Gas pipe to boiler

[Gasguru]

The original boiler was a combi and ran fine,when the hot water side started playing up we blanked it off and installed a water heater next to it.
Both worked fine off the 15mm gas pipe.

They APPEARED to run fine; it is likely though their performance (ie hot water output) was significantly reduced from the boilers capable output. Combi's and water heaters each have similar gas flow requirements. Customers remain unaware of the shortcomings but we see it everyday.

If the pipe run was indeed all 15mm then it was significantly undersized. A maximum of 1 mbar pressure drop is allowed from the meter outlet to the appliance inlet. It is not unusual to find drops of 10 mbar and boiler/water heater performance down by 30%.

When i asked if i could find a combi to run on 15mm pipe i meant not a condensing boiler as they need at least a 22mm pipe.

Pipe size has nothing to do with whether the boiler is standard efficiency or high efficiency (condensing). Pipe size is determined to give a MAXIMUM of 1 mbar drop. The size is calculated from the lenght of pipe run, number of bends/tees and the gas flow rate (ie the power of the appliance).

However older boilers/water heaters have a burner that will cope better with undersized pipework (ie it will ignite and run although on reduced performance). The most recent (fully pre-mixed burners) are not so tolerant of undersized pipework.

The fact remains it is ILLEGAL to install an appliance on undersized pipework and the result will lead to an underperforming boiler which is also potentially dangerous.

From BS 6891 Installation of low pressure gas pipework

"5.2.2 The pressure drop between the outlet of the meter and the points to be connected shall not exceed 1 mbar at maximum flow conditions (see Table 1)."

Do you have other gas appliances eg cooker/hob/fire, if so how are theyt connected - do they tee off this pipe run?


Have you considered running the gas pipework around the outside of the property? Or using 32mm plastic MDPE buried around the outside of the property? Or having the meter relocated?

 

[megawatt]

Sounds okay.

 

[dp123]

Don't know why £600 is in addition to the quote, as it is a must for the job I would have included this in the main quote.

£600 sounds over the top to me.

The original quote over the phone was approx £1400 the new quote is over £2000.

 

[Nixt]

Like I said OP in the first reply, the consumer usually hates the sound of the reply and you have gone on to display all of the typical ignorance when faced with this issue and continue despite all the independent free advice given to be in complete denial.

The data you require to work it out is freely available from manufacturers so there is no need to be 'ripped off'. How hollow your comments about rogue traders now become as you look for an installer to fit an appliance dangerously in order to satisfy your ignorant tightfistedness.

 

[dp123]

Do you have other gas appliances eg cooker/hob/fire, if so how are theyt connected - do they tee off this pipe run?

We only have a cooker now that we have gone onto coal in the living room.

Have you considered running the gas pipework around the outside of the property? Or using 32mm plastic MDPE buried around the outside of the property? Or having the meter relocated?

Its a terraced house and we are in the middle of it.
I don't think moving the meter would help as i think the main gas pipe runs the length of the front street.

 

[dp123]

Sounds okay.

 

[dp123]

Like I said OP in the first reply, the consumer usually hates the sound of the reply and you have gone on to display all of the typical ignorance when faced with this issue and continue despite all the independent free advice given to be in complete denial.

Wow do you ever have days when you give your shoulder a rest by taking the house sized chip off it?

I am neither ignorant or disputing the advice given,I realised straight away that if i have a new "condensing" boiler fitted i will need to get a bigger diameter gas pipe fitted.

I then asked if i could have a older combi (non condensing) boiler fitted to save the upheaval fitting the new pipe is going to cause.

The data you require to work it out is freely available from manufacturers so there is no need to be 'ripped off'.

You seem to forget i am not a gas fitter, when i asked the OP i was basically asking if the guy was stringing me a line to get more money out of the job which i now know he wasn't.
Do you really think the general public know there is data available to work it out,now who is being ignorant?

How hollow your comments about rogue traders now become as you look for an installer to fit an appliance dangerously in order to satisfy your ignorant tightfistedness.

FFS i am not looking for a installer to fit an appliance dangerously , i asked if its possible to buy a non condensing boiler that will work 100% efficiently on a 15mm gas pipe.
Talk about ignorant you assumed that money was the reason i didn't want the new pipe fitting when in fact its the mess the job is going to make and the fact I'm not too keen on having a plastic box running round half the kitchen.

