Dual refrigeration systems in a WIF simultaneous defrost control

I'm having to install two seperate units in a large walk-in freezer cabinet. This is because of the size of the cabinet and the lack of three phase so we are forced to use two single phase lower BTU systems. I'm realizing there's going to be a problem when it comes to defrost cycles. I'm also thinking of setting it up as a two-stage system to best utilize both separate refrigeration units. I can use any pointers and direction that anybody can provide. It's much appreciated

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There is nothing wrong or complicated with using more than one unit.
As for defrost don't over complicate it, I'm not 100% sure I know what
you mean with a two stage system.?

Either run both units off one controller and put them on defrost. You can add
separate power isolators to individualise the systems for maintenance and service.

Or you run them completely separate but make sure you defrost them at the same
time. If you try to defrost at different times you will just cause complications
and cause one or both evaporators to freeze up.

Make sure the evaporators airflow don't disturb each other so both on the same wall pointing
in the same direction would be preferable to each end pointing towards each other
but there are design guidelines for the evaporators and if you follow them, it should be
straight forward.

If you are using two independent units, consider oversizing them and having
a good controller to control temps. If each unit is only 50% of the duty and one fails you
will have a problem maintaining the temperature. If you sized each unit at 60% or even
75% capacity, with a good controller you could cycle both units when the room is down to
temp which will save on energy and in the event of one unit failing you will still have the
capacity to hold the temperature until repairs are made.

Consider putting door switches on to control the evap fans. Other than that there is
nothing complicated that should cause you any worry.

Rob

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