Can I remotely control a compressor using a Electric heater relay?

[Mr_fixit]

This is a question similar to another thread about using a thermostat relay to control a heater..., but with a different twist.

I MAYBE want to control my compressor in the detached garage about 100' from the house via a low voltage WIRED switch, or set of 2 switches, wired like a three way. Here's my idea. Will it work?.

I want to use a relay with the specs similar to those listed below that would normally switch on 30 amps of 240 volt electric heaters, by a single low voltage thermostat.
But , instead of using a thermostat, I can use a pair of low voltage 3 way switches, so I can operate the compressor either when I'm in the detached garage, from the garage, or when I'm in the house, since the house has air line plumbed into it from the detached garage. My compressor uses 30a 2 pole breaker (240volts).

Here's the specs, and the relay link https://www.supplyhouse.com/Honeywe...8rZ4yfa5_8sUoowf97WCzcf76EgSQ2i0aAgPyEALw_wcB
to the relay, ( WhicH I already have):

Use with two-wire, 24 Vac thermostat to control electric heating equipment such as baseboard, ceiling cable and duct heaters.

Specifications
Heater Relay with Spst switching
Switching: SPST
Electrical Connections (main): Leadwires
Electrical Contacts (Full Load): 7.0 A @ 208 Vac, 240 Vac, 277 Vac; 14 A @ 120 Vac
Electrical Ratings, Contacts (locked rotor): 42 A @ 208 Vac, 240 Vac, 277 Vac; 84 A @ 120 Vac
Electrical Ratings, Contacts (resistive): 22 A @ 120 Vac, 208 Vac, 240 Vac; 19 a @ 277 Vac
Frequency: 60 Hz, 50 Hz
Dimensions: 3 7/8 in. high x 2 13/16 in. wide x 1 1/2 in. deep
Temperature Ratings: -20 F to +150 F
Includes: Enclosure w/conduit bushing and integral transformer; dual load.

Features
Operate with each cycle of the thermostat (4 to 6 cycles per hour).
Each relay switches up to a 5,000 W load.
Contacts make and break in about 75 seconds.
Mount in any position.
Includes 1/2 in. (13 mm) male conduit bushing.

 

[Radix2]

How many actual HP is your compressor?

You can definately do what you want, that is a really expensive single pole relay with a long built in time delay that you don't need.

You should also use a 2-pole relay since you want the motor completely disconbected from power when off ( with your singe pole relay, the motor will always be at 120 v when off and test could be dangerous if you don't realize it.)

Look for a 2 pole defined purpose contactir(relay) with a 24v coil in the HP you need --$15-30 ( you will need a 24v transformer too).


For example this one is rated to 3hp - https://www.amazon.com/dp/B06X8Z255M/?tag=atomicindus08-20

 

[matt_i]

Sounds like you want a 4 way circuit....in other words, 3way, 4way, 3 way switches with the loop eventually going to the contactor. It could be 24vac with a HVAC transformer, 24vDC with a power supply, or simply 120vAC. Just choose your coil voltage as equivalent.

I do this exact same thing with my phase converter. There are 4 locations that all can turn it on or off. So I am running a 3way, 4 way, 4 way, 3 way in loop fashion which closes the contact on an ice cube relay. The dry contact going closed is what starts the phase converter.

Here's a control station, the ice cube relay and a wiring diagram. All of the indicator lights illuminate for notification. Sorry about the scratchy diagram...

 

[alfredeneuman]

Does the compressor motor have internal overload protection?

If it does a simple HP rated contactor will work.
If not, then you will need a genuine motor starter with the proper overloads for your motor.

 

[Git]

If your interested, and I don't want to get off track, but I think it is easier to use a motorized ball valve to shut the air off at the compressor which you could then control with a number of different devices - z wave switch, wifi switch, etc

 

[Mr_fixit]

If your interested, and I don't want to get off track, but I think it is easier to use a motorized ball valve to shut the air off at the compressor which you could then control with a number of different devices - z wave switch, wifi switch, etc

Ok, I'm already using this, Problem is I leave on the compressor, and remotely turn the electric ball valve on & off, using x-10. Problem is there's so many connections of air lines and quick disconnects, tire machine, sand blaster, underground lines in multiple buildings and to a pole outside that a small amount of air always leaks and I can't keep them all from leaking. so the compressor might cycle on and off all day long. So I now want to turn the compressor on & off, instead of what I thought would work better. (that doesn't)

 

[Mr_fixit]

Does the compressor motor have internal overload protection?

