I work at a piantball field and now that it is winter we are closing for the season. I have a 5kW heater and a 5000psi(not sure of the W) air compressor i need to put on a relay so that the heater goes on when it needs to and automatically shut off the compressor if it is running to save energy. not sure what i need to do this.

thanks guys

More info needed. If closing for the season, why is it necessary to maintain operation of the air compressor?

We are closed for the season but the compressor still needs to run because we do fix paintball markers/fill air tanks for a price, it just isn't used nearly as much as when people are filling their tanks up all day in summer and the heater doesnt need to be on.

I need to know what kind of device would allow me to do this, I would most likely be able to do the electrical part on my own.

Thanks!

Well, your probably talking about a 3 phase 5-6 HP motor. Hopefully you already have a motor starter and 3 phase protection already on the wall for this unit.

Without knowing what you have to work with, a 5-6 HP motor starter will be expensive. If you can interrupt the wires to the pressure switch (providing it is a switch) that may be one way of doing it. Since this compressor may also have sophisticated controls, like a pressure unloader, you have to carefully pick where you have to interrupt the circuit. The pressure switch is the most likely place.

You also need to know what voltage your interrupting at this point, 120 vac, 24 VDC, 208 VAC etc. and the currents the coil is interrupting. I doubt that the pressure switch is handling the motor directly like it would for 100 psi shop air.

Next problem is the heater. 5 KW isn't a lot of heat, so I suppose it's not the space. Again, you need to know how it's controlled and be able to sense when it's on. If this was a simple home heating system, the 24 VAC is usually applied to the W terminal when it's heating. You can also sense current, so your not making changes to anything except putting a wire through a contactless sensor.

Now, with a large compressor, you will have to build in an anti-short cycle system, so it can't come on right away. The unit may already have this. Pressure differentials (turn on/turn off) also provide it although won't with a power failure. So, again we are at somewhat of a loss.

I suppose your being billed by peak usage and not straight KWH.

The duty cycle of your heater may matter as well. How long is it on/off for? Redesigning it to use proportional control, if possible could also reduce your electric bill overall.

Again heater can mean space heater, water heater, building heater and compressor usually means some wimpy thing compared to what "we think"it is.

PB compressors can get fairly complex, such as this one with a PLC (Programmable Logic Controllers). http://www.bauercomp.com/uploads/pdf/MI%20mini%20&%20MAXI%20VT.pdf

The manufacturer of the compressor should probably be consulted once you know how, your going to determine the heater needs to run.

the compressor runs when the regulator gets down to a certain pressure and fills 3 bulk tanks to 4500psi because thats what we fill our paintball tanks with. It is wired directly into a 60amp breaker using 240volts (p=60x240=14.4kW?), . Its huge (probably 5f wide, 5f long and 4f high).

The only protection we have for the compressor that I know of is the breaker, I have no clue the power of the motor or the size. the label is really worn out and alot is unreadable.

We only have the shop(staff area) heated, it is wall mounted and just blows out hot air, we have set it to keep the room at 18 degrees, it runs here and there for a little while. The shop is properly insulated so it stays warm and only turns on when the temperature gets below 18.

Dunno if any of this helps, but thats all the info I have :S

This is a way of sensing whether the heater is operating or not. Ssac ECS41BC Universal AC Current Sensor (http://www.drillspot.com/products/43004/Ssac_ECS41BC_Universal_AC_Current_Sensor)

Placing a relay like on the fan power, the thermostat can sense whether or not the heater is on.

The compressor might then be single phase 208. Next you have to determine how the pressure switch is hooked up.

Does the pressure switch directly switch the power?
Is the compressor single or 3 phase? What voltage? What HP?
Any fancy controls besides a pressure switch?

Motors, especially 3 phase ones, that are expensive are usually protected with motor starters such as these. http://www.grainger.com/Grainger/nema-combination-starters/electrical/ecatalog/N-8fe/Ntt-5+hp+motor+starter?op=search&sst=All

It gives you an opportunity to add other controls in there as well and provides a disconnect at the equipment. Overloads can be solid state or sized for the motor. Solid state controls can do the three phase protection as well. Control voltages can be set with other transformers or power supplies, whether it be 120, 208, 24 vac or 24 vdc.