hey guys I'm a resi. so don't make fun of me. I'm going to do a leak check on a freezer tommorrow morn. Guy originally called me and said someone condemned his compressor and wanted a price over the phone to replace it. I told him I'd have to look at the job first. So I get there and just for grins and giggles turn the unit on to see what the compressor does. Sure enough it runs, just way into a vacuum. Turns out the flare fitting on the receiver is crap so I'm going back tommorrow. This is a 404 unit and there is no liquid king valve and the guy doesn't want to pay for me to put one on so how am I going to charge this thing? Thanks
I am the Stig
They were willing to have you put in a new compressor, but they can not appreciate the fact that you saved them a sh*tload of money. Honestly what is it going to cost in both time and materials to install a valve? You can always sweat in an access T, but that is not the point.
A receiver without a king valve?
R-404A Running in a vacuum?
I hope youre not getting in over your head!
I have seen a receiver without a king valve. I needed to replace the TXV, and was unable to pump the system down. Turned a simple job into recovering, repairing, installing valve, evacuating and recharging. What a waste of time. As for the vacuum, I agree, if the unit is running in a vacuum, there is more wrong than a low charge due to a bad flare.
do you have any head pressure? is it a pumpdown system? is there any reefer in it?
The more that I think about this, the more that I think you need to do more than just cut in valves and access fittings.
There should be a LPC to prevent operation in a vacuum, even if it is only an encapsulated type control to shut the compressor down.
If the LPC is absent or non-functional, what about other safety controls? Is there an Oil control? High pressure?
In the litigious business climate that seems to prevail these days, you need to cover YOUR assets, so to speak. If these devices are needed and not present, you need to install them, at the customer's cost.
They aren't luxuries, extras or add-ons, they are required operating and safety controls.
first i would say if the unit is running way deep into a vaccum and you yourself had not jumped out the safety then i would say either the safety is defective, set way to low or someonelse jumped it out. or on the other hand there is none (a no-no) might be able to ge away with it in a 3 phase type unit but i would not do it.
second if the unit has a leak and being that it is 404 you are going to have to re weigh it in in the liquid form due to fractionaliztion. at that point i would at least sweat in a schrader "t" on the liquid line and a new drier.
but the main part is if the customer would not let me do what i need to do to make it right. (safeties, access ports leak check etc) i would probably walk away from the job.
also i would check tstat and LL solenoid valve for operation. also possibly restricted screen on txv. (again you would have a better idea whats goi9g on if you could see what ur high sidfe was doing)
of course all this is a mute point because it sounds like the customer is cheap and even though you might be able to save him the cost of a compressor replacment he still don't get it.
i would rather walk away from it than have a customer bad mouth me because i did it the way he wants only to have it fail again and then him say i am a hacker. just aint worth it.
by the way is this a tin can or a semi hermetic compressor
Just my one cent (sorry money is tight nowadays ).
Hussman freezers (reach ins used in CVS and Target stores) do not have LPC's or receivers for that matter, and they use TXV's.
So look at pumping down into the condenser. Bad flare nut. Seen them too many times to count since most are made in "China" nowadays.
RAM Teaching Tomorrows Technicians Today.
i read the tread wrong. ok if this is like a true freezer i have seen them with out the pressure switch. but don't these at least have a cpr valve (well most of the larger reachin-so unit does not start up under load) maybe the cause of the problem.
Originally Posted by icehouse
i was thinking for some reason we were dicussing a walk-in freezer. only seen walk-ins as far as larkin goes. never seen a reach in
DOH! Never thought about self contained equipment.
Still, I just did a True with no access fittings. It has an access fitting on high and low sides now.
You may not be able to install valves and whatnot, but, since you may need to put in line piercing valves to be sure that the gas is recovered to repair the leak... You will have to repair the holes left by the valves. An access Tee is a good way to do that.
Hi guys thanks for your replies. I'll answer your questions and hopefully learn more from you vets.
The owner of the business showed me his appreciation for saving his compressor by letting me work on his system.
Yes, when I arrived the compressor was running about 10Hg in a vacuum, there was and still isn't a king valve before the receiver, the owner says he's going to replace the system soon and doesn't want to put alot of money into it. There wasn't more than a drop of juice in the system.
The flare on the receiver was crappy so I redid it. Noticed dye was in the system (bunch of green $#!t). Flushed with nitrogen, made sure system was calling to open solenoid disabled compressor then pressure tested. System held @ 200 psi for 30 min. New filter dryer, 250 micron vacuum and then charged the system to 40 psi and a reasonable split across condenser. Box was 83*. When I left suction was 29 psi and line temp was 43* I know alot of superheat but I didn't know what else to do. This was my first time working on low temp stuff and I like it.
BTW it was running in a vacuum because the dumbass before me adjusted the cut out at a vacuum. Ranco unit.
I am the Stig
So it does have an LPC. Set it to cut out around 2 psig so you do not run in a vacuum.
Low temp 404A should be 15-18# low side around 245# high side (ball park figures). Next time give compressor model number and I will use the performance calculator that "Icemiester" posted a link to.
RAM Teaching Tomorrows Technicians Today.
I think I set of for 5 and 350 on high side. Like I said I left it @ 29psi with 40 degrees superheat. So far no calls
Thanks for all your imput, I'll be hangin out here more I guess.
One more question. I looked and looked and did not find a LLS only TXV so I was under the impression that the thermostat controled the LLS but in this case what would the stat control? Contactor coil?
They used a Johnson controls thermostat (grey box w/ knob at top) with coiled copper pipe to a bulb thermometer (?) so when that makes what your best guess as to what happens? Or basically does the unit just cycle off lpc?
I am the Stig