HELP with a Traulsen Stand-up Freezer

[Kmm7162]

Hi,
I have been puzzled on a Stand-up Freezer.
Originally, I was dispatched to determine why the freezer was icing up and temp was increasing.
Eliminating the basic issues..... defrost timer working, defrost heater working, drain line not plugged up,low refrigerant, dirty evaporator coil, plugged filter drier causing a restriction, refrigerant line kinks....I surmised that the system was in a restricted stage. I consulted the manufacturer(Traulsen who confirmed my diagnosis) and we found that the capillary line was restricted. Ordering an OEM cap tube, I replaced the tubing, flushed the system and replaced the drier. Metering in the refrigerant charge, the system pulled down to temp soon and I determined that the system was repaired. I also found worn and destroyed door gaskets and told the store mgr that proper temp will not be achieved until the gaskets are replaced. Replacing the gaskets.....the freezer froze up again 2 days later. Mind you...the defrost timer is set for 30 minutes, 4 times a day. There is a defrost overload in place that shuts off the heaters if over temp is achieved.

I need help. The system is still freezing up. Temp is originally maintained after the coil is defrosted, but after 12 hours or so....ice build up is significant and the unit will not pull down under 30 degrees.

FYI...The refrigerant in the system is R-404a.
Operating pressures were 18 psi suction and 285 discharge with temp at 20 degrees. As the temp decreased the suction will drop.

I am assuming that the evaporator fan is not pulling the correct cfm....any other suggestions.

[Gary]

Is there a fan/termination switch?

[Kmm7162]

NO......there is only termination for the heater. There has been another company that was fired from the restaurant and I have no idea if they changed the design. I noticed that the liquid line was altered from 1/4" to 3/8 near the drier....field altered.

But that is a good call regarding the fan termination....if the klixon failed there would be a fan issue.

Again...my suspicion is that I eliminate all question and change out the fan motor. I confirmed with the mfr that the air blows thru the coil.....so the fan is moving air in the correct manner.

[Kmm7162]

and thank-you sir for responding.

[Gary]

A fan/termination (F/T) switch does two things: it terminates the defrost cycle and it delays the fan. If the defrost cycle terminates on time rather than on F/T then the coil will not fully defrost and warm moist air will be dumped into the freezer compartment.

Check your wiring diagram to see if it is supposed to have a F/T switch.

[Kmm7162]

mmmmmmmmm....great call....there is always BS involved when you get into a mess from another company and YOU have no techical background on previous repairs....thank-you again sir....I am very familiar on the 3way fan/defrost term control...and didnt realize that maybe there should be one installed...i will consult with the mfr tomorrow and be sure to post my results to you

[Gary]

When you fully (manually) defrost the coil, the system works properly.

You have confirmed that the defrost timer and heaters are working properly.

After two days the system does not work properly due to frost.

Therefore, the coil is not fully defrosting.

[Kmm7162]

yes..but the defrost timer is set for 4 times a day...30 minutes...I have watched the heaters shut off on temp overload before the 30 minutes time slot....the system stays off until the end of time setting. THERE is no x terminal release to knock off defrost like most commerical walkin freezers have....it basically stays in defrost for 30 minutes....but ALL the ice is melted every time....the fans come on immediately........and the temp drops to 5 degrees....i havent stayed longer to watch it go lower.....but after less than 2 days....there is ice on the coil....at times....i have come back to see ice...watch it go into defrost....and the ice melts....temp goes down to near zero again....But i only watch ONE cycle....I do not wait for the 4 hours before defrost again....NO TIME....

My thing is......fan cfm problems too?
I will call traulsen to determine if there IS A F/T required for this system. As of now there is not one....

I havent performed an efficiency ck on the compressor.....wondering out loud if there may be weak valves in the compressor????

I am searching here...this is that ONE job that makes me feel like a rookie again.

[philfridge]

Seems to me that you misdiagnosed the original fault of evaporator coil icing up. First of all this sounds like a defrost problem not a refrigeration fault. I am fairly sure that traulsen freezers use two klixons on the evaporator coil, one is the defrost termination thermostat and the other is the fan motor klixon. I would sugest first to adjust defrost timeclock to give a 30 min defrost every four hours and see if that resolves the issue of coil icing up. If not renew the defrost termination klixon as this is most likely to be at fault. As long as you can confirm the defrost timer and evaporator fan are ok I think this should work. Regards phil

[Gary]

Is the ice evenly distributed across the coil?

Is the face of the coil clean?

Is the fan blade cupping the air as opposed to backhanding it?

[philfridge]

yes..but the defrost timer is set for 4 times a day...30 minutes....But i only watch ONE cycle....I do not wait for the 4 hours before defrost again....NO TIME....

.

Like I said before you need to set the defrost timer to every four hours. At the moment you have a defrost every SIX hours which is possibly the problem

[Gary]

Too much frost and/or not enough defrost. Rather than just giving it more defrost, we should also consider why it is producing too much frost.

[Richvacr]

is the defrost timer working correctly - that is you set the time on it and come back in 4 hours and it advanced 4 hours and went through a defrost cycle

if all else fails but a defrost termination on it and add more defrost cycles.

[Kmm7162]

thank-you guys...ur advice is helpful...you know how it is...you can repair 99 units..but its that ONE that bites you in the butt...and you start 2nd guessing stuff.

i set 6 defrost cycles today....there has been 4 for 30 min. THE clock works...it is accurate...NO questions there.....tomorrow I will call the mfr to see if there is a defrost fan termination...there isnt one at the moment..and I havent had a lot of history repairing this unti. As I said...another company has worked on this freezer for a few years.

do you think the fan cfm is an issue to ck? I do know that the air is blowing thru the coil....the force seems strong to me when the coil is free of ice.

[philfridge]

Also check inside the cabinet that the customer is not blocking the air vents. Would not think evap fan motor is the problem if it's blowing through coil ok.