Wilo smart pump hunting

[Lower]

I installed a wilo smart pump approx 8 months ago and it has been working parfectly until today. I've now noticed that it's started hunting. It's fine when both the central heating and the hot water are on, but when it's just the central heating you can hear the pump constantly varying its speed.

Knackered pump or something else?

 

[hazetimesfive]

maybe its doing what it supposed to..

 

[Lower]

It's never done it before and the pump is rhythmically speeding up and slowing down about once every 3 seconds.

I then locked the hot water solenoid in the open position and its started doing it then too. All the trvs are fully open so I can only conclude its a faulty pump.

 

[hazetimesfive]

well its still in warranty, and you could always ask wilo, since they made the thing ... .. ..

 

[Lower]

I've tried, but their product support dept does not get back to you despite repeated calls and left messages.

In the mean time i've still got a hunting pump that needs something doing to it to prevent it from failing.

Any constructive advice or comments would be very much appreciated.

 

[SimonH2]

Go back to where you bought it and get them to badger Wilo ?
Does the Wilo have a number of setting options, it may be worth trying different setting and see if makes a difference.

One other possible thing I could think of would be if there is air in the system somewhere. If so, then that could compress (creating a momentarily increased flow rate) and trick the pump into thinking there's more flow capacity than there is - so it speeds up. Once the air is compressed, the flow rate drops, and so the pump backs off and reduces the pressure. Rinse and repeat ...
One possible location would be a rad with a lot of air in it - especially if the TRV is on the return side.

Also check (if you have an open vent system) if it's possible to pump up the vent pipe - it's possible there's a column of water oscillating up and down the pipe.

 

[Lower]

Its a closed system and the pressure is consistent.

It has a bypass valve, but its a fixed bypass rather than a sprung automatic type so shouldn't confuse the pump.

I've tried the different settings and they made no difference. I tried turning off the power supply to the pump to reset the 'smart' control, but with no effect.

However, the pump is now running normally again and i have purchased a spare that is sat waiting in case the current one goes nuts again.

 

[Lower]

Update

Managed to speak to a Wilo tech rep. He was useless.

I'd thought that the pump was running normally again, but it wasn't. It was running at full speed all the time so i assume that something has failed in the 'smart' control of the pump.

New pump went on on Tuesday night, system is now running quietly and properly again. Old pump will be going back to screwfix at the weekend.

 

[SimonH2]

Ah yes, we considered everything but the simplest - "it's faulty"