Can I power 2 x 3kw immersion heaters from a single 3 phase contactor?

[Philip Saunders]

Is it ok/advisable/legal to power 2 immersion heaters (both in the same cylinder) from a single 3-phase contactor?

I need to connec

 

[Rockingit]

As in, two single phase elements? If so then yes, subject to the overall design of the circuit being suitable for the loads and I'd strongly advise having separate protection for each after the contactor. The only 'technical' issue is that you'll have an unbalanced 3ph load because you'll only be using two of the lines.

If they're 3ph elements then same thing, just make sure that you have protection by a suitable 3p MCB after the contactor and before the element - you'll probably find this easiest by mounting the contactor and CPD's in a small DIN rail box all together.

 

[Rockingit]

Or are you talking about using a 3p device on a 1ph supply to just have one contactor not two??

 

[Philip Saunders]

Is it ok/advisable/legal to power 2 immersion heaters (both in the same cylinder) from a single 3-phase contactor?

I need to connect 2 immersion heaters and I have a redundant 3 phase timer-controlled contactor that would be ideal if I can use it. I know each heater would need its own fuse/DP switch, and I would need to run a neutral back to the panel.

 

[littlespark]

Is the coil of the contactor 3 phase? I wouldn’t think so... possibly 230v single phase, could even be 24 or 12v dc... you need to check that.

as for the contactor... it’s just a switch... 3 pole, not 3 phase. But it’s capable of switching 3 phase 400v

 

[Philip Saunders]

As in, two single phase elements? If so then yes, subject to the overall design of the circuit being suitable for the loads and I'd strongly advise having separate protection for each after the contactor. The only 'technical' issue is that you'll have an unbalanced 3ph load because you'll only be using two of the lines.

If they're 3ph elements then same thing, just make sure that you have protection by a suitable 3p MCB after the contactor and before the element - you'll probably find this easiest by mounting the contactor and CPD's in a small DIN rail box all together.

As in, two single phase elements? If so then yes, subject to the overall design of the circuit being suitable for the loads and I'd strongly advise having separate protection for each after the contactor. The only 'technical' issue is that you'll have an unbalanced 3ph load because you'll only be using two of the lines.

If they're 3ph elements then same thing, just make sure that you have protection by a suitable 3p MCB after the contactor and before the element - you'll probably find this easiest by mounting the contactor and CPD's in a small DIN rail box all together.

Yep thanks for that. They are single phase 240v heaters. I was planning to run each via a DP switch and an mcb or fuse. Is a DP switch actually required or will a single pole MCB be OK?

 

[Rockingit]

As Littlespark said, you'll need to check your coil voltage on the contactor (which will also - somewhere - in the switching circuit need a protective device [if it's 230 then just piggy back off the protected main circuit feeding all this]) but a 1p MCB satisfies the requirements for isolation.

Making an assumption that this is 2 x 3kW elements then I'd suggest your feed cable is likely to need to be at least 6mm.

Also..... if this is domestic then it falls under Part P as you're creating a new supply circuit/s

 

[Philip Saunders]

Is the coil of the contactor 3 phase? I wouldn’t think so... possibly 230v single phase, could even be 24 or 12v dc... you need to check that.

as for the contactor... it’s just a switch... 3 pole, not 3 phase. But it’s capable of switching 3 phase 400v

Coil is 240v single phase
Yes I'm aware the contactor is just a switch - this one happens to be switching 3 phases and is already installed. I just wanted to make sure I wasn't breaching any regulations by repurposing it to switch 2 independent single phase loads as opposed to the 3 phase motor that was there before.

 

[Philip Saunders]

As Littlespark said, you'll need to check your coil voltage on the contactor (which will also - somewhere - in the switching circuit need a protective device [if it's 230 then just piggy back off the protected main circuit feeding all this]) but a 1p MCB satisfies the requirements for isolation.

Making an assumption that this is 2 x 3kW elements then I'd suggest your feed cable is likely to need to be at least 6mm.

Also..... if this is domestic then it falls under Part P as you're creating a new supply circuit/s

Thanks..... I think that covers it. The feed cable I think is an imperial size of MICC but it's definitely larger than 6mm and I won't need to mess with it - that's the reason I want to repurpose what's there rather than replace it which would be an absolute pain.