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#201272 05/23/11 11:35 PM
Joined: Feb 2008
Posts: 193
I am pricing an install for a new butcher shop. It has a walk in cooler. I have not dealt with these very much. This one will have two doors with 3way switching outside. It calls for 2 strip lights inside as well as a fan.

What is the best way to enter and wire inside of these units? The plans call for seal-offs wherever the conduit enters the cooler. Are these the same seal-offs that are used in explosion proof installs?

Joined: Jan 2005
Posts: 5,370
Likes: 1
Cat Servant
There are a few details to pay particular attention to.

First, have a chat with the local health department. Since the cooler will be used for (unpackaged) food, it's likely they will want the piping stood off from the surfaces inside. Maybe Mineralacs will be enough; more likely they will want you to use the plastic stand-offs the HVAC guys use, that hold the pipe more than an inch away from the wall. This space is to facilitate cleaning.

If it's a freezer, you will need receptacles near the doors (inside) to power the heat tape that keeps the doors from freezing shut.

You do NOT need 'explosion proof' seals. Just stuff the conduit with a bit of duct seal or squirt in spray foam.

The cooling unit will need a disconnect switch, and you'll need to run power and t-stat cable from the inside 'evaporator' to the compressor outside. Of course, you'll need to mount a t-stat somewhere. The condenser outside will need a timer -the HVAC guys can tell you which one - to control the defrost cycle.

Just drill through the walls in the usual way; your boxex will close off the holes.

Lights are the usual vapor-tight ones, and Bell boxes work well. Teks screws will mount it all. There's usually a piolt light ot lit switch outside to tell everyone that the light is on.

Last edited by renosteinke; 05/24/11 08:18 AM.
Joined: Apr 2002
Posts: 7,333
Likes: 7
All I can add is that you mention 'strip' lights, which I take as fluorescent. IF you are supplying the fixtures, make sure the ballast is capable of the ambient temp in the 'box'.

Anything that you install on the interior has to be suitable for 'wash down'. WP in use covers on any outlets & switches. As Reno said....check with the local or county health dept. for any requirements.

Joined: Feb 2008
Posts: 193
Lighted switches, bell boxes, plasic standoffs, vapor tight lights no problem. However I think that the hvac wiring is more complicated than it appears at first. Do you know where I can look at a schematic of one. This would be helpful

Joined: Jan 2005
Posts: 5,370
Likes: 1
Cat Servant
On the inside of the cover to the condenser.

Joined: Feb 2008
Posts: 193
I don't have a condenser yet, I am pricing the job.

Joined: Nov 2007
Posts: 763
Some of them can get pretty elaborate with lockout relays, multiple evaporators and such, but the most basic walk-in coolers I have wired normally use a line voltage thermostat inside the box at the evaporator that controls the liquid line solenoid to shut off the compressor on the low pressure control. If itís a cooler only, it generally wonít need a defrost timer setup, because the evaporator doesnít get cold enough, but if itís both a cooler and freezer setup, it will have one. You might also have some door jamb and air pressure vent heaters to connect.
A condensate line heater is normally used in a freezer compartment. Iíve seen them either 120 or 208V, so I would check with the reefer guys on that because it may require add-on GFI/GFP protection.
For the interior wiring, I like to use EMT with pipe hangers, WP compression fittings and LFMC where needed along with WP metal boxes and covers, but Iíve also done coolers with PVC and FS boxes and LFNC where needed that worked out fine. Iíve seen some guys just use LFMC inside the walk-in secured directly on the surface with one-hole straps along regular dry location 4Ē boxes, so I guess it depends on what the walk-in is used for and your local requirements. I your case, they are storing fresh meat, so I think your state sanitary code is going to come into play.
I just use ordinary duct seal to pack the LB other fittings at penetrations and then run a bead of caulking around the outside of the fittings.
HeatCraft is a big name in walk-in refrigeration sytems. You can download other installation literature from their website, but the one in the link below is pretty typical of what you'll see. The wiring diagrams start on page 40.


Joined: Jun 2004
Posts: 1,273
IF you can, walk through and inspect an existing installation.

Many grocery stores permit civilians to enter the back warehouse. You could well talk your local grocer into letting you provide a free circuit inspection.


To prevent nasty call-backs you absolutely want to cork up the conduit penetrations. Any idea of wiring light fixtures from vertical penetrations directly above should be dismissed. The lenses will gradually fill with water.

( c.f. the jelly jar thread. )

Figure on EMT and Sealtite runs.

Figure on 3/4 minimum for box penetration. Use PVC for such since it's easier to trim and does not break the insulation. Obviously, provide a bonding jumper across it.

Be sure to provide drainage weep holes at low points in your system.

Treat everything as if it was 'outdoors.'

It gets dark inside and on top... General lighting doesn't cut it.

You'll need a long pilot bit to align your penetrations.

Time can be saved by using 45 degree Sealtite elbows -- sometimes. Most Sealtite runs will be 1/2" linking an integral T-stat relay that is set by the HVAC j-man. I've never encountered a T-stat independently mounted.

Figure on dedicated C/Bs since a tripped breaker is lethal.

The low power motors typically found in most chill boxes have internal protection for overloads. Meaning that the disconnecting means does not require fuses. A motor rated double-pole or triple-pole toggle switch gets it done.

Shun LBs, stay with 4-squares; exception: beauty effects.


I normally penetrate inside the left side of the condenser assembly from the inside out -- avoiding any seam.

Figure on bonding conductors running everywhere; I use solid.

A suitable scaffold will save labor at the condenser.

Topside, use a battery powered spot lamp.

Good luck.

Joined: Feb 2008
Posts: 193
Thanks for the info. Lots of good ideas that I certaintly had not thought of. It's good to have guys who do this stuff everyday. I go to church with the manager of a grocery store. I will check with him about a possible walk through.

I don't want to get too bound up in details, but I do want an idea of time and material for the quote. This helps alot.

Joined: Jul 2002
Posts: 8,432
Likes: 3
One thing that John(Reno) posted above worries me a tad.
Over here, with any freezer/chiller room, with door heaters, you are required to have the heat tape tails come out on the outside of the door.
These usually come out into an enclosure, where they are joined to a permanent supply (ie: is supplied from the refrigeration panel).

Using a recept and a plug in a place that is renowned for moisture is an accident waiting to happen.

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