Hot gas defrost controlled by JTL

[chilled2005]

hi ive been having probs with some cases ive recently been working on being controlled by JTL..... when a case goes on deforst and the pack sends saturated gas up the suction to the cases this gas is used to defrost the coild...all and well!!! WELL......why is it then that at the case end the jtl controller kills power to the liquid line solonid as it should but powers the suction solonoid valve which is normally open and shuts it?!?!?! not letting any hot gas into the evaporator??? i was thinking maybe a relay on the board was welded together but when its refrigeration its dead?? shouldnt it be live shutting the valve and the suction bypassing this valve through the one way valve???

[rbartlett]

slightly confused but is this a kool gas system?
if so the suction sol should close as the kool gas enters at the evap and would travel back to the comp unless it did

however I await further confitmation...

cheers

richard

[chilly]

Sounds like a carters pack cool gas defrost to me too, Is this on a safeways system??
Are all probes reading corectly, I dont remember suction solinoid valves, Used toi be a one yaw bypasing the liquis solinoid. Long time ago... Make sure your probes are reading correctly, Check derfrost term temp, and min def duration, Is coil icing up, What are the symptoms..

[chillin out]

Ive also never seen a suction s/v next to a case.
Packs with hot gas defrost work on mine by shuting suction s/v on pack sending hot gas up suction through evap then a bypass valve (missing out the tev and liquid s/v) then back to the liquid line header on the pack feeding the rest of the cases.

What happens when you disconnect the live from your suction s/v? will it then defrost?

[chilled2005]

hi....exactly my point .... when i diconnect the suction solonoid coil i hear the kool/saturated gas flow into the evaporator coil....therefore defrosting it!!! its a normally open valve...????

[chilly]

Is the suction soliniod on the pack or the case,

Either way it sounds like a normaly open valve, and the defroist is being terminated . What are the parameters for defrost on the JTL.
What are the temperatures when it defrosts, Have you stripped the case and looked for ice build up causing the probes to read incorect temps due to blocked air flows?

[Tim]

It sounds to me you have item number 75 set to d.con which is for electric defrost termination it should be set to d.tEr which is for hot gas defrost.

[Comms1]

High Chilled

The valve you are talking about is the termination valve in the case, the valve as you mentioned is normally open.
When the case either reaches its termination temprature or termination time this valve should close.
Once the case goes back onto Refrigeration this valve should open up again ready for the next defrost.
As mentioned by Tim check item 75.
Also check defrost set up, If its on Sat gas
1. Is it network initiated if so the controller needs to be set for this type of defrost.
2. If its Suction probe initiated make sure the suction probe works ok and is reading the correct temp.
3. Check what probe the defrost cycle terminates on and make sure thats not reading high which will terminate the cycle to quick.