What boiler to go with Solar thermal and wood burner

[geoffdg]

Hi all,

 

We are looking for some help with the best configuration of heating and hot water system. We will likely have oil on site, a wood burner and solar thermal panels. How would we put these together for the best system. We will have under floor heating. We could make room for a storage tank but we're thinking of just having an oil Combination boiler for the hot and heating until the Architect came up with solar thermal panels for SAP. We will only use the wood burner on occational cold evenings.

 

Any guidance would be appreciated.

Thanks,

Geoff

[ToughButterCup]

Just now, geoffdg said:

[...]

We will likely have oil on site, a wood burner and solar thermal panels.

[...]

 

Could I suggest you consider using Solar PV rather than solar thermal? A little while back, I worked through the same questions as you are currently investigating.

Just a quick site-wide search will bring up more than convincing evidence in favour  of PV in relation to heating water.

However, it would be useful to see if the technology  for solar thermal has moved on since I looked into the matter..

[geoffdg]

Recovering Academic, I agree that the PV seems the obvious choice, with no real science just gut feel and appears to be most people's choice. It was our Architect that suggested Solar thermal. It will be interesting what information comes back from this post.

[newhome]

I have solar thermal (not working at the mo but that’s a different story). It provides lots (too much) hot water in summer when you need less, and not enough in winter when you need more. PV clearly generates less in the winter too but you can use the PV for much more than just heating water so it’s much more useful. If I could wind the clock back I would go for PV over solar thermal. 

[scottishjohn]

first question must be --how good is build --is it near passiv --or old leaky thing

can you get mains gas?

[scottishjohn]

now virtually all grants +FIT gone on PV 

I do not see how it is viable to start  off now with PV

even if you can do it and fit it all yourself its still a lot of years just to get a draw +presuming no mechanical expenses like replacement of invertor 

[scottishjohn]

13 minutes ago, newhome said:

I have solar thermal (not working at the mo but that’s a different story). It provides lots (too much) hot water in summer when you need less, and not enough in winter when you need more. PV clearly generates less in the winter too but you can use the PV for much more than just heating water so it’s much more useful. If I could wind the clock back I would go for PV over solar thermal. 

like all thse things it comes down to designing the system .

but yes a simple non complex system will give you 80%of your hot water needs with 1 panel +heat store . and cost not much to do .

and if it is a modern close to passiv house --that will be your biggest heating expense  year round 

I am awaiting someone doing a new spreadsheet on actual costs on PV now grants have gone and pay back time .

the fact that no one seems to be pushing selling PV systems anymore ithink gives us the answer 

the 7year payback is now twice or more .

so come boys convince me I,m wrong with figures 

 

Edited February 11, 2019 by scottishjohn

[Jeremy Harris]

1 minute ago, scottishjohn said:

now virtually all grants +FIT gone on PV 

I do not see how it is viable to start  off now with PV

even if you can do it and fit it all yourself its still a lot of years just to get a draw +presuming no mechanical expenses like replacement of invertor 

 

Because PV is cheaper through life per kWp than solar thermal.  The price of PV has reduced a great deal over the past few years, whereas the price of solar thermal has pretty much stayed the same.

 

Add in that PV produces energy that can be used for many purposes, not just to heat hot water, and that even when the FiT ends there will still be an export payment, and it is really a bit of a no-brainer.

 

I'll just add that I spent the best part of a day last week trying to fix someone's evacuated tube solar thermal system.  It had been installed about 5 years ago and the installer had since gone bust, leaving the owner with no easy way to get the system fixed.  It was not a lot of fun crawling around in a loft replacing the faulty controller and then faffing around refilling and venting the system.  Made me thankful that I don't have to deal with all that complexity with our PV system.

[Mr Punter]

I was going to reply earlier but @JSHarris has it spot on.

[scottishjohn]

thats just  your view --

convincing numbers  for both the systems from scratch is what is needed -

 

[jack]

7 minutes ago, scottishjohn said:

convincing numbers  for both the systems from scratch is what is needed -

 

So crack on then. Let us know what you come up with. 

