Frequency of needing to bleed rad

84Zane

I have noticed that even after bleeding the top/last rad in our heating system approx a month ago, it is already only half heating up again & requiring bleeding.

Is this common? How often should you have to bleed a central heating system?

It is an old heat exchange system situated behind the fire in the living room & was serviced in the late summer.

Also I've noticed if the heating is set to be on for an extended amount of time (ie. the evening), the thermostat after a few hours seems to stop communicating with the heating & it doesn't switch the heating on. Even with the thermostat reading colder than the set room temp.

It does work however if I have the heating switch itself off for half an hour in the middle of the evening, any ideas???

Any advice would be grateful

latecomer

If it continually requires bleeding then there must be air getting into the system somewhere which would suggest a leak.

Is it an old fashioned mechanical thermostat or an electronic one? If its the former can you hear the click if you turn down the temp when the system isn't working during the evening?

andy208833

My gas central heating system has bleed points to let air out. If they are not set correctly then the air builds up in the system. Mine are hidden in the loft at the highest point of the system.

A.Penny.Saved

It could be due to corrosion of the radiators if there is no inhibitor in the system or if it needs replacing. But most likely air getting into the system or a combination of the two.

84Zane

Thanks for all your suggestions -

latecomer wrote: »

If it continually requires bleeding then there must be air getting into the system somewhere which would suggest a leak.

Is it an old fashioned mechanical thermostat or an electronic one? If its the former can you hear the click if you turn down the temp when the system isn't working during the evening?

It's an electronic thermostat & have tried turning it down to hear the click, how I worked out it wasn't working as it was registring the correct temp. & not what the heating was set at ie. a good 10 Deg difference when testing it!

I haven't found evidence of a leak from any of the rads, I haven't been into the loft as yet to see if there are any bleed points thou.

keystone

Highest rad in a system will accumulate any air. Its not uncommon. Microleaks will let air in and precious little water out and can be difficult to trace. Air will also accumulate if the boiler is boiling the water - which releases air of course.

Cheers

warpedchippie

I'm no expert with central heating systems, but I seem to remember a few years back having the same problem.

Pretty sure it was an empty expansion tank/dodgy ballcock valve in the loft.

When bleeding the rads the air was not being replaced by water from the expansion tank.

New valve done the trick.

Steve

iamcornholio

If there is an auto-air vent on the boiler, make sure the grub screw is loose to allow it to work and then you shouldn't need to vent the rads so much

Also check the pressure dial to see if pressure (ie water) is being lost from the circuit

One of these may help with the venting, but you need to sort out the underlying problem

For the thermostat, it might be dusty or any contacts might be sticking. Give it a clean inside or vacuum

John_the_Boy

Don't know how correct this is (BG told me so taken with a pinch of salt) but they said if you have too much inhibitor or different sorts in the system it can react and generate gas and make your rads need bleeding more. If you get a sulphurous smell when bleeding your radiator apparently this is because of the chemical reaction of the inhibitor!

Since having a new boiler and the system drained and just one lot of inhibitor in my system, it certainly needs to be bleed less than before so perhaps they have a point.

spiro

iamcornholio wrote: »

If there is an auto-air vent on the boiler, make sure the grub screw is loose to allow it to work and then you shouldn't need to vent the rads so much

Also check the pressure dial to see if pressure (ie water) is being lost from the circuit

One of these may help with the venting, but you need to sort out the underlying problem

For the thermostat, it might be dusty or any contacts might be sticking. Give it a clean inside or vacuum

Not very Money Saving as they are £10 each and need changing every 3-4 years.