Boiler Replacement

[mlynn1974]

We moved in to our house in 2007 in West Central Scotland. We have a Worcester Bosch 35 CDI II (Standard Efficiency) installed in 2006.
We have a 3 bedroom house, over 100 years old and not very well insulated downstairs. Upstairs is a dormer conversion and well insulated.
The boiler is maintained and tested every year by a large Scottish plumbing and maintenance company and previously Scottish Gas until they became too expensive. Since we moved in it has needed a new PRV, new fan, diverter valve and heat exchanger seals all done under a repair plan.

Jan 2024-Dec 2024 we used 26793kWh gas and 4385kWh electricity.
Jan 2023-Dec 2023 we used 24414kWh gas and 4412kWh electricity.
I know this is very high and almost twice the amount of gas that Ofgem think is average.

The problem is that we are paying £270 a month for gas and electricity combined from Octopus. When it was 3p/kWh and £130 a month we didn't care about how old or inefficient the boiler was but now I do.

Last year they quoted £3500 for a Worcester-Bosch 8000 35kW and £2500 for an Ideal incl. boiler and installation, flue, timer and filter. Scottish Gas had a similar price. All to save at best 20% on gas. It would take 10 years for it to pay for itself. We want to sell the house but I don't want to fork out £3500 on a new boiler. We should have probably replaced it in 2020 but we didn't think the price of gas would increase so much in 2021.

What would others recommend?

The WB8000 looks good but it seems it doesn't have a mechanical pressure gauge. It only shows the pressure on the digital display and it tops itself up if the pressure goes low. You might have a leak and never notice because it keeps topping itself up. Is that right?

 

[ericmark]

I use oil so not quite the same, however I want to clearly keep the bill down, so my aim is only to use heating as and when required. So my strategy is only heat rooms when required and only as much as required. Electric I use around 5 MWh per year. Can only say that because solar been installed for around 2 years, and it says I used 10.45 MWh since fitted. Only 6.32 MWh from the grid, so 3 MWh per year. So electric use nearly the same as you, but 5-bedroom house. I blame it on running 4 freezers?

But the CH boiler, the first thing is DHW, how is that heated? I moved from oil to electric in the summer, and that has really reduced my oil bill. The problem is heating up the boiler and pipes takes too much energy, so even when electric costs more, still pay less using electric.

Second is the CH, I use all programmable TRV heads, so room only heated when it is in use. Back in 2019 I got some of these for £15 each, since then the price has gone up, so tired these once hub bought then extra TRV heads only £30 each, but the last one, kit included "Room thermostat, 2 x radiator thermostats, hub, 6 x AA batteries, stand, wall bracket, 2 x ring nuts, 2 x Danfoss RA valve adaptors and 2 x M30 x 1.5mm valve adaptors." I actually only got one TRV head, hub and wall thermostat.

However, what ever boiler you get, you will want analogue control, so why not get the control first and see if that is enough?

So basic idea is the TRV head gradually increase or decreases the flow through the radiator and the by-pass valve opens if not using enough water to heat rooms, sending hot water back to the boiler which in turn turns the boiler output down (modulates the boiler) or with my old system causes the boiler to turn off/on (mark/space ratio) so the question is linked TRV head or stand alone TRV head.

If the radiator is on an inside wall, then linked TRV heads work well. On an outside wall, then maybe non-linked and a wall thermostat.

I have 10 programmable TRV's one of which is linked.

 

[cdbe]

If you want to sell the house why change a well maintained working boiler? If you want to because you think it will make it more sellable then maybe try one of those online box slinger types - Boxt.

 

[mlynn1974]

I wouldn't entertain Boxt. There is a pressure difference of 2 millibars in the pipework which one very diligent service engineer noticed. He said "on new installations we are allowed 0 difference". This is caused by different pipe diameters between the meter and the boiler. It tees off to the gas cooker under the floor so if this is an issue I'd rather have excellent fitters than Boxt.

If money was no object I'd get rid of the gas hob and replace it with an induction hob but that would require upgrading the cabling, circuit breaker, junction box and switch for the cooker.

Good point about the TRVs. We were re-piped and new TRVs fitted in 2011. There is no room thermostat (which now might be a requirement) because we have TRVs in every room.

During July and August this year we didn't use the central heating at all. Gas was only used for hot water and the gas hob which was only used every other day for about 20 minutes. We used exactly 74m3 of gas each month. I don't know if this is high. We have a mixer shower (not electric) and 4 of us use it every day.

 

[muggles]

As above, why replace a perfectly working boiler if you're looking to sell the place? Leave it as it is and it's the next owner's problem.

If you are determined to change it then the Vokera Pinnacle 35C would be an excellent choice. I doubt the prices you've been quoted up to now include any upgrades to the gas pipe though, they're very likely to be surprise extras as the job progresses

 

[Dereekoo]

I wouldn't entertain Boxt. There is a pressure difference of 2 millibars in the pipework which one very diligent service engineer noticed. He said "on new installations we are allowed 0 difference".

Frictionless pipework then?