Radiator keeps emptying when the gas central heating is not on.

[Ruth Simmonds]

My old boiler packed up and British Gas installed a new one. They moved it to the other side of the room, and had to move the water pipes. Apparently the position of the old one was no longer legal. Since then I have been having trouble with one of my radiators, having to bleed it daily.

On my annual service, I was told that there was air in the system, and that it would settle down. Several months later, my dad took a look at it, and when he took it off, it was completely empty of water. He replaced it, and when he put the system back on, he could hear the water pouring into it as though he was running a bath tap. At the same time, he heard an almighty sploshing sound from the cold water tank which is situated above the hot water cylinder in my hall cupboard (I live in a flat).

British Gas are coming out next week to do the annual service (now both boiler and radiators), and I intend to mention this to the engineer, but would like independent thoughts please.

 

[Burnerman]

Fresh water in your system does indeed produce some air until it is deoxygenated......this doesn't usually take too long. A dirty system also produces gas (hydrogen) which never disappears until the system is thoroughly flushed out and an inhibitor added.
See what British Gas say.....you could also tell us what sort of heating system you have (vented or sealed.)
John

 

[Ruth Simmonds]

Vented or sealed? Good question. I'll be honest and say I don't understand the difference. If you can tell me more about this, I'll try to answer as best I can.

 

[Burnerman]

If its a vented system, there will be two tanks in the loft.....one as a header tank for the boiler, the other a cold water supply for the copper cylinder that will be lurking somewhere.
A combi boiler, for example, doesn't have these. You haven't noticed any water running from an overflow outside, by any chance?
John

 

[Doggit]

And is there a pressure gauge on the boiler, but I suspect from your description of the sploshing noise from the cupboard, that you've got a vented system. Next time you vent air from the rad, put a match in front of the air jet, and see if it lights - that tells you it's hydrogen.

Has the change of location for the boiler caused the system to suck air in from the over flow pipe in the header tank, and it's then getting pushed in to the radiator.

 

[Ruth Simmonds]

Right, it is vented. I have no loft because it is a flat. There are just two tanks - a black open top 'bucket-like' cold water tank directly above the copper cylinder.

I put a match to the air but it did not light.

Water does run from the overflow outside. Could this be why the radiator is empty every morning?

 

[Doggit]

With a vented system, the heating goes on, and the hot water expands, and the excess flows up in to the overflow tank above the cylinder. Then when the heating goes off, the water cools, contracts, and then sinks back into the heating system, but for some reason, you're losing water via the overflow pipe, so that says that you've then got too much water in the header tank. Water can't flow out of the radiator, only round the system, so as the air doesn't burn when you bleed the rad, then it's air not hydrogen. This is where my knowledge is a bit lacking; you have to have the overflow at the right point in the system, otherwise the pump pushes water up into the header tank, rather than round the system, and that can introduce air into it, which is then getting pushed around the rads, and the empty one will be the nearest to the boiler on the flow side.

And if I'm right, the inhibitor will all have gone in the system, so you'll need to get BG to powerflush the system at their cost, and then add new stuff. But what was the reg that made them have to move it.

 

[Burnerman]

Have a look at your circulating pump......and set it to number 1, the slowest speed.
John

 

[Ruth Simmonds]

The boiler had to be moved because it was on the wall which was against the communal hallway, and the flue was deemed dangerous, so the new boiler was put on an inside wall, with a flue going out next to the kitchen window.

I'll take a look at the pump tomorrow.

Thank you, both. ☺

 

[jeff the gasman]

Shoddy workmanship.

 

[Ruth Simmonds]

A quick update. After turning the pump down, the radiators are all fine. No air in any of them, and the main one is no longer emptying.

Now I just have to see about replacing the inhibitor which was lost, but for now I am a happy bunny.

Thanks, once more, for the help/advice.

 

[Doggit]

Have a look at your circulating pump......and set it to number 1, the slowest speed.

So why was it the pump going too fast Burnerman.

 

[Burnerman]

I guess there has to be a balance between circulation through the radiators, and the water being pumped through the expansion pipe....careful system design can minimise this.
Let's hope the problem stays away!
John

 

[gassymark]

Hi new to this but just a thought BG may have connected the pipes wrong way round sending the flow up the vent as its a flat and not much head surprised they didn't close the system !