Hoshizaki Km-630MAB...not harvesting properly

[scesor5]

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.

[adam_s05]

Is it water cooled? If so the water reg valve could be leaking by on harvest.

[scesor5]

This unit is an air cooled unit

[iceman777]

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.

[scesor5]

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.

[iceman777]

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.

[itsiceman]

"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.

[scesor5]

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

[gsxrsquid]

"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.

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.

[itsiceman]

Hoshizaki said 50degree water was ok..what is the temp that you normally see?

What ever temp it comes out of the ground
Seen one running 38˚F and harvesting with a semi dirty evap.

Much longer than 3 Min. though.

Do you have the service manual scesor ?

I think you need to do a little more of the work on this one and start with the book

Check Page 15

http://www.hoshizakiamerica.com/manu...30M_B_serv.pdf

[itsiceman]

I see they list a 45˚F Min. water temp in that old manual but I don't believe it's the problem.

Also saw they list a 7 PSI Min. pressure

Anyone think they learned a thing or two since then

[allamericanclow]

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...

[allamericanclow]

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

[ahiggins91]

We had a manitowoc one time do just about the same thing, and we couldn't figure out why it wasn't harvesting all of the ice- everything looked fine one it, but when it went to harvest it only harvested about half the ice on the grid. after checking it and rechecking it several times, we found out that there were little burrs on the grid where someone had chipped away at the ice with something sharp- causing some of the ice to catch on the burrs and not drop.

[itsiceman]

sounds like a hot gas valve failing to open.

So is it a 3 min harvest or a 15 min. harvest?
No hot gas or bad TXV would get you a long harvest.

From what I'm getting from the story it sounds like its cycling too fast thru harvest but, with out a time............

To me sounds like the suction line is getting too warm too fast and not warming the whole plate to me but with out the suction temp..........

[allamericanclow]

3 min is a good valid harvest when u hear the crack u can hear the hotgass open pressure rise is fast. with a manotowic pressure needs to get over 50 for at full harvest. so if half the plate drops and half doesnt u can b assured the hotgas valve is bad.. unless ya pressure gets over 50... and it doesnt drop. well if u have an equal part that doesnt drop its the hotgas valve. and if u saw chipping on the plate from someone chipping ice then u need to get that person away from ur equipment... 3 words ho t gas valve. been there domne that u described it to a t as wlell as the manotowic

[itsiceman]

aac On a Hoshi 3 min sucks if all the ice has not fallen off yet.

For harvest cycles between the two

Mani uses HG and gravity only and sometimes air.

Hoshi uses water mainly and some HG.

IMO on a Hoshi the HG valve is there to just slam shut the txv

Manitowoc should be left out of this thread or the poor guy will be going in circles

[gsxrsquid]

aac On a Hoshi 3 min sucks if all the ice has not fallen off yet.

For harvest cycles between the two

Mani uses HG and gravity only and sometimes air.

Hoshi uses water mainly and some HG.

IMO on a Hoshi the HG valve is there to just slam shut the txv

Manitowoc should be left out of this thread or the poor guy will be going in circles

I was thinking the same thing. Mani and Hoshi are two different animals.

[ahc&r]

Didn't see a hi press reading, since u cleaned a plugged condenser the system may be under or over charged and or look at the headmaster. does the outdoor fans shut off. Imo Ur just running out of hot

[itsiceman]

I was thinking the same thing. Mani and Hoshi are two different animals.

This reminds me of Penn and Teller
when Penn tells you how Teller is doing the trick (even in slow mo) and you still can't see the slight of hand