Under gassed boiler

[TJ1]

My sister in law has just moved house and now finds the central heating is on a one pipe system. She called a gas fitter in as the radiators weren’t warm enough, only to fine the boiler is under gassed too. After he left she found the Gas Safe Certificate which stated a 36 cdi boiler had been fitted but a 38 cdi has actually been fitted, which is too big so now it’s under gassed.
Any ideas if she can get any redress on this mistake?

 

[ianmcd]

dont know about a 36CDI there is a 34CDI and a 38CDI but both have a maximum output of 30KW on central heating they are only different on hot water so wouldnt make any difference which one was fitted to the temp of the CH

 

[dilalio]

So what did she get left with after the recent RGI visit?

 

[TJ1]

Engineer assessor coming tomorrow to quote for mains gas pipe to the boiler. They obviously can’t redress the wrong information on the certificate as they didn’t do the original job. Also will quote for a 2 pipe system to be fitted.

 

[John D v2.0]

I think the problem is the one pipe system not the under gas. Even if the gas pipe was below spec, the low pressure wouldn't cause things to warm up notably less.

 

[muggles]

I think the problem is the one pipe system not the under gas. Even if the gas pipe was below spec, the low pressure wouldn't cause things to warm up notably less.

Really!? A boiler will produce its stated heat output even if it's not receiving the required amount of gas to burn? What is this witchcraft?

 

[TJ1]

Thanks to all who replied but really what could be done about the Gas Safe Certificate, surely it’s not worth the paper it’s written on if the details are incorrect. Had a smaller boiler (36cdi) been fitted it may not be so bad heat wise?

 

[John D v2.0]

Really!? A boiler will produce its stated heat output even if it's not receiving the required amount of gas to burn? What is this witchcraft?

No it won't and if you read carefully you will realise I didn't say that.
Your interpretation of my comments would only apply if the rated output of the radiators is greater than the available gas.
I'm sure they exist, but I've not seen a domestic property with close to 30kw of radiator/emitters.
For example If there are only 15kw of emitters and the gas pipe was only suitable for the slightly lower model of Combi it the rads would be toasty warm.

 

[Doggit]

Although you have a larger boiler than stated (yes, naughty) it'll modulate down to the gas available, so isn't an issue. I think you're approaching this from the wrong direction, and you'll get the gas pipe increased, and then still get no improvement. If there is only one pipe going round the house for the CH, then the heat will be getting drawn off by the first radiators, and there's be less for the subsequent ones. It's not efficient, and is more likely to be the problem, but it's an upheaval to correct, so they may (like you) have felt a bigger boiler would solve the problem. You need to go back to basics, calculate the heat requirements for each room, and then the boiler , and then correct the problem accordingly.

 

[gasbanni]

My sister in law has just moved house and now finds the central heating is on a one pipe system. She called a gas fitter in as the radiators weren’t warm enough, only to fine the boiler is under gassed too. After he left she found the Gas Safe Certificate which stated a 36 cdi boiler had been fitted but a 38 cdi has actually been fitted, which is too big so now it’s under gassed.
Any ideas if she can get any redress on this mistake?

How do you know it's under gassed ? Might not be ! The inlet pressure may be fine it may be modulating down due to the return temperature.

As a test turn everything up to max for a hour and see what happens.

 

[Terrywookfit]

Gas rate it to find what it is actually using.

 

[Daveydub]

If the gas safe certificate did not mention the undersized gas pipe then you could draw this to the attention of your solicitor who handled the purchase although from what I see of these things you will be unlikely to get anywhere unless you get £200 compensation & a £1200 solicitors bill. The one pipe system should have been picked up on survey but probably surveyor would note that no detailed examination etc etc plumbing & electrical. The gas pipe is going to be a fairly minor part of the cost and disruption of the job as a whole.

 

[ianmcd]

I really doubt if you would have that boiler installed on a one pipe system, it is possible but I would be very surprised