Serious Knocking at circulating pump?

eamon11

Hi Folks,

Question: today the oil furnace was only heating the rads closest to it, then the boiler timed out(cycled). After a few mins a very heavy knocking started at the pump beside the boiler as far as I can gather. It shook the furnace. The pressure release valve was spitting steam. Out of curiosity I turned the pump setting from 3 to 2. The banging etc stopped. I suppose it overheated but could the pump be failing on the 3 setting and working on the 2 setting? Now I have the boiler stat set at 80 and number 2 setting on the pump. The minute I change the setting back to 3 it starts banging again. The boiler cycles on a short time and off a good while. All rads are on and open(13) and the rads furthest from the boiler are luke/hot while the ones nearest the boiler are piping.

Ideas please?

Question: to change a circulating pump beside the boiler is it necessary to drain the heating system?

Thanks a lot in advance

Eamon

Carlow52

if the pump is fitted properly then there should be 2 flat screwdriver operated isolation valves either side of it that will allow you take it out without draining the system: u may have to drop the pressure, dont know
see here
http://www.screwfix.com/p/pump-valve-ball-22mm/13885

On the knocking cant help

eamon11

thanks carlow,

the system is cold now. I have turned the pump on and 3 setting. Banging like being hit with a haammer whih reverbrates around the whole house. Thing is, it seems more to come from the upper pipe around where the stat is(a few inches from the boiler) and not so much the pump itself. When I switch back to number 2 setting, the banging stops!! This check was done without the boiler being switched on.

eamon11

lads,

Banging defo seems to be in the top feed pipe from boiler. The pipe itself vibrates. someone must have an idea for this?

JohnnieK

The pump is not working and the boiler is over heating (badly by the sounds of it)

eamon11

thanks Johney,

but I am not sure that is the complete picture.

what about the fact that also when the system is cold( I did not start the boiler, just wired the pump direct) I turned the pump on at 3 setting. Banging like being hit with a haammer whih almost makes the top pipe shake. It certainly does vibrate a lot. Thing is, it seems more to come from the upper pipe around where the stat is(a few inches from the boiler) and not so much the pump itself. When I switch back to number 2 setting, the banging stops!! This check was done without the boiler being switched on.System cold. So no overheating involved. The heating seams to work fine on number 2 setting. Can the pump fail at one speed and work perfectly on another?

aujopimur

I'd say you need a new pump, you might get away by using the pump valves to isolate it for replacement, but be prepared for them to leak thus the need replace them as well which will require draining the system.
If you need to replace the valves use decent wheelhead type instead of the crappy slot type.

heinbloed

As aujopimur said already: the pump is done. The wheel might be worn down, unbalanced similar to an unbalanced car wheel which goes fine at low speed but starts to buckle when the speed increases.

Once exchanging the pump (there is no repair for it I'm afraid) install insulation valves as already recommended and get an A-rated pump.

Carlow52

aujopimur wrote: »

I'd say you need a new pump, you might get away by using the pump valves to isolate it for replacement, but be prepared for them to leak thus the need replace them as well which will require draining the system.
If you need to replace the valves use decent wheelhead type instead of the crappy slot type.

can u post image or link to what a wheelhead valve looks like pls?
Thanks

aujopimur

They are identical to the slot type except they have a spindle protruding from the body in place of the screwdriver slot.

eamon11

thanks a lot lads. I am going to change the pump only. The system was drained, cleaned and a new mix of inhibitor added to the water 8 months ago. I do not want to drain it again. I will chance it.
Any advice you can give me regarding installing the pump I would appreciate.
The isolation valves are there however they do not have a slot for screwdriver operation. There is a nib, flat on 2 sides and round on 2 sides. This can be operated with a pliers or an 8 or 6mm wrench, dont know which yet.
Are there new seals/gaskets I could buy which go between pump and isolation valve? Or will these be supplied with the pump.

Thanks again,

Eamon

aujopimur

The valves may or maynot leak it's worth a try, new pumps usually come with washers but check the box in case they've been nicked.
A 1/4 turn will close the valves.

eamon11

thanks aujo,

I am spraying the nut/thread which will be opened with WD40 for a few days. Might help to make a more stress free opening, might not, but worth a try.
You say only a 1/4 turn to close the valve? Should it not be a half turn?

Eamon

Billy Bunting

1/4 turn.

eamon11

cheers bill