Radiator needs bleeding daily

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Just had my Halstead Best boiler serviced -fan and circuit board replaced- and it is working nicely. The problem is that a huge amount of air is collecting in the radiator nearest the boiler. I called the Corgi engineer who carried out the service and he suggested corrosion was creating gasses and that the radiators probably needed replacing. Since the CH system was reliable -noisy boiler aside- before the service, I'm convinced that his diagnosis is incorrect. The radiator is half filling with air after only a couple of hours with the central heating on; this morning, it took about fifty seconds to expell all of the (slightly tangy smelling) air. Does anybody have any suggestions as to what can be casing this? The pump is a Grundfos Selectric UPS 15-50. Thanks in advance.
 
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It sounds to me as though the pump is sucking in, probably via the open vent over f&e tank. Would the boiler and this rad be upstairs?

I would check the pipe work in the airing cupboard, the cold fill and vent arrangement. You could check the sucking in by going into the loft with a jam jar of water, put this over the vent and get someone else to turn the heating on whilst you watch. The water will get sucked out of the jam jar.

The other way round could be that it is pumping over and sucking fresh water in from the cold fill on the f&e tank. Again you will see this whilst you are up there.

If this is the case perhaps fitting a Myson aerjec or similar will cure it ;)
 
agree with gas4u ,has he turned up the pump speed? this maycause air ingress the smell in the air out of the rad is a sign of corrosion
 
Thank you for your responses.

gas4you said:
Would the boiler and this rad be upstairs?

Both the boiler and the radiator are on the ground floor.



gas4you said:
I would check the pipe work in the airing cupboard, the cold fill and vent arrangement. You could check the sucking in by going into the loft with a jam jar of water, put this over the vent and get someone else to turn the heating on whilst you watch. The water will get sucked out of the jam jar.

The other way round could be that it is pumping over and sucking fresh water in from the cold fill on the f&e tank. Again you will see this whilst you are up there.

If this is the case perhaps fitting a Myson aerjec or similar will cure it ;)

Hmmm -the engineer didn't go near the loft, but...

combiman001 said:
has he turned up the pump speed?

He may well have done -is it safe to turn it back down again -and would it be clockwise up /anticlockwise -down?
 
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Turn it to the middle setting.

Another quick jam jar test is when you bleed the rad, hold jam jar upside down over bleed nipple to fill jam jar. If you put a match to it without turning it over it will go pop if it is hydrogen gas in it, a by-product of the corrosion process ;)
 
I tested the gas from the radiator but there was no pop. Wouldn't air that had been through the pipes smell slightly stale anyway?

As I previously posted, the rad closest to the boiler was literally filling up with air -it took over a minute to release the air if I left the CH on for a few hours.

It seems that the more I turn down the pump, the less air collects in the radiator.

Is it possible to turn the pump down too low... and if so, what would happen?
 
Certainly sounds like sucking in or pumping over for some reason.

Turning pump too low can cause rads furthest away not to get hot properly, but won't damage anything.

The system should be balanced with lockshield valves on rads and pump speed.

Try to describe the cold fill/vent arrangement in your airing cupboard where I presume your pump and controls will be?
 
gas4you said:
Turning pump too low can cause rads furthest away not to get hot properly, but won't damage anything.

That is excellent news.


gas4you said:
Try to describe the cold fill/vent arrangement in your airing cupboard where I presume your pump and controls will be?

The system fills form a large tank in the attic. It's an 30 year old system in a ground floor flat of a house conversion.
As I said, the system was working well for years until the fan and circuit board died on the boiler. I think the engineer who serviced the boiler must have turned up the pump.
 
That seems to have fixed it.

Many thanks for the help, Dave/gas4you. Guys like you who generously give up their time and expertise to help the clueless -and save us a small fortune in the process- are diamonds.
 

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