walkin freezer

[atozsvc]

Walkin have not work over yr.The freezer fan motor turn on when it is start,the fan terminator should be defective.Run over an hour,inside temp about 50 degree.
Evaporator coil just frost at frout not at the back tubing,by looking at side.
Weather at 90 suction temp #25 -7 degree evaporator suction tubing 40.
solid sight glass.Discharge pressure 260.
Please educate me what is wrong of this wqalkin.I think only the expansion valve may be the problem.Is is right?

[derek989]

what kind of refrigerant and is it a sealed or semi hermetic

[icemeister]

Walkin have not work over yr.The freezer fan motor turn on when it is start,the fan terminator should be defective.Run over an hour,inside temp about 50 degree.
Evaporator coil just frost at frout not at the back tubing,by looking at side.
Weather at 90 suction temp #25 -7 degree evaporator suction tubing 40.
solid sight glass.Discharge pressure 260.
Please educate me what is wrong of this wqalkin.I think only the expansion valve may be the problem.Is is right?

What is the model number of the expansion valve?

Since it's a freezer, I suspect you may have an expansion valve with an MOP type thermostatic element (powerhead). If it's a Sporlan valve, the number on the element will end with a "ZP" indicating it's an MOP valve.

MOP stands for Maximum Operating Pressure" and is used on low temperature applications to protect the compressor from overloading during a warm pulldown and after defrost periods. The valve limits the suction pressure to prevent this overloading.

The pressure range of the valve is usually around 30 psig for R404A, R408A, R402A and R502 so you are probably seeing the valve still within its throttling range because the box temperature is still too high. As the box temperature drops and the suction pressure drops, the valve will start to feed normally.

You may want to check the inlet screen on the expansion valve just to be sure you don't have a restriction there which would also prevent proper valve operation.

I doubt you have a bad expansion valve.

What refrigerant is in this system? You forgot to mention that.

That discharge pressure for a 90ºF ambient seems quite low for the suction pressure you stated. I would start focusing on the compressor. You may have bad valves.

[pdrake65]

More info would be needed to give you any advice about your system.

[atozsvc]

Icemeister and friends
Your right the valve is kt 43 rzp compressor# ava2490 zxt r404a.
Start 9 am this morning,till 12 noon try to adjust the exp. Up date is weather 80 sunny discharge #225 suction #20 evaporator coil suction 33.6 space tempature 31.4 at noon.Asked to keep running should go back to check monday.restaurent going to open next month.
THX

[atozsvc]

How I check the efficiency of the this hermatic compressor,normally I use the front seat method to test compressor.THX

[icemeister]

How I check the efficiency of the this hermatic compressor,normally I use the front seat method to test compressor.THX

Use the manufacturer's performance data to determine if the compressor is doing what it's supposed to do.

http://www.tcc-nacg.com/nacg_compres...AV182RT-012-J7

All you need is the suction pressure, discharge pressure and the supply voltage. Use the pressures to find the expected amperage from the performance table. Then correct that amperage for the actual supply voltage.

The performance chart amps are based on 230 V, so apply this correction factor:

Amperage Factor = 230 Volts / Actual Volts (NOTE: For 3 phase, use the average of the voltages.)

Example:

Let's say you measure 245V, 247V and 242V;

Average Voltage = (245 + 247 + 242) / 3 = 244.7V

Amperage Factor = 230 / 244.7 = .94

Now let's say you have 20# suction (-15ºF SST) and 225# discharge (96ºF SCT), from the performance table you will find that you should expect about 7.05 amps at 230V.

Now correcting for the actual voltage:

Expected Amps = 7.05 x .94 = 6.6 amps (at 244.7 volts)

If your measured amperage is within 5% of this value, the compressor is doing what it's supposed to do.

NOTE: To find performance data for other Tecumseh compressors, go here:

http://www.tcc-nacg.com/nacg_detailed_search.php

Enter the compressor model and click on Submit. Select your specific compressor from those listed and on the next page, select Performance from the navigation bar across the top.

[atozsvc]

THX for your years help

[Qamar]

Walkin have not work over yr.The freezer fan motor turn on when it is start,the fan terminator should be defective.Run over an hour,inside temp about 50 degree.
Evaporator coil just frost at frout not at the back tubing,by looking at side.
Weather at 90 suction temp #25 -7 degree evaporator suction tubing 40.
solid sight glass.Discharge pressure 260.
Please educate me what is wrong of this wqalkin.I think only the expansion valve may be the problem.Is is right?

fan terminator is defective

I was in the exactly situation replacing DTFD solve the problem

[timebuilder]

Walkin have not work over yr.The freezer fan motor turn on when it is start,the fan terminator should be defective.Run over an hour,inside temp about 50 degree.
Evaporator coil just frost at frout not at the back tubing,by looking at side.
Weather at 90 suction temp #25 -7 degree evaporator suction tubing 40.
solid sight glass.Discharge pressure 260.
Please educate me what is wrong of this wqalkin.I think only the expansion valve may be the problem.Is is right?

I'm quoting this post because there is a glaring clue here.

When you use a defrost termination switch, it usually activates a solenoid behind the time clock face to shift the timer contacts back into refrigeration mode. If it fails to get a signal from the defrost termination switch, the timer clock is supposed to take the unit out of defrost before you have run the heater elements for "over an hour."

I wonder. Was the defrost clock checked based on this clue?

My bet is "no."

[trippintl0]

The OP's English is somewhat difficult to understand, but my impression is that it ran for over an hour in refrigeration mode. Sounds to me like a refrigeration problem. I would suspect TXV not feeding properly or some type of restriction, although it could have also been compressor problem as Ice suggested to check. Hopefully he got it fixed back in 2010 when he posted the original question!

In response to Qamar, just because your freezer needed a DTFD switch doesn't mean they all will. Granted, if the fans are running before the coil is below freezing, it does sound like the fan delay switch may be stuck closed. Regardless, he watched the thing run for an hour, WITH evap fans running, and unit was running 47 degrees of superheat. Coil was starving and only frosting up a little. Suction pressure at 25# well below the 35# MOP limit of the TXV. How is the fan delay and defrost termination responsible for this happening? (Again, I'm not saying it couldn't be "bad", I'm just not sure how you arrived so confidently at the conclusion that this is the culprit of all his problems?)

Sorry if I am being offensive. But I worked several years in the retail automotive parts sales, listening to parts counter guys tell DIY mechanics, "Oh its gotta be the ___, cuz my car did that, and I changed the ___, and it was perfect after that." We had several wannabe mechanic parts guys, and they got a very high percentage of returns, since they really didn't have a clue WTF they were doing. So I shudder when I hear somebody say "I was in the exactly situation replacing ____ solve the problem," especially if the part you suggest doesn't really fit the symptoms.

Thanks!

[Qamar]

You are right I jump to conclusion w/out considering all the facts but his situation was so close to mine I could't resist
Thanks
no wannabe

[trippintl0]

Thanks, Qamar I'm impressed with your honesty. "I couldn't resist" Haha! I have also done the same thing. Not calling you a wannabe! Have a good week