Boiler Re-pipeing

[DavidGee]

I am looking to change my boiler which is coming up to 30 years old, the central heating system runs on microbore.

My next door neighbor has just had a quote (the properties are identical) but the gas engineer has informed him that new piping needs to be run to the boiler from the meter as the diameter is too small (I think that we have 15mm pipework)

Does anyone know if there is a current boiler that can be fitted to take the existing size pipework as running on the surface would cause quite a bit of upheaval.

Also would it be wise for the system to be powerflushed? the central heating system has never given any trouble and I recall being told that microbore systems could be damaged by this.

As always thanks for any information that you can provide.

David

 

[Chalked]

Go with the installers advise on re-piping the gas. It's probably been undersized from day one. It's not just the size, it's the distance. So it's a pipe upgrade no matter what boiler.
As for the power flush, it's hit and miss with microbore. If it's copper, I would do it. If it's plastic (hep2o) , I wouldn't touch it!.
Hope this helps.

 

[village idiot]

Except the boiler is just next to the gas meter, there is a 99.9% chance you have to upgrade pipe to at least 22mm

 

[newcastle phill]

Ultimately that will be decided by the demands of the new boiler and the gas rate it requires as stated in the manufacturer instructions.
Its not just the pipe size. Its also the pressure drop over distance, more so with undersizing.

 

[DavidGee]

Many thanks for the advice, just one point, the pipe size is original (from when the house is built) given that I have never had any problems with heating the house could retaining this pipework be an option (tbh not sure why a new boiler would need more gas)

Once again thanks for your help

David

 

[DavidGee]

Many thanks for the information, it's appriciated

David

 

[DavidGee]

Thank you for your help, it's appreciated.

David

 

[Chalked]

Many thanks for the advice, just one point, the pipe size is original (from when the house is built) given that I have never had any problems with heating the house could retaining this pipework be an option (tbh not sure why a new boiler would need more gas)

Once again thanks for your help

David

Modern condensing burners work completely different to old boilers, this means the flow of gas is critical.
Do you also have other gas appliances?
Would be an eye opener to gas rate your existing boiler.

 

[DavidGee]

The only other gas appliance i have is a cooker.

My existing boiler probably rates very badly, but the strange thing is my gas bill is quite good, it's below the average of other properties in the area and the only reason i am looking to change is that spare parts for it are getting harder to source.

Thanks again for your help

 

[AWheating]

Firstly it depends if the orignal boiler was ever installed correctly, if it was then a boiler of the same output should be fine if one can be found and is suitable for your systems requirements.

Most customers want a different boiler/ upgraded system which leads to a larger boiler outputs being required, its very common for a new gas supply to be required.

The biggest issue with fitting a modern boiler to an undersized gas supply apart from it being illegal is modern boilers pull on the gas supply, so if your boiler has an incorrect supply it will pull gas away from other appliances that may not have safety devices (like cookers) to protect against loss of the gas supply and lead to a gas escape that becomes dangerous resulting is damage to the property or loss of life.

There are plenty of engineers out there willing to fit boilers to undersized supplys, how they sleep at night putting customers lives at risk is hard to understand.

 

[happyflyer]

Would be an eye opener to gas rate your existing boiler.

Loves this bit, how right you are shows its never been clock against the meter, must be 1000s like this

 

[kris]

Hi david like already been said its most likely you will have to, there are sum boilers on the go that use a 15mm gas feed but not many , mostly are 22mm , It will depend on what boiler you go for and the distance the gas pipe at boiler is from your meter, my personal opinion is its all the better boilers that are 22mm,

 

[shytalk]

If upsizing the gas pipe internally is a no no, there is also the option of running it externally. Not the best solution but at least it won't freeze.

 

[DavidGee]

Thank you for your help.

I am pretty sure that the original boiler was installed properly, it is the original boiler and the house was constructed by a reputable house builder. The central heating has always worked well and it is only that spare parts for it a becoming scarce that I am looking to change it

As I am only going to contact firms who are endorsed by the manufacturers of the boiler I fit or well known national companies this should alleviate problems with the installation.

 

[DavidGee]

Thank you for suggestion ... I would love to do that but it's a terraced house...

 

[DavidGee]

Thanks you for the information, it's appreciated, it's looking pretty certain that I will have to upgrade the pipework to 22mm

 

[Nostrum]

It depends whether you are changing to a combi or a like for like to keep the cylinder also.

