Hoshizaki Km-630MAB...not harvesting properly
So to begin, I am working on this unit that had first a burned out water pump so that got replaced and from there we found more problems with this unit. After running the first cycle, we noticed that not all of the ice dropped, in fact,maybe about 3/4 of the ice produced never made its way down. After talking to the owner, I was able to finally spill the truth and telling me that for 7 years he didn't do any cleaning on it and while checking the evaporator, we noticed build up. So it got cleaning 3 times in a row with brushes through the evaporator and the distribution tubes as well with the solution that Hoshizaki suggests. Once that got done, we ran the unit again and noticed that the ice harvest increased by maybe dropping more than half the load or so...but obviously not enough so after inspecting the evaporator for faults or damages and after also having cleaned the outdoor coil(That was done with the replacement of the pump, it was really dirty), it still did the same thing. I didn't want to put my gauges until i had reached a point where i couldn't see a problem and this was it. The few ice cubes that it dropped, the size was good and nice shaped cubes. I plugged in my gauges and could only see suction pressure. While we turn on, theres the water fill and then the harvest cycle turns on for about 3 minutes and the pressure read 40-45 psi on R-502. When i called the manufacturer it told me it should be reading 60-75psi and when it switched to freeze cycle after 3 minutes I let the machine run for some time. 10 minutes into freeze cycle i read the pressures and it started at 40psi and worked its way down to 21psi no lower than 20psi. Asking the manufacturer, they told me that this was right on. The time for freeze cycle is spot on between 30-35 minutes when it switches to harvest. But it is at harvest when it can't perform. I was suggested that it could be the txv and that i should replace it thinking that it may be letting refrigerant through and cooling off the defrost refrigerant (this was suggested by the Hoshizaki tech) I am just wondering to see if I can get any ideas on this unit because it's def. picking my brain. I just want re-assurance in the Hoshizaki people. Could I also be looking at the problem with the defrost valve?
Thanks for anyone's input.
If any more info needed i'll be happy to provide.
Is it water cooled? If so the water reg valve could be leaking by on harvest.
This unit is an air cooled unit
What is the incoming water temp? What is the ambient temp? Do you get good waterflow through the inlet water valve during harvest so that it goes all the way to rear of evap plates? What is the discharge pressure?
Based on model # this is an air-cooled unit.
The water temperature ranges from 45-50 degrees and as the fan runs it increases a little more to no more than 60. The ambient temperature is about 70 degrees and the water flow in the evaporator to the rear of the evap plate is good, we inspected that previously since we were also recommended by hoshizaki to do that. The initial water pressure going into the ice machine is about 60psi.
That water temp sounds too cold, could be part of problem.
How long does it stay in harvest when it's dropping ice, and what is the head pressure in freeze and in harvest?
Suction line thermister is what takes it out of harvest when suction line reaches 50 degrees; something you could check with a temp probe.
"Could I also be looking at the problem with the defrost valve?"
The inlet water does most the harvest work on this machine.
It should run fine on that temp also.
Harvest time after freeze would help.
You should be able to measure temps to diagnose a bad txv in harvest.
As far as water pressure it will not tell you much on this machine.
You need a min flow rate of 2.11 GPM and need to measure it. Check the water inlet screen if you haven't already.
Did you clean the inside path through the evap while cleaning the outside ?
If it was as bad as it sounds that could be an issue.
Also FWIW I've seen plenty of separated evap tubing that will make ice fine but not harvest. This will kick you out early before all the cubes have dropped also.
Could be many things unfortunately.
“If You Can Dodge A Wrench You Can Dodge A Ball”
Hoshizaki said 50degree water was ok..what is the temp that you normally see?
I was able to get a head pressure and during freeze, it reads 206psi head and 26psi in suction on r-502
Ambient is 73 degrees
Now it switched to harvest and head pressure reads 210psi and suction reads 42psi
The harvest cycle is forced t(through the computer) to work at the longest time which is 3 minutes
When I touched the suction line right at the evaporator it was hot and this harvest(1st one after being cleaned thoroughly again) it dropped big majority of the ices cubes except 25 of them in certain areas.
The water temp is 52 degrees
Originally Posted by itsiceman
When I read the post my first thought was check the evap. Sometimes the plate can seperate enough that it causes problems. pull the top and the water distribution headers and look at the evap from the top down (assuming they don't have it in an alcove with a 2" clearance)the ice plate is soldered to teh evap coils. If the joint is bad it's time for a new evap.
I never put gauges on an ice machine unless I know for sure it is a refrigeration problem.
“If You Can Dodge A Wrench You Can Dodge A Ball”
sounds like a hot gas valve failing to open. does it have 2 hot gas vlaves? Anyhow thats where i would start if the pressures are there. Ask wat pressures shoul;d b at harvest if they dont get high enough it wont drop...Id save the charge in a clean bottle replace the valve. reuse charge... if pressures are right of course...
this sound like a good ANSWER. There could b seperations on solder joints but if u got a hot gas valves being 2 u can feel them at harvest if u place ur hand right after the valves and it gets redhot u got a block should only get redhot at the plate... some valves u can even take apart and clean may drop a few times only so replace it dont try to skimppp