 

[megawatt]

An underperforming boiler which is also potentially dangerous.

An explanation of why an underperforming boiler is also potentially dangerous may be a useful.

Could be a sticky perhaps?

DIY'ers may not understand why underperformance could be dangerous.

 

[dp123]

This is a little embarrassing

The wife has just told me the guy who gave the quote didn't look at the meter, (i assumed he had) i have just looked and it has a 22mm pipe coming from the meter and going under the floor.
At the garage end it comes out of the wall as a 15mm pipe and runs to the boiler approx 6 feet away,is there a chance he assumed the whole run would be 15mm because he only saw the pipe at the garage end?
We have another company visiting on Monday to give us a quote is it worth mentioning this to them or are they likely to have a look at the meter end as well as the garage end ?
Is there a way they can check the gas output to see if its up to the job as they cannot use the data mentioned in the earlier post ?

 

[ChrisR]

Easy mistayka to make, but it probably makes absolutely no difference. Old iron pipes are rough inside and very resistive, and you'll probably need at least 28mm anyway, as others have explained.

If your current boiler is working yes, you can check the pressure drop you're getting currently. As above, you're allowed 1mbar, and I wouldn't be surprised if you have half a dozen mbar drop. This may or may not have noticeably affected the operation of the old combi, or a new one come to that, but the point is that it would be illegal because of blanket regulations. Some boilers though, wouldn't even fire!

Would strongly recommend a larger combi than 24kW, say 30kW, to give better HW peformance (if supply is ok). That would mean a bigger pipe too.

Any chance you can go out of the front of the house, up the outside wall, across the loft, and down the back? Sometimes it works out better, and cheaper.

 

[dp123]

Any chance you can go out of the front of the house, up the outside wall, across the loft, and down the back? Sometimes it works out better, and cheaper.

Thanks for the info.
Access to the loft is in a walk in wardrobe and its not very big and having the gas pipe on the front wall of a terraced house would make me nervous, we have out fair share of vandalism in the area it would be too much of a temptation for the head dicks.
To be honest if we have to have the new pipe i would Rather it ran around the room as the fitter suggested, it may be a little unsightly in the kitchen but I'm sure we will get used to it, i would rather do it that way than start digging up the concrete floor.

Easy mistayka to make, but it probably makes absolutely no difference. Old iron pipes are rough inside and very resistive, and you'll probably need at least 28mm anyway, as others have explained.

I forgot to mention the pipe is 22mm copper.

 

[giblets]

I am neither ignorant or disputing the advice given,I realised straight away that if i have a new "condensing" boiler fitted i will need to get a bigger diameter gas pipe fitted.

I then asked if i could have a older combi (non condensing) boiler fitted to save the upheaval fitting the new pipe is going to cause.

Not perhaps ignorant but a little mis-guided maybe.

The salient word here is "combi" not "condensing". All combi's use vast amounts of gas to heat the water regardless of whether they are condensing or non-condensing.

Regretfully, thanks to John Prescott, you can only install condensing boilers now unless your property is assessed using a special survey procedure. Ask the chap who is coming on Monday about this. (Although, be warned that the assessment proceedure does not take into account the customer's requirements and wishes or the cost of the works.)

 

[doitall]

Actually the cost did come into it

 

[giblets]

Only if the additional cost of installing a condensing boiler is exceptionally high. In my mind the cost of either would be high owing to the installation of a correctly sized gas pipe (which would be needed by both types).

 

[dp123]

The salient word here is "combi" not "condensing". All combi's use vast amounts of gas to heat the water regardless of whether they are condensing or non-condensing.

Can you answer this question.

I had a combi boiler and it worked fine on the pipe that is still feeding the boiler and water heater,why is it now not capable of feeding a combi (not condensing) if i could get my hands on one?

I have discovered the gas pipe from the meter is 22mm but have no way of knowing how long the 22mm pipe is before it exits the wall as a 15mm pipe in the garage.
I have also accurately measured the distance from meter to garage and it is not 15 meters as originally guessed but 11.