System boiler making crunching noises....

[Bunker]

This is a circ pump question so not sure wether to put in Oil section or this one, probably best in this one..

Called to a custard last week with an external Grant (oil) system boiler making awful clattering crunchy noises. Boiler running on and off, no circulation.
Easy diagnosis - impeller has come off - surely.
Took pump off, sure enough, runs but no movement on the impellor.
Fitted new pump and happy days.
I did notice the pump, which was mounted directly on top of the boiler (inside the cab obviously), had a melted switch box, custard had said it smelt of burning too.
Anyhoo, this was end of last week.
Custard just texted me now to say same noise again.....

Any suggestions?
Thanks

 

[EPH]

Sick of changing expansion vessels on those, could be as simple as lack of pressure and the pump making the same noise? Unlikely to be another pump with melted controls, don't think I've ever seen that.

 

[Ermintrude]

Carp in system.

 

[Bunker]

would lack of pressure make the pump noisy?

 

[EPH]

would lack of pressure make the pump noisy?

Yes, could be full of air around the pump.

Top it up and see, had it twice this week where the pressure builds straight up from 1 bar and discharges in less than 10 minutes, believe the PRV on those is only 2.5 bar?

 

[Bunker]

Ok Thanks v much, it has a history of losing pressure (exp vessel is fine believe it or not!). I think there might be a bad leak somewhere as last visit showed all upstairs rads empty....AAVs and PRVs already replaced a while back.
If you're right, then thats probably what destroyed the last pump and the boiler getting too hot, pump fitted badly with the elec box pushed into the insulation on the top of the boiler.
Bum, alot of work to do me thinks....

 

[tamz]

These grant externals are terrible for the pumps shearing (both of them) and the ch one melting.
I had one where it melted the replacement in 2 weeks. I pulled the insulation clear of the pump and it has been fine since.
Also bad for trapped air if the pipes drop down the back and into the house.
Sounds like you may have a leak somewhere.

 

[EPH]

I've been to probably three of these in the last 4 months where the DHW bottom pump valve is turned off??

 

[tamz]

I've been to probably three of these in the last 4 months where the DHW bottom pump valve is turned off??

Fairies from the bottom of the garden :smile:

 

[Chalked]

I have ad one where the aav leaked and dripped onto the pump electrics, this then fried the pump. They really ate poorly designed.:33:

 

[lame plumber]

Carp in system.

muck clogging the pump as mentioned, the pump will die fairly quickly again,needs flushing through with a good cleaner

 

[Bunker]

Carp in system.

No, I had a look, definitely no fish in there....