Heating pump challenges

[curiousdog]

I have what I think is a conventional heating system (perhaps, maybe) and have had several challenges over the years, must to do with the motorised flow-control valve breaking.

More recently I have a concern with the pump. It's installed vertically pushing against gravrity up to the valve where it splits to the heating and the storage tank. On setting 1 it runs very quietly but the pressure seems to be very low and the radiators don't really heat up as they should. The water in the storage tank also takes forever to re-heat. I am pretty sure there are no airlocks anywhere.

So, logically, I tried to set the pump speed to 2. The pump speed picks up and makes a lot more noise and then stops and restarts itself. There also seems to be a lot more noise in the pipes, water sounds. But the end result of all this is a lot of air that I have to keep\bleeding out every 15 minutes.

So, is the pump faulty?

Should it be installed vertically pushing against gravity?

There is only a 4" run of pipiong between the pump and the valve. Could this be a problem?

thanks for any assistance/advice anyone can offer

[Roger Mills]

I doubt it.

Yes, that's fine!

No, that's fine!

Is it an open vented system (with a small fill & expansion tank in the attic)? If so, it's very likely that the higher pump speed is causing it to 'pump over'. This means that, when the pump is running, there is a constant flow of water out of the up and over vent pipe back into the tank. This is very bad, and will result in a lot of air being introduced into the system. It usually results from the vent and fill pipes not being connected into the system in the right way, and is likely to need some pipework changes to fix - or conversion to a non-vented (pressurised) system if your boiler is suitable.

[Ed Sirett]

Just as likely is that thew higher speed is causing air to drawn down into the circuit.

Unless the positioned of the vent and feed pipes are known relative to the pump we can only speculate.

[John]

Mindset change required - consider it to be a "Circulator" rather than a pump. The heating circuit is a loop - the "circulator is merely making the water flow around the circuit. The height of the system has no effect.

[Bob Mannix]

Yes to that but [and see other thread on Bubbling Central Heating System] it could be an incorrectly installed vent pipe. On setting 1 the negative presssure at an incorrectly installed vent pipe position is not enough to suck air down. On setting 2 it is. Not saying this IS the problem, but it might be.

[Ed Sirett]

I disagree, at least in the way you have expressed it. Where the feed pipe joins the circuit, the height of the header tank and the position of the circulator within the circuit are absolutely crucial to the correct operation or otherwise of the heating system.

Last week my apprentice and I fixed a system where the feed pipe had been installed after the pump. We moved it to the right place but also had to spend half a day powerflushing the system to remove (most of) the effects of the misplaced pipe.

[John]