 

One factor to consider is that solar thermal is eligible for the RHI. 

[scottishjohn]

25 minutes ago, jack said:

 

So crack on then. Let us know what you come up with. 

 

One factor to consider is that solar thermal is eligible for the RHI. 

yes solar is eligible for RHI

[recoveringbuilder]

We put in a thermal store and biomass stove which we will get RHI payments for, the thermal store can take solar thermal too and the installer was promoting it however solar thermal is not legible for RHI payments , this came straight from the energy saving trust 

[newhome]

51 minutes ago, JSHarris said:

I'll just add that I spent the best part of a day last week trying to fix someone's evacuated tube solar thermal system.  It had been installed about 5 years ago and the installer had since gone bust, leaving the owner with no easy way to get the system fixed.  It was not a lot of fun crawling around in a loft replacing the faulty controller and then faffing around refilling and venting the system.  Made me thankful that I don't have to deal with all that complexity with our PV system.

 

Can’t even get anyone to fix mine at all up here so it’s a useless white elephant on the roof. Needs roof access and they run a mile once that’s understood. Original installer is still in business but says ‘he doesn’t fit those systems now’ so won’t service it. 

 

It wasn’t RHI but under the old approved installer scheme and he took the whole grant to fit 2 panels on the roof and add the controller. Almost 2.5k. Not bad money considering the effort involved. Arse. 

[newhome]

1 minute ago, Christine Walker said:

however solar thermal is not legible for RHI payments , this came straight from the energy saving trust 

 

Not eligible for space heating. For DHW only it’s eligible but if you have a TS it will be used for both space heating and DHW I imagine so it would be ineligible in that scenario. God knows why you can use the sun for DHW but not space heating. Madness! I asked the woman from the Energy Saving Trust who came to the house and she had no idea either. 

[Jeremy Harris]

6 minutes ago, newhome said:

 

Can’t even get anyone to fix mine at all up here so it’s a useless white elephant on the roof. Needs roof access and they run a mile once that’s understood. Original installer is still in business but says ‘he doesn’t fit those systems now’ so won’t service it. 

 

It wasn’t RHI but under the old approved installer scheme and he took the whole grant to fit 2 panels on the roof and add the controller. Almost 2.5k. Not bad money considering the effort involved. Arse. 

 

I'm afraid I'm not going to volunteer to look at another solar thermal system ever again.  I agreed to look at the one I managed to get going last week without realising just what a PITA the thing was to access.  The pump and controller were right at the back of the loft space, in a shallow roof pitch bungalow that had masses of fibreglass loft insulation. 

 

[scottishjohn]

1 minute ago, newhome said:

 

Not eligible for space heating. For DHW only it’s eligible but if you have a TS it will be used for both space heating and DHW I imagine so it would be ineligible in that scenario. God knows why you can use the sun for DHW but not space heating. Madness! I asked the woman from the Energy Saving Trust who came to the house and she had no idea either. 

unless its changed it should be ,but yes as you say not for space heating  last time i asked 

I looked at it  when i changed to ASHP,

but the extra i was going to get OVER that I already got for ASHP made it not worth getting an MCS  to fit it .

I used plumbed eco dan solar cylinder +controller,but as far as they were concerned no solar was connected.

doing it again i would not do it that way as the protocol for DHW on plumbed cylinder  would reduce the hours i could get from solar ,when that should be first priority for DHW at all times

 

 

 

 

 

[ProDave]

2 minutes ago, JSHarris said:

 

I'm afraid I'm not going to volunteer to look at another solar thermal system ever again.  I agreed to look at the one I managed to get going last week without realising just what a PITA the thing was to access.  The pump and controller were right at the back of the loft space, in a shallow roof pitch bungalow that had masses of fibreglass loft insulation. 

