Wet UFH pumps causing RCD tripping

[ACL]

If the RCD is going at 19mA you've got very little overhead at all for 'normal' leakage. If you've a decent mA leakage clamp meter then now's the time to use it. If it were me I think I'd be looking to find ways of breaking that down into at least a couple of separate circuits and spreading the discrimination. You can always use a contactor to bring them back together again.

No leakage clamp meter as yet, any recommendations?
There is no N link between the boiler and the UFH as the wiring centres use a 0v built in relay to send the demand signal.
The remote Grundfos pumps and 2 port valves are controlled by the boiler spur, so I could separate the UFH and the boiler to 2 RCBOs

 

[ACL]

Not being used is irrelevant if the isolator is on.

True.
Whilst the house was being second fixed, the ovens were not in and the UFH worked fine.
It did work happily for about 4 weeks with the ovens and hob connected though.
I'll isolate the ovens and hob then test.

 

[loz2754]

If you've tested all cabling for insulation resistance, and there is no fault, then surely that's as far as your responsibility goes?
I would be careful about splitting up the circuit, as most domestic heating systems are supposed to be capable of being isolated from a single device.

 

[ACL]

If you've tested all cabling for insulation resistance, and there is no fault, then surely that's as far as your responsibility goes?
I would be careful about splitting up the circuit, as most domestic heating systems are supposed to be capable of being isolated from a single device.

You'd think that was the end of my responsibility but the plumber is pointing fingers. The bit that gets me is they spec'd and supplied the system then when it trips they say it's an electrical fault. They even sent a plumber in to check it, who told the customer the 100A MCB ( not an MCB an RCD) was too small, was overloading and needed to be upgraded!!!!!!!

 

[Rockingit]

You'd think that was the end of my responsibility but the plumber is pointing fingers. The bit that gets me is they spec'd and supplied the system then when it trips they say it's an electrical fault. They even sent a plumber in to check it, who told the customer the 100A MCB ( not an MCB an RCD) was too small, was overloading and needed to be upgraded!!!!!!!

Since when did we start listening to wet pants?

 

[ACL]

Since when did we start listening to wet pants?

We don't listen to them, but customers will listen to the last person in the building unfortunately.
It took a while but I finally convinced the customer and the plumber that the 100A RCD didn't need to be upgraded.

 

[UNG]

Turning on the UFH, the wiring centres go through a start up process then send power to the Neostats. They in turn go through a start up process and then turn on sending a signal back to the wiring centre to turn the boiler on. It's at this point that the RCD trips.

The RCD generally trips over night so other appliances are on but not being used.
Forgot to mention this is a new build and all appliances are new.
I will try to move to an RCBO to test.

One post seems to contradict the other here, you can't start the system but then it trips overnight

RCD ramp test indicates that it's tripping around 19mA.
1/2 test indicates no problems.

If a brand new RCD is tripping at that level I would be speaking to the manufacturer about a replacement, out of the box problems with RCD's seem to be getting more common in the last few years

 

[mattg4321]

Is that 19ma ramp test with all loads disconnected?

 

[brianmoooore]

IIRC, the acceptable range for a 30mA RCD is 15mA to 30mA. I.e. 30mA +0%/-50%.

 

[mattg4321]

Possibly it is. Imo most decent rcd I’ve ramp tested with all loads disconnected are about 24-27ma. 19 is low imo. Perhaps because of cumulative earth leakage, perhaps by design, perhaps faulty.

OP says it’s Hager. Usually these are around 25ma in my experience and reliable and good quality