SSR for Class 1 Div 2
SSR for Class 1 Div 2
(OP)
I need to source a SSR for a class 1 div 2 installation. The SSR will be installed inside a plastic enclosure. Fun part: I need to switch 30 amps /480 VAC
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RE: SSR for Class 1 Div 2
RE: SSR for Class 1 Div 2
Operahouse is correct on the box.
I don't see how that is going to work since the SSR will develop heat. Assuming 3 phase.
3V x 30A x 3 = 270W
That is very hard to get out of a metal box. Out of a plastic box? Dang near impossible!
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: SSR for Class 1 Div 2
I would say 100 - 120 W total losses at full load. OK, that's also a lot of heat. But it should be possible to get it out of a plastic enclosure. It may have to be a little larger than you want it to be. But it should be possible.
Gunnar Englund
www.gke.org
RE: SSR for Class 1 Div 2
RE: SSR for Class 1 Div 2
RE: SSR for Class 1 Div 2
Why do you need an SSR? It is not uncommon to use an electromechanical contactor housed in an Ex'D' flameproof enclosure (explosion proof to the US). These are available more readily from commercial sources.
You will probably (i.e. almost definitely) find that the cost of a standard contactor in an Ex'D' enclosure is substantially cheaper than trying to gain one-off hazardous area approval for something you build yourself. In the UK this is time--consuming and expensive. I doubt it is any different elsewhere.
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I don't suffer from insanity. I enjoy it...
RE: SSR for Class 1 Div 2
The customer has indicated that an Explosion Proof enclosure is unacceptable. One train of thought was to employ a hermetically sealed switch/contactor inside the plastic/terminal enclosure. Locating a cost effective 22 amp hermetically sealed switch has proven to be difficult at best.
Thanks
RE: SSR for Class 1 Div 2
2HD = 2x96 = 192
2WD = 2x96 = 192
HW = 256
= 640sq.in., roughly what you need in steel.
Plastic (assuming PVC) has roughly 60% of the heat transfer coefficient of steel, so the box exposed surface area needs to be 60% larger in that material:
640/.6=1066 sq.in. and if you go backwards through the steps from there you will end up with a plastic box that is 24x20x6 for that little 30A SSR.
After all that, you still need to find an SSR that has a Cl.1 Div.2 rating. I don't know of any. Notice BTW if your ambient is 40C and the relay is rated 40C, no box size will suffice! You will then also need to find an SSR rated for 50C enclosed, another difficulty.
Mercury displacement relays are available in Cl.1 Div.2 in that size range easily. They have virtually no heat dissipation and if already listed as Cl.1 Div.2 they can be put in any environmentally suitable box. RoHS may preclude you from using them now however, you would need to check into that.
http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: SSR for Class 1 Div 2
RE: SSR for Class 1 Div 2
I think you might be thinking of Cl.1 Div.1 applications where the explosive vapors are present all of the time. Cl.1 Div.2 is only in unusual circumstances and hermetically sealed relays are widely acceptable there.
http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: SSR for Class 1 Div 2
Have you asked the customer what they propose as an alternative and asked for suggested suppliers? It is all too easy for a customer to state what they don't want, and leave you with a spec which is either impossible or impractical to meet. I think you're in the latter position - technically possible, but impractical to implement.
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I don't suffer from insanity. I enjoy it...
RE: SSR for Class 1 Div 2
The customer is infatuated with the plastic enclosure. It is sort of their "brand". It is used in their hazardous and nonhazardous installations. In the past, for their 11.0 Amp application they have used a mechanically actuated hermetic microswtich. Now they are asking for the 30A model, no luck locating a commercially available/cost effective switch.
scottyUK your last statement should be my signature at work!
RE: SSR for Class 1 Div 2
http://www.mdius.com/relays.php
If you scroll down this web page, you'll see that the 35-60A relays can be ordered as Class 1 Div. 2 by adding an "X" to the part number. Just double check your group numbers too.
http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: SSR for Class 1 Div 2
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com