Manitowoc Ice Machine

[mandrieux]

I was working on a Manitowoc Ice Machine the other day. The problem wasn't obvious to me at first so I printed out the user manual online.

The machine was going off on 3 consecutive harvests over 3.5 minutes. The only parts I found to be malfunctioning were the dump valve coil and the plug/gasket with it was dried, cracked, and ripped. I replaced those parts and the machine has been working fine for the last 2 weeks.

Can anyone tell me why the dump valve would cause the machine to do what it did? The only thing I've thought of that remotly makes sense is maybe the PH of the water was off after circulating mostly the same water for so long. Any ideas? Thanks.

Model# BD0452A
Serial# 940464529
115V
60Hz
1PH
HP81(R-402B) Refrigerant

[icemeister]

You didn't specifically say, but you imply the the ice formation was normal and dump valve was failing to open on harvest initiation. You are correct that without a purge of fresh water during harvest the impurities in the sump water will build up and may have some bearing on the increased harvest time.

Additionally, with proper purge the flow to the evaporator will stop when the dump valve opens. If it continues to flow for the full 45 second time the pump runs after harvest initiation, the proper draining of the melt water behind the slab will be delayed. This melt water must drain away so air can get behind the slab to break the vacuum holding it from dropping.

[idontgetit]

If it was leaking by it at times may have had a very thin slab and would not hae enough wieght to slide off the plate as well. It is not an uncommon problem, but usally there is just something stuck under it holding it open.

[mandrieux]

Thanks Ice... That makes a lot of sense.

By the way... the sheet of ice did look great. The machine was functioning perfectly other than the dump valve. I can see where someone could reset the machine and think it was working fine then. It wasn't until looking further that I found the dump valve wasn't working. No water was passing through it.

So it sounds like your thought of the melt water not draining and therefore not breaking the vacuum is correct. Thanks again.

[yotaman16]

good call.. I know some of the new manitowocs use an air compressor to break that vacuum now. They just hit the ice with a little shot of air on the back to help release the ice.. Never would have thought a dump valve would have not alowed the machine to harvest tho..

[jonbailey19808]

In the new S series flow charts which will work for older models too, on the machine will not harvest flow chart one of the questions is "is the dump valve opening in harvest?"

Yes a stuck closed dump valve can make a machine fail to harvest. Unlike some ice machines Manitowoc cubers do not use water assisted harvest. So they should be no water following over the evap in the harvest mode at all.

The water will cause the ice to melt and you could have a 'melt-out' in the harvest cycle. As the water pump runs in the start of harvest and it can either go down the dump valve or over the evap, if the dump valve is stuck closed you bet its going to go over the evap.

Air assisted harvest is use on S1000 or larger machines only.:)

[mrldcty]

I'm having a similar issue with the same model. Water runs over evap. during harvest cycle. The dump valve works fine during initial purge and refill. Then, during harvest the water flow is over evap, not down dump. So it appears that dump valve works OK but is not energized during harvest. Any ideas?

Service manual does not specifically address this issue.

[jonbailey19808]

Dump valve should be energized during the harvest cycle. If it does not have power to it during harvest something is wrong with the board. However, most boards will fail to put power to the harvest valve at all in any cycle when that part of them fail so i would triple check your findings before you invest alot of money in a new control board.

[SBKold]

Im bringing this post post back to light in reference to my other post on a S1002.

I hope im correct in assuming this is a S1000 model.

Could my dump valve be causing this same harvest failure condition?

I notice water slightly leaking from the valve today...only while purging but valve is still functioning.

I planned on replacing valve for leak not thinking it could cause my condition.

It is an air assisted harvest unit.