WIF massive ice build up on distribution/TEV only

[Meakoda]

Hello everyone,

I had an odd issues that I ran into the other day that I was looking for some insight on. A major chain customer has a W-I-F that they have had for over 3 years. I was on site servicing another piece of equipment when he mentioned issues with ice development on the TXV side of the evap. coils of his freezer.

When I inspected I saw only 1 huge block of ice encompassing the entire left panel section with none on the evaporator. The customer states he has not had any cooling issues with this freezer although I suspected possible high recovery times.

After removing the ice, found evaporator superheat extremely high (37) w/ box temp. of approx. (+20 F). Condenser coils that were 90% clogged on roof and very low pressures of 19/225-230 404a w/ ambients of approx (+78 F) after coils were cleaned. Subcooling of (6). Compressor Superheat was approx (56). NOTE: Sight glass full

Also I found out that the refrigeration system was undersized for the Box size.

Box Size = 560 cu Ft.
Evap= 7500 BTU
Cond = 1 1/2 HP

Spoke with a heat craft rep. and he said for the Box size that I should be running approx.
Evap= 9000 to 9600 BTU
Cond = 2 1/2 to 3 HP

Keep in mind, according to the owner, he has not had any service calls on this unit apparently in 3 years which I find hard to believe.

I ended up adjusting the TXV to lower both my super heats values as well as increased my over all pressures. I also, understand you cannot get a correct superheat value till the box is close to temperature due to the TXV throttling. NOTE: Bulb mounted correctly.

After I was done adjusting the TXV, w/ box temp at approx (+7 F) and ambient condenser temps of (80-82 F) I increased my pressures to 21/250 w/ compressor superheat of approx (30) and evap superheat of approx (10), Subcooling (10). I did not have further time to watch the unit as I was sent off on an emergency, I am under the assumption that the super heat values will lower a bit more as it comes down in temperature some more.

I do plan on returning throughout the week for a follow up check.

My questions are.....

1) Did I do the right thing?
2) Was the ice build up from the distribution lines a bi-product of the undersized refrigeration unit?
3) How the heck has he not had a service call from the unit being undersized?


Thanks in advance for any helpful comments.

-Meakoda

[lowcool]

is their a side panel fitted?

[Magoo]

Distributor bundle ice build up generally means the distributor tail diameter and length are selected incorrectly to match the orifice size in the distributor head.
Too much flashing liquid in the tails. The liquid should be liquid until rearching the coil, and defrost at each defrost cycle. Will also mean the system is operating inefficiently.

[Meakoda]

is their a side panel fitted?

Ye,s there is def. a side panel.

[Meakoda]

Distributor bundle ice build up generally means the distributor tail diameter and length are selected incorrectly to match the orifice size in the distributor head.
Too much flashing liquid in the tails. The liquid should be liquid until rearching the coil, and defrost at each defrost cycle. Will also mean the system is operating inefficiently.

After I de-iced the side section and turned the unit on, the ice build up prior to adjustments was very significant, after adjustments it appeared to come to a hault some.

I just feel he MUST have had a service call with in 3 years and is not telling me about it, based on how quickly it previously was building up.

I am just worried that I made attempts to correct one problem and might be causing others.

BTW I have never run into the "distributor tail diameter and length are selected incorrectly to match the orifice size in the distributor head. " that I am aware of, but it absolutely makes sence and is something to keep in mind.

Thanks,

-Meakoda

[Peter_1]

I read your post in IP units -which is very hard for u Europeans - and I think you did a good job, a very good job.
You know what you're doing and I don't think you introduced new problems in this system.
Ice build up is due to moisture in the system and extremely low temperatures where the moisture freezes.
If your SH was extremely high, then you were evaporating very low, speeding up ice build-up.
I don't think the ice build -up was due to the undersized unit but due to the low evaporating temperature.
The box size isn't the determining factor for the sizing of your system: it's the heat load that matters.
A small unit will only run a longer time than a big unit but this doesn't mean necessarily that this is a wrong setup.
What I mostly do is before I turn on a TEV is looking how it was set originally to see if someone altered the factory settings. With some valves (like the Danfoss TE2 ones) , you can verify this easily by counting the turns.