Dual Thermostat wanted

[blacklight186]

Hi guys...

I'm searching for a Dual Thermostat to support equipment rated 220-240 VAC and 16A of current..

Stego ZR 011 almost meets my requirementshttp://www.electriciansforums.net/r...e/fileadmin/Bilder/PDF/English_US/ZR011us.pdf but it's rated only 10 Amps ...

I've searched the Farnell and RS websites...

Could someone suggest a manufacturer please? At this point, I would be willing to go for two single thermostats of that rating if dual is not available..

Thanks!

 

[Mr Brady]

Hi, don't know of a suitable thermostat but how about using contactors? Merlin Gerin make mcb sized, DPx20a that din rail mount.
They even do a normally closed version.

 

[blacklight186]

actually the device is to be placed betwen a 220-240 VAC supply and a UPS rated for 220-240 VAC and 16 amps... The UPS powers my company servers... UPS+servers are in an air-conditioned room...

when the temperature of the room reaches 30 degrees, I want an indicator light/buzzer to go off... when the temperature of room reaches 40 degrees, I want the device to trip the supply to the UPS so that the UPS will auto-shutdown our company servers...

actually such an incident happened recently where the air-conditioning in the server room failed.. so we want to prevent server damage from overheating...

thats why I thought of using a thermostat.. I'm not sure if contactor could be used here?...

 

[Mr Brady]

Hi there, well the light/buzzer side of it is straightforward enough, you could even incorporate an autodialler if the place is'nt occupied 24/7.

The idea with the contactor is that it carries the 16a load and is in turn controlled by the thermostat, but I would suggest you include a manual reset button, or have very large, clearly worded signs as when the temperature dropped the ups would power up again, with a potential risk to life (I have the scars to prove it).

Interrupting the supply to initiate an orderly shutdown sounds a bit "brute force" have you checked the ups installation manual ? it may have a subtler means of shutdown control.

Hope this helps, Richard.

 

[blacklight186]

mister brady i'm a bit confused... regarding the tripping above 40 degrees... you're saying that the wiring is 240VAC to contactor and contactor to the UPS and inbetween somewhere comes the thermostat acting as a switch for the wiring? in that case shudn't the thermostat also be rated 16 amps..

which means you're saying that I should go two single thermostats (as I'm not able to find dual thermostats for 16 amps)

and i'm a bit confused about how the wiring you meant is done.. could you please clarify?

thanks

 

[Mr Brady]

Ok, a contactor is an electrically operated switch designed to control currents that are too heavy for a normal switch to cope with.
So as you said the circuit passes from the mcb through the contactor then on to the ups, from the live side of the contactor (mcb side) you would take a feed to the thermostat, the switched live returning from the stat connects to one of the coil terminals on the contactor the other terminal is connected to neutral.

So that's the basic circuit (not including manual reset button), looking at the pdf of your chosen stat you would connect to load one (heating) as upon rise of temperature it would open causing the contactor to disconnect the ups.

Load two (cooling) would be used to raise the alarm as it closes on rise of temperature.

As a ups is a 24/7 piece of kit and these controls would'nt operate (hopefully) very often, for long term reliability, it would be best to use a normally closed (breaks upon energising) contactor and a different stat, (designed for cooling), one which closes on reaching 40c
The basic circuit would be the same, has that cleared things up or have I confused you more!
Taking another look at the pdf, model no:01176.0-00 would appear to be suitable for a normally closed contactor
Richard