If it does a simple HP rated contactor will work.
If not, then you will need a genuine motor starter with the proper overloads for your motor.

Ok, maybe this is simpler than I thought, I have a 5hp (true) baldor motor aka Frankencompressor, that does already use a proper magnetic starter. I just don't understand how magnetic starter circuits work in my head.

I understand 3 & 4 way switches, completely, though. so maybe I can control the magnetic starter with a 120 volt wired 3 & 4 way setup?

Help me understand...?

 

[Mr_fixit]

How many actual HP is your compressor?

You can definately do what you want, that is a really expensive single pole relay with a long built in time delay that you don't need.

You should also use a 2-pole relay since you want the motor completely disconbected from power when off ( with your singe pole relay, the motor will always be at 120 v when off and test could be dangerous if you don't realize it.)

Look for a 2 pole defined purpose contactir(relay) with a 24v coil in the HP you need --$15-30 ( you will need a 24v transformer too).


For example this one is rated to 3hp - https://www.amazon.com/dp/B06X8Z255M/?tag=atomicindus08-20

I should probably take a pic of what I'm already using...

 

[Mr_fixit]

Frankencompressor pics:

 

[walta]

The relay you linked to is not rated for use with a motor. If you used it to switch the motor current it would likely work for a while but fail before long.

From your photo it looks like the compressor has a motor starter. If you put the relay in series with the pressure switch your relay should work well.


Walta

 

[TRWham]

Contactors are high current capacity relays and are used whenever you want to control a high amperage load (usually a motor or heater) without switching the current directly through the control contacts, and are especially useful when you want multiple control inputs (e.g. pressure, temperature, manual switch, maybe a timer, etc.). A direct on line starter is a contactor that switches the full line current via a separate control circuit that energizes the contactor electromagnetic coil (thus the term "magnetic" starter). Starters usually have some form of current overload sensing and control (as yours does), but internally protected motors will not need that. Some starters provide reduced current starting for very large motors, but not in this case.

Who wired that starter and understands what it does and how it does it? In particular, what does that brown switch do? I am guessing it makes & breaks the control circuit to turn the compressor on and off, if so, perhaps you could simply use an X10 device in its place and achieve remote control. There are a lot of wires in that starter and it's difficult to trace them in the photograph.

Whatever you do, ensure the pressure switch (and any other safeties) remain in the control circuit. Otherwise, you could be running without pressure control and be solely dependent on the pressure relief valve.

 

[Radix2]

Since you have a motor starter(relay) already, you can either just put your remote switch in series with the coil of that starter ( then you will be switching line voltage) or, if you want low voltage put a small spst relay in series and run low voltage wiring to control it to your house.

No need for a new high current relay.

The idea above is a good one as well if you have x10 type of stuff in place

 

[wyliesdiesels]

Ok, maybe this is simpler than I thought, I have a 5hp (true) baldor motor aka Frankencompressor, that does already use a proper magnetic starter. I just don't understand how magnetic starter circuits work in my head.

I understand 3 & 4 way switches, completely, though. so maybe I can control the magnetic starter with a 120 volt wired 3 & 4 way setup?

Help me understand...?

Adding a heater relay is not needed and just adds unnecessary complexity.

A magnetic starter works the same as a relay. When the coil is energized, the contact armature is pulled in and completes the circuit between line in and the motor windings.

You could do the 3way/4way switch circuit as described above to turn the starter on and off. One caveat is the switches need to be rated for 240v or you can switch the coil to 24v and add a 24v control transformer.

 

[matt_i]

In my mind a relay, a contactor, a motor starter, a magnetic starter are all the same electromagnetic coil-operated device at heart. Its just a matter of the coil voltage, how much heat the contacts can take which more or less equates to the size of the device...ice cubes to NEMA-rated starters, and then little accessories like overload sections, which are a separate animal but are closely grafted on.

 

[wyliesdiesels]

Since OP has lots of leaks, he could also put an electronic solenoid valve on the line right after the air dryer(if so equiped) and remotely operate it from each desired location. This would cut down on compressor cycling.

 

[walta]

I think a relay connected to the pressure switch is necessary as I do not see a transformer in the motor starter so the coil in the motor starter is likely to 240 volts.

Personal I am more comfortable lower voltage circuits when spread around the building.

This relay costs a lot less and should work just fine in the control circuit.

https://www.amazon.com/dp/B000LEUJU6/?tag=atomicindus08-20


Walta