Is my pump really working....??

[Dodgemonkey]

No doubt this has been asked plenty of times, please excuse my ignorance in not finding a suitable thread on this so far.

Vented central heating and hot water system, Y plan, Grundfos Selectric 15-50 circulating pump....

Boiler (glow worm) making some knocking and banging noises.

My plan was to: Drain down and introduce Sentinel X800 Jetflo directly into the system, run for an hour or so, then drain down again, before refilling and adding Sentinel X200 descaler and running that for a couple of weeks (I know it may be run indefinitely), then drain once again, refill and add a standard inhibitor, such as X100.
However, after intially firing, with the cleanser added, the boiler locked out, and I noticed that whilst there was heat in the initial 22mm length of boiler flow pipework, as it progressed closer to the pump, the pipe got colder, with no sign of heat before or after the pump. Pump body running hot, but cold pipework either side of it. Am I correct in assuming pump failure? It's whirring, but ideally I'd like tangible evidence it's pumping, or not, before I go and replace it.
System was powerflushed about 6 years ago.
Thanks for any helpful suggestions.

Mike

 

[newbuildinstaller]

The pump is empty, if you keep running it empty it will burn out then it will be broken!!!!!! Bleed the pump or idealy find the RV35 in the cylinder cupboard and open that till water comes out. search RV35 in google if you dont know what to look for

Oh and the boiler overheated as the pipework is airlocked thats why it went off

 

[kevplumb]

The pump is empty, if you keep running it empty it will burn out then it will be broken!!!!!! Bleed the pump or idealy find the RV35 in the cylinder cupboard and open that till water comes out. search RV35 in google if you dont know what to look for

oy smug ass it's a diyer your talking to yer not in the CC now

now tell im what it is

 

[newbuildinstaller]

ha ha me smug noooooooooooo. Just trying to help, RV35 is a air vent used to bleed the boiler flow and returns it will be on a vertical section of the pipework (usually 15mm) in the cylinder cupboard supposedly at the highest point. It is brass and will have a flat head screwdriver slot used to open it. Open it slightly till water comes out.

Might even be two, look either side of the 3 way valve above the pump

 

[Dodgemonkey]

Ta muchly, I did that already. Yep there are two RV35s, both on vertical 15mm pipework, though one of 'em hasn't got the slotted head to it. Bleed screw on the pump was also loosened, a little water came out of the pump but that's all.

Give the pump body a little knock to dislodge any debris, maybe?

 

[newbuildinstaller]

so nothing came out the RV35s?

 

[Dodgemonkey]

Air initially, then some brackish looking primary fluid...

 

[Dodgemonkey]

Update on this....I re-checked the pump bleed valve, and re-checked the RV35 bleed points. Power off, pump bleed valve removed and checked for easy rotation of pump spindle. Free as a bird. Power on, spindle is rotating like a good 'un. But, pump is faintly buzzing and its body soon gets warm, although there's no hot water anywhere near it. After a very short period of banging and clattering, the boiler locks out, and there's a lot of venting going on up in the loft. Anything else I can finally check before I lob this thing out of my window and fork out for a replacement?

Thanks,

Mike

 

[kevplumb]

close the valves and remove the head (4 allen screws) the impeller might not be on the shaft

 

[Dodgemonkey]

Thanks fella, will try. I'm deffo erring to pump failure, but we'll see for sure.

Mike

 

[m1key00]

Are you sure there's water in it?

Sounds to me like its running dry, blocked cold feed maybe? try draining a bit of water out and as its running check the header tank is refilling.

 

[FriedFreddy]

I think I have just had this problem (sounds EXACTLY like my initial issue)

crack the top pump nut on the gate valve and see if any water comes out (I actually removed the pump completely and opened the top pump gate valve to fully open and still did not get any water come out) - if no water you have a blocked feed from the F&E tank and/or the 4 way copper bottle doohickey (dunno what it's called but from your pics I have the same deal & it was also blocked)

Lez

 

[Dodgemonkey]

Good call boys, that's my next move - remove the pump and see what comes out of the gate valve on the suction side when I carefully re-open it. I'll keep you posted.
Thanks,

Mike

 

[Dodgemonkey]

Update on this, and a fault found. So, it is with profound embarrassment I admit that, to test the flow leg from the f & e wasn't blocked, I drained down, then removed the pump from the flow pipework, as well as the 3-port immediately above it. Then I fabricated a basic length of pipe in its place, terminating over a large receptacle.
A slow fill of the f & e followed, and the plan was to check there was a free flow down the 22mm copper flow and out over the receptacle. A reasonably good plan I thought, and it started that way, proving that the pump wasn't being starved at least.
But, yours truly hadn't capped the remaining open ends of the heating/hot water and bypass legs once the 3-port had been removed, so.....loads of sparkling water started to find its way out of those other 3 open ends.
Lucky I can decorate....hehe.
Anyway, the fault...
A jammed impeller. Spindle was being driven, but the impeller wasn't.

So, very well done KEVPLUMB, you were spot on in your diagnosis.
Hope this is useful to others.

Mike

 

[kevplumb]

aye i'm not bad for a nupty installer -----------------------------------------------------------------------------------------------------------------------------------------^

howay only need another 2