mini-split load management

[EdT]

I recently installed a pair of mini-splits in my new two story shop building. My power company provides an incentive for allowing them to install load managers on AC systems so they can better manage the peak loads during the summer. They were not able to do so on the mini-splits because, unlike a "conventional" system, the control circuit runs at line voltage and the load manager is set up to interupt the "normal" low voltage control signal to the contactor for the compressor. Anyone have a solution for this problem?

 

[alecmcmahon]

I recently installed a pair of mini-splits in my new two story shop building. My power company provides an incentive for allowing them to install load managers on AC systems so they can better manage the peak loads during the summer. They were not able to do so on the mini-splits because, unlike a "conventional" system, the control circuit runs at line voltage and the load manager is set up to interupt the "normal" low voltage control signal to the contactor for the compressor. Anyone have a solution for this problem?

Is there load manage simply a 24 volt feed that they turn on and off at their will?

I suppose a 120v or 220v(whatever you ac is ) contact with a 24volt control inline between power feed and A/C would work.

If they are supplying the 24volts when they are allowing you to run it, it will pull the contact in, and when they kill the 24volts during high peak times it will release the contact killing the power.

 

[Jackfre]

While not familiar with the details of your local program, I'd suggest finding out what the actual power curve is on the particular units you own and submit them for consideration. With the possible exception of water source heat pumps, nothing comes near the system efficiencies of the best mini-splits. What make and models do you have?

 

[EdT]

I'm not an A/C expert, but I think a conventional system uses 24 volts for the control circuitry. So, when the t'stat asks for cool a 24volt signal is sent to the contactor for the compressor which is energized by the 24 volts and switches the 240 to the compressor "on". The load management system is a radio activated switch that simply interupts the control signal to the compressor for a short period of time. This allows the power company to reduce their demand at peak times and the "off" period is brief enough that it is not easily noticed by the user. On the mini splits I have, the control is accomplished by line voltage which is switched inside the indoor unit and sent via some 14Ga. wire to the coil in the contactor to switch the compresor "on". My guess is that the 240v control voltage is not compatible with the standard switching capability of the remotely operated load manager. So, I thought that someone may have already crossed this bridge and could tell me if such a device exists.

 

[klhitman]

i see what your problem is. i would add a line voltage transformer to 24 vac and a 24vac relay and run your your line voltage trough the NO contacts and then come off your transformer(hot side) to your local power conservation box the back to the coil side of the relay and take the common straight to the other side of the relay coil and that would kill you line voltage. in theory doing the same thing as a normal 24 volt system.

if i had a good skills drawing i would make you a drawing

 

[VHF]

Load managers that can directly switch 240VAC loads do exist... I have one on my electric water heater.*

The type normally used for central A/C just has a dry contact relay which is opened to interupt the 24VAC control signal to the outdoor compressor/fan unit. The indoor fan is left running so at least there is air circulation even though the cooling has been interupted. This would not be the case with interupting 240VAC power to your mini-split.

If you utility also does water heater load management they might able to configue one of the 240VAC load managers to the air conditioning "program" to use with your mini-split.

*(My utility provided a 50 gallon Marathon super-insulated lifetime warranty water heater for free in exchange for being able to switch it off for up to 4 hours during peak loads. They usually switch it off from 5:30pm to 9:30pm on hot days when everyone is running their A/C and their electric stoves at the same time.)

 

[EdT]

Thanks for the feedback. I'll check and see if they offer load management for water heaters. I can coble up something witha 24volt relay etc. the problem there is getting the utility to accept it. They, understandably, deal pretty much with cut and dry stuff and they're not very adventuresome.

 

[brewchief]

I would start with a call to the manufacturer of the mini split, I bet you're not the first person to run into this problem and they may have an easy solution.