Another pump continuously running...

[Agile]

I gather they incorporated their choice of limiting the inrush current in a new pump supply lead.

That is simpler for many installers to fit and being larger easier to justify charging for it as I seem to think they did, but I could have forgotten. I never became involved with any and would just fit an NTC myself.

It is easy to specify but when the pump makers have their "cure" then that should be used to maintain any warranty on the pump.

 

[Gasguru]

I posted the link to the Grundfos cable earlier (maybe they're still available as old new stock) but that would appear to be an interim bodge by Grundfos.
Once the NTC is hot (through the pump current draw) its resistance will fall and it will no longer offer protection if the supply is cut and the capacitor discharges.
Allowing a minute or 2 for the NTC to cool down and its resistance to rise is not always likely hence the better guaranteed solution of a PTC and shunt relay operating after the capacitor has charged.
Getting relays off Vaillant pcbs requires special low temperature/high thermal mass solder that remains molten for several seconds whilst each joint is heated...the relay pins are very tight in the board.

 

[SgtFoley]

Thank you guys.
I will order and fit the 'suppressor cable'...
I pressed Grundfos but I can't imagine they will get back to me very quickly.

Is there a chance the suppressor cable fixes the problem completely? i.e. could the relay be temporarily sticking on each current spike? I guess not if the spike is from charging the capacitor (then it would stick every time. or be fully welded by now)... but if it's an externally caused spike maybe?

It will be hard to tell if I fixed anything since it seems to work most of the time.

 

[Gasguru]

Fit the lead and time will tell...

There's several leads on ebay, search for 98525489

 

[Gasguru]

Date codes on the pump...

https://www.google.com/url?sa=i&url...ved=0CAkQjhxqFwoTCPji_fqu0_ACFQAAAAAdAAAAABAE

 

[Harry Bloomfield]

Is there a chance the suppressor cable fixes the problem completely? i.e. could the relay be temporarily sticking on each current spike? I guess not if the spike is from charging the capacitor (then it would stick every time. or be fully welded by now)... but if it's an externally caused spike maybe?

There are lots of posts about the issue, on various sites. My guess would be that if the welding is only irregular, then you will most likely be fine just fitting the new cable. I have come across similar problems before and applying such a fix, has proven permanent, but there are no guarantees. Often just giving the relay case a sharp tap, when the coil is powered down, is enough to cause the contacts to un-weld.

 

[SgtFoley]

Cable on the way...
Thank you all for your help and expertise.
I learnt a lot, and certainly enough to do a lot of damage!