Motorised valves or multiple pumps??

[Bob Minchin]

Reading here of various problems with motorised valves from time to time, I wonder if it might be better to install multiple pumps instead when I re-do my heating system.

Any thoughts/experiences?

Bob

[charles]

They do fail eventually. I had to replace one, fitted in 1988, a couple of yeasr ago. The O-Ring failed resulting in a steady drip of water.

[Graham.]

I would just steer clear of 3 port mid-position valves, the 2 port ones are reliable, and when they do fail it's the motor, and that's easy and cheap to replace. The "wet" parts of my Honeywell Motorised Valves are about 35 years old.

[fred]

In article , Bob Minchin writes

Just thoughts but I think the risk of gravity or other spurious circulation in the pump off loop(s) is too great, it doesn't take much flow to get a rad to the just warm stage.

[<me9]

My current system originally had 3 port valves, changed* / repaired on average every 6 months. Since modifying for 2 port valves I've only had one change in near 20 years.

• Usually micro-switches. I kept a spare head and changed just the switches after the first two failures.

[Roger Mills]

I wouldn't! If you have multiple zones with a single boiler, and one pump per zone - which I think is what you're suggesting - you'll need some logic to fire the boiler when one or more zones are calling for heat. This is so easy with multiple 2-port valves and a single pump. You'll also need to make sure that there's no unintended flow in zones which are nor calling for heat. A non-running pump doesn't block the flow in the way in which a closed zone valve does. Also, if your boiler needs pump over-run with a by-pass circuit, I've no idea how to implement that with multiple pumps!