tradesman qualifications

[what..the?]

For my project in excess of £100k I need a roofer, builder, electrican and plumber, I am asking local tradesmen to quote so I can compare but what qualifications do I need to ask for or check for the various trades?

[The Builder]

Also, something I think Al might have not explained......... a Combi (instantaneous - as you need it) can also be a condensing boiler just as a standard boiler (storage in cylinder) can be condensing........ 90% (?) efficient as opposed to old gas or oil boilers which, in the old days, might be only 60%

[AlBags]

Hi BN.
You have to ask yourself .. Do I have both of these? ...

Family with 5 bedroom house, and big HW demands at certain times of day (mornings & early evenings)
Powerful showers required.

Generally, Combis will not cope with this. Some have small 'instant HW-store' .. but it's small.

[AlBags]

Thanks B.
Yes, I didn't do that quite right!

[what..the?]

so you'd have a combi and then the showers would have to be electric power showers? I suppose the power of a standard shower (not power) on a combi system would depend on the water pressure in the house

I wonder what the cost effectiveness of an oil combi and electric shower would be? over an oil condensing system ?

[what..the?]

so a combi can also condense ???

I will have to read stuff online to teach me how a heating system works, any recommended layman's terms sites?

I don't understand how a combi or a condenser heats the radiators either?

[AlBags]

The Combi would have difficulty keeping up with the hot demand .. unless it was a big one .. and most are not particularly fast at delivering very 'hot' water.
An answer 'could be' one like this with thermal store .. you need to check figures .. and depending on BTU sizing, may not be big enough ..
http://www.discounted...8_CF_RS_Condensi.html

[AlBags]

Yes .. Condensing Combi.

[CailinDeas]

Make sure all tradesmen are insured.

[AlBags]

If I was running a Combi Condenser, I'd make sure I was heating hot water too .. and using that .. especially as the heating would likely be on at the time there was large HW demand.
These boilers have to be sized correctly and run long enough to get them into 'condensing mode' .. there are optimum send and return HW temperatures for them to work efficiently.

[what..the?]

the house currently has an exterior boiler (don't know what type) and we have been suggested by project manager to replace with exterior condensing, do they do exterior combi?

[AlBags]

That would be one of these Condensing Combis ..
Only problem is .. They do not do an integral hot water store I believe.
You would have to ask them how/if one could be incorporated.
http://www.discounted...ernal_Oil_Boiler.html

You will need to ensure proper thermal calculation is done to size the system .. You can use an online software tool to this aim.
Let me know if you need help with this, and I'll post a link to a calculator.

[what..the?]

thanks for all that,

don't need the link at this moment in time but thanks

[boxtops]

That's what we have, what-the - combi condensing boiler for the baths and hot water, and central heating, and instant heat electric showers in the bathrooms. Works really well.