Advice on Customer Request

I will be replacing a server on a large process line and the server cabinet is on machine. Summer ambient is about 110F max



For cooling they want 2 small Hoffman AC Units (1 can handle the heat load)and the proposed ac units have the remote management so you will get a notification on the HMI as well as an email with any temp related issues.

They want to do something like a lead lag with these so that the lag cycles 1 time for every 15 times of the lead.

The ac unts have there own built in thermostats to cycle them on / off

So I need a way to do the lead lag setup and I need to give an alarm if doors are open because I don't want to tun the AC off with an open door like your normally would since the server needs the cooling all the time.

I was thinking of a small AB plc with 2 of these wall mount temp sensors http://www.omega.com/googlebase/product.html?pn=EWS-RTD&gclid=COn3vdmNssQCFVU2gQodTSgAXg
going to analog Inputs as well as both door switch as inputs and do lead lag logic in the PLC and have relay outputs cl;ose the dry contact door switch inputs an each unit as the unit will not run if the door switch contact is open.

Looking for any other thoughts, Ideas or advice. Moving server cabinet to a different location or to a server room is not an option in this case.

maybe install Air Curtain at the door

osmanmom said:

maybe install Air Curtain at the door

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Thanks but I don't think that will fit the Bill for these guys.

Which model of A/C unit are you using?...could just hard wire to the thermostat depending on which one you're using.

RET said:

Which model of A/C unit are you using?...could just hard wire to the thermostat depending on which one you're using.

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It willl be Hoffman Spectracool units. They don't dave any terminations fro external T-Stats.

External T-Stat alaone will not solve the laed lag requirement.

The Plc Kid said:

It willl be Hoffman Spectracool units. They don't dave any terminations fro external T-Stats.

External T-Stat alaone will not solve the laed lag requirement.

Click to expand...

Don't be pedantic.

The idea was that if the unit supplied customer connections, you could supply the thermostat contacts through the PLC you had in mind, then with a cabinet RTD you could control the operation of the two units.

Good luck.