Everyones wasting their time as you clearly don't listen. Just go and have it installed regardless of whether pipe size is adequate or not. There are plenty who will do it. One of those rogue traders for instance. But of course rogue traders to your brand of punter is OK as long as their corner cutting saves you money and inconvenience.
Gas pipe to boiler
- Thread starter dp123
- Start date
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No, can't be a***d to tell you again and again and again. God help the installer that gets the job.
Why don't you get some cheap East European labour.....they don't give a f**k about gas pipe sizes or your safety.
As ChrisR mentioned before, you (well, an RGI) can determine the actual pressure drop on the existing pipe by running the existing combi and gas rating it. This will indicate whether a new combi might be OK or not.
I disagree with the others that there is no chance of the existing pipework being acceptable. It may be that the hidden main run is 22mm (as I said before) and it only reduces to 15mm just before it becomes visible in the garage. That exposed section of 15mm could easily be replaced by 22mm or even 28mm at relatively little expense.
Also a condensing combi will require slightly less gas (maybe 15% less)than a non-condensing boiler, so that will improve the situation anyway. Most band A condensing boilers are very tolerant of high pressure drops and will operate perfectly with an inlet pressure of around 14 mbar (a 7 mbar pressure drop!) although the gas safety regulations only allow a 1 mbar pressure drop.
I disagree with the others that there is no chance of the existing pipework being acceptable. It may be that the hidden main run is 22mm (as I said before) and it only reduces to 15mm just before it becomes visible in the garage. That exposed section of 15mm could easily be replaced by 22mm or even 28mm at relatively little expense.
Also a condensing combi will require slightly less gas (maybe 15% less)than a non-condensing boiler, so that will improve the situation anyway. Most band A condensing boilers are very tolerant of high pressure drops and will operate perfectly with an inlet pressure of around 14 mbar (a 7 mbar pressure drop!) although the gas safety regulations only allow a 1 mbar pressure drop.
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Are you suggesting the OP and his installers ignore the GSIU regs and MI's?
He'll be lucky to only get 1 mbar drop with just 11m equivalent lenght on just a 24Kw combi (say 2.6 m flow). He's told us its 11m and that's without adding the fittings loss. It is also likely the cooker is tee'd off this supply potentially adding say another 15Kw.
No more so than all the reputable boiler manufacturers (e.g. Viessmann, Ideal) who make a point of stating in their MIs (no apostrophe!) that their boilers will operate fine on 14 mbar or less inlet pressure.
Ideal are not a reputable boiler manufacturer. Does it actually state that in the MI or is it just technical saying what you'd like to hear? Most technical support is bo**ocks. What happens if the street pressure then drops to say 15mbar, happens all the time round here. What about the cooker?
Agreed, but they used to be.
Yes, in the case of Viessmann and Ideal for sure, and possibly others. To quote from Viessmann (Vitodens 100 24kW) MI (p.52) - "minimum working pressure 12 mbar- maximum working pressure 20 mbar".
Thanks great answer.
I will make sure the guy that visits tomorrow knows its 22mm at the meter end if he doesn't look. (bearing in mind the last guy didn't)
No, can't be a***d to tell you again and again and again. God help the installer that gets the job.
Thanks for the misquote,you conveniently missed the bit below.
So as i have now been informed the existing pipe "may" be up to the job as the 15mm part could be the last 2 meters.
If its not then its back to plan a and having a pipe installed that is up to the job,i never had any intention of fitting a condensing boiler to a pipe that is not up to the job.
I would like to thank all here that have given helpful advice.
..
Make sure that he gas rates the existing boiler (assuming that it's working) and measures the working pressure at the meter outlet and the boiler inlet, then post the figures here. If the guy doesn't know how to do this, or even why it needs doing, ditch him.
Thanks again.
I don't know if this will present a problem ,the old combi does work but the hot water side packed up so has been blanked off, a main medway was installed next to it to provide hot water ,would this effect the test?
dp123 you're missing the (installer's) point.
If a drop of more than 1mbar exists then it's an illegal installation.
The fact that some boilers are more tolerant than others is of no help to you.
Corgi are informed of all new installations, and may inspect.
If they find one where the gas pipe is undersized (drop more than 1 mbar), the installer's in trouble and may be instructred to replace the pipe at his own cost.
It makes almost no difference whether the boiler's condensing or not.
Your Main Medway is 24kW, so the same as a basic combi.
The reason for the regulation is sound. If you have an applince like a fire or cooker near the boiler, it may happen to be on, at a low setting, while the boiler is off. Under those conditions the (pipe) supply pressure to it would be perhaps 21 mbar. When the boiler comes on, the pipe pressure may drop considerably - I've see 10mbar. That makes the fire or cooker go OUT. Then you have unlit gas escaping into the room. When the boiler goes off again, you have MORE unlit gas escaping into the room.
You have perhaps been given Too Much Information in the posts above, without the background to understand.
To summarise, you MIGHT be able to have just the visible parts of the pipe increased in size to 28mm. You won't be certain until an engineer tries, but bear in mind you may have to replace the lot, with 28mm or above.
If a drop of more than 1mbar exists then it's an illegal installation.
The fact that some boilers are more tolerant than others is of no help to you.
Corgi are informed of all new installations, and may inspect.
If they find one where the gas pipe is undersized (drop more than 1 mbar), the installer's in trouble and may be instructred to replace the pipe at his own cost.
It makes almost no difference whether the boiler's condensing or not.
Your Main Medway is 24kW, so the same as a basic combi.
The reason for the regulation is sound. If you have an applince like a fire or cooker near the boiler, it may happen to be on, at a low setting, while the boiler is off. Under those conditions the (pipe) supply pressure to it would be perhaps 21 mbar. When the boiler comes on, the pipe pressure may drop considerably - I've see 10mbar. That makes the fire or cooker go OUT. Then you have unlit gas escaping into the room. When the boiler goes off again, you have MORE unlit gas escaping into the room.
You have perhaps been given Too Much Information in the posts above, without the background to understand.
To summarise, you MIGHT be able to have just the visible parts of the pipe increased in size to 28mm. You won't be certain until an engineer tries, but bear in mind you may have to replace the lot, with 28mm or above.
ChrisR, you're missing my point. All we know is that there is about 2 metres of 15mm to the boiler in the garage. The rest of the run (11 metres) might all be in 22mm for all we know. Even allowing for fittings (equivalent length say 15 metres x 22mm and 3 metres x 15mm) we may have a situation where more than half the pressure drop is caused by the 3 metres of 15mm! This is exposed and can easily be upgraded to 22mm or even 28mm as necessary. We would then have the equivalent of say 18 metres of 22mm which, according to the tables, can accommodate 3 m³/h with a 1 mbar drop, adequate for a combi boiler.
Not missing your point at all , CH. As I said, "MIGHT", and you won't know until you measure it.
The OP is getting hung up on condensing vs non condensing boilers and whether it "works" or not, which as you know, is NOT the point.
The OP is getting hung up on condensing vs non condensing boilers and whether it "works" or not, which as you know, is NOT the point.
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