I just bought an older trailer with a new thermoking unit installed this year. I have a quick question regarding the auto defrost...
I was running strawberries out of salinas and I happened to pull up to fuel at the same time I noticed the unit was in defrost.
I had the temp set at 34 and watched the temp climb to 54 during the defrost and then it came back down to 34. all of this over a period of 20-30minutes
I think that this may be a bit high...i took it to thermoking and the guys there really didn't seem to be interested...they pulled the report and to them it cools, defrost and cools again...they think its normal..
my other refer, same style unit, the defrost temp is usually about 40 when set the unit at 34.
Also, not really sure how the reefer works.... when the unit is set to 34 and the display shows 35....is that the temperature of the box or the temperature of the air blowing out....
meaning, when the defrost goes to 54 degrees, is that the temperature of the enitre box and my strawberries or just the guts of the unit...I don't have one of those doors in the back to stick a thermometer, but I read that putting a thermometer up the drain will do the same...
the strawberries needed to be at 34...but running the SW the outside temps were well above 100 degrees inturn raising the box temp to 37.....i asked the broker that if at 34 on the unit and the box reads 37, should I just drop the unit temp to 32 in turn to make the box reach 35....
he advised that this is a bad idea as the product close to the unit may freeze...he said that as long as the unit is set at the right temp according to the bill of lading, the receiver shouldn't have a problem...
is there a way to adjust for the outside temp or should you just let the unit do what its supposed to...
does someone have a diagram showing how the reefer works inside the box...like where the air comes from where it goes...what the bulkhead does...how the produce chute works....that would be great
Thermoking SB 210 Defrost Cycle
The parameters can be changed but it's not really necessary from factory with a new unit. Defrost cycle is not long enough to affect the pulp temperature of the product.
Like Balakov said make sure you are on continuous. Make sure your air chute is not damaged. It's important for proper air circulation.
A little hint... Strawberries the window is 32-36 degrees with 34 being the preferred temp. You have to know your unit and like with strawberries you want to run 34 but if you are in 90 degree weather you have to compensate and run your box temp about 2 degrees lower. 32 won't hurt a thing and it will pulp out at 34. Turn your box temp back to 34 when the sun starts to go down. If it's cloudy out in the day time or it's around 70 or lower outside just run normally. If it's about 80 out then I would drop it 1 degree to 33. Another hint in extreme heat keep your doors closed in the daytime and do your pulping in the early morning or night time. Last I've seen it's pretty hot in Salina's. I bet your pulp is around 35-36. That ought to be a clue to compensate your reefer temp. You don't pulp by what your reefer says. Get back there and probe your product and see what the thermometer says then you know where you stand.
The opposite goes for winter. If you are running in extreme cold with a huge difference in your product temperature then add a degree or two from what they want. Examples banana's 60 degrees is the preferred temp. If I was in freezing temps I would raise the temp to 61. Down around 20 I would run at 62. One load I sat in St.Paul, MN all weekend on a load in -15 degree weather. I kept my box on 64. My load pulped out perfectly at 60. The other two drivers had their loads rejected.
Strawberries are real sensitive and can rapidly deteriorate if not taken care of properly. They will give off ethylene and you see them little black hairs wilting. The customer doesn't like that. Keep the pulp at 34 and the airflow moving and you'll be okay. Some companies will cover a pallet of strawberries in a plastic bag and filled with CO2. If you ever get one of those they run hotter. Definitely run at 32.
Here's a little chart to help you out with produce. The middle temp is the ultimate temp. It's basically 34, 50 and 60. If any doubt ask your dispatcher.
Another thing to add, always pulp your load at the receiver and note it. You'll see variances from the shipper. The product might of come straight from the field and hasn't been chilled down yet or fully. Produce will lose up to 800 lbs of water moisture across a 3 day trip. That's handy to know if you are running heavy and fueling is a problem. Finally always pulp at the receiver upon docking. CYA!Last edited: Jul 7, 2013
jbatmick Thanks this.
If the air chute is not holed the coldest temp is in the back part of the trailer cause most of air cold is directed there thru it.....if u have it holed than spreads more evenly, happens to have a reefer with 4 additional sensors inside all tide up to a special little box/reader/temp printer and always the back sensors are colder than the front ones.....my chute is not holed...trl is not used for produce
I'm pretty sure the temp displayed is return air but during defrost its not the return air from the box. I wouldn't worry about it too much. A few minutes in defrost isn't going to ruin a load. If the bills say 34 degrees then that's what I'd set the unit at and on continuous. I never monkeyed around with running strawberries at 32 or anything like that because of the danger of freeze on the tops of the pallets. It's probably pretty unlikely since usually the ones I hauled were bagged but still seemed like it could be dangerous. You'll probably get 15 different answers on this though.
When unit goes into defrost there is a door that closes and warm air is circulated around evaporator to melt the ice that accumulates on evap. Also when hauling frozen foods in high temps and high humidity it's a good idea to manually defrost every few hrs. Defrost cycle affects box temp very little. Box temp is return air temp, drawn in from bottom of unit. That's why you want floor of trl unobstructed for that return air flow.