liquid return through suction line after hot gas defrost period

[coldkeeper1]

I´m not sure if any of you have faced this problem: in a low temperature supermarket rack system with hot gas defrost, just after the re-activation of refrigeration following a defrost period, liquid refrigerant was pouring back to the suction manifold.

I was having a hard time trying to troubleshoot such a situation last week, until an old-timer gave to me what seemed to be the pefect cure.
He advised me to forget about the standard thermostat-based evaporator fan control and instead rely on a contactor wired to the refrigeration-on rack relay for that particular circuit. In this way, the evaporator fans would be turned on by the contactor only after the liquid line solenoid and epr valve are activated.

He believes that this liquid pouring down into the suction manifold is nothing but a consequence of the evaporator fan thermostat turning on the fans too early after defrost, something that makes the hot gas still trapped in the evaporator to liquify, returning through the suction line once refrigeration re-activates.

I applied his suggestion and it seemed to work fine in my particular problem. I hope this comment would be helpful to someone else.

[smpsmp45]

YEs The point is indeed imporatant

[chillin out]

I am glad it sorted out your problem. Although I just can't see that this would work.

During every hot gas defrost you will get the gas condensing to liquid.
Why would the fans have come on before the liquid line solenoid opens if they were wired through a stat?
The size of the suction header should have been big enough to stop liquid hitting the comps, plus the fact that the lines to the comps are recessed into the header.

Also, it sounds like your system is designed to send the dishcharge down to the cases and then back up to the cond instead of sending the discharge down to the cases and then back up to meet the liquid line then, because the second option needs the hot gas condensed in order to satisfy the liquid demand.
There are also many other points about hot gas defrost that sounds like it differs to your system.

Chillin:):)