Pump not spinning until pump bleed valve opened

[alan333]

Hi,
I had my CH powerflushed a few days ago and on two occasions since then the pump has refused to start. You can hear it humming but it doesn't seem to be spinning. Opening the bleed valve directly above the pump and allowing a little air to bleed out causes a gurgle and the punp kicks in.

What's the problem? Just air in the system, or the pump on the way out, or the powerflush moved some gunk to the pump, or anything else?

System is about 15 yrs old, gravity fed from tank in loft. Also does DHW cylinder.

Thanks

 

[muggles]

Sounds like air in the system combined with poor system design to me

 

[longdogs]

Have you tried bleeding the pump with the heating (and pump) switched off.

 

[alan333]

Thanks for the replies.

Sorry, I should have said that after discovering the pump humming I switched off the heating (DHW was off) then bled the air out, then switched the heating back on and the pump started instantly. (I've also bled the rads with CH/DHW off, only a drop of air from 2 rads of the 12).

I should maybe also mention I've lived in the house for about 5 years and it's never happened until this powerflush. Maybe also relevant - I had a new actuator fitted the day before the powerflush to cure a problem where the hot water was heating all the time the CH was on.

The guy is coming back to have another go at getting one particular rad hotter, so I just want to be armed with as much info as possible so he can't pull the wool over me. It looks like you're both suggesting air in the system rather than a knackered pump tho?

 

[longdogs]

Thanks for the replies.

Sorry, I should have said that after discovering the pump humming I switched off the heating (DHW was off) then bled the air out, then switched the heating back on and the pump started instantly. (I've also bled the rads with CH/DHW off, only a drop of air from 2 rads of the 12).

I should maybe also mention I've lived in the house for about 5 years and it's never happened until this powerflush. Maybe also relevant - I had a new actuator fitted the day before the powerflush to cure a problem where the hot water was heating all the time the CH was on.

The guy is coming back to have another go at getting one particular rad hotter, so I just want to be armed with as much info as possible so he can't pull the wool over me. It looks like you're both suggesting air in the system rather than a knackered pump tho?

Yes, air in the pump will cause it to overheat and possibly burn out.

 

[alan333]

Thanks again. It seems to be working ok today. Hopefully it's cured