Hoshizaki - txv hunting

[VAV616]

KM630-mae

old r22 ref cuber.
the water system is working fine, about 30 min cycles, but its only dropping about 60% as much weight as it should be.

110 cond temp, 10 degrees subcooling - evap temp starts off around 30 and drops to about 0
only thing strange is the superheat hunting. if your watching the suction pipe, while the evap is down at the end of the cycle near 0, the suction line is at about 10 degrees and then floats up to about 30 and then suddenly drops back to 10 and slowly works it way back up to 30, does this continuously throughout the cycle. now, ive got the sensing bulb nice and tight and completely wrapped in foam, likewise the valve itself is still encased in the factory insulation.

Im guessing its time for a new txv - f/d - vac and weigh in the charge
Am i missing anything?

[lynn comstock]

...only thing strange is the superheat hunting. if your watching the suction pipe, while the evap is down at the end of the cycle near 0 °F ? , the suction line is at about 10 degrees and then floats up to about 30 and then suddenly drops back to 10 and slowly works it way back up to 30, does this continuously throughout the cycle. now, ive got the sensing bulb nice and tight and completely wrapped in foam, likewise the valve itself is still encased in the factory insulation.

Im guessing its time for a new txv - f/d - vac and weigh in the charge
Am i missing anything?

Normal hunting is caused by an oversized valve and has regular up and down cycle times. The suddenness of the valve opening makes me think that the valve is "sticking" from wax or oil breakdown sludge or water. Heating the valve as a TEST could soften the sticky stuff and force a valve opening during the hunting cycle. If so a new drier with wax removal capacity makes a likely fix to the problem. Valve failure does not sound likely.

[VAV616]

yes i mean the evap temp is 0 degrees. so the superheat is floating between about 10 and 30 degrees, with the sharp drop-off back to 10 then slowly working its way back up.

what do you mean by "heating" the valve?
i've seen some test the reaction of the refrigerant in the sensing bulb
by placing their hand on the bulb to warm it up and see if the
suction line reading drops, proving the valve responds.

but i get the feeling that is not what you are talking about.
should i actually heat the valve with a torch?
probably the map instead of oxy/acc, just to free up
the build-up in the valve?
and i have seen acid clean-up driers, will they also clean up wax?
I normally install regular sporlan f/d, which is what it has on it now.
these guys are pretty bad about keeping the filters and condenser clean.
they dont want to call me until it just wont work hardly at all.

[VAV616]

i found this for sporlan driers
http://www.totaline.com/dl/PAGE%20K4...L%20DRIERS.pdf

it says
SPECIAL
APPLICATIONS — A special “HH” core
Catch-All Filter Drier is available to remove
wax which frequently causes difficulty on low
temperature Refrigerant 22 and 502 systems

but the only HH dryers they show on the chart are suction line.
I called one of my local ref wholesalers and he said the smallest
he has in HH is 163. I think ive got an 052 or 082 on it now.
so the 163 is twice the size and 3/8 fittings instead of 1/4.

maybe it is worth it to use some reducing fittings and add some extra ref to the charge so I can use the wax removal drier?

[lynn comstock]

By heating the valve I mean the valve body itself. That is where wax or moisture would collect. Use a soft flame and touch the valve body every few seconds until it is uncomfortably warm but not hot. If that forces the valve to release, the sticking is probably caused by wax, oil breakdown gunk or moisture.

IF there is no response, I would change the valve as the valve push pin may have oil breakdown deposits (varnish) on it. In either case, I would replace the liquid line drier and install an HH suction line drier.

I am glad not to be an average person.

[jleebald]

Here our latest C-052-CAP-TT-HH. It would be a good choice if you have a wax problem.

http://www.sporlanonline.com/40-337.htm

[VAV616]

you know I called several places and nobody had an HH smaller
than a 163 for the liquid side.
so i put a regular 052 on the liquid and an 164SHH on the suction

still dont quite have all the capacity i should though even with the
new valve : {

[lynn comstock]

you know I called several places and nobody had an HH smaller
than a 163 for the liquid side.
so i put a regular 052 on the liquid and an 164SHH on the suction I would do that rather than increase the gas charge with a larger drier.

still dont quite have all the capacity i should though even with the
new valve : {

Temperatures and pressures, SH and SC would help us help you.

