Air in system

[rob75]

Hi,

I have an Ecodon 7.5kw which supplies heating and hot water in my 3 bed home. Of late I am needing to bleed a couple of radiators every couple of days. For example top of the landing rad had to be bled on Saturday and then again on Monday night, and it's probably 2/3 full of air.

From what I have read the most common cause of this is a leak in the system, the only works I have done of late has been upstairs and if I had a leak I would see wet patches on the ceilings of the downstairs rooms.

So I am beginning to wonder if the ASHP might be the cause. I have had it just over 6 years and to date it hasn't been serviced. Do these units need to be serviced and does anyone think this could be the cause of air in my system, as i really can't fathom what else could be the cause.

Thanks in advance.

Rob.

[marc5180]

You either have ingress of air somewhere or corrosion occurring in the system which is causing hydrogen to generate in the system through a chemical reaction.

Is there inhibiter in the system?

Does the heating pump sound quiet or noisy, is it cavitating?

[chemi-cool]

Air can only enter the system where the pressure is negative.
best is to connect a few pressure gauges and check for anomaly behaviour of the system.

[rob75]

Thanks for the replies and apologies for the slow response.

The ASHP isn't making any strange noises, sounds like it always has done currently when it is working.

What is an inhibitor? I don't recall hearing or seeing one of these when I ordered the system.

I do have an underfloor heating loop which comes off a manifold which I don't ever use, wondering it this could be the cause. Might be an idea to see if this can be bled or the loop closed off?

Rob.

[hyperion]

Normally it is recommended to use a heat pump inhibitor combined with antifreeze, such as Fernox HP5 at the correct solution strength to give protection down to -15degC.
If the underfloor loop is not in use and has not been completely bled of air, this might be the source of air ingress into the system, but I would suspect it is a result of the chemical reaction mentioned by Marc.
Whilst it would be advantagous to have the Ecodan serviced regularly like most boilers, the main problems start when the circultion becomes poorer due to sludge build-ups etc.
If you drain a small quantity of water from one of the radiators and the water comes out black, then you have got sediment build up.
If left untreated this could have a long term detrimental effect on the efficiency of the plate heat exchanger in the Ecodan unit.