 

That was a poor install then,

 

I have seen several and done the wiring for 2, and in all cases the pump and controller was in the plant room next to the thermal store.  The only wiring in the roof was the temperature probe back down to the controller.  I believe on the plumbing side there is a bleed valve at the highest point in the sustem but that should be inside the roof and accessible.

[scottishjohn]

3 minutes ago, JSHarris said:

 

I'm afraid I'm not going to volunteer to look at another solar thermal system ever again.  I agreed to look at the one I managed to get going last week without realising just what a PITA the thing was to access.  The pump and controller were right at the back of the loft space, in a shallow roof pitch bungalow that had masses of fibreglass loft insulation. 

 

yes a bad installation by  the sound if  hiding it all away 

[newhome]

1 minute ago, ProDave said:

 

I have seen several and done the wiring for 2, and in all cases the pump and controller was in the plant room next to the thermal store.  The only wiring in the roof was the temperature probe back down to the controller.  I believe on the plumbing side there is a bleed valve at the highest point in the sustem but that should be inside the roof and accessible.

 

That’s how mine is set up but the AAV is on the ridge of the roof and not accessible from the loft afaik. 

[scottishjohn]

2 minutes ago, ProDave said:

That was a poor install then,

 

I have seen several and done the wiring for 2, and in all cases the pump and controller was in the plant room next to the thermal store.  The only wiring in the roof was the temperature probe back down to the controller.  I believe on the plumbing side there is a bleed valve at the highest point in the sustem but that should be inside the roof and accessible.

yes the first system i was supplied had that ,but i changed it for an auto air bleed unit and a little running soon bleeds out the air ,very little actual volume of water in  the system 

[Gone West]

1 hour ago, JSHarris said:

even when the FiT ends there will still be an export payment,

Do you happen to know if it is necessary to have the install done under the MCS in order to receive the export payments after FiT ends.

[Jeremy Harris]

3 minutes ago, ProDave said:

That was a poor install then,

 

I have seen several and done the wiring for 2, and in all cases the pump and controller was in the plant room next to the thermal store.  The only wiring in the roof was the temperature probe back down to the controller.  I believe on the plumbing side there is a bleed valve at the highest point in the sustem but that should be inside the roof and accessible.

 

2 minutes ago, scottishjohn said:

yes a bad installation by  the sound if  hiding it all away 

 

Pretty much the only place to put the kit, really, as there was no easy way to get the pipework down to any other space in the house.  It was a 3 bedroom bungalow built around 30 years ago at a guess, with an oil fired central heating system, with the boiler in the kitchen and the tank completely filling what had been an airing cupboard.  The original hot water cylinder had been removed and replaced with a bigger one when the evacuated panels were fitted.  It would have made more sense, in terms of maintainability, if the installer had fitted a smaller cylinder and left space in the cupboard for the pump and controller, but it may be that the bigger tank was needed to best utilise the solar thermal.

[Jeremy Harris]

Just now, PeterStarck said:

Do you happen to know if it is necessary to have the install done under the MCS in order to receive the export payments after FiT ends.

 

At the moment it's still at the consultation stage, and I've not seen anything that's definitive, other than that there will be an export payment system to replace the export payment element of the FiT.  My guess is that there will be an insistence on smart metering in order to get the export payment, but there is a potential snag in that, although smart meters can measure and record export they aren't yet approved to do so.

[scottishjohn]

2 minutes ago, JSHarris said:

 

 

Pretty much the only place to put the kit, really, as there was no easy way to get the pipework down to any other space in the house.  It was a 3 bedroom bungalow built around 30 years ago at a guess, with an oil fired central heating system, with the boiler in the kitchen and the tank completely filling what had been an airing cupboard.  The original hot water cylinder had been removed and replaced with a bigger one when the evacuated panels were fitted.  It would have made more sense, in terms of maintainability, if the installer had fitted a smaller cylinder and left space in the cupboard for the pump and controller, but it may be that the bigger tank was needed to best utilise the solar thermal.

retro fits are always going to be problems .

from new you just wouldn,t do that