mystery shock

[mills]

Advice needed please.
On the central heating water pipe system I have two Grunfos pumps. One pumping the heating circuit, one pumping to the hot water cylinder. Both pumps stopped working. They are individually plugged in to the electric supply via round 3 pin 2 amp plugs. Other appliances in the same power supply ie boiler, and switches still have power. There is no power from the two sockets supplying the pumps.
When I removed the plugs from sockets I got a small shock when inspecting the plug pin and casing screw, Whilst the plug, cable and pump aren't connected to anything.
Questions;
1 Could the water pipe its self be be carrying electric current or was it a static build up from the pump and why?
The sockets have their own little fuse box with trip switches (which werent tripped),
2 will replacing the fuses be ok or may there be a bigger problem underlying.
Other factors, the water in the cylinder seemed super hot than usual, and I have recently replaced some copper pipe in the radiator circuit for plastic
many thanks,
Simon

 

[Lectrician]

You tell us if the fuses have blown - we can't tell you!

Was it the earth pin that gave you a belt? If so, it does suggest the pipework is carrying a voltage from somewhere.

We can't really help as we do not know where the pumps are fed from - there must be joint box/wiring centre or something where the timeclock and boiler etc are connected - this must all be part and parcel of the same thing.

Is there a cylinder stat and room stat? do these work?

 

[mills]

Thanks for the quick reply.
1. There are no fuses in the plugs (they are the old round pin type), there is a secondary junction box with a range of the large trip switch type fuses supplying everything in the boiler room, which werent tripped, I don't know if they blow without tripping? The same junction box supplies the boiler and other switches which are all working ok.
2 I don't know which pin I touched, I wasn't expecting it, and haven't gone back to check
3 There is a cylinder and room stat, (differnt part of the house)I don't know how to check them, but they have been working because I've lived here for some years.
Hope this helps a bit more

 

[Iggifer]

Advice needed please.
Other factors, the water in the cylinder seemed super hot than usual, and I have recently replaced some copper pipe in the radiator circuit for plastic
many thanks,
Simon

You really should fit an earth clamp either side of where you have added the PVC piping and connect with an earth cable in line with what size supplementary bonding you have elsewhere, possibly 6mm. If you don't you run the risk radiators not being earthed

 

[RF Lighting]

And that would be a problem because?

 

[securespark]

Since when has supplementarty been 6?

 

[RF Lighting]

And why would you use bonding to earth a radiator?

 

[ricicle]

Bring back DC

 

[Iggifer]

Perhaps a little overzealous of me. 4mm

 

[RF Lighting]

But why install it at all?

 

[Lectrician]

Thanks for the quick reply.
1. There are no fuses in the plugs (they are the old round pin type), there is a secondary junction box with a range of the large trip switch type fuses supplying everything in the boiler room, which werent tripped

Well that confuses me a tad, because in your original post you said:

2 will replacing the fuses be ok or may there be a bigger problem underlying.

This is why I said you had better test the fuses, as we can't tell if they are blown!

 

[mikejd]

Surely this is just a shock from the capacitor used to run the single phase motor in the pump? He did say it was a small shock... Just a thought??

 

[bernardgreen]

Since it is un-likely the pumps have to run 24 hours 7 days a week they will almost certainly be controlled by relays in the control system of the boiler. Hence the use of round pin plugs to prevent other appliances being plugged into the controlled sockets

The reason there is no "power" at the pumps sockets is most likely to be a fault in the control system or wiring of the control system. Possible a fuse in the control system.

No "power" is no voltage of 230 volt between Live and Neutral. As the OP was getting a shock it might be the Live is live but the neutral is disconnected.

 

[mills]

Thanks for thinking about this one so far.
Update to info given;
1 The Honeywell Motorised Valves are working in line with the thermostats, but not switching on the pump.
2 I say pump singular, because the pump working the hot water for the hot water cylinder has come to life on it's own?
3 The shock I got from the pump that is still not working seems to have been a 'one off'. It's no longer giving off a shock.
4 (Lectrician) When I said replacing the fuses, I meant the trip fuses in the box. (which didn't trip)
5 (Iggifer) I didn't think earthing the replacement bedroom rad was needed. It now has a non conductive pipework, plastic ?
Many thanks

 

[bernardgreen]

1 The Honeywell Motorised Valves are working in line with the thermostats, but not switching on the pump.

The micro-switches used in many motorised valves are not the most robust items and are a common cause of pumps and / or boiler not operating when the valve is opened. If you have a voltmeter and know what you are doing you can measure the voltages in the system to find out if the micro switch is switching correctly.