Need help with Pizza Table
Hello,
I’ve been browsing some of the forums and have found tons of useful information. I’m going to throw my situation out there in hopes of any feedback. I am a total amateur at this, I just picked up a gage set and have the necessary hand tools. Got a cylinder of 134a and friend in HVAC that I bug all the time. I have a Randell Pizza prep table that lost its compressor. Had my buddy replace the compressor and recharge it. Unit fired up fine but the suction line at the compressor would ice up. Eventually a patch of ice would form on the compressor. We shut it down and I called a company to come look at it. They played with it for a while found a few other issues, a leak and loose wires, eventually pointed it to superheat and txv issue. Guy claimed it was a bad valve and wanted another 500 to replace it. That’s were that ended and I decided to fix it on my own. I went out got a gage set spoke with my buddy and started messing around. First thing was adjusting the txv, (which I had no idea how aside from turn, wait for ice, turn again). Then I discovered there’s 2 txvs, one in the cooler part at the evaporator and one for the table top which appears to be a sealed plate of some sort, completely inaccessible aside from the 2 pipes coming out of the top. (my “pro” was measuring and adjusting the wrong line and txv).
As of tonight I can adjust one section of the system at a time to the point it appears to be working correctly. To me that’s warm compressor, no ice at compressor but some on lines and evaporator temp of mid 30’s F. The problem is when I turn both sections on at the same time the line ices up again and I wined up back at square one, sitting on my milk crate doing my ¼ turns. I’ve read a few posts on setting the txv and am going to attempt the right way tomorrow with a meter and proper tools.
I guess I have a few main questions:
Do I have to do something special when setting two txvs for 2 different parts of the system? I should also mention the cooler is obviously always on, but the table top is only used during the day.
Is it ok for the evaporator coil to form some ice?
Is it ok for it to partially ice up which it seams to be doing?
Is it ok for the lines to have Ice, and or the section line at the compressor to?
Should the compressor be cold, warm, or hot?
This is kind of where I’m at right now any insight would be very helpful as sometimes I’m not even sure what I’m looking at.
Thanks in advance.
Re: Need help with Pizza Table
I'd say the compressor should be warm with ice half way to it but not actually at it or on it, I'd tune the all ways on circuit first then fire on the one that is turned off next and tune it after you have tuned the cooler and with it running IE:
Cooler = C1
Table top = C2
Tune C1 till ice is half way to the compressor but no closer, whilst C1 is running turn on C2 and tune it till ice was at the same level as C1, then slowly tune it so ice goes farther away from the compressor then insulate the lines, let run for a while and check to ensure no frost is forming on the side of compressor.
Again you start this by shutting down C2 and tuning C1 first, since C1 is your consonant. This is a very rough way of doing it but will at least get you there to some degree, then once you have gauge's and a therm, you can further tune it to ideal superheat.
Re: Need help with Pizza Table
Quote:
you can further tune it to ideal superheat.
Providing you have the correct charge in the first place ;)
Re: Need help with Pizza Table
A couple of comments:
If you have ice on the suction lines, that is different than frost. If the suction line has frost on it a little past the TXV bulb, that might seem reasonable. Depending of course on the actual suction temperature and pressure. Superheat is still superheat.
Second... Don't adjust TXV's by a frost line pattern. That's being lazy. Use the gauges and temperatures to determine the superheat. Any service person should have these available.
The other logic I agree with in principle. If the condenser is clean, and the site glass shows a dry color, then adjust the TXV that is on all the time. This might take an hour or so to reach a stable superheat.
Then adjust the remaining valve. Please also note frank's comment below.
Re: Need help with Pizza Table
Quote:
Originally Posted by Solonor
Hello,
I’ve been browsing some of the forums and have found tons of useful information. I’m going to throw my situation out there in hopes of any feedback. I am a total amateur at this, I just picked up a gage set and have the necessary hand tools. Got a cylinder of 134a and friend in HVAC that I bug all the time. I have a Randell Pizza prep table that lost its compressor. Had my buddy replace the compressor and recharge it. Unit fired up fine but the suction line at the compressor would ice up. Eventually a patch of ice would form on the compressor. We shut it down and I called a company to come look at it. They played with it for a while found a few other issues, a leak and loose wires, eventually pointed it to superheat and txv issue. Guy claimed it was a bad valve and wanted another 500 to replace it. That’s were that ended and I decided to fix it on my own. I went out got a gage set spoke with my buddy and started messing around. First thing was adjusting the txv, (which I had no idea how aside from turn, wait for ice, turn again). Then I discovered there’s 2 txvs, one in the cooler part at the evaporator and one for the table top which appears to be a sealed plate of some sort, completely inaccessible aside from the 2 pipes coming out of the top. (my “pro” was measuring and adjusting the wrong line and txv).
As of tonight I can adjust one section of the system at a time to the point it appears to be working correctly. To me that’s warm compressor, no ice at compressor but some on lines and evaporator temp of mid 30’s F. The problem is when I turn both sections on at the same time the line ices up again and I wined up back at square one, sitting on my milk crate doing my ¼ turns. I’ve read a few posts on setting the txv and am going to attempt the right way tomorrow with a meter and proper tools.
I guess I have a few main questions:
Do I have to do something special when setting two txvs for 2 different parts of the system? I should also mention the cooler is obviously always on, but the table top is only used during the day.
Is it ok for the evaporator coil to form some ice?
Is it ok for it to partially ice up which it seams to be doing?
Is it ok for the lines to have Ice, and or the section line at the compressor to?
Should the compressor be cold, warm, or hot?
This is kind of where I’m at right now any insight would be very helpful as sometimes I’m not even sure what I’m looking at.
Thanks in advance.
Where are the TXV probes placed, on their own separate suctions (thats the way they should be) or on the same common suction line.
Kind Regards Andy:)
Re: Need help with Pizza Table
Thanks for the responses guys, how do I determine if I have the correct charge? The site glass is clean and dry but if I shut it off and let it sit for awhile i can bump it and see liquid in it. It goes away when I turn it back on. Also the pressures don’t seam constant. Sometimes ill have a high side of 180psi other times it’ll run around 125. The suction seams low too, no matter how I tune it its never more than 11psi currently running around 2 to 5 psi. I have a feeling its not charged correctly, but with a full site glass when running, I don’t know if there’s another way to check it.
PS the txv bulbs are both placed on the suction lines within an inch or so of there respective coils.
Re: Need help with Pizza Table
If all was okay before the compressor was changed, this tells me ye over-charged the system.
Recover the gas charge and recharge again, slowly
this time.
System can still frost back even with a TXV.
Wont be easy now though because the valves have been adjusted. :eek:
