Options for boiler update

FreeBear

A couple of safety issues with the Potterton Powermax boilers.

Every time the burner is removed, the gasket must be replaced. Failure to do so could see combustion gasses leaking out. Suffice to say, the gasket is now obsolete.

Earlier models (prior to 2006) were prone to corrosion on the integral flue/condensate collector. Coupled with drift of the gas valve settings, excess Carbon Monoxide could be produced and escape.

The flue is apparently made from predominately aluminium, which corroded is the presence of acidic condensate.

It is essential that you get yourself a Carbon Monoxide (that is CO, not CO2) alarm. It could save your life.

In light of the above safety concerns, I'd be inclined to side with BG. A replacement boiler is probably prudent. A combi will supply you with plenty of hot water at mains pressure. But with just four radiators, you want one that will modulate down very low. WB Greenstar 4000 & 8000 along with Viessmann 050 & 100 will go down to ~3.2kW - Bot manufacturers also do system boilers if you really want a DHW tank. If you go for a system boiler, don't get conned in to anything bigger than 12-18kW, and still keep an eye on minimum output.

Biggish_who

ThisIsWeird said:

Biggish_who said:

ThisIsWeird said:

The way to fix your power max he is to get someone other than BG out :-).
As you say, tho', it is considered weird by many. But just keep asking around.
In essence, keep an existing boiler running for as long as possible, until it is genuinely ber.

Thanks. Yes that's part of the reason I wanted to get rid of it, as I know it's generally hated by all! 
But it's worked well up to now, but would I not also save money on energy bills getting something modern and efficient?
I definitely want it replaced before they ban boilers, which I think is 2035(?)  

I'm pretty sure it's 'condensing', isn't it? In which case, a more modern boiler would only provide a marginal efficiency improvement over it. Plucking a figure out of t'air, you might save - ooh - £50 per year? And spend - ooooh - £2.5k replacing it?
That clearly wouldn't make financial sense.
Sil has one, and I've carried out a couple of basic jobs on it - replacing the pressure release valve, for example. I recall access was easier than on most boilers.
And it just 'works' - it provides oodles of instant DHW at a cracking flow rate.
Yes, many local GSs were wary for some reason, but there was one who was happy to work on them, which was good news as the whole estate had them fitted.
Gas boilers will be available for a good while yet. General sensible consensus is to keep your existing boiler running for as long as possible. Replace only when needed.
There appears to be a steady improvement in design and efficiency, particularly in alternative energy systems. When the time finally comes, you might just choose a heat pump 'cos it'll be cheap and effective enough :-)

Thanks for replying.

Yes it is 'condensing' from what I can gather. So I guess I'm not saving much on gas!

I don't know about £2.5k... I'm budgeting about double that, as it's gonna be a complicated install which requires scaffolding etc.

So yeah I can see the logic of keeping it as long as I can.

However, I'm not sure about oodles of hot water. I cannot, for example fill the bath before the tank runs out! (And therefore can't have a piping hot bath unless I top-up with the kettle!)

So I'd want a slightly bigger tank.

Admittedly it's a big expenditure, but I see it as an investment. Something I know won't be on its last legs, and something I know I won't struggle to find an engineer to fix & service when required! 

A heat pump would be virtually impossible for my property! 

Biggish_who

FreeBear said:

A couple of safety issues with the Potterton Powermax boilers.

Every time the burner is removed, the gasket must be replaced. Failure to do so could see combustion gasses leaking out. Suffice to say, the gasket is now obsolete.

Earlier models (prior to 2006) were prone to corrosion on the integral flue/condensate collector. Coupled with drift of the gas valve settings, excess Carbon Monoxide could be produced and escape.

The flue is apparently made from predominately aluminium, which corroded is the presence of acidic condensate.

It is essential that you get yourself a Carbon Monoxide (that is CO, not CO2) alarm. It could save your life.

In light of the above safety concerns, I'd be inclined to side with BG. A replacement boiler is probably prudent. A combi will supply you with plenty of hot water at mains pressure. But with just four radiators, you want one that will modulate down very low. WB Greenstar 4000 & 8000 along with Viessmann 050 & 100 will go down to ~3.2kW - Bot manufacturers also do system boilers if you really want a DHW tank. If you go for a system boiler, don't get conned in to anything bigger than 12-18kW, and still keep an eye on minimum output.

Thanks for replying.

Well yes it's always been serviced (last time a week ago) and I assume they check all that. 

I have always had a carbon monoxide alarm close to the boiler. There was a known issue with an aluminium flue collector or something, but that was replaced my the manufacturer for no cost a few years back.

However if there are still safety issues then of course I'd want it replaced asap. 

I'm still not sold on a combi due as I've heard lots about the low HW flow & not being ideal for 2 bathroom properties! 

