Grundfos scala 2 water pump

Doop

Hi,

Not sure if this should be an electrical question but just wanted to see if anyone has any experience of this.

We have a Grundfos scala 2 water pump installed downstairs in the utility room to send water up to the upstairs bathroom (is my understanding). Recently we started getting sporadic tripping of the electrical board the main MCB (?). It was very sparodic and hard to determine what was causing it. Long story short I now know its the pump, everything works fine if the pump is powered off at the spur, and once you flip it on it trips the board. You can re-set the board and the pump works until the next time it decides to trip.

I called a plumber out to replace the pump but he just said its working fine no leaks etc and replacing it may not resolve the issue of the tripped switch (at that time we weren't 100% sure it was the pump). So I called an electrician and he opened up the pump again no signs of a leak or anything (I believe this pumps have a reputation for internal leaks). Electircan said he sees no issue with the pump or the way its wired in. He said its probably something else in the house causing the trip. (we now know its not).

I'm a bit of a loss with what to do? just take the plunge to replace the pump for €1000 odd euro and hope that resolves it? Try re-wiring the spur to the pump? Its very frustrating!!

Any thoughts appreciated!

Lenar3556

Those pumps gave a lot of trouble, but I wasn’t aware intermittent tripping was one of the issues.

What exactly is tripping? Is it an RCD which protects several circuits? It can be very difficult to narrow this down to the exact cause. It could well be a fault elsewhere in the circuit which only manifests itself when the pump is running (as consequently there is current on the circuit).

An electrician should be able to test both the pump and circuits on the RCD for leakage. It may also be a good idea to fit an RCBO to the pump circuit so as it is isolated from the remainder of the circuits.

I wouldn’t be shelling out on a new pump just yet.

Doop

https://www.boards.ie/discussion/comment/122801644#Comment_122801644

Thanks so much for the advice, yes it is the RCD that protects several circuits that trips. I spent a lot of time, dropping the other circuits breakers to test if it was elsewhere in the house causing the trip, so I managed to rule out the other circuits bar the one the pump is on.

I should have mentioned the pump was installed around 2020 so should still well be in its life expectancy. I think you are right I should try get the electrician back, I'll ask about a dedicated RCBO for the pump… however the distruciton board is the opposite side of the house.. I presume this would mean running a dedicated cable from the board to the pump?

Lenar3556

https://www.boards.ie/discussion/comment/122801661#Comment_122801661

Well for a start, I would just replace the MCB which supplies the pump (and whatever else) with an RCBO, but if you wanted to go a step further you could power the pump from a dedicated circuit and run an extension lead to it as a temporary measure.

What you did dropping other circuit breakers does not conclusively prove your case that the pump is the issue. The circuit breakers only provide single pole isolation. You could have a neutral earth fault for example elsewhere in the installation.

10-10-20

The electrician should be able to run an IR (insulation resistance) test on the pump, this would test the insulation between the ground and the live and neutral; then get him to measure the ground current (leakage) into the RCD when the pump is isolated and then in-circuit. A small earth leakage on the pump might partially be the source of the overall earth leakage in the house as what can happen is if there are other devices on the same RCD which also have high leakage - these can all accumulate and cause the RCD to trip when the pump kicks in.

Example being - if you had a high earth leakage of 15mA on a washing machine, plus the plump has a high leakage of 15mA when running - then that would equal or better the 30mA limit on the RCD and cause it to trip.

(from the manual for the Scala:)

DANGER
‐ The pump must be earthed.