Temperature Change

[quepasa001]

Newbie here trying to understand the Thermo King reefer. Here is the dilemma...
We have a load that needs to delivered from CA to the East Coast. The required temperature is a continous -5. My Thermo King is reaching that temperature, however after reaching it, engine revs down and temperature rises to 5.5 or 5.6 and then it kicks in again and brings it back down to -5. Is there something wrong with the unit, the settings, or is this normal? Any help is appreciated.

[CondoCruiser]

I would call your shop and see what they say and bring it to your dispatchers attention. Always CYA.

Personally, I think you're okay without looking at the unit. You're average temp is 0 which is more than adequate. Anything below 10 degrees and the product ain't gonna get hurt. Older units will struggle sometimes. It might need some maintenance or due to humidity it's hanging in defrost mode longer than normal.

Telling you to run boxed frozen on continuous is just some desk jockey brainstorming. But they pay the bill. It'll do just fine on cycle also. You might see if it runs tighter parameters on cycle since it might dodge the defrost mode. Across the desert sun I would keep it on continuous. At night you have the option of cycle.

[GAlanFink]

Just as Condo suggests, always verify with the Shipper what the range is for proper temperature. Thermo-King's (in my humble opinion) are far better than Carriers but do cycle if placed in cycle mode.

The problem lies in the word 'continuous'. This suggests to me that you need to set the -5 degree parameter and not cycle the unit. The idea is to maintain the temperature as close to that as possible and it appears you're Compressor is allowing a 10 degree variance. That's pretty substantial.

Call your dispatcher and follow company advice (get it confirmed on Qualcomm or People Net if you have computer logs). Word of mouth, I have found, is worthless.

[Sly Fox]

Other than ice cream, anything below 0 can cycle. I don't think I've ever hauled a load below -0 that didn't say "at or below" rather than just the "-5, -10, etc". And usually the carrier or broker was more than comfortable keeping it on cycle. My guess is with the humidity you're forcing a very frequent defrost that, when done, will see an elevated temperature. It also 'runs down' the reefer while in defrost mode.

[DirtyBob]

10 degrees is a pretty big swing for continuous. Like these guys said, seems kind of pointless for a -5 load. I had a similar problem once and the shop said, "Frozen is frozen."

[spacetrucker88]

can you put a pulp therometer in side or in the vent door if you have one

[spacetrucker88]

the next question will be what is a pulp thermometer or what is a vent door, I would assume your dispatcher does not even know what a reefer trailer looks like much less how to operate one

[Hammilton]

We've got mostly newerish thermo king units and a few carriers. The thermo kings are much nicer, IMHO, easier to use. We run everything on cycle, and I've seen it hit 42F in defrost. That was pretty scary, actually, because it was a load of very temp sensitive donut substrate. Is a 10 degree swing really that unusual? I don't think I'd worry much if I saw that the reefer was at 5F on product I was unloading unless there was signs of temp abuse. I doubt my guys would even mention that to me.

[GAlanFink]

I'm thinking the -5 requirement may have been put into place by the Shipper so that the reefer sits around that desired 0. A ten degree swing is not that uncommon with recycling in a hot environment but the recycle is necessary to minimize ice buildup on the unit.
I wouldn't worry too much about it,... just make sure that 'green' light is always on from your driver's mirror view and keep on trucking (and filling your reefer and fuel tanks).