Back boilers a good idea?

akira181

I'm needing to get the plaster in my living room walls redone as a lot of it sounds hollow and there's floor to ceiling cracks all over the wall, which are spreading into the original tenement cornicing. I know there's a fireplace that has been boarded over and I believe the original hearth is still under the carpet as there's something stone sounding underneath when tapped. I'll know more when I'm able to pull the carpet back.

I'm planning on seeing if we can open the fireplace back up when the plaster is redone, line the chimney, and get a "smokeless" wood burning stove installed.

As the majority of our time (me and the other half) is spent in the living room, where the suspected fireplace is, the stove would be lit for heating long before turning the combi on. The rest of the house we don't really mind being cold unless there are guests staying over.

So a wood burning stove would make sense I think, but what about adding a modern back boiler to heat a radiator or two as well? I'd still use the combi for hot water as I'd like to avoid installing a hot water cylinder (I got space in the loft but would rather not).

victor2

Can you even get them now? They were terribly inefficient and I believe it's almost impossible to repair old ones, never mind buy a new one.

FreeBear

A word of caution on the plastering side - If you are going to be using a gypsum plaster such as Thistle Multifinish, you need to be aware that it will only tolerate temperatures up to 50°C. Above this, the plaster starts to crack and flake off the wall.

I have a multifuel stove in my lounge along with sensors buried in the wall. Just above the stove, I regularly record temperatures well over 100°C dropping to around 60°C at ceiling level. A combination of Vitcas heat resistant plaster and lime plaster has proven to be tolerant of the high temperatures to date.

You could fit a back boiler stove, but most of them are pretty powerful beasts which might be too big for one room - Salamander do a dinky little back boiler for their diminutive Hobbit stove. Details are very limited on their web site, but don't expect to plumb in huge radiators. May be enough to run a 700-1000W (2400-3400BTU) radiator.

wigglygiggly

We used to rent a house with a stove and it was meant to heat up the rads in the bedrooms above it. Lukewarm would be optimistic tbh. Bedrooms always felt absolutely freezing in the winter, so no, I couldn't recommend it.

akira181

victor2 said:

Can you even get them now? They were terribly inefficient and I believe it's almost impossible to repair old ones, never mind buy a new one.

You can get modern back boiler stoves with around 80% efficiency. Not great but not terrible either. More than enough to spread a little heat around the house, which would be sufficient when we don't have guests.

FreeBear said:

A word of caution on the plastering side - If you are going to be using a gypsum plaster such as Thistle Multifinish, you need to be aware that it will only tolerate temperatures up to 50°C. Above this, the plaster starts to crack and flake off the wall.

I have a multifuel stove in my lounge along with sensors buried in the wall. Just above the stove, I regularly record temperatures well over 100°C dropping to around 60°C at ceiling level. A combination of Vitcas heat resistant plaster and lime plaster has proven to be tolerant of the high temperatures to date.

You could fit a back boiler stove, but most of them are pretty powerful beasts which might be too big for one room - Salamander do a dinky little back boiler for their diminutive Hobbit stove. Details are very limited on their web site, but don't expect to plumb in huge radiators. May be enough to run a 700-1000W (2400-3400BTU) radiator.

Thanks for the tip, I was considering looking for a plasterer that still uses lime plaster as it's an old tenement building from 1900s and I was told lime plaster was better for the walls than the modern stuff. More reason to do that if I go the stove route then.

I was looking at the Parkray-Hunter Aspect 14 boiler stove or something along those lines. Nominal heat output 10.3kw, 4.8kw to water, 5.5km to room. According to online calculators, my living room needs 21k BTU or 6.3 kW. So slightly more than the stove can provide if the calc is accurate but just means the fire will be lit a little longer than normal, which it will probably be anyway. My partner would have a fire in summer and open the windows for "the ambience" if she could get away with it.

And the back boiler can take the chill out the bedroom and bathroom, no need to be hot. Or at least that's the thinking

wigglygiggly said:

We used to rent a house with a stove and it was meant to heat up the rads in the bedrooms above it. Lukewarm would be optimistic tbh. Bedrooms always felt absolutely freezing in the winter, so no, I couldn't recommend it.

I'm not expecting it to heat the house based on approx 5kw output but take the chill out the bedroom/bathroom would be enough.

Just unsure if being able to spread 5kw around the house is worth the extra expense and complexity

FreeBear

akira181 said: I was looking at the Parkray-Hunter Aspect 14 boiler stove or something along those lines. Nominal heat output 10.3kw, 4.8kw to water, 5.5km to room.

Unless the stove is room sealed, you will need quite a large vent put in an outside wall - This is going to let a lot of cold air in along with a fair bit of noise. If you are in a town, the noise might be a problem.

One more thing to add - Do you like spiders ?

Bringing in logs from outside will introduce spiders in to your home, and possibly a few other bugs overwintering under bark.

Eldi_Dos

@ akira181

Are you allowed a wood burning stove in a tenement?
Does the Clean Air Act allow it in your area.

Bendy_House

Not sure how you can have a back boiler without a water reservoir of some kind? There has to be some way of coping should, say, the pump fail and it starts to overheat. LOTS of boiling water...

I think I would stick with a heat-only, and you can allow some to escape out t'door and upstairs.

Apodemus

Bendy_House said:

Not sure how you can have a back boiler without a water reservoir of some kind? There has to be some way of coping should, say, the pump fail and it starts to overheat. LOTS of boiling water...

I think I would stick with a heat-only, and you can allow some to escape out t'door and upstairs.

I agree with you on this one!  We have a stove top fan on our lounge wood-burner and if we aim it out of the door, we manage to circulate a lot more heat to the rest of the house. 

Bendy_House

I also very much doubt whether the cost of a boiler/rad install - which I bet will easily match/exceed that of the stove itself - would be long-term value.

Woolsery

You can't get owt fer nowt. We inherited an 8-9kW stove when we came here. It ran some radiators very badly and devoured logs like the beast it was. In essence it exported a lot of the heat we should have felt in our living room.

We replaced said stove with a 5kW Woodwarm and suddenly felt cosy. We also used far fewer logs in an evening. OK we did a lot of work on the house too, but the stove near the middle of the building heats several rooms in average conditions and we have the option to close doors or use the oil boiler at more extreme times.