Pool Pump intermittent RCBO trip

[EastCoastPete]

Hello All,
Am checking a fault on someone elses install which is about 18 months old. Customer says it starts and operates ok then he stops to take a break ( it's a small pool with pumped flow to swim against), then tries to restart and the RCBO goes. So, I know it's hot when it happens but that's it at the moment
Wylex 32A C type on the tester goes at 21mA on both cycles and breaks in; x1 29.2/19.1 & x5 8.9/19.1 mS

Thanks for any observations,
Pete

 

[radiohead]

Whats the pump rating? is there any other load on the device or is it pump only?
Edit, sorry just seen the attached pics which answers the pump rating

 

[James]

Is there another rcbo in the board that you can swap it with?

Other than that, ir test the motor when it is hot.

 

[EastCoastPete]

Is there another rcbo in the board that you can swap it with?

Other than that, ir test the motor when it is hot.

Yes, thanks, I'll test the motor that way and I can swop to another RCBO. let you know
Cheers,
Pete

 

[Lucien Nunes]

Is the RCBO tripping on overcurrent or leakage?

 

[Mike Johnson]

Has this always happened or is it a new fault?
Does the motor have an inverter?
Have you checked the starter condenser?
What's the curve on the RCBO?

 

[EastCoastPete]

Hello Mike,
This has happened since installation apparently. I don't know if the speed is VFD or inverter, it's a operated from a remote with incremental steps. I've not looked at the start capacitor yet and I don't know how to establish the curve of a particular RCBO. The pump is for hydraulic power to a propeller as part of a system marketed as 'Fastlane Endless Pools',
There's no paperwork but I found the manual. Schematic attached. The actual pool was locked when I was there but I'm back out Monday.
Thanks for your time
Pete
[automerge]1581064034[/automerge]
Hello Lucien,
Overcurrent from heat I think, but I'm fishing here....

 

[Wilko]

Hi - if it happened from new, that suggests to me design flaw, not wired correctly or faulty equipment. Perhaps the motor is loading the RCBO sufficiently that it warms up and trips on restarting, C rated or not. Have you confirmed the motor current?

 

[EastCoastPete]

Morning Wilko,
Aye, that was my line of thought so far, so Monday I'll get into it better and more measurements. The spec is ok for the RCBO but the motor may not feel that way. The CU is a mess and for a new install there's no paperwork at all...

 

[Lucien Nunes]

I don't know if the speed is VFD or inverter, it's a operated from a remote with incremental steps.

The motor is started DOL and runs at constant speed. The variable water flow is achieved by a proportional solenoid valve diverting the hydraulic pump output away from the hydraulic motor.

'Code G' on the rating plate indicates locked-rotor load is in the range 5.6-6.3 kVA per hp, (IIRC NEMA rated hp, not multiplied by the service factor)
Worst case starting current will be 5 x 6300 / 230 = 137A on a C32 RCBO
137/32 = 4.3 x In which gives a tripping time of around 2-10 seconds.

I would assume the pump starts fully relieved by the valve but even so, that looks fairly borderline for tripping on starting current.

 

[EastCoastPete]

The motor is started DOL and runs at constant speed. The variable water flow is achieved by a proportional solenoid valve diverting the hydraulic pump output away from the hydraulic motor.

'Code G' on the rating plate indicates locked-rotor load is in the range 5.6-6.3 kVA per hp, (IIRC NEMA rated hp, not multiplied by the service factor)
Worst case starting current will be 5 x 6300 / 230 = 137A on a C32 RCBO
137/32 = 4.3 x In which gives a tripping time of around 2-10 seconds.

I would assume the pump starts fully relieved by the valve but even so, that looks fairly borderline for tripping on starting current.

Got that Lucien, a lot cleared there,I was missing the point between start control and use control.
Thanks,
Pete

 

[Mike Johnson]

I think Lucian has hit the nail on the head, marginal for a 32Amp type C RCBO perhaps try a hither rating or D type to confirm?

 

[EastCoastPete]

Hello All, and thank you again for the input...it took a while to get back out there, weather/van bother. Anyway, the capacitors are good and charging, insulation from coils to frame is good. The motor runs at 15amps according to my clamp meter and start current read at 25A though I know this is false, I guess a hand held meter's not going to be fast enough to read the initial spike? I made a few calls and have been advised by an installer (who does a lot of these through the pool company) that it should not be on an RCBO, certainly the spec says MCB/RCD (RCCB) and apparently the combination device is more susceptible to induced volatge from the others in the CU? He reckoned to run a sub circuit from a c type MCB to RCD. I have just enough Zs to try d type if needed.
Pete

 

[radiohead]

Hello All, and thank you again for the input...it took a while to get back out there, weather/van bother. Anyway, the capacitors are good and charging, insulation from coils to frame is good. The motor runs at 15amps according to my clamp meter and start current read at 25A though I know this is false, I guess a hand held meter's not going to be fast enough to read the initial spike? I made a few calls and have been advised by an installer (who does a lot of these through the pool company) that it should not be on an RCBO, certainly the spec says MCB/RCD (RCCB) and apparently the combination device is more susceptible to induced volatge from the others in the CU? He reckoned to run a sub circuit from a c type MCB to RCD. I have just enough Zs to try d type if needed.
Pete

If an RCD is protecting the circuit you can use the max Zs for that rather than the OCPD. Go straight for a type D without any worries of being close to the max Zs.