New Boiler Advice for our house

Alice_Carden

I need some advice on my boiler please.

Current boiler is Ecotech plus 31 for a 4 bed semi, 2 bathroom, 1800 sq ft house and 11 radiators.

In 2019 we are planning to extend and were thinking what would be the most appropriate combi boiler for the following:

5 bed and 3 bathrooms, 14 radiators. 2,500 sq ft.

BTU Radiator output 70,000 (I have calculated this from cubic sizes using B&Q tool)

We are 2 people at the moment and rarely are two showers/bath on at same time.

I read that a system boiler might be an option, but I want to know if we can achieve a good result with a combi. At present the boiler is in the kitchen and space is limited. We don't really want the additional expense and disruption of relocating it elsewhere and options for where are limited.

Alex1983

You should have a system boiler and unvented cyclinder. If your keeping a combi you may as well leave the Ecotec in.

Alice_Carden

I thought that was the case.

Would the exisiting Valliant Ecotec Plus 31 be ok for our needs or would it struggle/underperform?

Is it worth the expense of £1,400 for a 35kw or £2,500 for a >40Kw (supply and fit) or there is no real benefit?

tacpot12

You can achieve good results with the Combi Boiler you have got now, but with the limitation that you can't run more than one hot tap/shower at the same time. The Ecotec Plus 831 will supply the heating system with 110,000 BTU, so if you are confident in you calculation it will be more than enough to keep the house warm even in a very cold winter. There is such a gap between your 70,000 figure and the 110,000 that the boiler will supply that I think you will be fine even if your calculation is not inaccurate.

If you swap to a larger Combi boiler, you won't see any appreciable improvement in the flow of hot water at the taps, so will still be limited as to the number of taps/showers than can be operated at once. A 40Kw combi boiler might provide only 25% more flow rate than the 24Kw combi boiler you have currently - the problem is that as the flow rate goes up, the size of the heat exchanger needed increases rapidly, and the boiler isn't physically big enough to heat up the greater water flow. Also, the hot taps on the ground floor will tend to receive more of the available flow than showers on the upper floor due to gravity and the flow restriction caused by the shower head.

The advantage of a system boiler will be that you can run multiple taps and showers at the same time, but you will need to find space for a hot water cylinder; the system boiler can still be located in the kitchen in the same place as the existing combi. Relocating boilers to the attic is becoming more popular these days, but switching to a system boiler is still a big job.

If you are installing a new shower, you could consider installing an electric one. Get one rated at 10.5Kw at you will get a reasonable flow of hot water even in winter. The usual problem with installing an electric shower is running the large cable needed from the shower to the consumer unit.

Alice_Carden

Thanks tacpot12. We are hoping to install a new shower in the family bathroom next year. It is directly above the CU so going electric is an option, although our existing CU is at full capacity. I assume an electric shower would need its own circuit/ RCD on the CU.

macman

Yes, it must have a dedicated circuit, which in this case will need an additional RCD installing alongside your existing CU.

southcoastrgi

A combi isn't suitable for a 3 bathroom house, follow Alex's advice

Alice_Carden

southcoastrgi wrote: »

A combi isn't suitable for a 3 bathroom house, follow Alex's advice

Yes, I have tackled this