Split A/C unit

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SHEA 31979

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BROOKLYN, NEW YORK
I have not seen the unit yet but a customer told me his A/C guy was supplying his home with 2 - 208V, 15AMP units. This is a residential single phase home. Has anyone seen this before and if so how did you wire it just with two hot's and no neutral ? Again i haven't seen the units as of yet, just curious for some insight in this matter, thank you all for your responses in advance.
 
Funny, I will be wiring a couple of ductless splits tomorrow night.

All the ones I have done in the past along with the two tomorrow night have you bring a branch circuit out to the condenser outside and then from the outdoor unit you bring a feed back inside to the evaporator unit.


In my case it is 30 amp circuit to the outdoor unit and back in with a 15 amp circuit to the inside unit. You will really need to see the instructions before ordering supplies.

Oh yeah, I have never done one that needed a neutral.
 
SHEA L.U. #3 said:
I have not seen the unit yet but a customer told me his A/C guy was supplying his home with 2 - 208V, 15AMP units. This is a residential single phase home. Has anyone seen this before and if so how did you wire it just with two hot's and no neutral ? Again i haven't seen the units as of yet, just curious for some insight in this matter, thank you all for your responses in advance.
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no neutral needed. Most units I have seen were 208/240 volt.
 
iwire said:
Funny, I will be wiring a couple of ductless splits tomorrow night.

All the ones I have done in the past along with the two tomorrow night have you bring a branch circuit out to the condenser outside and then from the outdoor unit you bring a feed back inside to the evaporator unit.


In my case it is 30 amp circuit to the outdoor unit and back in with a 15 amp circuit to the inside unit. You will really need to see the instructions before ordering supplies.

Oh yeah, I have never done one that needed a neutral.
Click to expand...

I never even thought about running #14 to indoor unit. I like that!
I believe this can be done because it has a fuse protecting these wires inside the condenser correct?
 
The ONLY a/c units that I have inspected or installed that required a neutral have been gas split units where the blower is 115 volt.
(I seem to recall one min-split that had a separate 120v fan circuit years ago).
 
There are so many systems out there. Some units have a rubber cord that is to be run between the units while others need 240 V at both units and the a/c guys run the control wire. Generally with those units I run a wire to the outside disconnect and the wire to the inside unit is often run to the outdoor unit itself. Basically it is powered thru the outdoor unit.

You will probably need a dp switch in the wall near the inside unit as a disconnect. On a retro install they install the units as we wire them as you don't want to have to take the wall unit down.
 
Dennis Alwon said:
You will probably need a dp switch in the wall near the inside unit as a disconnect. On a retro install they install the units as we wire them as you don't want to have to take the wall unit down.
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Can you use a breaker lockout in lieu of the 2 pole switch?
 
infinity said:
Can you use a breaker lockout in lieu of the 2 pole switch?
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I am not sure but I do believe that some areas will not allow it since it is part of the HVAC-- In that case I would say no. Now some units may have a small enough motor that no disconnect is required.
 
Dennis Alwon said:
I am not sure but I do believe that some areas will not allow it since it is part of the HVAC-- In that case I would say no. Now some units may have a small enough motor that no disconnect is required.
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And as far as input voltage rating is concerned, some few (and I wish there were more) mini-splits contain an internal inverter/VFD to allow the compressor to be run at reduced speed. Since those will be rectifying the input AC anyway they can be designed for a wider voltage range without tap changes OR changes to their cooling rating.
 
GoldDigger said:
And as far as input voltage rating is concerned, some few (and I wish there were more) mini-splits contain an internal inverter/VFD to allow the compressor to be run at reduced speed. Since those will be rectifying the input AC anyway they can be designed for a wider voltage range without tap changes OR changes to their cooling rating.
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Do they vary compressor speed or just switch a valve making a different refrigerant circuit effectively making a two stage compressor?
 
kwired said:
Do they vary compressor speed or just switch a valve making a different refrigerant circuit effectively making a two stage compressor?
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The descriptions I have seen imply that the compressor speed is changed and do not mention valves. A side benefit is a very soft start which is advantageous for off-grid PV systems.
 
GoldDigger said:
The descriptions I have seen imply that the compressor speed is changed and do not mention valves. A side benefit is a very soft start which is advantageous for off-grid PV systems.
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I haven't had a lot of experience with mini systems, but with the higher SEER larger systems they are using what they call two stage compressors. The compressor isn't really two speed they just switch a solenoid valve in the refrigerant circuit to get two different performance levels out of the system.
 
kwired said:
I haven't had a lot of experience with mini systems, but with the higher SEER larger systems they are using what they call two stage compressors. The compressor isn't really two speed they just switch a solenoid valve in the refrigerant circuit to get two different performance levels out of the system.
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With a positive displacement compressor, the change in the refrigerant circuit would have to provide an easier flow for the refrigerant so that there would not be so much back pressure on the compressor at the same volume, or else they would have to also slow down the compressor. I will take a look at the specs I can find.
 
GoldDigger said:
With a positive displacement compressor, the change in the refrigerant circuit would have to provide an easier flow for the refrigerant so that there would not be so much back pressure on the compressor at the same volume, or else they would have to also slow down the compressor. I will take a look at the specs I can find.
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Not so certain about less pressure meaning less load on the motor, refrigerant compressors are loaded heavier when they are pumping more heat, more heat being moved usually equates to higher head pressure though.

Would really need to study the refrigerant cycle a little harder to understand this better, but that is exactly what my two stage heat pump has in it. A simple solenoid valve being switched on is all that is electrically different between stage 1 and stage 2. The rest is in how the refrigerant circuit responds to that action, the compressor is a single speed PSC motor.
 
Dennis Alwon said:
There are so many systems out there. Some units have a rubber cord that is to be run between the units while others need 240 V at both units and the a/c guys run the control wire.

You will probably need a dp switch in the wall near the inside unit as a disconnect. On a retro install they install the units as we wire them as you don't want to have to take the wall unit down.
Click to expand...

How can rubber cord be used for a permanent wiring method?

The instructions with the units I have seen say a disconnect must be provided near the unit.

But there is a 3-wire interconnect, so can it be done with a double-pole switch?
 
shortcircuit2 said:
How can rubber cord be used for a permanent wiring method?

The instructions with the units I have seen say a disconnect must be provided near the unit.

But there is a 3-wire interconnect, so can it be done with a double-pole switch?
Click to expand...

I don't see how the cord is compliant. I believe when there is a 3 wire cord that the third wire is a signal wire that communicates between the 2 units. I have heard that the instruction state to use a 3 pole switch but other than that I don't see why the signal wire needs to be switched.
 
Dennis Alwon said:
I don't see how the cord is compliant. I believe when there is a 3 wire cord that the third wire is a signal wire that communicates between the 2 units. I have heard that the instruction state to use a 3 pole switch but other than that I don't see why the signal wire needs to be switched.
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If the signal wire is switching a 240 volt signal there would be backfeed from the other side of the 240 volts.
 
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