There is no guarantee but it is quite likely a 12kw heat only boiler (cylinder retained) may be suitable on the existing supply, which would most likely suffice your needs for heating and hot water.

its an awkward situation for all as you will never truly know until the boiler is fitted and running.

The problem arises when you want a combi boiler to replace a cylinder and heat only boiler.

 

[stevetheplumber]

Firstly it depends if the orignal boiler was ever installed correctly, if it was then a boiler of the same output should be fine if one can be found and is suitable for your systems requirements.

Most customers want a different boiler/ upgraded system which leads to a larger boiler outputs being required, its very common for a new gas supply to be required.

The biggest issue with fitting a modern boiler to an undersized gas supply apart from it being illegal is modern boilers pull on the gas supply, so if your boiler has an incorrect supply it will pull gas away from other appliances that may not have safety devices (like cookers) to protect against loss of the gas supply and lead to a gas escape that becomes dangerous resulting is damage to the property or loss of life.

There are plenty of engineers out there willing to fit boilers to undersized supplys, how they sleep at night putting customers lives at risk is hard to understand.

thats incorrect zero govenor boilers do not pull on the supply if the did we would have had to change our pipe sizing to still have a 1 mb drop personally ive had no updates requiring me to change pipe sizing methods

 

[newcastle phill]

Pull on the gas supply......??????

Explain what you mean ??

If what I think your saying happens when your doing a working pressure with other appliances on same or different leg's youve got serious pipe sizing issues or mahoosive appliances on a tiny meter or dicky reg.

Zero govenors dont pull any more or less than older conventionally regulated appliances on the supply
They still have a like for like consumption gas rate kw per kw.
30kw will always require the same amount of energy / gas rate regardless.
And its nowhere near 6m^ cube a typical domestic reg/meter can put out
The zero regulators are just basically balanced/modulate against atmospheric pressure and the fan rate and hence you normally cant do a burner pressure as its zero at whatever modulation......

 

[jase158]

As I am only going to contact well known national companies this should alleviate problems with the installation.

Quickest way to get ripped off!!!

 

[Ermintrude]

Thank you for your help.

I am pretty sure that the original boiler was installed properly, it is the original boiler and the house was constructed by a reputable house builder. The central heating has always worked well and it is only that spare parts for it a becoming scarce that I am looking to change it

As I am only going to contact firms who are endorsed by the manufacturers of the boiler I fit or well known national companies this should alleviate problems with the installation.

Well know national companies are some of the biggest cow boys. We identify a high percentage of poorly or incorrectly installed appliances which have been illegally maintained for years in some cases decades. If the same bloke services it he's not going to shop himself nor will a colleague as it looks bad on company. Gas safe will do nothing to big boys.

 

[Ermintrude]

Pull on the gas supply......??????

Explain what you mean ??

If what I think your saying happens when your doing a working pressure with other appliances on same or different leg's youve got serious pipe sizing issues or mahoosive appliances on a tiny meter or dicky reg.

Zero govenors dont pull any more or less than older conventionally regulated appliances.
They still have a like for like consumption gas rate kw per kw.
30kw will always require the same gas rate regardless.
The zero regulators are just basically balanced/modulate against atmospheric pressure and the fan rate and hence you normally cant do a burner pressure

If your op is low at boiler due to pressure drop, gas rate the appliance and see how much higher it is. When the fan spins it creates negative pressure around the Venturi in the mixing chamber pre burner , on logic it's the open cone before fan, on gianni burners it's worse because the Venturi is closed and then the fan literally sucks in gas. Hence -2 or lower on outlet if gas valve.

28kw with 15 at inlet will gas rate at about 3.2m3/h

 

[stevetheplumber]

sorry ermi your wrong there is no suction on the gas pipe work before the valve
if you have a 30kw conventional boiler with20mb inlet and 1 mb of drop on the pipework and you fit another 30k zero govenor boiler you will still have 20mb and 1 mb drop so wheres this suction?if there was a suction effect on the pipework we would need a different set of pipe sizing tables

 

[newcastle phill]

I thimk he means after the zero govenor in the venturi/plenum.
The negative pressure is created there what in turn opens the zero guv.
Working pressure at appliance inlet shud be normal like any other...

 

[mutley racers]

And how comes if the gas carcass is too small, you say the gas rate will be higher?