evaporater freeze ups

[mk98064]

I have condensing unit for 6 drawer sandwhich cooler I am having trouble omptimizing to keep box cold enough without evap turning to block of ice. Just recharged with 134 and does better on temp. Has A419 Johnson controller, current cut in setpoint at 32 and dif at 6 and have evap fan on N. C. side of contactor hoping. Has heat strip in condensate pan with no help to evaporater. At what ever setpoints I freeze up in a week. Hope to reach out for help

[jhd1234]

I have condensing unit for 6 drawer sandwhich cooler I am having trouble omptimizing to keep box cold enough without evap turning to block of ice. Just recharged with 134 and does better on temp. Has A419 Johnson controller, current cut in setpoint at 32 and dif at 6 and have evap fan on N. C. side of contactor hoping. Has heat strip in condensate pan with no help to evaporater. At what ever setpoints I freeze up in a week. Hope to reach out for help

I'm a little confused about the evaporator fan. Is it cycling on/off with the condensing unit? On this type of unit, I feel the evaporator fan should run all the time. It sounds like you have the temp cut in set for 32F and the cut out at 26F? Is that correct? If yes, at those temps you'll need a heat providing drfrosting method [electric defrost or hot gas defrost, evaporator fan off during defrost]. Is this box at the cooking station? What condition are the drawers and gaskets in?

[mk98064]

yes it is under a cooking station and evap fan does not cycle off, Also looke like I may have posted on wrong forum?

[FEISTY]

You found the right place for help. I come across these chef base units all the time. If this is manufactured by Traulsen they sometimes set these boxes up with freezer designs and put defrost heaters in the evap unit. This is ONLY MY OPINION so do with it what you will. I do not care for the electronic temp controls as we switch out more of them for mechanical style with bulb sensor in return air flow. Set to 35-37 degrees F and let her fly. Do you have a defrost timer in system? Check to see if it is set to operate properly. With heater assisted defrost, evap fans should cycle off and not cycle on until evap coil is down to design temp so you don't get snow. And most important...gaskets MUST BE GOOD CONDITION and drawers must be closed 100% especially at night. Open 1 night and ice will form on coil that normal defrost cycle won't clear. Hope this helps some !!

[mk98064]

thanks for feedback, and yes could be Traulson as designed by Bargreens. Have tweeked drawers to fit well. no electric defrost and I tried to install strip on evap hooked to N.O side of contactor but decided not to use without safeties. After vac and recgarge with 134a unit ran for 6 weeks before freezing as it was a manual defrost 1x p/week. I have several working techs try to get unit to operate stand alone and no luck. I was certified enough for test pass but found lacking the experiece as mostly I do PM and air handler/controls work. Grateful to be able to read forums as certianly see it a big area to learn. Will keepo at it as chef does not health dept tags

[jhd1234]

hmm
If the place is closed at night how about if you install a defrost timer to defrost at night or whatever time the box is not heavily used? It would be a simple off-cycle defrost. Wire the timer NC contacts in series with the temperature control and leave the evaporator fan running during defrost.

[mk98064]

I will try to get defrost timer installed as per your directions. Thanks so much........