True unit temp issue

[ectofix]

Please forgive me for not knowing more as I’ve been away from refrigeration for awhile…and I’d left that side of our trade not as seasoned as I’d like to be.  I don’t remember when or if I ever worked on that particular model.  But…my little bit here may (or not) be helpful nonetheless.

 

I’ll assume that you accurately weighed your charge into the unit.

 

A question for you.  Was the ORIGINAL OEM thermostat an “air” or “coil” sensing type?

 

Just wondering because most prep tables I’ve encountered were coil sensing, while places like eTundra says that particular OEM thermostat (True PN 800382) IS air-sensing – which confuses me.  I think eTundra tries too hard to pin things down and occasionally get it wrong.  The picture of the thermostat on PartsTOWN (replaced by PN 988284) looks like a coil-sensing style.

 

The specs on your Ranco indicates it’s coil sensing.  I couldn’t find any on the OEM (a Danfoss product)

 

I’m thinking that if you get freezing temps with the OEM thermostat, but too warm with the aftermarket Ranco, then it’s possible the original was bad and the aftermarket Ranco somehow isn’t suited for that operating range.  But then – that’s where coil-sensing thermostats will get you…

 

If that section within the evaporator in which a coil-sensing type thermostat is mounted just happens to not be cooling properly due to a refrigerant flow issue (restriction), then it may be warmer at that point in the coil than it should be and therefore cause the problem you’d described regarding the original thermostat.  As such, the box temp goes into a freezing range before the thermostat (the cut-out point of the thermostat) before it can satisfy.

 

Your discharge pressure seems a bit low, but not too aweful.  However, your low side pressure looks pretty good otherwise.

 

I’m thinking it’s a control issue and you should get you an OEM thermostat, which – by the way – is a DanFoss part number 077B6856.

[ectofix]

Here’s you a parts list for the True TSSU series:  http://download.partstown.com/is-bin/intershop.static/WFS/Reedy-PartsTown-Site/-/en_US/manuals/TSSU-48_pm.pdf

[thetechnician]

True coolers require an oem control their parameters don’t always work with a universal control

[iceman1008]

Sorry for the late update.

 

So I figured I was overthinking the problem. The original problem was with the cap tube and had nothing to do with the original temp control. So I put the old control back in the unit. I have been having an issue with my charging scale lately with the weighed in charge units under 1LB. I borrowed my friends charging scale and weighed in a new charge. The unit came down to temp, then shut off, and is holding perfect temps now. Needless to say I will be buying a new scale. Thank you all for the tips and advice!

[ectofix]

Thanks for the update!

 

I like updates.  In my past experiences at another forum, it was an understood courtesy to provide an update when others responded to your call for help.  I’ve not seen that same courtesy take a hold here much on TechTOWN yet.

 

Oftentimes when we offer our help, we’ll go to the trouble of putting some bit of thought into it, maybe even do a little research, then type it all out and post it (sometimes on a cumbersome smartphone) – then never hear back from the OP that was asking for help.  After that happens on a repeated basis, one tends to get discouraged from bothering to offer advice when it’s solicited.

 

My apologies for going off-topic.  I’m happy to hear your problem is resolved.

[davejohnsonnola]

Nice to see not only update but an admission of error, either in malfunctioning test equipment used or a bad application of knowledge.

 

We are not perfect, nor are the tools and equipment we use.

 

Ectofix, just a word of appreciation for your detailed and extensive effort and time put into your responses here and on HVAC-talk forums. If there are others to which you contribute, or if you do youtube or other format/forum, I will happily subscribe.