Boiler regulations? Gas pipe diameter & thermostat

[bookworm]

I need to have a new boiler installed and have been given quotes for different brands and different 'opinions':
Worcester Bosch 24 kw
Worcester Bosch 28 kw
Valiant 28 kw
Potterton 24 kw

Two of the plumbers have commented that the pipeworks of the house are small and needs to be replaced with 22mm diameter ones.
Two other plumbers haven't mentioned the pipeworks, and haven't suggested a thermostat to be installed, which we do not have at present (the above two plumbers have suggested).

One of the plumber that suggested pipework has said that he will install the boiler first, and then see whether it will work and pass the tests. If not, pipework will need to be carried.

I have also been given different time frames on the completion of the work. Ranging from 1 day to 3 days.

I'm getting confused, and don't know which boiler & plumber to go with. Please help with any advice/info.
Thanks very much.

 

[weareleeds]

To comply with part l you now need a stat go for a vaillant ecomax 828/2 with 22mm pipes (15mm will only carry 15,000 btu's) Don't use a plumber get a heating engineer or call bg (pay more but will have less problems in future) Anyone quoting under £2,800 is too cheap

 

[Agile]

You seem to be missing some important points!

1. You need at least a 28 kW boiler to give good hot water.

2. We assume you already have a combi boiler ???

3. The most important point is power flushing the system !!!

4. You cannot fit a boiler and power flush in one day !!!

5. The make is less importantant than the quality of installation.

Tony

 

[corgiman]

also the calculations as to gas pipe diameter can and should be done before the boiler is fitted as if the pipe is undersized your boiler cannot be commisioned and you wont be able to use it

not a good suggestion to say we will pop the boiler on and see, not very professional is it?

 

[Agile]

It does not sound very professional but its often difficult to predict the flow resistance when the route of a gas pipe under floors cannot be inspected.

If its marginal then it seems a good idea to do that rather than to upsize the pipe when it may not be necessary.

I would say that its 100 times more professional to consider the gas flow than to ignore it like so many installers seem to do!

Tony

 

[corgiman]

too true tony, I have gone to lots of 28kw and above combis and found the gas supply appalingly undersized.

I think that a reasonably educated guess can be made as to the flow resistance even if you cannot see the pipework, as it doesnt take your brains to imagine where the original installer would have run them.

I pretty much always upgrade the diameter of the gas supply to at least 28mm to new combis nowadays due to their size, no way is an existing line going to keep up with a 30kw combi slammed on to it, and they are only getting bigger.

 

[Soggy_weetabix]

If I could just add to this thread.......standard U4 meter.

A 160000 BTU input boiler is installed.
Then you find 2 DFE's, and a range cooker installed.

All gas

And the 'conciencoius' (spelt wrong no doubt) plumber puts in 28mm not knowing the meter will only 'throw' 212000 btu's anyway.

Seen it twice in last month, when pipe sizing really has been irrelevent when the meter wont pass the gas.

David

 

[corgiman]

seen the same me self soggy. but i rarely see more than a boiler, hob and maybe a 7kw dfe

 

[Gasguru]

A few years ago went to do a landlord gas safety record and found 3 combi's off a single U6 meter!

 

[ACOperson]

Tony, I slightly disagree with your point about the make of the boiler being unimportant. As you know I go to between 3-6 new (6-18 months old) Ideal Icos/Isar boilers a week with the firm I work for which have developed various faults and collectively need thousands of pounds worth of parts to keep them going.

Would you say to someone who had a Potterton Suprima installed that the installation was more important than the fact they have a boiler with underliable electrics?

 

[Slugbabydotcom]

the meter will only 'throw' 212000 btu's anyway.

Thanks for the info ... I've recently sinned
but thanks to you I can put it right

 

[ChrisR]

Bookworm you must be confused by now!
Law says you have to have a room thermostat and thermostatic rad valves on at least your bedrooms.

What have you got now? If you have a combi already then it's easy to measure the gas pressure at that to see if your GAS pipe is big enough. Gas supplies to combis need to be at least 22mm unless they're a metre or two from the gas meter.

The Heating pipes from the boiler need to be 22mm.
The water supply is important for any combi installation - it should have been checked.

None of the makes you've mentioned are bad boilers. Check the guarantees. Some Baxi/Potterton ones are 5 years.
Most folk would choose 28kW or more to give good HW flow at the tap.

Your existing system will need to be made clean properly or your new boiler will be ruined. If it's a combi system it possibly won't be too bad, but if it was ever an old vented system it could be awful. Your quoters will have made some sort of assessment of that (hopefully). You should have been advised of possibilities of small leaks showing up after cleaning, eg at old rad valves.

Guys installing every day can be surprisingly quick. When BG tried to recruit me they were paying for 10 hours, to powerflush, and change a combi "But you'll be getting it done in a day" (£200!).
2 guys together could do it in a day, but if there are any changes at all to the exisiting system (such as a new gas pipe) then extra time vanishes rapidly. 3 days, for one guy doing it properly, could well be spot on.
One day may be possible for a single worker, if, and if... but is pushing it.

Check the corgi registrations, check that the gas work will be "notified", and electrical work too if it will be in a kitchen (or bathroom).


---

Gas guys - don't forget "diversity", and that a meter spec allows it to drop 2mbar at maximum throughput !

 

[bookworm]

Dear all
Thanks so much for help/info/advice.
Yep, still a little confused as to which plumber to go to. BG has given me a quote, but it's twice as much as the Potterton plumber.
The Potterton plumber told me that the Worcester 24 and 28 junior boilers are not 'as good' as the Pottertons because it cannot control the water temperature.
One plumber did say he didn't like power flushes because it could result in small leaks, and he preferred using chemical flushes.
Oh, I wish I could click my fingers, and the work would be done with no worries.