[VAV616]

the charge seems right on now, 10 degrees subcool
superheat still hunts a little but no drastic swings.
it supposed to drop about 13 pounds, i didnt weigh
the batch since i redid it, its making more than they use
which i think is gonna be good enough.
Im gonna go back and weigh it one time and if its dropping
at least 11 pounds im gonna call that as good as it
gets for a +15yo machine.

[trippintl0]

I saw a box of these in our parts dept and hoping to try one out here soon if customer approves the cap tube estimate...My service mgr said from now on we put these on every cap tube replacement.

[trippintl0]

VAV, I'm a little confused about how you're testing this machine. Here's my perspective:

A Hoshi fills the water sump to overflow the standpipe. Water should always overflow the standpipe in the sump prior to the freeze cycle starting. Therefore you will always have the same size batch of water to produce ice with.

The harvest is initiated when the water level gets low enough. Therefore, your quantity of ice is fixed. The only variable is how long it takes to produce a batch of ice.

If I'm reading your post right, you are weighing the batches of ice and saying you don't have enough volume of ice per batch, correct?

It sounds like you may still have an issue with a check valve leaking through causing water to trickle down drain and produce smaller cubes, or maybe an issue with slow water fill so the sump isn't full, causing thin cubes.

Next, I have several Hoshi books and they do list typical operating pressures, but they make no mention of subcooling or superheat. How do you know what the correct subcooling and superheat should be? The only thing we know is nameplate charge, is that how you recharged or did you charge by subcooling?

Now hear me out, I'm not trying to be condescending, I only know the way I was trained and I'm fairly new to all this. My approach is to start with proper water flow and clean water circuit, clean condenser, clean evaporator, confirm no separation of evaporator plates, etc. Then if TXV is not acting right, go back with OEM TXV, drier, and weigh the charge. Check pressures and times by the book and that's it.

The book does list the weight of each batch, I have just never actually used it to diagnose. I've never checked superheat on a Hoshi, only a Scotsman because Scotsman does list the recommended superheat in their manuals.

What say you?

[VAV616]

k, the amount of water that should be frozen by the time the
float comes down should be the same, I agree and ive been thinking
that same thing.

so then why is it still dropping less even though the float has dropped?
i guess the only thing left is the water valve, but it must not be leaking by much, ive got the float marked where it was in the first place. and im not
getting 60 min cycles. i guess if its just trickling warm water into the sump then my evap just wont pull down quite as fast or as far as it should?

i have verified that there is no water at all coming down the drain in freeze.
and i have looked under the grate and into the sump and seen the water level up to just below the overfill drain hole.

for the charge i have studied the hoshi manual for the unit and the pocket tech book for the E or r22 models, and ive seen the pressure charts they have for 5 min into the freeze, and those matched up - i weighed the charge and measured the subcooling just to confirm that it looked right.
i checked superheat just to witness the activity of the new txv i installed.

i did notice that the end of the freeze my evap temp was still 5-0 degrees.
I cant remember if before it would pull down to something more like -10?

the hoshizaki chart shows @ 90degree ambient and 70 degree water (actually maybe a bit lower than that, its 95+ outside, 81-85 in the kit)
490 pounds production 24 h
40 min freeze cycle
14 pound batch

high side 279# low 46# - 5 min into freeze
high side 246# @ 80 ambient
which is right on what i was getting.

So has it been your experience that as soon as you mess with one of these things it it always more than just one problem?
when i walked up to this thing it just needed a water pump - and i can understand now that a new pump is gonna put more pressure on things like the check valve.
but even once i got the short cycles fixed , then it has capacity issues.
and it was undercharged.
they insist it was making plenty of ice before the water pump went out.
idk maybe thats not true.

but now im stuck looking like a parts changer and have spent way too much time on it. lucky for me their are right across the street and more of a personal friend.

now i think that whenever i have to mess with one of these things im going to pretty much rebuild several pieces if i have to touch it at all,

[trippintl0]

Several things jump out at me in your reply.

1. "Float marked where it was" Float should be at lowest possible setting for proper sized cubes. IF the float has been raised often it is because a technician raised it to prevent freeze-up or bridging of cubes, which could be caused by scaled up evaporator, evaporator plates separated, water inlet valve leaking by adding extra water to sump during freeze cycle, or possible because it was low on gas and wasn't harvesting properly. So now that you've fixed the refrigeration issue, with the float moved up, you're making thinner cubes and less volume of ice per cycle. That's a possibility.

2. During every harvest cycle, you should see water flowing down the drain from the water sump being 100% full and going over the standpipe in the sump. If you don't, you have a water supply issue, period. Check for clogged filters, improper water line supply, and dirty mesh screen on water inlet valve.

