Combi Boiler Heating Only

[sub7even75]

Hey,

 

So I have a house around 100 years old, so no cavity walls, cold in the winter.  The previous owner some years back fitted an Air Source Heating System, so we have vents into every room.  The old gas system was removed.  Now he was a heating engineer and I guess 15 years ago, 1 - electric was cheap.  2 - Insulation may not have been a huge factor when fitting these systems.  Old house + ASHP = crap efficiency.

 

My idea is to maybe have a combi boiler fitted - position to be decided (outside wall) just to run a radiator system.  I currently have a cold water/hot water tank in the loft which I would like to retain.

 

I do alot of the work myself but with heating, plumbing I bring in the specialists, but before moving ahead I need clarification on some things, I need help 🙂

 

1.  Can I fit a combi boiler and maintain the tanks in the loft?  So the combi just runs a radiator circuit?.

2.  The tanks for hot water are fine, as I also have a digital shower system in the loft that runs from them, and an extra pump for the hot water to the bathroom as we have a free standing bath and the taps needed the pressure for the hot.

3.  Can a combi boiler be mounted onto a SIP as the gas point is on a wall of a small conservatory which I plan to remove and rebuild the top half (on the brick wall) with SIPs and clad etc, new roof slate with insulated cavity which I am thinking I can run the hot pipes in to the upstairs to start the radiator runs, as I can take the floors up between the rooms to hide the piping.  (Sorry this might be to much info).

 

I guess I cannot really move on unless running both systems is possible.  If its possible, the logistics I can work out.

 

Thanks for reading I look forward to any help.

 

Simon

[SteamyTea]

20 minutes ago, sub7even75 said:

Old house + ASHP = crap efficiency

Welcome

Or it is just sized, or set up, incorrectly.

 

A lot more information would be needed to find out what is possible.

There are loads of topics on here about heat pumps not working right, it is nearly always a commissioning problem.  They are not run like a gas boiler.

Have a hunt around on here and see if there is a similar problem for a similar size and age house.

Then when you see the answer is to insulate and improve airtightness, you will know what to get on with.

 

 

[JohnMo]

If you are not after hot water on demand from the boiler, no need for a combi.

 

If you are just doing central heating any suitably sized system gas boiler will do, you may be better having it as a pressurised system, just to keep air out and therefore less corrosion build up.  Will be a simple system.

 

[sub7even75]

Thanks for your comments guys.

 

Regarding the ASHP.  The problem isnt the set up, its the heat loss through single skin walls.  To be really efficient insulation is key, otherwise the system is always fighting the heat loss.  Electricity being so high does not help either.  I have a well insulated loft, new double glazing all round and new composited front door.  These systems just dont work well with old houses, the government likes you to think everyone can have them, but rising costs and houses you cannot insulate unless you go external just dont work together.

 

I have thought of many different systems, the only problem is space.  Have no airing cupboard, only space for this is the loft and Im trying to keep away from there.  Its a bit of a nightmare to be fair.  The house has been done up so contemporary and modern theres just no place for anything.  A headache that my wife makes worse lol.

[JohnMo]

Heat pump efficiency is directly linked to flow temp, the lower you can get the more efficient. What are your flow temps? Can you fit bigger radiators?

[SteamyTea]

2 hours ago, JohnMo said:

Heat pump efficiency is directly linked to flow temp

More a case of one of the things that affects total system efficiency.

Drop the flow temperature too much and the CoP collapses as there is no usable power leaving the Carnot Cycle.

[sub7even75]

Sorry maybe I didn't explain well enough.  The system is air source, so top of stairs has ceiling vent, outside pump/AC unit.  We can switch between heating or air conditioning. House has to circulate the air vented into each room then recycled back to be warmed via the ceiling vent at top of stairs  Like I said great system in a very air tight insulated house but when your walls are single skin no insulation the heat is escaping and the system never works efficiently as it's always fighting to get the temperature to stay at the thermostat setting.  Expensive at current rates.

 

 

[Olf]

So it is actually a proper air conditioning system (cooling + heating), air-to-air, and unlikely to have heatpump - which is a bummer, as makes it less efficient than modern solutions. Keep it, it will still be useful especially for cooling in the summer.

As for the main problem: If you want to keep existing water tanks (assumed immersion heated) as is, then indeed system boiler is the way to go. Not combi, as you have no use for DHW part of it, and so installation gets cheaper.

Do consider using new system gas boiler for heating tank(s) too, even with investment in coil you may end up saving long term.

Installing boiler and rads is costly and disruptive, do calculations if fitting modern (higher output, heat pump based) AC unit may not be a better option after all.

Whatever you do, think about how you could insulate the building (internal walls, loft, doors/windows, reducing draughts etc) as whatever heat source you want to use, the less losses to fight, the cheaper it will be to install and run.