yet).
I had intended that stove & oil would heat cylinder, and underfloor and dhw would feed off as needed. (also had 7 small rads for just in case).

First plumber could not get his head around plumbing the triple coil tank right, and I think it needs fixed: Currently plumbed as.
Oil & Stove are 'T''d to underfloor
Oil & Stove also feed coils in the tank.
DHW comes off the top.
Oil and Manifolds have independent timing, which I correlate (ie: not tank controlled).
I think this is wrong.

My issue is oil consumption is too high. I had hoped to heat cylinder in spurts and Ufh would draw down the heat over time...thereby saving oil.

Now a new plumber is saying my tank is too small, replace with an 800ltr triple coil, go with tank controlling the boiler and forget the stove/have stove feed rads only.
Seems a shame to get no bang for buck for ufh from the stove, which was my original intention...

So, help needed
Q1-Do you think 260ltr tank is too small to be a thermal store (350sqm of ufh)

Q2-Is tank control of boiler effective/cost effective

Q3-In summer months, when oil is normally off, surely its expensive to keep so much water hot using oil, if only demand is dhw.

Q4-UFH does work, just expensive to run. I could just forget about the (just in case) rads as they need higher temps. Thoughts on stove only feeding thermal stove cylinder ? (I have attic rads x4 for overtemp if needed)

Q5-The mixing value on my manifolds when max'd only supply ~33deg to ufh. Should this not be 40-45deg range ?

Q6-Had considered a submersed sensor in the stove pipe feeding cylinder for accurate control, but can't find any on the market.

Sorry, if this is too long...but thanks for reading/helping..

Cerbera

I'll update this if / when it gets sorted but I'm not saying too much for now as I've had to "apply a little bit of pressure" and we are hopefully heading the right direction.

shane0007

Cappry wrote: »

We then bypassed the stat at the stove and placed a pipe mounted stat before the tank, which I now manually turn on and off. Its a pain and potentially dangerous should I forget one day.

Totally wrong and dangerous.

Cappry wrote: »

Now a new plumber is saying my tank is too small, replace with an 800ltr triple coil, go with tank controlling the boiler and forget the stove/have stove feed rads only.

800 Litre is way too large for your installation. Are you using an unnatural amount of DHW? 260 Litre is generally fine. The average person uses approx 45 litres of hot water per day so you can work out from there.

Is the installer talking about installing an 800 Litre buffer tank, 800 Litre Thermal Store or an 800 Litre DHW cylinder? The three are different.

Cappry wrote: »

Q1-Do you think 260ltr tank is too small to be a thermal store (350sqm of ufh)

Q2-Is tank control of boiler effective/cost effective

Q3-In summer months, when oil is normally off, surely its expensive to keep so much water hot using oil, if only demand is dhw.

Q4-UFH does work, just expensive to run. I could just forget about the (just in case) rads as they need higher temps. Thoughts on stove only feeding thermal stove cylinder ? (I have attic rads x4 for overtemp if needed)

Q5-The mixing value on my manifolds when max'd only supply ~33deg to ufh. Should this not be 40-45deg range ?

Q6-Had considered a submersed sensor in the stove pipe feeding cylinder for accurate control, but can't find any on the market.

Sorry, if this is too long...but thanks for reading/helping..

Q1. Generally yes. 500 litre buffers are best. Thermal stores generally have a DHW coil to heat DHW. The thermal store must be kept at a constant high temperature to meet the DHW demands so they are generally much more expensive to run, especially when other sources are drawing from it also. You will also need a substantial solar array to contribute to this in the future.

Q2. It is all to do with control. Poor control means expensive to run. Excellent control means most efficient.

Q3. Yes. I normally install a Winter/Summer switch in conjunction with a 3 port valve to buy pass the buffer for DHW, but this will not really work with a thermal store, only with a buffer.

Q4. It shouldn't be. I would look at the UFH controls to improve. If it is poorly installed, then you will have to live with it as remedial works can be very expensive with UFH.

Q5. Your set up is definitely incorrect. They should indeed be 45C.

Q6. Never heard of it!

Cappry

Q1-Do you think 260ltr tank is too small to be a thermal store (350sqm of ufh)
Shane: Generally yes. 500 litre buffers are best. Thermal stores generally have a DHW coil to heat DHW. The thermal store must be kept at a constant high temperature to meet the DHW demands so they are generally much more expensive to run, especially when other sources are drawing from it also. You will also need a substantial solar array to contribute to this in the future.
Dermot: Current is a 260 litre thermal store: Constant high temp was my concern too. House inhabited by 2 adults & 3 young kids. Very low dhw usage <50ltrs/day. Have heard of triple coil tanks with small dhw tank on top..any good ?
Friend proposed adding a buffer tank and connect to existing 260 litre..possibly cheaper: ie: get Dhw reserve, and use existing to merging sources for area heating....good idea ?


Q2-Is tank control of boiler effective/cost effective
SHane: It is all to do with control. Poor control means expensive to run. Excellent control means most efficient.
Spent lots on control. 14 stats/zones. Central touch pad control. (Heatmiser system)...Initially let it loose (cylinder controlling boiler) and two rooms demanded heat for ~90hrs of the week....so reverted to timing as cheaper..not ideal. But cylinder stat is junk. Advice please...

