Gas Meter and boiler pipe sizing

[NannyMaria]

Hello.

My husband had 3 separate gas engineers round to quote for a new heat only boiler, the one we currently have is a Neatheat Profile, its old and im very surprised it still works, the boiler came with the property which we purchased around 12 years ago.

The problem we're facing is the size of the gas pipe. its a 15mm gas pipe to the boiler. the gas pipe from our gas meter outside im being told it 22mm and it runs under a suspended concrete floor and comes out from the wall about 4ft off the floor just below the boiler as 15mm, Neil estimated the gas pipe length to be around 12 meters. the gas boiler is the only gas appliance we have in the property. we have 5 radiators and 3 hot taps (2 in bathroom and 1 kitchen)

2 of the quotes are charging for a new gas pipe to be installed which for the gas pipe installation alone is £2100 and £2459, we live in a mid terrace and the gas meter is in the front garden, the new gas pipe would have to run the length of the lounge along the skirting board through the bottom step of our stair case through a wall and into the back of the kitchen cabinets. this is going to look terrible.

the second boiler guy said he can fit a like for like boiler and didn't even mention the gas pipe and his quote is almost £3000 cheaper than the other 2 quotes, the quote £2940 which includes a Worcester 12kW boiler, flue, filter, installation and removal of the old boiler. we are really worried over the gas pipe and Neil phoned him back p and explained about the gas pipe but he said the 15mm is fine. how can it be fine when the other 2 are adamant the gas pipe needs upgraded?

what do we need to do?. shall we take his word and get him back for the install or do we need another boiler installer n out for a quote?, we cant understand why the quotes and the information we receiving is so different?.

 

[oldbuffer]

1. What boiler(s) (type, power in kW) were the quotes including pipe size upgrades for?
2. 15mm will support a 12kW load over a distance of just under 12 metres. But note that:
2.1 This is theoretical and assumes there are no bends or joins in the pipework, which is most unlikely.
2.2 Each elbow (90 degree) , elbow / bend (45 degree) or tee in the run impedes the flow. To allow for this an equivalent length is added to the actual pipe length. The addition varies by type of fitting / bend, but if you allow 1/2 metre per fitting you won't be far out. Don't forget there are likely to be four elbows at the meter (out, left/right/back, down, one directional to under floor), and a further one at least at the boiler.
3. On the positive size, gas is compressible, so the whole length of the pipe does not have to be the same. For example, it might be possible to use 22 or even 28 mm pipe behind kitchen cabinets while retaining 15 mm to that point. Depending on the length of run and number of fittings / bends this might be sufficient.
4. It might also be possible to run larger diameter pipework externally, up into the loft, across and down the outside.
5. The reason for carefully specifying pipe sizes is that the gas pressure measured at the meter, and that measured at the appliance, must not differ by more than a one millibar drop with the appliance running full blast.
6. It should be possible to measure the pressure drop across the system using the existing boiler with it running at full power,

 

[Madrab]

Unfortunately it's not one for the forum, we have no idea what the current pipe sizing is, how much of the current pipe is 22mm and how much is 15mm.

Really hard too for the installers to know if the pipe is all encased in concrete. All that could be done is a pressure test with the current boiler, though that will also depend on which Netaheat it is and what burner pressure has been set. Sounds like the 2 installers quoting for the new pipework are defaulting to replacing the pipework anyway to be sure.

The chap that's offering a like for like may have already done the gas pressure test and checked the rating of the current boiler and has ascertained that the gas pipe is large enough for a similar sized boiler. Either that or just assuming that the current gas pipe is large enough. Again though impossible for anyone here to say.

 

[denso13]

which includes a Worcester 12kW boiler

What size is the existing boiler?