240 three phase to single phase control board autoclave

Thread Starter

Serfdumb

Joined Jun 18, 2021
7
Hey guys, I purchased an electric autoclave that was supposed to be 240v single phase but it showed up as 240v 3 phase instead. I contacted the seller and they basically told me I’m SOL, no returns. The unit consists of a 6kw heater element and control board to cycle heater on based on temperature input. I’ve read through the forums on converting the heater element to single phase and it seems simple enough, but the question I have is about the control board itself. The power comes into a contactor that has some small accessory wires which I’m assuming power the control board, I’m wondering if it will be possible to feed single phase power to it and maintain the functionality of the board. I’ll attach some pictures, thanks for the replies
 

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Dodgydave

Joined Jun 22, 2012
10,085
It's juast a matter of connecting the 3 phases together making one phase. But the problem is if the contactor coil is across two phases it won't operate, if it's across a phase and Neutral then it should work, Also the transformers should be across a phase and Neutral too ..
 

Ian0

Joined Aug 7, 2020
3,754
Are the heating elements wired star with no neutral? I see only three wires in the photo, and three terminals commoned.
If so, that star point needs to go to neutral when the lives are commoned.
The transformers are phase-to-neutral because they are labelled “220V”, not “380V”
 

MaxHeadRoom

Joined Jul 18, 2013
23,906
If you connect the commoned point of the three to neutral and power all three elements with 240v 1ph then they could be over-powered, as they all go to a star point indicating a series connection.
There was a very similar post here a couple of weeks ago with a pool heater similar arangement.
 

Ian0

Joined Aug 7, 2020
3,754
If you connect the commoned point of the three to neutral and power all three elements with 240v 1ph then they could be over-powered, as they all go to a star point indicating a series connection.
There was a very similar post here a couple of weeks ago with a pool heater similar arangement.
on 3 phase, the star point would be at neutral potential, even if it wasn’t connected to neutral.
 

MaxHeadRoom

Joined Jul 18, 2013
23,906
I agree, but you cannot parallel connect all three to 240v 1ph with N to the star point in that set up.
You will over-current the elements.
Unless it was intended for 380v 3ph
 

Ian0

Joined Aug 7, 2020
3,754
I agree, but you cannot parallel connect all three to 240v 1ph with N to the star point in that set up.
You will over-current the elements.
Unless it was intended for 380v 3ph
If they were wired star, then each element would have been getting the phase-to-netural voltage.
I don't quite know which country it came from or where it is being used, but red-yellow-blue looks like an old British colour code (in which case it would be expecting 240V ph-n or 415V ph-ph. However, the transformers are labelled 220V.
 

LesJones

Joined Jan 8, 2017
3,570
Disconnect one of the three wires from the heater terminal and measure the resistance between that terminal and the star point. As you say the total power rating is 6 Kw each element must be 2 Kw. With that information we can work out the voltage required across each element. (That will be the phase to neutral voltage the way it is configured at the moment.)

Les.
 

Thread Starter

Serfdumb

Joined Jun 18, 2021
7
Are the heating elements wired star with no neutral? I see only three wires in the photo, and three terminals commoned.
If so, that star point needs to go to neutral when the lives are commoned.
The transformers are phase-to-neutral because they are labelled “220V”, not “380V”
If you connect the commoned point of the three to neutral and power all three elements with 240v 1ph then they could be over-powered, as they all go to a star point indicating a series connection.
There was a very similar post here a couple of weeks ago with a pool heater similar arangement.
yes I found that post, this is how I was planning on wiring the heater elements 1624122565289.png
 

MaxHeadRoom

Joined Jul 18, 2013
23,906
yes I found that post, this is how I was planning on wiring the heater elements

"If you connect the commoned point of the three to neutral and power all three elements with 240v 1ph then they could be over-powered, as they all go to a star point indicating a series connection.
There was a very similar post here a couple of weeks ago with a pool heater similar arrangement"
(MaxHeadRoom).
With what voltage supply?
 

