One for all the boiler/heating gurus

We have an Alpha Intec 28s which has been a constant source of pain for the last 2.5 years. Our house is pretty big – 1800s , 4 bedrooms, big open plan area etc so not small. There are 17 radiators al with good TRVs

We have had constant issues with pressure losses which have been basically as a result of the boiler having to spank itself to keep up. We’ve managed to limp it along by getting to balanced and not touching ANYTHING. Anyway it’s now chucking a new error (electricity supply voltage low). We’re so fed up of a cold house we might just bite he bullet and get something bigger but as utter boiler noobies I need some advice. Any words of wisdom ?

Not sure if a boiler working hard creates a pressure loss. More likely undersized expansion vessel causing intermittent discharge from safety valve.

You will need to size the expansion vessel properly if you have a large system as the one fitted in the boiler is unlikely to be large enough.

Have you got a trv on every rad. Most boilers need at least one rad open (although some systems have a bypass or shut off to negate this). No idea if yours does, just something to consider

I’ve fund alpha boilers to be pretty good. I find most problems are to do with a bad install not the boiler.
Where the prv discharges outside stick a bottle under it and see if that is the source of your pressure loss.
But Bear is bang on incorrect expansion sizing is where I would be looking or no pressure n expansion

Bear – yes that’s what happens. The last guy said basically it’s right on the edge but we can add another one (for a lot of cash) so my question, assuming this new problem is fixable, is whether Alpha are decent and we do it to give it some more capacity. It’s dropping pressure every day or so. This new electrical error is permanent now so we have no heat but curiously it seems to have come back alive and delivered hot water.
EDIT: so apparently we can add (or replace) the expansion vessel for something bigger. Or do we just bugger it and buy a bigger capacity boiler full stop ? It’s on a BG homecare so they are coming tomorrow to try and fix this new electrical error. If I was going to replace or increase I would use a local we know is good.

I seriously know nothing about boilers – we didn’t have heating in NZ !

Adding extra expansion vessel shouldn’t be too costly. A new one would need to be bigger and suspect it wouldn’t fit within the boiler anyway.
I’ve no real experience experience of installing Alphas repaired a few. I prefer Worcester but others will slate them, a lot depends on the installation.

Ta-I’ll ask some questions then.

New fault is an odd one. Reports low voltage but works for a while, seems to get chuffin hot and pressure goes into red then it chucks his error – elec supply voltage low.

Anyhoo, let’s see what happens and I might be back to ask what boiler to get – That’s my new bike fund as wel.

“electricity supply voltage low” is worth investigating. It either means the boiler thinks the supply voltage is low when it isn’t (possible fault in cable to boiler, needs fixing before it catches fire; or fault in boiler electrics) or that the mains voltage really is low, which is something to take up with your electricity supplier. It may be that extra load from elsewhere is dropping the voltage and they need to tweak the transformer tappings.

I had a quick check of the electrics earlier and there’s no obvious loss of power to the boiler – checked at input to fused switch exit and boiler entry. Who knows. Nothing else has been introduced to the circuits in the timeframe of the issue.

Summary: main board is cooked which has caused the electrical fault, new one ordered to be fitted Wednesday.
Longer term the boiler output is too small for the size of rads its tryign to drive, theres 15 large radiators in the house and the assesment is we would need a 40Kw boiler to properly run them as opposed to 29kw which is what we have. Its been set at 70 degrees as thats as hot as it will run before it dumps its pressure, while we can put a bigger expansion vessel on the problem is still output.
So, what’s a good make of 40Kw boiler, in Edinburgh for idea of cost !

Just a cheeky build on the OPs post – has anyone installed / used a storage Combo boiler – the ones with a 20L hot water tank built in?

I’m looking at one of these (either Vaillant or Glow worm) to replace an exist Condensing system boiler and hot water tank. We’ve got around 17 rads but rarely use the shower and bath at the same time – so don’t use huge amounts of hot water. The online info suggests this should work ok but has anyone got any real-world experience?

2 smaller boilers linked together with a proper cascade control, will give you both reliability and increased efficiency.

Thing is we wouldn’t have space for 2 boilers, one larger one yes but not 2.