Line voltage wiring outside of heat pump condensor unit. I could use some help

[David Goodman]

I have a fan control pressure switch that for time savings and reduced cost would best be installed outside of a heat pump condenser unit at the suction line service valve. The switch goes in series with the fan control from the defrost control board. So, it is carrying one leg of 240V for the condenser fan motor.

The wires are marked as follows:

E172774 AWM STYLE 3175 XL PE 600V 125˚C 18 AWG LL84983 ....

Parts of those marking I understand.

Is there a code accepted way of installing this outside the condenser unit and running the wires inside?

If there is, then please point me in the right direction. It would cost several hundred dollars more to install it inside the condenser unit.

 

[iwire]

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Is there a code accepted way of installing this outside the condenser unit and running the wires inside?

Run the refrigerant line though an enclosure and mount the device inside that. Run LFMC from there to where it is supplied from.

Other than that I don't see a way.

 

[Stebs]

How would it save a lot by putting it outside? system will still have to be evacuated and the switch brazed in and system pulled down and recharged.

 

[David Goodman]

How would it save a lot by putting it outside? system will still have to be evacuated and the switch brazed in and system pulled down and recharged.

This can screw directly onto the service valve, or it can be put on a "t" if you still need to read pressures or add refrigerant at that point. So, no recovery, no evacuation, and no recharging of the system.

 

[David Goodman]

Run the refrigerant line though an enclosure and mount the device inside that. Run LFMC from there to where it is supplied from.

Other than that I don't see a way.

I had thought about the enclosure idea. I have no idea what UL listed enclosure could be used. I don't know enough about what is available. It would have to be something of a clam shell design. So that the refrigerant lines would not have to be cut in order to enclose the service valve all the way to the condenser unit case.

 

[iwire]

I had thought about the enclosure idea. I have no idea what UL listed enclosure could be used. I don't know enough about what is available. It would have to be something of a clam shell design. So that the refrigerant lines would not have to be cut in order to enclose the service valve all the way to the condenser unit case.

Can you get the same type of switch but with a 1/2" pipe nipple or coupling on it?

Here is an example of a solenoid valve, notice it has leads but they come out of a 1/2" coupling so you can thread fittings into it.

 

[David Goodman]

If there are any manufacturers of enclosures on this site, then please consider designing this part.

States like California have adopted mechanical or residential codes that include requiring "locking caps" on accessible service ports. This enclosure could be designed to meet the requirements of making the valves inaccessible. The locking caps cost about $10 each. An enclosure with a cost of of $20 would make it competitive with what is currently available, and it would serve the added purpose of enclosing the wiring for the switch I am discussing.

 

[David Goodman]

Can you get the same type of switch but with a 1/2" pipe nipple or coupling on it?

Here is an example of a solenoid valve, notice it has leads but they come out of a 1/2" coupling so you can thread fittings into it.

I was completely unaware that something like that could be threaded. That is awesome!

There are other styles of pressure switches, but ones I am familiar with are much more expensive. This part is under $15.00.

 

[StarCat]

Control Application Questions

Control Application Questions

I have a fan control pressure switch that for time savings and reduced cost would best be installed outside of a heat pump condenser unit at the suction line service valve. The switch goes in series with the fan control from the defrost control board. So, it is carrying one leg of 240V for the condenser fan motor.

The wires are marked as follows:

E172774 AWM STYLE 3175 XL PE 600V 125˚C 18 AWG LL84983 ....

Parts of those marking I understand.

Is there a code accepted way of installing this outside the condenser unit and running the wires inside?

If there is, then please point me in the right direction. It would cost several hundred dollars more to install it inside the condenser unit.

I have to question the application of a fan control to a heat pump because you can only use such on the cooling cycle. As thus, unless you have a way to insure that its not active during the heating cycle which seems unlikely based on the series wiring noted, the control should not be used.
Again, the only time you want the fan to cycle is during cooling mode, and definitely not during heating mode. Those controls also typically operate on the low voiltage side of the system.

 

[David Goodman]

I have to question the application of a fan control to a heat pump because you can only use such on the cooling cycle. As thus, unless you have a way to insure that its not active during the heating cycle which seems unlikely based on the series wiring noted, the control should not be used.
Again, the only time you want the fan to cycle is during cooling mode, and definitely not during heating mode. Those controls also typically operate on the low voiltage side of the system.

It is in the heating cycle that this application can actually be helpful.

In mild weather conditions, let's say 50 -65˚ F, the head pressure on a heat pump can built up high enough to shut the compressor down on high pressure. By cycling off the condenser fan when when the head pressure approaches the high pressure limit, the head pressure can drop back down and keep the compressor running. In heat mode, less air moves through the outdoor coil with the fan off. So, with less air moving, there is less heat transfer to the refrigerant. With less heat, there is lower pressure.

Since the pressure switch is on the suction line, it only sees high pressure in heat pump mode. The switch doesn't affect cooling mode.

I put one in yesterday as a test. It cycled just as intended. I should have been taking amp reading on the compressor while it cycled. I'm sure I would have seen a pretty healthy drop as the fan cycled off.

I think I found a cost effective way to move everything inside the condenser unit. So that no line voltage wires are left outside.

Thank you for your interest.