Loads of air in central heating.

[Mdljk]

Water can expand into the vent pipe as it heats up within the system but systems are not designed for water to be pushed up the vent pipe all the time the pump is working. Running a pump faster than necessary can lead to premature failure. A system may rely on the pump being on its max setting in order for all rads to get sufficient heat. But if that leads to pumping-over then careful balancing of all rads can help without increasing pump speed.

 

[John.g]

Hi, the pump is a Wilo Gold RS60.
I was asking if having the pump too high is likely to cause pumping back, is that the only problem with having it on too high a setting?

I’ll have to check!

Running on a high pump setting shouldn't IMO cause any major problems for the pump life, its better to have hot rads than to have a pump that only lasts for say 15/18 years instead of say 20!.

If you have a zoned system or if the rads are fitted with TRVs then while you may not get pump over/pump back with all rads open then you may get it with reduced flow rate which results in increased pump head and may cause it. I would suggest checking the F&F tank for pump over (under these reduced flow rate conditions) through the vent or pump back through the cold feed make up which would result in air being pulled in through the vent pipe, (“cold” feed pipe will be hot). If you are getting problems then turn the pump speed to 2 and see how you get on. Looking ahead to pump replacement time make sure you install a (A rated) pump that has a good number of PP (proportional pressure) AND CP (constant pressure) settings, a Wilo Yonis Pico 1-6 will give you all this but the choice is yours or your plumber, a CP setting may then be more appropriate in your case as you can maintain the highest pump head possible without getting pump over etc as the pump head will be maintained constant irrespective of the required flow rate, it will also give you the maximum head (without pump over) to help you with your “3 rads problem”.

Member Tiggy 1955 (post #77 above) had a pump over/back problem which was very interesting, if you read it through you may find it interesting/informative.

Air in CH system and hot water returning to FE tank via the cold feed

 

[Chris12345678]

Thanks.
Something to read in bed!

I have bought autovents for all the radiators now.
The Alladin Micro vent that screws into a 1/8” nipple looks a bit fragile if it gets knocked though?!

 

[John.g]

Thanks.
Something to read in bed!

I have bought autovents for all the radiators now.
The Alladin Micro vent that screws into a 1/8” nipple looks a bit fragile if it gets knocked though?!

Have you checked the F&E tank, I don't have the pump curves for the
RS 60 but any 6M pump running on speed 3 will certainly tend to pump over or whatever especially as zoning or TRVs shut off.