Wiring walk-in cooler/freezer

T

Therealcrt

Senior Member
Location
Kansas City
Occupation
Electrician
I’ll try to give as much detail as possible for this project bare with me and let me hear your input

Note; this specific cooler manufacturer says not to penetrate roof only through side walls.

This is an exterior walk-in that sits about 3 foot away from the building on a concrete pad. I stubbed out the circuits on the side of the building and will plan on going into back of a WP box then liquid tight from there to the necessary locations. Prints call for a 120v circuit for the cooler light/door heat. A 208v circuit for the condenser on the rooftop and a 208v circuit for the evaporator inside. So I stubbed out those 3 circuits. My plan was this: liquid tight from WP box to a disconnect mounted on the side of the building, then from disconnect straight to the condenser. Next I was gonna liquid tight from WP box down to the exterior of the cooler wall to a WP box then through the wall from back of box to the inside of the cooler to another WP box to get the other 2 circuits inside. And install a WP single pole switch as disconnecting means for the light/door heat. Then from that box, liquid tight to the already provided light that is integrated to the door heat already. And then another liquid tight to the evaporator and mount another WP box where I’ll install the disconnect (double pole switch)

If anyone has suggestions please iM open and humble enough to learn new things and try them out thanks
 
I would suggest the disconnect for the condenser be close to the condenser for the person servicing it. If it can be reached from the condenser it is probably fine. Other than that there may be some control wiring needed between the condenser and the evaporator for controls. Like defrost timer and thermostat etc (don't know if your responsible for that) if it is required. Just something to check on.

Is it a cooler (40 degrees) or a freezer (0 degrees)?

Some need wiring between the evap and condenser some do not. Also sometimes the 208 for the evap come from the condenser.

Just a few things to look out for. Also 120 volt recpt to service the condenser? I guess it wouldn't be considered a roof top so probably not needed.
 
hbiss said:
I would not do that. No need for it and a real problem if it gets shut off by stupid employees.

-Hal
Click to expand...


Yeh I agree strongly, you don’t want that door heater to be turned off.

Also, I would suggest you get the cut sheet for the condenser and evaporator before pulling the circuits because while your prints may call for a separate circuit for the evaporator, it’s more common that the 208v evap circuit feeds directly from the condenser. The prints may very well be correct though. Some of these units will get separate circuits and the condenser will kick on when it detects coolant flow from the evaporator.


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Might be a bigger job than you thought.

Last cooler I installed (at a church food bank 4 years ago) was small 120 sq ft separate building. One light, one 120V heater, one outlet, and one 240v 9000BTU hr cooling unit.

The local AHJ here insisted (incorrectly IMO and most others here) that the interpretation of 225.39(D) meant that it needed a 60A breaker and 6AWG feeder and service panel, etc. He wanted 2 ground rods also!. Learned a long time ago with the local AHJ to just 'kiss a$$' and do as 'told' to 'meet code'.

SO, just 'for kicks', better check with your local AHJ. Esp if inspector is known to have different sets of interpretation of jobs done by his buddies vs. volunteer electricians.
 
Therealcrt said:
I’ll try to give as much detail as possible for this project bare with me and let me hear your input

Note; this specific cooler manufacturer says not to penetrate roof only through side walls.

This is an exterior walk-in that sits about 3 foot away from the building on a concrete pad. I stubbed out the circuits on the side of the building and will plan on going into back of a WP box then liquid tight from there to the necessary locations. Prints call for a 120v circuit for the cooler light/door heat. A 208v circuit for the condenser on the rooftop and a 208v circuit for the evaporator inside. So I stubbed out those 3 circuits. My plan was this: liquid tight from WP box to a disconnect mounted on the side of the building, then from disconnect straight to the condenser. Next I was gonna liquid tight from WP box down to the exterior of the cooler wall to a WP box then through the wall from back of box to the inside of the cooler to another WP box to get the other 2 circuits inside. And install a WP single pole switch as disconnecting means for the light/door heat. Then from that box, liquid tight to the already provided light that is integrated to the door heat already. And then another liquid tight to the evaporator and mount another WP box where I’ll install the disconnect (double pole switch)

If anyone has suggestions please iM open and humble enough to learn new things and try them out thanks
Click to expand...
Most I've done, particularly a stand alone unit, I'd usually provide a 120 volt circuit that powers the door heater, light and possibly the evaporator fan(s) if it is 120 volts. The compressor circuit usually also powers the defrost heater as they both are controlled through the defrost timer. You possibly can have a defrost termination thermostat that will need a return lead back to the defrost timer to end the defrost cycle if it has sensed defrosting is completed before timer times out.

Something you haven't mentioned is you will most likely need a loop for main thermostat from inside cooler to whatever controls the compressor whether it be direct control (smaller compressor could be), contactor, or sometimes they operate a solenoid valve in refrigerant line and there is already a pressure switch in the unit that will shut it down on pressure once that valve closes and pressure builds up. Open valve and it starts again on pressure drop.

Evaporator fans may or may not shut off when in defrost, usually up to refrigeration guys on whether that is necessary or not depending on setup this may involve additional wiring, controls, etc.
 
If the evap coil is in a freezer (0 deg) then it will usually have electric defrost heaters. Normally the defrost time clock (or newer electronic controls cycle the compressor off the evap fan off and the heater on for defrost. The defrost is usually time terminated (like a 20-30 min defrost 4 times a day...adjustable) and or temperature terminated ...the defrost end when the box gets warm ...or both

If it is a walk in cooler (38-40 deg) I have seen them set up the same as freezers or it could just be a timed defrost shut off the compressor for a timed period keep the evap fans on to blow air over the coil to defrost.

The evap temp is usually about 10 degrees less that the box temp so a cooler running at 38-40 will have a coil temp of 28-30 and since it is below 32 it will build a little frost and ice and my not need electric defrost.

Freezers always need electric or hot gas defrost because the coil temp will run at -10 or so.

Hot gas defrost turns the compressor into a heat pump basically to have hot discharge gas melt the coil
 
hbiss said:
That especially, but also you don't want the lights to go out either while somebody is inside. There should be a glow-in-the-dark door handle but still...

-Hal
Click to expand...

It’s been a couple years now since I was still doing electrical work but the last few coolers I saw on our jobs had a “nightlight” above the door to help find your way out. It was a small glass bubble with an led module inside.


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