Central heating overflow

[Rob Nicholson]

Anyone know of a page on the web that shows and describes the purpose and positioning of the central heating overflow?

I've been wondering why air is getting into my system as one radiator is almost emptying. Bleed it and it fills up again but soon starts to empty again. So I think to myself, hmm, if water is going in and then disappearing from the system, it must be going somewhere. At first I assumed there was a radiator leak but nope, they all seem fine. I'd noticed a while ago that the roof was wet and thought "strange" but it took a while to connect the two. It's dripping slowly, enough probably to empty this one radiator over a few weeks.

I'm going to get a local heating engineer in but just want to know a bit more before I speak to him.

Thanks, Rob.

[mike ring]

"Rob Nicholson" wrote in news:qFpae.2137$ [e-mail]:

It's possible your pump is set too high and is sucking in air through the vent pipe.

This rad may be the first convenient place for the air to settle - is it nearest the pump?

Try setting the pump speed down a notch.

mike

[Rob Nicholson]

Ahh ha.... thanks for the rapid reply as I think you've hit the proverbial nail on the head. The pump was replaced a couple years ago by a plumber out of the yellow pages after it failed. He mentioned then that "something was wrong so that it's possible that air will be drawn into the system". I forgot what the "something" was and the pump being too high is probably exactly what he said. It is very high, seated about a 6" *above* the boiler upstairs in the back bedroom. The overflow pipe must be about the same height coming out of the same wall as the pump.

It is indeed...

Will do as a short term fix.

Many thanks, Rob.

[Dave Plowman (News)]

There's no need to run the pump any faster than needed to get circulation to the most 'difficult' rad. And with a properly balanced system, this will often be the minimum setting.

[Alan]

In message , Rob Nicholson wrote

This may the long only term fix you have to make.

You may have to re-balance the system to ensure that all radiators get hot but if the system worked prior to the new pump being fitted there is no reason why it shouldn't work again after the pump has been adjusted to the correct speed.

[Rob Nicholson]

Will have a gander later - have to remove a lot of boxes to get access :-)

[Set Square]

Is it a vented or sealed (pressurised) system? In other words, is the overflow coming from the small fill & vent tank or from the pressure relief valve?

Does your system have corrosion inhibitor in it?

[Rob Nicholson]

Once again, I'll have to check.

Not anymore since I had to drain the system to replace a radiator. Good reminder thought to add some back.

Cheers, Rob.

[mike ring]

"Rob Nicholson" wrote in news:Leqae.1865$ [e-mail]:

It is very high, seated about a 6" *above* the boiler upstairs in the back bedroom. The overflow pipe must be about the same height coming out of the same

I just re-read this and realised you took me literally! I meant the pump was set to too high power; Like Sam Weller?, I havent got multimillion power Xray eyes to inspect your system from Sarfessex.

If it works it's ok at that level, with just one caveat.

When refilling my hovel's system (top-down bungerlow) I need to blast airlocks out by closing loops and setting the pump tp warp speed.

In your case that might not work because you'd suck n as fast as you blew out.

But as the others have said, if the system runs properly as is, there's no need for tha aggro of moving it

mike

[Rob Nicholson]

That happens on t'internet :-)

I do suspect there is something amis with the position/plumbing around the pump. But it does need a pair of expert eyes to look at it. Fortuntately, there is a very good local plumber that I trust to access the problem.

Rob.