New boiler sizing

ComicGeek

https://forums.moneysavingexpert.com/discussion/comment/81971334#Comment_81971334

The Vaillant controllers aren't great either. Only work via internet access, and I have had a control box fried due to voltage surges in our electricity supply. We have regular power cuts and it causes havoc with our heating controls - I have to manually turn everything off and on again once power is restored, and reset the hub a few times to get everything working. In the meantime the boiler is running flat out, with heating full on even in summer, until communication with the thermostat is finally restored!

That was the previous generation controller, I haven't used the latest Vaillant controller yet but no manufacturer is spending money on good quality components any more. Even the latest Vaillant boiler models use cheaper internal components, so difficult these days to know what the most reliable models are.

shiraz99

At this rate I may end up just getting my existing boiler overhauled via a fixed price repair. At least that'll give me a few more years not to have to think about it 😂

One of the chaps quoting for the 36kW WB just informed me that I would probably have to have most of my gas pipe changed to 28mm, which will be an absolute ballache given the pipework runs under the house and difficult to access.

FreeBear

Perhaps worth getting a quote for a heat pump then (if the CH pipework isn't microbore).

shiraz99

https://forums.moneysavingexpert.com/discussion/comment/81972101#Comment_81972101

Even more of a headache given the age of the property and cost to run a heat pump without also having to consider the complete package of insulation upgrades, solar, batteries and let alone finding somewhere to put back in a water tank for DHW.

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/81972060#Comment_81972060

Ah, of course. The larger gas pull from a 36kW+ combi working flat out usually does require a gas supply pipe upgrade. In that case, you'd be absolutely bonkers to consider it.

And the other conclusion I've arrived at is, if you can, keep what you have going for as long as makes economic sense.

A new boiler might possibly improve efficiency by, ooh, 10%, but it'll require a ~£3k outlay, and that's a lot of years to recoup. And, as with all technology, Heat Pumps and other alternatives are both improving in effectiveness, and falling in cost.

Nurse the baby along. 😊

shiraz99

https://forums.moneysavingexpert.com/discussion/comment/81972266#Comment_81972266

Not so sure it's about gas demand, after all I do have a 37kW boiler at the moment. I think this is more about gas regs and having to size pipes now to attempt to avoid pressure drops. It actually makes it difficult for installers to correctly measure pipework they often can't see so they will generally size up just to be safe.

WIAWSNB

Yes, the pipe size has to maintain a set pressure at the boiler when the boiler is going flat-out, and also any other demand on the same supply such as a gas hob.

I guess modern boilers will be far more critical of this.

I was very surprised when I fitted my own 30kW combi, the calcs made it clear the pipe had to be 22mm, which I duly laid. The connection to the boiler was 15…

FreeBear

https://forums.moneysavingexpert.com/discussion/comment/81972155#Comment_81972155

Insulation upgrade is worth doing regardless of the heat source - I've been insulating *this late 1920s semi (as well as plugging cold draughts) and have managed to cut gas consumption from 8000kWh to just 3000kWh p.a.

Solar and batteries, whilst a useful means of reducing electricity bills, is not a prerequisite for a heat pump. Yes, a heat pump will increase overall electricity consumption, you gain by not using gas and paying the standing charge. With a well tuned system and on an appropriate tariff, you should find the running costs to be lower than a gas boiler. There is a heat pump section of the forum if you want to ask more questions → https://forums.moneysavingexpert.com/categories/heat-pumps

And you could find someone local and compare notes through this web site → https://www.visitaheatpump.com/