Stupid Question about central heating pump

[Belboz]

Hello all and festive greetings..

I think my central heating pump may be seized. Having searched on here for advice on previous threads, I am aware that the pump could possibly be freed by turning the impeller with a screwdriver. My stupid question is whether the pump needs to be isolated using the valves either side first? Reason I ask is that I have partially unscrewed the central screw on the pump in order to access the inner shaft and, as expected, some water came out. However, it doesn't seem to stop coming our hence the stupid question....

 

[JohnD]

it should not be necessary, only a few drops or a dribble should come out, so a small bowl or basin should catch it. Perhaps on yours the seal round the spindle is very badly worn. Sometimes the valves are jammed and may break when turned. A photo might help.

Is the pump getting hotter than the two pipes going into it? What makes you think it is seized?

If you bleed the highest radiator in the house, does water squirt out forcefully?

 

[Belboz]

Thanks for the swift reply JohnD. Reason I asked is that I had a bowl and cloth but the water dribbling out didn't appear to lessen. I estimate about 3/4 of a pint dribbled out so I re-tightened the screw and decided to post on here before doing anything further. TBH, I expected a small bowl's worth to come out but not as much as 3/4 pint with no sign of stopping.

 

[JohnD]

it must be badly worn.

What about the heat and the reason and the bleeding?

 

[Belboz]

Shouldn't be that badly worn IMHO - the pump (Wilo 25/4 - 130) was only replaced in late November 2012. Anyhoo, this is my one-off attempt at a possible fix before calling the engineer. Not sure it's the pump but see what you think (you did ask..)

Setup is normal back boiler system with cylinder, 2- valves, F&E etc. Old-style programmer unit with switches for heating and hot water. Hot water works fine - no issues. Central Heating was working fine but noticed the other day that it had come on and then stopped heating the rads about 30 minutes in. Switched it off and then on again. There was an almost inaudible click but unable to tell whether from pump or one of the valve units. Nothing happened. Switched it off and on again. Still nothing. Tapped central spindle (following advice from various sources) on pump then tried again. Pump began to run but ceased running about 20 minutes later. Pump is getting red hot as are the pipes either side.

F&E tank is filled. Have bled radiators just in case of an air lock (albeit unlikely as all rads have been working fine up until a couple of days ago)

I am assuming (yep - dangerous I know) that it might be the pump seizing.

 

[45yearsagasman]

From your description of the symptoms and you saying that the hot water side is working perfectly, I would be firstly looking at the heating zone valve. It is that valve which controls the switching on of the pump and boiler during a heating period. The hot water valve does the same.

 

[Belboz]

Thanks 45yagm.... had considered that it could be the valve but that's an engineer job. Any way of checking that (e.g. manual opening)

 

[45yearsagasman]

Not really. It needs voltage checks to determine the fault. Yours sounds intermittent and not so simple to diagnose. Latching the valve may not activate the internal switch.

 

[Belboz]

Thanks for the reply. Sounds like (as I suspected) I need the engineer. Oh well, over Xmas the wife can put an extra jumper on. Was hoping it could have been an easy to free pump but I should have known it wouldn't be that simple.

Thanks to you both.

 

[DaveHerns]

What sort of valve is it? You may be able to change the actuator easily

 

[Agile]

Using a listening stick like a screwdriver you should be able to hear the pump turning or making a buzzing sound if not.

Why do you expect the water to stop coming out?

Just remove the screw and try to free the shaft quickly. On a Wilo pump it needs a 5 mm or 6 mm flat bladed screwdriver.

Tony

 

[Belboz]

Dave - it's an old Honeywell valve head (no bump)

Tony- pump not buzzing. As for expecting the water to stop then that's down to stuff I have read on the web but mostly (if not entirely) my own stupidity (hence the topic title)

Having considered what has been said on here, I have re-visited the pipework. On switching the heating to ON, there is a click from within one of the 2-port valve 'boxes'. Pump does not activate nor does boiler fire up.

Am I right in thinking that the system is set up so that the valve opens on switching the heating to ON then starts the pump and calls for heat from the boiler? Assuming that is correct then would an issue with the valve/motor/wiring then prevent any call to start the pump and start the boiler heating the water?

Am I also right in thinking that an issue with the boiler thermostat wouldn't show up with the hot water system because the hot water is governed by the cylinder thermostat and not the boiler one? Reason I ask is that I am thinking about the causes of the lack of CH other than a possible valve/pump issue.

Clearly, if the issue is likely to be inside the boiler or the actual 2-port valve then that requires the engineer.

I know that replacing the motor (as opposed to the whole valve) is possible but the 'box' has no bump so I am guessing would require draining the system?

Any advice would be appreciated.

Thanks

 

[Belboz]

Did a bit more 'digging' today. Took the cover off the 'box' on top of the CH valve. Blew the dust bunnies out of it and then watched whilst I switched the CH to ON. It appeared that the gears turned a bit then turned back a bit. The pump and CH failed to come on. Switched off then did the same again. This time the gears appeared to turn more than they did the first time and suddenly the pump and boiler came on. Unfortunately, the radiators then began to heat up but then stopped after twenty minutes.

I am thinking that either (a) the whole valve needs replacing or (b) the head unit needs replacing because the motor appears to be working. However, if the gears are partly stripped, am thinking this could be down to a problematic valve which may just do the same thing to a new head unit. Perhaps better to replace the entire valve unit?

Secondly, why does the heating stop? Is the valve just opening partly and then causing the pump to overheat so it switches off? Trying to figure out why the CH works intermittently albeit this could be an issue with the CH valve.

Any thoughts?

 

[Daveydub]

Turn cylinder stat up full and put to hw only on t.clock. Does pump/boiler now operate? If yes, unhook cyl stat from tank and manually open valve. Heating & hw will now operate in w. only position. Water (at tap) will be hotter than you are used to so warn everyone. Any room stat will now have no function. Ptting heating on will "lose" the manual open position so stick with w.only

 

[Belboz]

Thanks for the reply Daveydub. Have tried something similar using the FAQs posted on here (cylinder stat to 70, boiler stat to 1 , CH valve manually open and Hot Water [only] to ON) The rads do start to heat up but the pump, valve head and surrounding pipework got VERY hot (too hot to touch) so I switched it off again.

Concern is that I do damage to the components??

Could it be the valve is not fully opening even in the MANUAL OPEN position hence the extra heat generated? Guessing if that answer is YES then the whole valve unit will need replacing by the engineer and not just the motor assembly.

In short, should I run it like that or not??

Thanks to all who have responded thus far.