Hot Gas Reheat

[tanksboard]

Hey Guys,

I was wondering if I could get some advice as to the best methods of controlling and piping hot gas reheat coils. Here are a few questions/thoughts that I have.

I am tapping the discharge of my compressor and running to a stepper motor modulating valve. From there, the refrigerant cycles through my reheat coil and is dumped back into the discharge line through a check valve. Using this method, I have no real means to force X amount of refrigerant into the reheat coil even if the modulating valve is 100% open. Therefore, I thought about putting the modulating valve on the inlet of the condenser and a solenoid on the incoming side of the reheat coil. This way I can open the solenoid and throttle in as much refrigerant as required using the modulating valve. Do you guys see an easier/better way to do this? Do you guys have a good way of ensuring oil return back to the compressor and not getting stuck in the reheat coil while the circuit is shut down?

[tanksboard]

bump it up

[chillerman2006]

Bump away Tanks ... I aint got a scooby doo what it is your doing

Explain some more and someone might be able to help

[The Viking]

The "standard" would be to have 100% of the hot gas through the heat exchanger 100% of the time and then to modulate/control on the secondary side.

[Glenn Moore]

There are several ways to control the system it depends on what you need to achieve.
If you are controlling the reheat coil temperature then you can fit your stepper valve on the inlet of the reheat coil and then fit a differential pressure regulator at the inlet to the main condenser. So when the stepper valve throttles to close on the reheat coil the differential valve on the condenser starts to open due to the differential pressure increasing between the discharge pressure and the liquid outlet pressure.
If you fit something like a Danfoss ICV 3 valve at the condenser inlet using a pilot differential CVPP valve and also a EVMNO solenoid pilot , the ICV valve could modulate on the differential pilot control , and when the RE heat is not required the solenoid can be used to fully open the ICV valve. You need to fit check valves at the coil outlets to prevent liquid back up under certain conditions.

[tanksboard]

Thank you very much Glenn for your help

[Glenn Moore]

Hi tanksboard
Your very welcome hope it helps Glenn

[tanksboard]

Hi tanksboard
Your very welcome hope it helps Glenn

Hey Glenn,

I am having trouble finding any information on the differential pressure regulator. Do you have any documentation that explains how it operates? I've never worked with one and don't fully understand its operating principles. Thanks again for your help!