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  1. #1
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    720

    would love some help with freezing evap

    have a really old federal deli case. r12 with k body semi hermetic. it does have 2 evap fans, coil runs along the length of the front bottom, fans on back side bottom of case. 1/2 hp k body, 1/2 ton txv, about 6-8 foot case no model # left. evap coil froze solid, seriously froze. unit has no defrost clock, an air sensing t-stat, running on 414b. superheat a little high at 17 degrees. head 190, low 24 at 45 box temp. (ran out of time after dethawing and running, they were closing) does pull down but seems pretty slow to do so.

    my plan- add a 9000 series defrost clock, give it a couple good 1 hour defrosts overnight, also add a white roders 16901 and make it coil sensing at 41 cut in, 23 cut out. does this sound good? this is a really good customer that needs to keep this going a little longer. BTW i had about 6 degrees subcool, no reciever, at the 45 degree box.

    my other thought is to go to 416a along with clock and stat to try and help high head in hot ambient. really appreciate any help. thanks

  2. #2
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    I'd try to lower the SH a few degrees which would bring the suction temp/pressure up a bit too. This should also shorten the refrig cycle possibly slowing the growth of the ice.
    Last edited by Capz; 07-05-2013 at 12:38 AM. Reason: Rewording

  3. #3
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    368
    Darn oddball refrigerants! Does that 414b follow R12 p/t ? or give corresponding temps to me, also temp at condensing unit.

  4. #4
    Join Date
    Jun 2009
    Location
    DFW, TX
    Posts
    645
    Keep in mind a weak compressor will run very long cycle times which may cause a freeze up as well. (Or any kind of refrigeration issue - high superheat, dirty condenser, low refrigerant charge etc.)

    Many display cases use a low pressure control to control the temperature and provide automatic defrost. Set LP control for whatever pressures correspond to roughly 20*f cut out, and 37*f cut in.

    Defrost timer is not a bad idea, no matter what temperature control you use. However a 1609101 is never a good idea to me... If you want to use a thermostat, either use a coil-sensing like an A12-700 or use an electronic like an ETC-111000 or equivalent. An ETC has the advantage in that you can stick it in the coil, supply air, or return air and adjust the settings for whatever you want. In my opinion on display cases, a pressure control may be the best choice, and usually the cheapest (especially if there is already a pressure control on the unit).

  5. #5
    Join Date
    Dec 2009
    Location
    B.C.
    Posts
    26
    Your idea of a time clock will fix it. But, you're just giving it an 'off cycle'. Maybe the high ambient temp is infiltrating into the case and forcing this unit to run for long periods of time without any air defrosts. I would consider ways to lighten it's thermal load like: Upgrading the lighting to LED or swapping out the old shaded pole fan motors for PSC fan motors. You could sell a customer on the fan motors just by comparing the Watt consumption.

  6. #6
    Join Date
    Aug 2006
    Location
    st.petersburg,fl
    Posts
    802
    Valve should be sized to the Evap not compressor also 416a would ba a better choice than Hot Shot, also would bring that sub cool up to around 15 , and a timer would be a very good idea... That is where I'd start...

    Hope this helps...
    Isn't sanity just a one-trick pony anyway? I mean, all you get is that one trick, rational thinking, but when you're good and crazy, well, the sky's the limit!

  7. #7
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    720
    valve was ff 1/2c sporlan, and compressor is 1/2 hp semi. no ifo on model,serial# not sure about evap, but it does seem like it's matched up correct. Federal said the cases from that time period had a low pressure control for temp control. I'm thinking the 416a may help too. sight glass is bubbling alot with the 414b, but head is already 190-200, so can't add anymore(no reciever). hoping with 416a i may be able to clear glass, wich should lower sh, wich should make case pull down quicker also?

  8. #8
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    790
    Quote Originally Posted by SurreyStevo View Post
    Your idea of a time clock will fix it. But, you're just giving it an 'off cycle'. Maybe the high ambient temp is infiltrating into the case and forcing this unit to run for long periods of time without any air defrosts. I would consider ways to lighten it's thermal load like: Upgrading the lighting to LED or swapping out the old shaded pole fan motors for PSC fan motors. You could sell a customer on the fan motors just by comparing the Watt consumption.
    I'd like to see your math on that.

  9. #9
    Join Date
    Aug 2006
    Location
    st.petersburg,fl
    Posts
    802
    Quote Originally Posted by kklobas View Post
    valve was ff 1/2c sporlan, and compressor is 1/2 hp semi. no ifo on model,serial# not sure about evap, but it does seem like it's matched up correct. Federal said the cases from that time period had a low pressure control for temp control. I'm thinking the 416a may help too. sight glass is bubbling alot with the 414b, but head is already 190-200, so can't add anymore(no reciever). hoping with 416a i may be able to clear glass, wich should lower sh, wich should make case pull down quicker also?
    You need a liquid seal on the TEVs or system will not operate properly, and why can't you bump the charge up some more? Hot Shot runs high head from the 22 content, What is the Temp in the box? The pressures will fall as the temp comes down... What is your SC? Also what are the compressor barrel and hot gas line temps? Also need model number of compressor so we know what the BTUs are @ +25? Then we would have an idea if valve is correct or close since you don't have any other numbers...
    Isn't sanity just a one-trick pony anyway? I mean, all you get is that one trick, rational thinking, but when you're good and crazy, well, the sky's the limit!

  10. #10
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    720
    I added a paragon 9045 time clock and a low pressure control for temp based on federal saying that is what it came with originally, also put 416a in. I'll have to get comp. model # i know it's a k body air cooled 1/2 hp, but don't have full model right now
    I do have about 12-14 subcool now (no receiver) but superheat is high at 20-22. I removed screen, it's clean. Adjusted txv, suction came up a little but line temp stayed at about 48 with 25 degree coil. Running 15 psi low side, 135 high side at 40 deg. Box pulls down really slow, almost seemed worse after opening txv.
    It was real slow with hot shot too, will stop back this afternoon and see.

  11. #11
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    720
    Found it in my notes m# kam2-0050-1aa
    S# 69102096

    FYI it was about 80 deg. Ambient with above conditions

  12. #12
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    368
    Quote Originally Posted by kklobas View Post
    valve was ff 1/2c sporlan, and compressor is 1/2 hp semi. no ifo on model,serial# not sure about evap, but it does seem like it's matched up correct. Federal said the cases from that time period had a low pressure control for temp control. I'm thinking the 416a may help too. sight glass is bubbling alot with the 414b, but head is already 190-200, so can't add anymore(no reciever). hoping with 416a i may be able to clear glass, wich should lower sh, wich should make case pull down quicker also?
    We must assume that this case had worked as equipped before.

    Non Rx system, original complaint solid frost, then hi head, lo suction, hi SC, hi SH and can't clear glass. No control with txv.

    Did you check the drier?

  13. #13
    Join Date
    Mar 2013
    Location
    swan valley idaho
    Posts
    720
    yes had 104 degrees on both sides of drier when i checked. sub cool is good i would think at 12-14. it does cool, but takes about 4 hours to pull from 60 to 40. it's an 8 foot long deli case. i know SH is high, but it seemed like box started warming up as i opened txv. I'm hoping to check it this afternoon now that it's had all night to run.

    how long would you expect it to take a deli case like this to pull down. It does have 2 evap fans,1 coil

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