Refrigeration reheat inquiring

[cme]

I have a project involving a 70 ton rooftop MAU seving a science lab. 100% OSA.

Basis of design is around AAON with a modulating hot gas reheat coil / scheme.

I'm looking at McQuay RPS model and their reheat scheme is via a subcooling coil between the condenser and TXV.

Would welcome your input / experiences with these units and or schemes.

 

[tombmech]

I cannot speak to your specific unit, but I have had nasty problems with other McQuay equipment using waste heat as reheat. My personal preference is to keep the refrigeration components as uncomplicated as possible. You are generally looking at high dollar equipment with the compressors, and refrigerant leaks can be a huge maintenance issue.

It's possible that if it's all self-contained in a unitary rooftop, that may minimize the potential problems. Nevertheless, caution is advised.

 

[stanlsimon]

In supermarkets it is common to use the hot gas discharge from the compressors to operate a reheat coil.

I'm not sure how much heat would be available if the refrigerant has already gone through the condenser. It seems like your coil size (and air pressure drop) would be less if you used the hottest fluid. Don't know what refrigerant you are using.

Getting it factory piped would be great. Anything done in the field may be lacking quality.