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SPST relay with multiple coil contacts (A or B, OR: A and B)

SPST relay with multiple coil contacts (A or B, OR: A and B)

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  #1  
Old 03-10-14, 03:08 PM
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SPST relay with multiple coil contacts (A or B, OR: A and B)

Hi everyone, I'm running a dedicated 20A circuit to a portable A/C unit in a telecom/server closet and right now I was controlling with a timer (Hydrofarm TM01715D) and powering off at night for utility savings however the room is getting too hot and passive ventilation hasn't been enough so I'd like to setup a way of controlling the power either via the timer or via a thermostat control.

Back in my college days I used to work with HVAC and control systems with 24v relays for all kinds of things (AC, duct actuators, clocks, etc) except that was a long time ago and I'm really not sure if what I'm looking for exists.

This is for my home so I'm on a shoestring budget and since I already have the timer I was going to look at getting an Elitech STC-1000 and looking for 120VAC relays. Problem is I don't know if such a relay exists for what I'm looking to do.

I want to have my line come in and I'll add a junction box to wire up the thermostat and timer, and I want their output to drive relays which will inturn drive a main relay but I wasn't aware of a relay which was SPST and had multiple coil controls such that I could say Timer OR Thermostat OR BOTH.

I've attached a diagram, if anyone knows of a relay that does what I'm thinking please let me know.

Thanks in advance!
 
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  #2  
Old 03-10-14, 05:15 PM
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Sure would be easier to use a programable thermostat and a fan center with built in relay ,you would power the fan center with 120v,use the relay to power your outlet and you would have the 24 volts to power the Tstat. You could probably find a fan center on Ebay.New Honeywell R8285A 1048 Furnace Fan Center Transformer Relay | eBay
 
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Old 03-10-14, 05:48 PM
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You could use some diodes and drive a DC relay to get either or both to run it.
 
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Old 03-11-14, 05:30 AM
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If your timer is already set up to work the a/c, just install a line voltage thermostat paralleled with the timer and avoid using relays and contactors.
 
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Old 03-12-14, 03:41 AM
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Portable a/c units have a built in thermostat that work fairly well.
Why not just plug in the unit and set the thermostat?

Some units have an econo setting that will shut off the fan when the temp is satisfied.
 
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Old 03-22-14, 06:36 PM
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Thanks for the reply, I was looking for something to run the thermostat controls independent of the timer. I want it to always run from 6:45a to 10:45p, but at night since it's in my guest room closet I want to limit it's operation to only turn on when my custom cabinet with servers, networking equipment get too hot (78 deg F room temp is about 98-102 on my CPU in the cabinet). This not only to try and get some utility savings but hopefully to be less interruptive on my guests sleep.

I let the thermostat on my A/C unit run at 69 for the room temp and during the day my CPU in my hotest server stays at around 71-72 F.

The problem is the cabinet I built was designed to limit noise and I didn't build enough airflow into it to just use passive cooling in the closet at night. Here's a pic of it not quite finished, still another tower to go in the bottom and several Small Form Factor systems in the top cab.
 
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Old 03-22-14, 06:40 PM
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Thanks for the reply, I have the Tripplite SRCOOL-12K and unfortunately it does not turn off the fan even when the room is at the desired temperature
 
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Old 03-22-14, 06:47 PM
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So I picked up some items off ebay which I think will do what I need but before I hook it all up I was hoping someone could tell me if what I'm worried about might happen.

I got an NTE R04-11A30-120 DPDT D5 2 Form "C" which I plan to use with sources from my timer and thermostat but my worry is if both operate at the same time (say the room reaches 79deg and it's in the daytime when my A/C is already operating on the timer) will the poles if tied together create a 240V output? or since they are comming from the same circuit will they only be 120? I'm uploading a new attachment to show what I mean. [ATTACH=CONFIG]28737[/ATTACH]
 
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Old 03-23-14, 04:43 AM
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Wirenut's suggestion in post #4 above is all you need to do. Anything else adds potential fail points.
 
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Old 03-23-14, 07:50 PM
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Thanks Rick, I saw Wirenut's suggestion, but I don't understand parallelled, and I was thinking he meant setting up in series such that the timer would supply the thermostat and that's not what I'm looking to accomplish.

I want for my Timer to power the Circuit in the daytime 6:45a - 10:45p and then cut off at night.

I want at night the Thermostat to power the Circuit only if the room temperature reaches a certain temperature.

Now that I've figured out my DPDT contacts and coils I realize that it likely won't do what I want, again I'm hoping to power the circuit to my 24v adaptor which will close the relay for the 20amp circuit.

Again I'm still trying to find a way for two different controls to run a coil and if there is such a relay in existence. My diagram in post #8 shows the neutrals hooked up to the control wires (took me a while to figure it out today with continuity and voltage tests because the relay block itself isn't labeled and while I'm sure it's obvious to skilled electricians who do this work day in and day out circuits to me are complex for anything beyond standard 120v outlets and a 240v appliance outlet)

I'm thinking a second timer to control the thermostat at night and connecting both my original timer and thermostat up to the coil controls only one should be energized at a time by the timing.

If I hook up two devices the same way does AC have any kind of backflow (not sure what it would be called, I'm thinking like a diode in DC, I guess it's called DIAC) that could create trouble at the timer or thermostat?
 
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Old 03-23-14, 08:11 PM
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I realized after I was just typing that last reply that I don't need to control the coil at night, I just need to use the NO contact.
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