Even the environmental benefit is not clear cut - not all leccy comes from renewables!

What is the problem with the existing boiler? It is only 20 years old.

I have looked at the economics of replacing my boiler at home. It takes a long time to repay the capital cost, even though a newer one would be more efficient. so over the medium term, it is not worth it.

The existing radiators may not be suitable for the cooler temperature of the circulating water.

By far the biggest problem (at least in my case) is the number of heat pumps required. There may be large 3-phase commercial ones, but otherwise the requirement may be for ten 3 kW input/10 kW output pumps. Where would they go, and if listed, would the planning authorities consent?

I've got to agree with Chris, even though I'm an advocate for Heat Pumps, in your situation, just fit a new gas boiler.

I'd be looking at the heat loss though, 100kW is an awful lot, I maintain an hotel with around 30 rooms, that runs on 108kW (two 55kW boilers) with loads of radiators and hot water use. An oversized boiler is very inefficient, so getting the right size is important.

If it had to be a new system, air to air would be my best choice, a far easier install, cheaper than fitting an air source HP , and running cost advantages too, air source HPs are best if run all, or most of, the time - they are not good at heating an area quickly. Air to Air is quick to heat up, can be used intermittently, and if needed, can be used for cooling. You will however have the 2 or 3 outdoor units, which could be fitted on a roof if needed.

I would go for the gas boiler everytime at least with that you know it will heat the hall and do it reliably those little blue flames always do the business. Heatpumps like a lot if eco technology is a bit iffy at best.

It is not clear what the reason for the recommended change of boiler is - are parts now hard to get hold of ? I'd expect a 2004 model to be pretty efficient and capable of modulating down - domestic boilers were all condensing by then... The time to install a heat pump if you are not under time pressure is probably after most "heating engineers" have got used to them, at the moment round here at least there are a lot of installers used to boilers and a few brave and expensive souls doing heat  pumps, but I expect that to change in the next few years.

While we still have gas, and the gas to leccy price ratio per kW is more than the efficacy of the heat pumps, then the gas has the economic benefit. (although according to this article, its getting close)

Payback times are a funny thing,.

On our scout HQ (not listed mind) we stuck solar panels on all available south facing surfaces, and have taken about £1000 off the annual leccy bill. If it was not for a very savvy treasurer getting most of it paid for by others, that would take about 20 years to pay back at that rate !

but with solar power and battery, perhaps a heat pump would look more attractive...

I presume all that can be insulated, clad or triple glazed without offending the planning types, already has been ? The removal of consumption of any heat altogether if you can do it is a better bet.

Mike.

mapj1 said:

but with solar power and battery, perhaps a heat pump would look more attractive...

Presumably, the village hall has a requirement for hot water, so solar power could eliminate the requirement for gas totally in the warmer months. However, a few kW of solar is unlikely to have a great impact on space heating.

How often is the village hall heated? If it is intermittent, the system needs to be powerful enough to raise the temperature, not merely maintain it.

I suspect that the question is somewhat complicated, which is where a heating engineer might earn his (or her) salt.

Is the heating demand really in the region of 100 KW  ? That seems an awful lot unless the premises are a lot larger than most village halls.

A decent heat pump should have an average COP of at least 3, but could reasonably drop to 2 in cold weather. Therefore to produce 100 KW of heat in cold weather will require 50 KW of electricity. Presuming a guess at the other loads, that suggests a MINIMUM Supply of 3 phase at 100 amps. Any significant electric cooking, or a decent stage lighting set up could push that to 3 phase at 160 amps or even more. Is this available ?

P.S. I doubt that the joints in the heating pipes are actually caulked lead. More likely to be "rust joints" A relatively loose fitting joint in which the gap was filled with a paste containing a mixture of Sal Almoniac and iron fillings. When first erected, such joints tended to leak but soon became strong and watertight, as the iron fillings rusted and increased in volume.

broadgage said:

When first erected, such joints tended to leak but soon became strong and watertight, as the iron fillings rusted and increased in volume.

Fascinating! Rust normally equals leaking.

Rust joints only worked well for water, steam, or gases containing water vapour. Prohibited for gas supply pipes within buildings but sometimes used for gas mains in the street.

Drifting slightly O/T, I recall a story of an electrical engineer, without railway experience, who had to supervise the construction of a tender for a steam locomotive* The water tank leaked from the joints. This was cured by the addition of fine iron fillings to the water which was stirred around. This promptly reduced the leakage as the iron filings blocked up the holes, after a few days leakage was eliminated as the iron filings rusted and expanded.

*The locomotive was ordered from England, and shipped to somewhere in South America. It arrived without a tender and was required to be put to use urgently. It was common to supply steam locomotives WITHOUT a tender, this being manufactured locally, or the tender from the previous engine being re-used.

I agree that gas is currently the best way of heating a village hall, but saying HPs are 'iffy at best' is totally wrong. The only way they will not work is when they are poorly designed/fitted, which can happen with any heating system badly fitted.

You can't just replace an old gas boiler with a heat pump. Boilers typically worked on a water temperature of 80 degrees C. Heat pumps probably only 50 degrees, so to get the same heat output, all the radiators will need replacing with ones having a larger surface area (8/5 times larger approx) 

regards burn