ThisIsWeird

Biggish_who said:

Yes it is 'condensing' from what I can gather. So I guess I'm not saving much on gas!
I don't know about £2.5k... I'm budgeting about double that, as it's gonna be a complicated install which requires scaffolding etc.
So yeah I can see the logic of keeping it as long as I can.
However, I'm not sure about oodles of hot water. I cannot, for example fill the bath before the tank runs out! (And therefore can't have a piping hot bath unless I top-up with the kettle!)
So I'd want a slightly bigger tank.
Admittedly it's a big expenditure, but I see it as an investment. Something I know won't be on its last legs, and something I know I won't struggle to find an engineer to fix & service when required! 
A heat pump would be virtually impossible for my property! 

If you like your baths, then - yes - I can see it will struggle. A tweak to help that situation would be to increase the DHW temp, say to 70oC, so you'd need to add some more cold to get the required bath water temp = more overall volume. That, of course, brings the serious risk of scalds when using all hot taps, if they don't have thermostats on them (and I doubt they will).

Taking into account everything, including comments from other posters, an unvented cylinder of your preferred size coupled to a system boiler sounds like the best option.

SIL's Pottie has plastic flue pipes, one for inlet and one exhaust, and they run through the loft to exit the roof. I wonder if any modern system boilers have that flue option too?

FreeBear

Biggish_who said: I'm still not sold on a combi due as I've heard lots about the low HW flow & not being ideal for 2 bathroom properties! 

I switched from a gravity fed DHW system to a combi in 2023. Hot water at mains pressure was a revelation, and no more waiting for a tank to heat up. I only have the one bathroom, so the setup suits me. If you're wanting a system boiler, at a minimum, you'd probably want a 180l DHW tank at a minimum.

An alternative would be the Viessmann 111-W which has a built-in 46l tank to supply that initial burst of hot water. But at just over £2K, not a particularly cheap boiler (although it will modulate down to ~3.2kW).

Biggish_who

FreeBear said:

Biggish_who said: I'm still not sold on a combi due as I've heard lots about the low HW flow & not being ideal for 2 bathroom properties! 

I switched from a gravity fed DHW system to a combi in 2023. Hot water at mains pressure was a revelation, and no more waiting for a tank to heat up. I only have the one bathroom, so the setup suits me. If you're wanting a system boiler, at a minimum, you'd probably want a 180l DHW tank at a minimum.

An alternative would be the Viessmann 111-W which has a built-in 46l tank to supply that initial burst of hot water. But at just over £2K, not a particularly cheap boiler (although it will modulate down to ~3.2kW).

Yes if I thought I had a good enough gas pipe for a 30kw combi boiler, I'd probably be okay with the HW flow on that. But I don't think I will, based on what BG engineer has told me.

A new gas supply from the meter is virtually impossible due to layout, etc.  

Biggish_who

FreeBear said:

Biggish_who said: I'm still not sold on a combi due as I've heard lots about the low HW flow & not being ideal for 2 bathroom properties! 

I switched from a gravity fed DHW system to a combi in 2023. Hot water at mains pressure was a revelation, and no more waiting for a tank to heat up. I only have the one bathroom, so the setup suits me. If you're wanting a system boiler, at a minimum, you'd probably want a 180l DHW tank at a minimum.

An alternative would be the Viessmann 111-W which has a built-in 46l tank to supply that initial burst of hot water. But at just over £2K, not a particularly cheap boiler (although it will modulate down to ~3.2kW).

Also 180L sounds like a lot for the tank.

Bear in mind I currently only have an 85L tank, and apart from not quite being enough for a piping hot bath, it's never been an issue any other time.

Bigphil1474

OP, I'm not a boiler expert, but if it was me I'd look to replace it during the summer months when it's less of an issue and heating engineers will be less busy. Maybe find a locally recommended one, get them to quote and see if they'll do it a bit cheaper if it's programmed in during the summer months. We had our old Baxi boiler go on Christmas Eve quite a few years ago and even though BIL was a heating engineer, it took a few days for him to be able to fix it. Wouldn't want to go through that again.

ThisIsWeird

Biggish_who said:

Yes if I thought I had a good enough gas pipe for a 30kw combi boiler, I'd probably be okay with the HW flow on that. But I don't think I will, based on what BG engineer has told me.
A new gas supply from the meter is virtually impossible due to layout, etc.  

I have a 30kW combi in a 3-bed, 3-bathroom house, and the flow is superb for showers. 

Painfully slow process for baths, tho' - so we only shower.

Biggish_who

Bigphil1474 said:

OP, I'm not a boiler expert, but if it was me I'd look to replace it during the summer months when it's less of an issue and heating engineers will be less busy. Maybe find a locally recommended one, get them to quote and see if they'll do it a bit cheaper if it's programmed in during the summer months. We had our old Baxi boiler go on Christmas Eve quite a few years ago and even though BIL was a heating engineer, it took a few days for him to be able to fix it. Wouldn't want to go through that again.

Thank you, yes I think you're right. It would be crazy to do it in the winter when I actually need the heating! Not unless I absolutely had to!