Urgent boiler replacement

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Discovered, on getting an engineer in to fix what I'd thought was probably a minor fault preventing the boiler from working, that it has had to be condemned (and yes, justifiably - you should see the insides! Ye gods ...). The house (probably 1000-odd sq. ft.) is a fairly typical 3-bed layout upstairs: two large bedrooms along the party wall; a smaller third bedroom containing the boiler/cylinder and the bathroom (above the kitchen) on the outside wall, separated from each other by the stairwell. It's a condensing boiler - cylinder piping goes up into loft, across the stairwell and into the bathroom, so takes a long time for hot water to reach the bath. Cold water tanks in an elevated position in the loft. We were already considering a partial bathroom refit (https://www.diynot.com/diy/threads/re-jigging-part-of-bathroom-considerations.627991), but having to replace the boiler as well has added even more complexity.

It's a two-person household, both preferring baths to showering (and the bath is P-shaped, so larger volume than usual), although the hot-water demand isn't particularly high. There's a pump operating both for the shower and for the bath, which I find a bit odd anyway. Looks as though the controls for both may be a crosswater valve - certainly there's a thermostat, as the bath is a walk-in one.

Heating-wise, the radiators are fairly elderly, and large - the engineer advises that if we went for a combi we'd probably need to replace them as they wouldn't withstand the added pressure. The ideal place for a combi would obviously be the kitchen, except that it's already really poky, and we can't afford to lose any more cupboard space. We don't as yet have any form of rear extension (although if we did we might want to put in a downstairs loo, but probably nothing more), and the garage is detached.

Futureproofing (if there is such a thing): The engineer has suggested that an electric boiler might be a possibility, but I don't know anything about those - and am not sure I want to rely on only one power source for everything anyway. He's also recommended that if we go for a gas boiler we make sure it's hydrogen-ready as well.
Another consideration is that we might want to install solar panels at some stage, so might need to retain a cylinder.

Obviously, I'm getting people to come in and quote, but we'd like to get this done soonest, and I'd like to cover as many bases as possible in advance, so if there are various factors I should consider please let me know. I am reading a number of the "boiler replacement" threads, but would still appreciate any feedback, especially as several of them are very old and the situation may have changed in the meantime.
 
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The engineer has suggested that an electric boiler might be a possibility,
Forget that. Absolutely no way that could ever be a viable choice.

He's also recommended that if we go for a gas boiler we make sure it's hydrogen-ready as well.
Forget that as well. Hydrogen will never be a fuel for home heating. Those promoting it are the tools of the fossil fuel industry who will use any lies they can to extend the use of gas for a bit longer.

Another consideration is that we might want to install solar panels at some stage, so might need to retain a cylinder.
Valid.

not sure I want to rely on only one power source for everything
You already do. Gas boilers do not work without electricity.
 
Don't be rushed into anything, yes you want it doing reasonably soon but the weather isn't so cold now that you can't survive without heating for a few weeks, and presumably you have an immersion heater in your cylinder for hot water.

Do you actually want a combi or is that just what's being pushed at you?

Avoid electric boilers, they cost around 3-4 times as much as gas to run.

Pretty much every boiler now available is confirmed hydrogen ready at a 20% blend, but personally I don't think hydrogen is ever going to be a thing. It's way too dangerous, complicated, and expensive.

As for pressurising your existing radiators, I've been in this job now for 19 years and only remember one occasion where sealing a system resulted in a leak. Worth giving it a go and finding out, anyway. But get them flushed thoroughly.
 
Thank you both for your feedback. Can't be rushed into anything - we finally have an electrician booked in for the next couple of weeks, so this will have to wait until after! We only moved in last summer, so haven't tried the immersion heater yet. I hope it still works okay, although at the rate we're going ... (how on earth an estate agent can sell a property as being "well maintained" without evidence I don't know). Still, we have kettles and a large washbasin ...

No, a combi was only one suggestion. Had one in our old flat, and it worked well enough, but actually did I see someone saying you couldn't use them in conjunction with a pump? We have a pump on the bath and shower, so if that's the case it may be a no-no anyway.
 
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Personal opinion: keep cylinder existing or replaced, flush heating system, if there isn't an immersion heater in the cylinder take the opportunity to get one fitted, replace boiler, straight swap, easy. Any boiler is 20% hydrogen at the moment and hydrogen is currently being injected into the grid, I think 8%. In the middle of the year the next generation of boilers will be neat hydrogen ready but I can only see that coming in certain areas on communal tanks and that's a stretch.

Maybe the earlier installer meant heat pump; it's an option with a £7500 grant to soften the blow but put in correctly it could save money and CO2 but it will be probably in excess of £10,000 if it's done to maximise the potential of the system (and that's after the grant). There are ways of doing it cheaper but they reduce the potential savings. There is a real shortage of good knowledgeable installers at the moment and this is likely to be the case for some time to come plus servicing costs are higher.
 
Yes, I think we're probably inclining towards a straight swap at the moment.

I looked into electric boilers and did one manufacturer's "can we fit one" test, which said no, they couldn't, as we didn't have the necessary space. Plus they are far more expensive - and if the immersion heater is anything to go by (smart meters can be useful) will be incredibly expensive to run.

A heat pump is out of the question due to the house's lack of insulation, anyway.
 
What is your existing boiler make and model?

I have managed to get many old boilers working again. That would give you a while to get a better idea of the best way forward.

I think adding hydrogen to the gas supply is a good idea but not one the Gov seems to be progressing very much.

Heat pumps have their place where electricity generation is green but not otherwise in my view. The Gov are talking about fitting some gas powered generating stations which I see as a very bad idea.
 
A heat pump is out of the question due to the house's lack of insulation, anyway.
Heat pumps do not require massive amounts of insulation.

If your house is poorly insulated you will require a much more powerful heat pump - just as you would need a much more powerful gas boiler, oil boiler, electric furnace, coal fire or whatever other heat source is used when compared to a well insulated property.
 
Heat pumps do not require massive amounts of insulation.

If your house is poorly insulated you will require a much more powerful heat pump - just as you would need a much more powerful gas boiler, oil boiler, electric furnace, coal fire or whatever other heat source is used when compared to a well insulated property.
It's not quite a simple as that. A heat pump has to run more or less continually for the low temperature of the water flow to the radiators to be able to maintain the desired temperature in the house. A lack of insulation will have a great effect on the ability of the heat pump to maintain this temperature because of continual heat loss, and it might mean that the desired temperature is never achieved.
With a gas or oil boiler the flow temperature to the radiators can be much higher, so the boiler on-times can be timed for when you need heat and the radiators will then rapidly bring the house up to the desired temperature. Of course the worse the insulation the higher will be gas or oil consumption but it won't materially affect the ability of the system to get to the required temperature.
 
All buildings have continual heat loss if the interior temperature is above that of the exterior.
If a heat pump can't heat the building then it's undersized, incorrectly installed or both.
 

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