Q3-In summer months, when oil is normally off, surely its expensive to keep so much water hot using oil, if only demand is dhw.
Shane: Yes. I normally install a Winter/Summer switch in conjunction with a 3 port valve to buy pass the buffer for DHW, but this will not really work with a thermal store, only with a buffer.
Sounds like my concern about keeping all that water hot is valid. Not a good idea. No budget for Solar at the moment..So, if I add a buffer tank for dhw and use existing 260 litre for heating...would that work ?...What size should buffer be...ie: 260 + ??

Q4-UFH does work, just expensive to run. I could just forget about the (just in case) rads as they need higher temps. Thoughts on stove only feeding thermal stove cylinder ? (I have attic rads x4 for overtemp if needed)
Shane: It shouldn't be. I would look at the UFH controls to improve. If it is poorly installed, then you will have to live with it as remedial works can be very expensive with UFH.
---as oil feeds direct to ufh I had thought this was among causes for high costs...original idea was heat volume of water and have ufh draw it/temp down and oil to kick in for topping only....Is this vaible at all...or just a pipe dream ?
Bought a kit, installed piping as per design, 150mm space around perimeter, 200mm in centre of rooms. Manifold has pump & mixing value...I suspect mixing value impedes 45deg getting to ufh pipes...so possibly new manifolds x 3..(ouch)

Q5: All clarified, 45 degrees it is...thanks..

Q6: Will keep on looking..

Cheers, Dermot

Q4-UFH does work, just expensive to run. I could just forget about the (just in case) rads as they need higher temps. Thoughts on stove only feeding thermal stove cylinder ? (I have attic rads x4 for overtemp if needed)
Q4-UFH does work, just expensive to run. I could just forget about the (just in case) rads as they need higher temps. Thoughts on stove only feeding thermal stove cylinder ? (I have attic rads x4 for overtemp if needed)

shane0007

Q1. Tank in tank has same issues as thermal store. Basically the same thing but not, sort of speak. I would always try to encorporate a separte DHW cylinder.

Q2. You may have spent lots on controls, but that does not mean you have excellent controls. For example, you are wasting energy putting 33C to the floors. Advice - I could not offer proper advice remotely. Every system/installation is different.

Q3. I generally try to install buffers of 500 Litres. Much each to achieve design temperature, i.e. 35 mins from 10C to 70C with 35kW boiler and 55mins from 10C to 70C with 26kW. Approx! Bypassed then for DHW when required.

Q4. Oil directly to UFH generally will cause short cycling of the boiler which is expensive. A buffer will eliminate this along with a modulating circulating pump.

Q.5 Yup

Q.6 Yup

Off to bed now, fingy's tired! Early start.

Cappry

Q1. Tank in tank has same issues as thermal store. Basically the same thing but not, sort of speak. I would always try to encorporate a separte DHW cylinder.
Dermot 3: Thanks, I will consider.

Q2. You may have spent lots on controls, but that does not mean you have excellent controls. For example, you are wasting energy putting 33C to the floors. Advice - I could not offer proper advice remotely. Every system/installation is different.
Dermot 3: Sound:

Q3. I generally try to install buffers of 500 Litres. Much each to achieve design temperature, i.e. 35 mins from 10C to 70C with 35kW boiler and 55mins from 10C to 70C with 26kW. Approx! Bypassed then for DHW when required.
Dermot 3: There are lots of terms about that I'm not up to speed on: I have a triple heat source, triple coil cylinder contributing 95% to UFH and 5% to rads. Would you say this is a buffer or thermal store or ??....and is adding a seperate dhw tank to my system possible (you think)

Q4. Oil directly to UFH generally will cause short cycling of the boiler which is expensive. A buffer will eliminate this along with a modulating circulating pump.
Dermot 3: Again, clarification on the buffer...Do I have a buffer, would this be before the tank I already have....

Q.5 Yup...cool
Q.6 Yup...cool

Off to bed now, fingy's tired! Early start.[/QUOTE]

shane0007

I am not sure what you have. Do you have any technical data which would be on a data label on the cylinder/tank?

froshtyv

shane0007 wrote: »

Q1. Tank in tank has same issues as thermal store. Basically the same thing but not, sort of speak. I would always try to encorporate a separte DHW cylinder.

Q2. You may have spent lots on controls, but that does not mean you have excellent controls. For example, you are wasting energy putting 33C to the floors. Advice - I could not offer proper advice remotely. Every system/installation is different.

Q3. I generally try to install buffers of 500 Litres. Much each to achieve design temperature, i.e. 35 mins from 10C to 70C with 35kW boiler and 55mins from 10C to 70C with 26kW. Approx! Bypassed then for DHW when required.

Q4. Oil directly to UFH generally will cause short cycling of the boiler which is expensive. A buffer will eliminate this along with a modulating circulating pump.

Q.5 Yup

Q.6 Yup

Off to bed now, fingy's tired! Early start.

Bang on.

Your oil burner is designed to heat water at high temperatures ie 60 degrees. Your underfloor will be generally set at 40. Your boiler will need a set period of time until it reaches its maximum efficiency. By feeding your UFH directly off the boiler you arent letting the boiler reach its maximum efficency, its turning off to quickly thus its cycling which is hugely inefficient, which is why your oil bill is high.

By letting the Oil burner heat a buffer tank, and then connecting the UFH to the buffer tank you stop the cycling of the boiler.