Combi v Conventional Boiler?

fagun

We have an old (non-condensing) conventional boiler. We're getting some plumbing works done, and thought it's the right time to replace the boiler for energy efficiency and cost saving purposes. But we can't decide on combi v conventional. Looking for some advice as well as suggested models.
Relevant details:
- 4 bedroom Semi
- Presently 1 bathroom with power shower
- Tanks and Pump currently in the loft
- New mains pipe into the house, but older pipes in the house
- Pressure seems Ok, but was a bit weak on the shower before we put the power shower in
- Looking to do a loft conversion, including adding a shower / toilet upstairs. We think that there'll be sufficient space, even with the tanks.
We like our power shower, so are worried that mains pressure won't be enough.
Grateful for any advice.
Thanks

Skiduck

I would not recommend a combi on the face of it:
Firstly, you feel it lacks pressure - is that your kitchen tap aswell? if so, a combi would be a bad choice.
Secondly, you would have to replace your power shower
Thirdly, if you have never had a combi boiler before, it is a slight gamble on whether you would like it or not
Forthly, if you are going to do a loft conversion, look at sealed systems with unvented cylinders, you would get rid of the tanks in your loft without needing a combi boiler.

MarkyMarkD

Sensible advice from Skiduck.

I wouldn't get forced down the combi route without good reason - there are as many disadvantages as advantages.

fagun

Skiduck wrote:

I would not recommend a combi on the face of it:
Firstly, you feel it lacks pressure - is that your kitchen tap aswell? if so, a combi would be a bad choice.
Secondly, you would have to replace your power shower
Thirdly, if you have never had a combi boiler before, it is a slight gamble on whether you would like it or not
Forthly, if you are going to do a loft conversion, look at sealed systems with unvented cylinders, you would get rid of the tanks in your loft without needing a combi boiler.

Ta - we're anti-combi (as you can rpobably tell from the way I presented the facts). Only reason for considering it, is that our plumber suggested we could save £200-300 on our gas bill, compared to a conventional boiler.

As far as water pressure is concerned, its fine (especially in the kitchen), it's just that we do like our power shower. The plumber suggested that we can get showers that provide extra force that are compatible with combis.

Anyway, I think I'll stick with a conventional boiler. What are these sealed systems? Do they work with power showers? Please point me in the direction of any relevant websites.

Cardew

I would go along with the advice from the 2 posts above.

I have both systems - the combi in an annex - and the conventional system is much preferable.

I would be interested in any data on the running costs of the 2 systems for similar output.

fagun

I posted the same question on DIYNot.com. Someone there suggested installing the combi but connecting it to the hot water tank. And then when we do the loft conversion, conencting the combi directly to the new shower. Sounds like the best of both worlds - but I still haven't got any confirmation on the economics.

MarkyMarkD

fagun wrote:

Only reason for considering it, is that our plumber suggested we could save £200-300 on our gas bill, compared to a conventional boiler.

That sounds like a completely ridiculous savings quote.

Even with the awful gas price increases, we are only paying around £600 pa for our gas central heating with a 22 year old conventional boiler.

Now, whilst I can believe that a new conventional boiler will be more efficient than that (maybe 20-25% better - or paying around £450 pa) I can't believe that a new combi is going to save a FURTHER £200-300 over that.

kenshaz

Builders of new homes ,never put Combi's in ,because they will not cope with multi on-suites,which is what the modern home has ,they are designed for the mean ,rather have the luxary of tanks of hot water ,for power showers etc

fagun

MarkyMarkD wrote:

That sounds like a completely ridiculous savings quote.

Even with the awful gas price increases, we are only paying around £600 pa for our gas central heating with a 22 year old conventional boiler.

Now, whilst I can believe that a new conventional boiler will be more efficient than that (maybe 20-25% better - or paying around £450 pa) I can't believe that a new combi is going to save a FURTHER £200-300 over that.

At present we're paying £90 / month which includes an element of catch-up since we significantly underpaid last year. So if we can reduce from say £70 to £50 it seems worth considering. But I don't know how realistic the savings are.Where is Moneysavingplumber when you need him???

caveat_emptor

fagun wrote:

At present we're paying £90 / month which includes an element of catch-up since we significantly underpaid last year. So if we can reduce from say £70 to £50 it seems worth considering. But I don't know how realistic the savings are.Where is Moneysavingplumber when you need him???

If you have a loft conversion and want it heated you'll have to fit a combi as there is unlikely to be enough height above the rad. for a header tank. You'll only get about a 12% improvement in efficiency by fitting a condensing boiler as the old non-condensing type were about 80% efficient whereas the condensers are 90%.

Skiduck

caveat_emptor wrote:

If you have a loft conversion and want it heated you'll have to fit a combi as there is unlikely to be enough height above the rad. for a header tank. You'll only get about a 12% improvement in efficiency by fitting a condensing boiler as the old non-condensing type were about 80% efficient whereas the condensers are 90%.

you can check you boiler's efficiency here:

http://www.sedbuk.com/cgi-local/searchpg.cgi