No hot water since drain-down

[Dan Robinson]

Thankfully.

 

[corgiman]

Thankfully.

I would have thought that the installer would have upgraded the system when he installed that

in the words of the god Ian Drury

"what a waste"

 

[mpirie]

Hi guys,

I connected a piece of hose to the service valve with the other end in the bathroom sink, and opened the valve allowing it to run through, before closing the valve.

Unfortunately, it's made no difference, and the boiler still cut's out from overheating before the water gets hot.

So am I right in thinking I have an air lock somewhere in the hot water system that's stopping the water from circulating, thus tripping the overheat?

Next step....dig out the Aqua-Vac !!

Thanks, Mike

 

[Dan Robinson]

Did water actually come out?

 

[mpirie]

Hi Dan, yep loads of water.

I let it run while checking the header tank in the loft. It was a bit dirty, but not too bad.

Could I use the gravity return valve at the top of the boiler to bleed any air, or back-flush it?

 

[Dan Robinson]

eeeerrr,, not sure what you mean - and me heads hurting.
Did the header tank fill as water ran from the vent?


Looking at the picture of the bottom of your cylinder I can see that the vent you have connected used to be the feed form the header tank. Where does that go know? Has it been linked into the vent by the base of the header or something?


Somone has been tinkering havn't they . Possibly the pevious owners?

Also am I right it saying that the pipes leaving hte boiler are actuall 22mm?

There is a lot of horizontal pipe work that will play merry hell with gravity circuits.

 

[mpirie]

Hi Dan,

Yes, water filled the header from the main supply, as I drained the water from the vent to the right of the cylinder.

All the pipes from the tans are 22mm, though the hot water one's go up to 28mm not far from the boiler.

If someone has tinkered with the plumbing, i doubt it was the previous owner - though who knows??

I noticed on the wiring diagram on the inside of the boiler cover and the GlowWorm manual, that gravity systems are supposed to have a link to short out the cut-off switch......but mine doesn't have one....would that be effectively the same as "boiling" the boiler?

 

[ChrisR]

Yes it would I should think.
If you could get a connection to the vent pipe, that might get the air out.
WOrht trying the aquavac.

 

[JohnD]

I wonder if it would fix it if you drained out, then refilled from the bottom by putting a hose on a drain cock, thus pushing the water and air up and away.

 

[mpirie]

Hi, I noticed there's a drain cock on the gravity return above the boiler.

Could I connect mains pressure cold (from the garden tap) to this and use the mains pressure to backflush the system and push out any airlock?

This method would imply that mains water will flow back into the header, so I'd need to look out for overflowing from the header - correct?

The hot water seems to heat up when the heating is on, but when I switch the heating off, leaving the hot water on, the boiler switches off soon afterwards, almost as if it was already hot??