Gas off, turn boiler off?

[David]

They are doing gas main replacement work in our street. The information prior to this suggested that the gas people would need access to check that the boiler was turned off, then access again when the gas came back on to confirm everything was working.

They just turned it off around 06:30 without any checks. The CH was still running. I assume that it failed safe when the gas pressure dropped!

I've switched to frost protect for the moment.

Will the combi boiler just kick back in when gas pressure is returned, or is it better to turn the power to the boiler off then back on again when gas pressure is returned?

IIRC when it is powered on after being powered off it runs a purge cycle before going on to normal operations, but I am not sure if this is just water, or water and gas.

Cheers

Dave R

[Andy Burns]

more likely flame failure device?

I'd just switch it off, it's not as though it do any frost protecting.

They ought to do a proper purge before you use any gas appliances, interesting to know if you have to insist on it

any gas cooker, fire?

[Tim+]

Shouldn’t be an issue with any modern(ish) boiler with electronic ignition. At worst, if it doesn’t relight quickly enough it may lock-out and will need a mains power cycle to encourage it to go through the ignition sequence again.

If you have a gas cooker I’d be inclined to run that first until you have a steady flame to ensure that the gas mixture has settled down.

Tim

[David]

Gas hob.

Cheers

Dave R

[David]

Interesting to watch. They have broken the old iron(?) main outside each house and you can see them pushing the new yellow plastic pipe through from a reel using an attachment for a small digger.

One other interesting thing. The yellow pipe from the mains to our meter is small - looks like a garden hose pipe size. This is much smaller than the copper from the meter to the boiler and hob. I assume that the mains is at higher pressure and so doesn't need a larger bore, which is needed on the other side of the meter to feed the boiler.

Good to replace the old pipe - there have been a few investigations over the last few years where holes have been bored in the footpath to try and locate a leak.

Cheers

Dave R

[David]

I've turned it off now. Despite being on "frost protect" 5C setting a pump was running I'll wait until everything is on again then run the gas hob for a bit before I turn it back on.

Cheers

Dave R

[Andy Burns]

yes their pipe to the street is on the outside of the regulator (metal can on the anaconda) is usually up to 75 mbar, your pipe on the inside max 21 mbar.

[Andy Burns]

They'll probably visit you to turn it back on.

[Brian]

I vaguely recall some work being done on the gas pipe / main in a previous house.

As I recall, we were told/ asked to turn off all gas appliances ( in our case a boiler an a fire) and wait for someone to call.

Late in the afternoon / early evening ( I think around 5/ 5:30), someone turned up. From memory, he lit the fire first, then the boiler. Waited a bit and left.

No big deal, I think it was fairly warm at the time and we weren’t inconvenienced.

[SteveW]

We got home from work and found that the guys tasked to turn it back on had already been down the road and buggered off. Every house where there was no-one in at the time was left isolated!

We had to phone and demand that someone came out.

[Tim+]

I would’ve just turned the gas back on myself unless they’d locked it off somehow.

Tim

[SteveW]

Correct. I think that when they have installed the plastic pipe, they can increase the supply pressure to the road, allowing the same or more gas to flow, when needed, despite the plastic pipe reducing the bore so much, so that the supply pipe does not become a limiting factor for a combi-boiler, cooker and a couple of fires being on at the same time.

[SteveW]

They left it isolated outside somewhere. I'm sure I could have investigated.

[Tim+]

Your meter cupboard is the only tap between the mains and you house usually.

Tim

[SteveW]

Our meter is inside the house, as is the lever valve. However, where the pipe enters the house, it rises from the ground for a couple of feet and then enters a fitting. The fitting is cylindrical, with a square headed, screwed plug on the top and an outlet on the back of the cylinder, just below the top and going through the wall. There may be an isolator in there, similar to the type for gas fires (remove screw top and then open or close the valve inside).

As the holes they'd dug were still open at this point, it is also possible that they'd clamped the yellow plastic pipes closed just after the gas main, as is done with the blue or black water pipe during repairs.

[David]

Yes. Turned it back on at the outside meter. Came in to confirm boiler turned back on. Asked for a hot tap to be run whilst they checked the pressure at the meter. All good, and gone.

Cheers

Dave R

[Andy Burns]

Sounds like nobody does the "proper" purging procedure now, per

[David]

Probably because modern boilers detect pressure loss and close gas valve? For a short time when the gas has been turned off at the meter and the pipework is still full of gas that might be all that is needed.

No idea what they do with old appliances.

Cheers

Dave R