Brief history about this unit. It was put in two years ago and from what they tell me, it's always sounded like crap. This is the loudest compressor I have ever heard.
The problem coming up is that this unit is staying in harvest past the 3.5 minutes harvest limit and going back into freeze cycle. The unit has been cleaned. Evap isn't in great shape but I have seen worse still in working order.
The evap was sprayed with food grade silicone to aid in the sheet dropping. But it isn't helping enough to get the sheet to drop before 3.5 minutes. Its dropping on average 10 seconds after the restart of the freeze cycle.
The pressures spec out according to the manitowoc handbook in the harvest cycle and the freeze cycle. But for the last minute or two of the freeze cycle the suction is about 3-4 psi below manitowoc specs of 40-25 psi.
Book calls for 150 degrees six inches from the compressor during the end of the freeze cycle right before harvest. I measured 143 degrees.
Both harvest valves are energizing during harvest and the suction is 73-75 psi the entire time. Head pressure is about 165 psi.
From what I can tell others have worked on this equipment before. There are dates wrote on components inside the unit. Compressor changed out in 2010, filter dryer changed 2011.
Here is another kicker that has me acting silly. This machine is making wonderful ice. From start to finish, about 15 minutes. Specs say freeze cycle should be 10-11 minutes with 1-2.5 minutes of harvest.
But during operation the compressor appears to be getting liquid refrigerant back. If the txv was slightly flooding the evap, wouldnt that keep my suction pressure out of spec? In a nut shell the top part of the compressor is getting frost on it. LIke the whole top of the compressor.
Any insight would be appreciated. I have spoken to others at the company that I work with and thought that this forum would be able to offer different views on the situation.
Check superheat of txvs. How old is the machine? Is nickle coating still intact? Evaporator may be still dirty. Have you cleaned it? Sounds like ref coming back too cold and preventing discharge from reaching proper temp for harvest.
Flooding TXV will cause lower than normal discharge temps and difficulty harvesting because you don't build up enough heat to harvest.
If I were you I'd work Manitowocs refrigeration diagnostic chart thats in the book.
I was thinking that too. But wouldn't a flooding txv raise the suction beyond the specs listed in the book?
The machine is a 98 model and the evap isn't that great. No nick left on it at all. Its in a bar/rest and they have already bypassed the filter system.
As for the txv,,, it can tell its been replaced at one time or another, it's a danfoss and whoever changed it overtightened the clamp way to much.
Boss man told me to go out there tomorrow and pull the charge and weigh it back in tomorrow, which I will do.
Or should I just skip his advice and just get a cup of warm water and see if the txv is really controling the superheat, lol, last I checked do what your boss tells you to do. Even if you are right, your still wrong.
it takes less refrigerant to make a sheet of ice than it does to successfully harvest it. you can't harvest unless you build up enough heat during the freeze cycle. your only a few degrees lower for discharge line temp @ EOF than what's called for so i don't know how close you are to the "cut off". the fact your missing nickel is not good lol. is the evap clean otherwise? .. does it matter at this point with nickel being gone idk ... I've helped some run down machines limp along but they never would equal charts. Manitowoc times for production are for clean machines with nickel lol. how thick is the bridge at harvest initiation? .. don't let it harvest till you build up above 150 just to see what happens.
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I had a similar issue everything looked right just long harvests my issue was one of the hot gas valves was not opening fully but the suction pressure looked good. Replaced both valves and it worked great.
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every response so far is what I have been thinking. Usually I don't have this much of a problem with IM's. But this is the time where I have many different variables that come into play.
to hvac wiz,,, when it harvests it's perfect ice. if I made it any thicker the bridge would be to thick.
my main issue is one of fear and the dreaded call back. In one hand,,,I wanna tell the customer that their machine is 14 years old and to be happy that they got that much use out of it.
In the other hand,, I wanna help them. If I change the txv (after I pull the charge, it's what I was told to do) I want them to get their money's worth. And if their evap is toast, replacing txv will do nothing to help them.
Or should I just man up and tell them, (and my boss) that they have multiple issues and that it's just not worth fixing.
If the evap is missing nickel, I say hack it and get a new one. 14 years is a good run for an ice machine.
push the new machine. the new indigo machine is pretty sweet
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The bosses idea of pulling the charge is not bad but I would weigh the gas you pull to verify if the charge is right.
Manitowocs will freeze good under charged by not harvest.
Your boss is absolutely right. Weigh in the charge. The best way to diagnose is to know that the charge is correct first.
If it was me, I would go there prepared to recover and weigh in the charge. But I would just talk to the customer and let them know, "I know it has a refrigeration issue because of low discharge temps and flooding during freeze. Pulling the charge is time consuming and is not the end of the repair - if it's low then I need to leak check; if its correct then we have a component not working right. And after the repair, you still have a bad evaporator. Don't get me wrong, I am happy to service it for you, but I want to make sure you fully understand, that this machine is in bad shape. Your money may be better spent towards a new machine."
Another thing to check is make sure none of the slats of the evaporator grid are loose. If you can wiggle them or pull them out with needle nose pliers then that is really bad. That alone will cause a unit not to harvest in 3 minutes even if the refrigeration system is working correctly.
Our company's recommendation is always that when an ice machine needs an evaporator, its time for a new ice machine.
why do you say that it is flooding to the compressor? Because the manitowoc compressors on the qy machines always have frost through the freeze cycle going to the compressor especial toward the end of the freeze. The key to the refrigerant pressures on the Qy machines is at the very end of the harvest cycle if it ever so slightly different from the book there is a problem. From your info about the sheets not falling off as long as the nickel is still on the evaps I would look into the cool vapor solenoid valves not opening all the way.