View Full Version : Industrial Style HG Bypass Valve Question

07-08-2014, 09:19 AM
This valve is being used as a hot gas bypass on an air conditioning system. The 1/4" tubing on the right - what pressure should that be connected to? Does it need to be run all the way back to the compressor or can be tied in near the evap coil?

07-08-2014, 10:29 AM
Is this it?


Note the flange ring - usually located on valve outlet.

08-08-2014, 01:36 AM
That certainly looks a lot like the valve that I have. There must be numbers on it somewhere but I haven't been able to see anything yet. It is in a bad spot, I'll check again. The main question was where that monitor line had to be hooked up. Whoever installed this valve ran it all the way back to the compressor, I suppose that would be to have a more accurate reading of what's going on with the suction pressure and to get away from where the hot gas is being injected in the evap coil.

08-08-2014, 08:49 AM
You may not find any markings on valve except if there is something it's on a tag on top part of valve like A4A port 3/4 or 1" for a 2 bolt valve like this.
i cannot see any reason pilot has to run back near compressor suction, unless there is another pressure regulator or control valve in the line between it & compressor.
It's basically a false load valve to keep compressor running.

Can you explain system a bit more so we understand it.

10-08-2014, 09:12 AM
It is dependant on the required function of the valve. Does this go into a distributor upstream of an EXV?

26-08-2014, 11:40 PM
That's an old one. The mounting of the solenoid passing the pilot stream piped such that the solenoid body is a separate piece from the adapter on the regulator went away with the introduction of Modudapter valves in something like 1974. That big cast solenoid coil cover went away before that.....
So actually this could be an A4COES or an A4AOES. Either way: the question tubing needs to be equalized to the pressure you are trying to manage, and if its false loading the compressor with no hold back type devices between the compressor and the evap then the evap suction is fine. If there is more than one evap to this specific bank of evaporators it can be marginally more complicated than that but there is still no need to take it back to the compressor