3. I feel for you because there's nothing worse than standing in front of an ice machine for 40 minutes to produce one measly batch of ice.

4. Confirm the ambient temp right at the screen on front cover where incoming air goes into machine. You may have a situation where hot air is recirculating. This will increase freeze time and decrease production. Obviously dirty condenser will do the same. Hoshi self contained condensers are hard to clean. I like to remove condenser fan and brush, blow, or NuBrite/water hose from inside out. I've never seen an old self contained Hoshi with a clean condenser except after I've washed it.

5. Confirm all plastic insulation panels in place while timing cycle. A Hoshi tech once told me a missing front evaporator insulation panel can add 4-5 minutes to a freeze cycle.

6. Pull off top insulation panel toward end of freeze and look down and make sure you don't have any areas with little to no ice, this can be caused by separation of evaporator plates. I have seen Hoshi's with separated evaporator plates that have half of a sheet not form ice which causes the good plates to make extra thick ice, so a technician will raise the float switch to compensate to make normal sized cubes.

7. If the evaporator has scale buildup you will see a rounded back on the cubes after they drop, indicating cubes don't want to drop and you are getting "melt-away." This will decrease production.

8. Don't ever believe when a store says "it used to make more ice." Honestly it sounds like you've already got the machine fixed. a 600 pound machine in an 85 degree kitchen ain't jack diddly squat. If the machine is on a large bin then I always explain up front, "This machine drops ice once an hour. It will not fill up the bin for 24-36 hours, and if you continue to use more ice than it produces it will never catch up. You need to buy ice and fill the bin." Because we get so many nuisance calls where we just fixed an ice machine, and customer pokes there head in an hour later and says, "Its still empty!" And they call back and say, "It's not dropping ice!" Meanwhile the servers are scooping all the ice out every time it does finally drop.

9. Parts I always change? Yes. First thing I do on any Hoshi is clean the float switch, change the float switch connector (rubber boot under switch), replace the check valve seat and spring. (Unless the machine is new or very clean, which is rare.) Then I fix the major issue. Then I give an estimate to de-scale the evaporator and sanitize. Often times once you've cleaned the trash out of float switch and sump and cleaned the condenser, you find there's nothing else wrong.

10. I never weigh the ice. If cycle time is correct and the cubes look normal then the ice machine is working to its full capacity.

[VAV616]

i did change the water filter, clean the condenser and use cleaner on the water circuit when i first did this one.
so im pretty sure thee only problems left are the water valve, and this evap plates you mentioned. I dont see a detailed discussion about them in the manual.

i mention the float position because that is where i got it to work best for time and size when they first asked me to resurrect this dinosaur last year.
and that point is maybe almost half way along the slide.
could it have had the evaporator problem all along i guess?
ill climb up there and take a look at the end of freeze tommorrow, and im gonna go ahead and get a fill valve for it just to be sure.

but with the evap plates, is that repairable? or do you have to replace the evaporator?

[trippintl0]

Well if evaporator plates are separated from the refrigerant lines on such a small machine you'd probably not make much ice or not be able to harvest it, honestly.

To check it, remove the water distribution tubes and pop out the little plastic water guides on top of the evaporator, and wiggle the stainless steel plates. If its separated from the tubing it will be obvious, you can see it and feel the plate move away from the tubing that is sandwiched between the plates. You can also check from the bottom of the evaporator wiggling as well.

Really I think the reason you have a smaller volume of ice per batch than the book is pretty obvious now. All the Hoshi tests are with float in the lowest position. This makes most amount of ice per cycle. You have the float halfway. So you are using less water per batch of ice, therefore less weight.

If evaporator plates are actually separated then the evaporator would need to be replaced. And anybody in their right mind would replace the machine. Though we do them every now and then at our company, I never have personally.

Good luck with it!

[VAV616]

Water Valve.

/sigh

the whole time I didnt suspect it because i knew i had changed it just last year.
turns out, after checking my records, I changed that sept 1, 2009, almost 2 years ago.

i could blow through it backwards just a bit, so the new pump was putting enough pressure on it to open it and leak just a little water in.

now ive got the float almost all the way down and it still hits 42 min freeze.

thanks for the help guys

[napoleon-dynomite]

Excellent thread!! The Hoshi Tech books do offer a wealth of information and surprisingly the same material can be found easily online.

This forum kicks @ss!!!