compressor/evap sizing number check... and problems too !

[knighty]

we have a 26foot freezer at work (the back from a lorry)

original lorry freezer unit as removed (above the cab thing) and a 2nd hand (6months old normal freezer room system) system was fitted to the side of the box...

it's been running great for about 4 years.... but we decided to move (slide) the box forward a few feet to make more room... and when we did the solenoid on the liquid line entering the box caught on a roof joist and bent the pipe a bit.... the freezer still ran ok, but wasn't bringing temp down as quick as normal... the pipe wasn't kinked, just a bit bent/restricted...

so i phoned the refridg. guy we normally used and asked him to come take a look when he was in the area (as there was no hurry)... he came a couple of days later and had a quick look...

I thought i could have probably bent the pipe back straight... but i didn't want to risk cracking it / making it leak and he agreed.... as it was bent right where it went into the solenoid he just disconnected the pipe, shortened it an 2inchs and re-conected... (he added some gas too, saying losing some was inevitable)

(remember it was running pretty much ok at this point, could hold -18'C without any real problems)....

he was pretty late fixing it so I didn't really have any time to check it was running ok....

the next morning when i came in it was only down to -13'C ! and didn't manage to get any lower than that all day... then the next morning... it was still only -13'C...

(mornings are the best time for temp checking for us... as we open the door a lot during the day... i always check the freezers in the morning and make sure they they're down to temp)


so i phoned him back up...but he couldn't make it out for a couple of days as he was already fully booked up... he didn't want to recommend anyone (which is understandable tbh).. so i picked the closest place to me in the phone book i could find....

the guy came out and had a look..... he thought maybe the first guy had let some moisture into the system or added the wrong kind of gas...

(which seamed reasonable to me)

I talked to him for while... but he made a couple of mistakes while i was there... he didn't recognise that the compressor had a delta star starter (for the 3 phase) and thought that the extra contacts/timer were for the defrost and that the defrost was permanently on... (it wasn't)

he also thought the compressor wasn't shutting off when he turned the defrost clock round to defrost... when really it was just pumping down (it was pretty obv. from the sound of the compressor that this is what was happening)

this new guy said that the compressor is a good one and pretty new (i checked the label after he went and it said year 2000) but that the evap. is old undersized junk and needs replacing....

can someone check and see if these are sized right ?
he was pretty keen to fit a new evep for me... but because it's worked perfectly for 4 years I'm not sure what to think....

from the compressor I have....

Copeland
Glacier
Model: ZF15K4E - TDF - 551
Serial Number: 00B291982 C

and from the evap...

Friga - Bohn
LUC 650 STH NF
SER 0009F
SER 0127D


are these units sized correctly ?

any ideas on what could be causing the problems ?

the 2nd guy added a little more gas and the room is down to -16'C on a morning... but no lower...

someone has written R22 on the evap... but this 2nd guy said maybe the gas had been changed after that was written (before I had it)

he said a new evap and changing to 404A would make a massive differance....

sorry to ramble on and talk so much.... I'm dyslexic.. sometimes the details don't come out in the right order / so if I don't ramble i miss things out !

thanks in advance !

Alan :-)

[SteinarN]

The compressor has a capasity of 4 to 4.5 kW at -30C evaporating. I dont have any data on that evaporator, but a new evaporator called LUC 645C has a rated capasity of 5.8 kW at DT1=8K and -28C evaporating. I believe the evaporator has a suficcient capasity, especially as it worked satisfactory before.

Most likely fault is lack of refrigerant.

What type of refrigerant did the last guy put in? What type of refrigerant is on the label on the expansion valve? Is there a liquid line sight glass or a receiver sight glass on the system? if so, what is they indicating?

[knighty]

hi steinarn, and thanks for posting back to me !

I'm not sure of the original refrigerant when it was installed, it was the gas that the refridge guy pumped down from the previous install.. (didn't need any extra gas due to shorter pipe runs)

I'm not sure what the guy who fixed the bent pipe used... I'll check the receipt when I can and see if that says anything ?

this last guy used R22

not sure if the expansion valve has a label, I'll check that too !

the liquid line sight glass if full of liquid, when it starts up a couple of bubbles pass... but they clear up quick !

the sight glass on the compressor before this last guy gassed it up was either all liquid or all gass... I couldn't see anything so assumed it was all liquid...

since this last guy gassed it up, liquid line is still all liquid but compressor sight glass is now about 85% full of liquid and 15% gas

(just thinking aloud here, but maybe it had too much gas in it (full sight glass), and this last guy after saying he'd add some actually let some out?!?)

the freezer was actually down to -18'C this morning !... but once we opened the door a couple of times the temp shot up and struggled to come back down... it didn't make it past -13'C after approx. 3 hours with the doors closed and continues running.

I should also point out, the temp probe is right next to the back of the evap (about 15cm away from the fins where air is sucked in) so the temp displayed on the gauge has always dropped really quick in the past !... the fact that it's taking a long time now shows it must be really struggling!

I'll check up on the things I said I would and then get back to you...

tho I thought I should also say that the liquid exit line from the compressor is hot, hot enough that you can't keep your hand on it of you'll be burnt.... to me in the past this has always been a rough gauge to show that a unit is working ok.... liquid exit from the condenser is slightly warm, but only just, cooler than i would wash my hands with... also, the suction line is icing right back to the compressor.


I'm thinking if it's running R22 the best idea might be to have the expansion valve changed for a 404A one and have it de-gassed, vacuumed out, flushed with nitrogen and then filled with 404A ?
(is this overkill?)

thanks for the input !

Alan :-)

[knighty]

hi

sorry it took me so long to get back we're rushed off our feet at work right now so I didn't have time to take the side off the evap. and check the expansion valve...

the expansion valve is for R22... I guess we have to assume the last guy put R22 in it... so maybe the guy who worked on it in the middle didn't put enough gas in or put 404 in ?

it's working a LOT better now that it's not so warm here... tho I don't think it's back to 100%... I also turned the temp down to -22'C (from-18),, I figure there's a couple of ton of long term stock in there... so on the low load days / weekends it'll bring down the temp of that and give us a bit of a head start for the days that we add fresh stock !

the compressor will need to be moved soon anyway... so would changing over to 404 then make much difference ?

some time soon we'll be changing our freezers around and this one will be more important / have more fresh stock put in it for freezing... (we will also be adding another compressor/evap to it)

I think (guess) it's not running *quite* right and the high ambient temps caused more problems than they normally would...

I was thinking it could be a good idea to add a water cooled heat exchanger to the system for the really hot days, and to have it put in the system right after the condenser (just before the accumulator), is this the right spot to have it fitted ?

(was thinking even if i just used a beer flash cooler (or 3) to cool the water that it would make a big difference for the really hot days!)

thanks

Alan.


p.s. thanks for all the help, I really appreciate you guys taking the time to help a non-fridgie like me !