A couple of years ago I had a commercial PV immersion controller installed. No problems.
Recently the consumer unit I fitted 25 years ago was replaced by an electrician. I noticed a sporadic clicking noise from the new CU. Eventually I traced this to the MCB protecting the immersion circuit.
I believe the PV controller operates in burst fire mode. Is this causing the solenoid in the MCB to make the noise? And should it? I never heard any noise from the corresponding MCB on the old CU.
The clicking is not loud and is in the garage, so it's not causing a problem. But I'm concerned that the lifetime of the MCB may be reduced.
Is this normal behaviour for an MCB with a PV controller?
Re: Noise with PV immersion controller
@arnoldh,
Doesn't sound very healthy - you have already checked the tightness of the upper and lower clamps (with power off of course)? Which brand of MCB? A closeup of the trip markings would be useful.
Re: Noise with PV immersion controller
Thanks for the reply.
I've not checked the tightness of the connections - it means opening up the CU with the feed in live. I'll let the electrician that fitted it do that if it becomes necessary. At the moment I'm just trying to get feedback whether this behaviour is normal before I ask the fitter to come back.
This is the MCB. The PV controller is this one.
Re: Noise with PV immersion controller
Before trying to think of a complicated reason, is your MCB reset properly? Try tripping it manually and close it up again, and see if the noise is still present.
My first thought was there is a capacitor in the controller that's taking a large-ish inrush current, and your MCB is seeing that for an instant and thinking about tripping on instantaneous overload ("magnetic"), and that's what you can hear.
Does it happen irrespective of the amount of surplus PV you have, or is it noticeable/worse when you're diverting at about half-power?
Re: Noise with PV immersion controller
Yes, the MCB is reset correctly. It had been switched on and off a couple of times to confirm I'd got the right circuit.
Good point about the amount of surplus power. I've just switched the controller to boost mode, which I believe should turn the heater on fully with no power reduction. I can still hear a faint buzzing/clicking. The MCB is probably quieter than when the controller is only diverting part of the current, but I can't confirm because whatever sun there was has disappeared. I will experiment more when the sun returns.
But I'm now confused why I'm hearing any noise if the controller is passing full power. Unless of course there is a loose connection.
Re: Noise with PV immersion controller
"why I'm hearing any noise if the controller is passing full power..."
... is probably because that's its maximum power, but not exactly 100% power. The triac - which I assume is what the switch is - will be turning on when the voltage has risen to maybe 5 or 10 V. There very little power in that triangle that's missed, but the step as the triac turns on is enough to rattle something in your MCB.
Your first step is to check all the connections. I'd do that live using a type-tested insulated screwdriver and not think twice, but if you have any concerns at all, get the electrician back. The second thought is that there is something rattling about inside your MCB, and another one might not do this. I don't think any MCB should in fact make a noise as you describe, so it may well be grounds for getting it changed in any case.
Re: Noise with PV immersion controller
Robert,
Thanks. That all makes sense.