Thread Starter

Serfdumb

Joined Jun 18, 2021
7
If they were wired star, then each element would have been getting the phase-to-netural voltage.
I don't quite know which country it came from or where it is being used, but red-yellow-blue looks like an old British colour code (in which case it would be expecting 240V ph-n or 415V ph-ph. However, the transformers are labelled 220V.
It is from India, and being used in the us, thank you guys for all the replies this community is amazing. I’m wondering if it would be easier to just buy a vfd and run it on three phase?
 

Ian0

Joined Aug 7, 2020
3,754
No need to - looking at the first photo, I see 6 element connections, three are commoned. That indicates that they are 220-240V elements, wired in star, although the star is not connected to neutral. If they were 380-415V elements wired in delta, there would be three pairs of connections.
So the red-yellow-blue wires go to live, and the common terminal where the three elements join goes to neutral.
(This is not entirely surprising, as there probably IS a single-phase version available, and the manufacturer would not want to stock both 230V elements and 400V elements)
I hope that those 220V transformers don't overheat on 240V, but they would not be too much trouble to replace by 240V-rated ones.
 

Thread Starter

Serfdumb

Joined Jun 18, 2021
7
No need to - looking at the first photo, I see 6 element connections, three are commoned. That indicates that they are 220-240V elements, wired in star, although the star is not connected to neutral. If they were 380-415V elements wired in delta, there would be three pairs of connections.
So the red-yellow-blue wires go to live, and the common terminal where the three elements join goes to neutral.
(This is not entirely surprising, as there probably IS a single-phase version available, and the manufacturer would not want to stock both 230V elements and 400V elements)
I hope that those 220V transformers don't overheat on 240V, but they would not be too much trouble to replace by 240V-rated ones.
Thank you all for your patience, this has me scratching my head. The feed wire for PCB comes off one of the 3phase legs and goes to primary side of transformer which is labeled 110v, with the other wire on primary side of transformer going to neutral. The secondary side is labeled 220v. Why would they step up from 110 to 220? Wouldn’t the single leg tap already be @220? Could this be wired for 110 3 phase, it makes no sense to me
 

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LesJones

Joined Jan 8, 2017
3,570
If the device originated in India the 3 phase supply would have been 400 volts(Between phases.) at 50 hz so I would expect the elements to run on about 240 volts. As it will be used in the US 240 volts 60 hz is available so the elements could just be run in parallel. (I think it is worth measuring the resistance of an element to see if it ties up with the 6 Kw rating.) The fact that the transformers will now be running at 60 hz will reduce the problem of them running slightly above their rated voltage.
This ONLY make sense if there was a neutral connection to supply the transformers. It would also be interesting to know the contactor coil voltage rating.

Les.
 

Ian0

Joined Aug 7, 2020
3,754
If the device originated in India the 3 phase supply would have been 400 volts(Between phases.) at 50 hz so I would expect the elements to run on about 240 volts. As it will be used in the US 240 volts 60 hz is available so the elements could just be run in parallel. (I think it is worth measuring the resistance of an element to see if it ties up with the 6 Kw rating.) The fact that the transformers will now be running at 60 hz will reduce the problem of them rubbing slightly above their rated voltage.
This ONLY make sense if there was a neutral connection to supply the transformers. It would also be interesting to know the contactor coil voltage rating.

Les.
I think India is 240V so 3-phase would be 415V (but we're splitting hairs here) because the British built it before the EU made us re-label the UK supply as 230V.
There must be a neutral connection to the transformers, as they are 220V transformers. Try finding an off-the-shelf transformer with a 400V primary!
Good point about the transformers on 60Hz.
Contactor coil voltage rating is the only sticking point.
 

Thread Starter

Serfdumb

Joined Jun 18, 2021
7
Good luck. !
I think India is 240V so 3-phase would be 415V (but we're splitting hairs here) because the British built it before the EU made us re-label the UK supply as 230V.
There must be a neutral connection to the transformers, as they are 220V transformers. Try finding an off-the-shelf transformer with a 400V primary!
Good point about the transformers on 60Hz.
Contactor coil voltage rating is the only sticking point.
This is the reply when I asked what voltage the unit was wired for “The unit is designed as per USA Standards 110 volts three Phase.” This company is a joke, lesson learned about buying from India I guess. The resistance on each heating element is 8ohm
 
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