The datasheet for the Cerbo GX (v2) says the relay can only do 125AC, which implies you can use them to switch mains in the US but not in the UK/Europe. Is that really true?
I want to switch a standard DIN contactor with mine, but I’m in the UK so that expects 250V AC switching voltage. Datasheet says 2.2W so that would be 10mA@250V. Is the Cerbo relay not going to like that?
Actually it seems the contactor is available with 12VDC 24VDC or 240VAC coils. Unfortunately the switching voltages I have available are 48VDC (from the battery) and 250VAC, so if the Cerbo really can’t switch euro-mains then I’ll have to find a 48V contactor or work out how to drive a 24V coil from a 48V source.
(or replace the Cerbo relay with a 250V one which would be a faff. )
I guess this is the offgrid heritage showing through, so the relays are designed for battery-voltage coil operation, and the 125VAC just comes for free when you buy a 6A 30V/1A 70V relay.
It is always best to use the relay as a signal a contactor, rather than a direct load control.
The difference between 120vac and 250vac is the arc draw. Stick to the datasheet.
Coil voltage can be separate from signal A1 and A2, here is an example. and then you don’t have to ‘colour outside the lines’ to get the job done.
As an added benefit if something happens on the load side you burn a £12 contactor rather than the whole Cerbo
I know. Maybe you misread my post? That’s what I’m doing: using the Cerbo relay to drive a chunky one. I’d have to be very dumb to try and use it to run a 3kW mains immersion directly. But the point is that the overlap of available voltages (48DC, 250AC), cerbo-safe voltages (<70DC, <125AC), and easily available 20A DIN contactors (12DC,24DC,250VAC), provides zero solutions.
Hence the query about ‘colouring outside the lines’.
Do you mean the propensity for arcing on opening the relay contacts? I don’t have the datasheet for whatever relays are in the cerbo. The question was whether this is actually a problem at very low currents (10mA, 2W), even with a higher voltage. Obviously it would be a problem at 6A - the top end of the rating. Maybe the contact spacing is so small that it still is - I don’t know, and I agree it not an ideal thing to experiment with as burning one out would be inconvenient.
The simplest solution appears to be to use a pair of 24V relay coils in series with the 48DC supply (and use the contacts in parallel for the immersion load to be a bit nicer to them too). And I happen to have two of those lying about, so I’ll see how that goes.
Weird. No idea where that appear from. Should have proof read after pasting the link for the contactor. Apologies.
The contactor was an example. Not a solution as i don’t even know what you are switching. What voltage is the heater?
I do know a few installers who have damaged (welded and a different one burned out) cerbo relays due to direct load switching, (back emf) so will usually recommend it is just used as a signal as it is easier to replace an outside component. (Even by ‘logical’ reasoning 125vac 6A could mean the relay is 230vac 3A. There is probably a good reason why 230vac has not been specified.)
(Or recommend to use a flyback diode or a snubber circuit dependant on applications.)
240V. Standard UK 3kW immersion. (mine actually seems to draw 3.2kW, so 14A, according to the AC load monitoring here). So a fairly large, but entirely resistive, load, likely to be run continuously for 30mins to an hour.
You could always get a shelley or a sonoff and remote switch the contractor with 240v.
The shelley allows iot and hardwired switching. (Although maybe 14A is too close to the 16A rating)
Then node red is still available.
You also get funny little din mount Power supplies. So 24v coil is also not a terrible hardship
Do you have an inverter with ac2 out in use already?
Shelly’s don’t like 13A for any long periods. Been there and it overheats and switches off. I’m driving a contactor via the Shelly to work around this.
No. I already have a manual immersion switch. I’m trying to make it GX-relay switched, and thus easily integrated into automations that might, for example, turn the immersion on when it’s sunny and the battery is going to be full today.
[quote]You could always get a shelley or a sonoff and remote switch the contractor with 240v.
The shelley allows iot and hardwired switching. (Although maybe 14A is too close to the 16A rating)
Then node red is still available.
[/quote]
I could, but I already have a remote-controllable automation system with built-in relays (CerboGX), so adding a shelly just adds complication and cost.
[quote]
You also get funny little din mount Power supplies. So 24v coil is also not a terrible hardship
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That is quite a good idea. I had noted that I could get a 48->24V buck PSU for less than £2 from alibaba. A DIN-rail version of that would be neater. Although I don’t have another spare slot until the CU is reconfigured to use MCBOs rather than shared RCDs.
But in fact I made it work by pairing two 24V relays yesterday. The only issue is visible arcing when it turns off the load. So I will add a snubber, and if that fixes it I’ll call it good enough, put it in a nice box, and see how it goes.
My ACout2 is not in use. I am using AC-in and AC-out-1. Why do you ask?