what boiler for very low gas user

[bettyflo]

Hi All

I want to change boiler but I am not sure what type is relevant for my usage.
I have a Potterton Suprima 70 (from 1999) and it runs 20mn a day. With this, I have enough hot water for my central heating and washing dishes, shower etc. My annual gas bill is ~£250.

I hear a lot about combi boilers but I am not sure switching to one would be my best option. Whilst any new boiler will be more efficient and I’d potentially save the space occupied by the hot water storage and cold water tanks , what concerns me is that I would probably use more gas. Admittedly the new boiler would turn on each time I need hot water, instead of using the hot water from the tank.

My needs are modest (gas wise) and paying around £1800-£2500 for something that may increase my gas bill instead of lowering it does not make sense.


Also worth noting the cold water pressure on mains is good, but for some reason, the hot water pressure is crap ( if it weren’t for the help of a salamander pump)

I am in a 675sq ft flat, 2 beds and 2 baths (one is electric shower), and 4 radiators switched on out of 7, all year around. I think a 15kw boiler is adequate for this.


Can someone advise on the boiler type I should consider?
many thanks

 

[Chester]

You'd probably use less gas with a combi. Sounds like you have a vented hot water cylinder hence the pressure is not very good, at the moment when your hot water cylinder is calling to be heated up you are heating the whole cylinder up instead of only what you need.

 

[gmartine]

Unless you're desperate to reclaim the space occupied by your HW cylinder or the pump noise is unbearable keep your existing set up, a new boiler will be more efficient but you're not going to save a huge amount based on your existing usage. A 11kw (heat only) boiler to replace like for like what you have will be more than adequate but let the quoting engineer work out your requirements. Combi boilers are inherently more complex and arguably less efficient at providing hot water depending on your usage.

 

[johnduffell]

You didn't mention why you want to change your boiler? You'll be extremely lucky to get back the capital cost in savings, stick with what you have and maybe add more insulation to the water cylinder. Losses from a Combi will be similar to a well insulated cylinder depending on usage pattern and pipe work runs. If you only use a basin full of water a day the Combi might win on gas usage, but an 10 quid elec kettle would beat both long term cost.
Heating a whole cylinder isn't a problem, as once it's warm most of the heat input is replacing what you used, it doesn't go cold very quickly.

 

[bettyflo]

You didn't mention why you want to change your boiler? You'll be extremely lucky to get back the capital cost in savings, stick with what you have and maybe add more insulation to the water cylinder. .

I have been told by my plumber 2 years ago that my boiler was tired (it's 19 years old) and fortunately it's not packed up yet. So I am aware it needs changing and I'd rather do it now, in the summer, when I have time to plan, rather than wait for it to pack up when I need it the most in the winter.
I know I will not recup the cost of a new boiler because I am such a low user. However I am trying to be a bit green and control my electricity and gas spending

 

[bettyflo]

Combi boilers are inherently more complex and arguably less efficient at providing hot water depending on your usage.

OH really? i thought combi boilers were MORE efficient !
You added "depending on usage" so would a combi be more efficient for a low user?

 

[johnduffell]

i thought combi boilers were MORE efficient !

No, condensing boilers are more efficient than the old type. But the old type were phased out anyway.
Combi just means everything is built into the boiler rather than separate components. A bit like a washer dryer has everything in one box.
Depending on usage means if you use half an hour of a shower once a week with the boiler temperature on 35c, the Combi will be better.
If you use the hot tap for a minute each time 30 times a day, or have the pre heat/comfort mode switched on and use it in small bursts, the cylinder will be more efficient.

 

[bettyflo]

Depending on usage means if you use half an hour of a shower once a week with the boiler temperature on 35c, the Combi will be better.
If you use the hot tap for a minute each time 30 times a day, or have the pre heat/comfort mode switched on and use it in small bursts, the cylinder will be more efficient.

thank you johnduffel, I think I understand what you mean. I appreciate your advice.