Pottery kiln - what size contactor

Thread Starter

jevpots

Joined Jan 15, 2020
14
I'm having to replace a contactor in a pottery kiln. All the manufactures info is rubbed off the old one. It is a 2 pole NO with 240v coil. The kiln is rated at 6.5Kw and uses two banks of elements for the heating. Each bank is switched by one of the contactor poles.
The old contactor looks the same size as commonly seen 20 amp DP contactors. However, 20 amp, to me, seemed on the low side. I'm not clear if the 20amp spec refers to the whole contactor or if each pole is rated 20amps - in which case it should be ok. I could go for a 40amp contactor but that would take up more space which is already quite limited. Grateful for any thoughts.
 

Reloadron

Joined Jan 15, 2015
7,546
The kiln is rated at 6.5Kw and uses two banks of elements for the heating.
So my read is a Total of 6.5 KW for the elements as in 3.25 KW for each element? Should that be true I get 6500 watts / 220 volts = about 30 amps or each element about 15 amps per relay contact. You want a relay with the contacts rated for about 20 amps (leaving a margin having a 220 volt coil. You likely want: Open-Style Relay, DPST-NO, 6 Terminals, 240V AC Input as I am not seeing any 220 volt coils. A Google of "open-style relay dpst-no 6 terminals 240v 240vac relay" should bring up plenty of hits including relays (or contactors) with your rated load current. I am also assuming you want open frame type relay or contactor?

Ron
 

Thread Starter

jevpots

Joined Jan 15, 2020
14
Many Thanks for your speedy reply Ron. You've sorted my confusion and confirmed that the 20amp rating refers to each contact and not the whole device. Yes easy for me to source the 20 amp version. Thanks again John
 

Reloadron

Joined Jan 15, 2015
7,546
For longer contact life, I would go with 30A contacts, unless that significantly increases the price.
Now that you mention it I have likely seen more 30 and 40 amp contactors as being more common place. I found a 3 phase 40 Amp old Potter and Brumfield laying in my assorted junk but it has a 120 volt coil. P40P42A12P1-120 . About had a coronary seeing what these things cost these days. :) Keep thinking I have more of these things around here somewhere. :) Unfortunately 120 volt coil.

Ron
 

drjohsmith

Joined Dec 13, 2021
852
Yes - Its only the live feed to each element bank which is switched. The neutrals are joined and unswitched. Is that what you mean?
FYI
Don't get a un branded part,
From say China.
This thing is probably going to be in a warm place,
And I've seen some real bad cheap relays, rated 20 amps, but turn out to be re branded 10 amp parts.
Pay the money, do it once.
 
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