why does my Hobart AM15 dishwasher keeps steaming when cycle is complete?fixbear updated 2 years, 5 months ago 1 Member · 35 Posts
MemberNovember 27, 2017 at 12:00 am
Rinse temperature was over 200 then p3 code came on. I changed rinse sensor in the tank and it seemed to work fine for a few days. Water kept spraying after rinse so I cleaned fill valve. Now it just steams at the end of the cycle until I shut the machine down
fixbear - ADK NYMemberNovember 27, 2017 at 4:50 pm
Check your booster controls and heat relay. The rinse is directly out of the booster. It will have a primary control and a safety. The tank temp and tank heater has nothing to do with it. As for fill valve, are you referring to the solenoid valve for water or the anti syphon valve on top. If the booster goes over 212F at sea level it will continue to push water out the rinse arms from the water in it boiling..
ectofix - NashvilleMemberNovember 27, 2017 at 5:32 pm
Along with what fixbear said, I’d be taking a closer look at that fill valve again. I’ve never had much luck with just cleaning a solenoid valve. I’d go ahead and rebuild it.
- If your dish machine’s serial no. is before 231154994, a valve rebuild kit part number is 00-893101. When bought from Hobart (or PartsTOWN), it costs roughly 60% of the price of a new solenoid valve.
- If your dish machine’s serial no. is 231154994 or after, a rebuild kit isn’t listed in their parts manual.
Here is Hobart’s latest & greatest parts manual: AM15 SERIES DISHWASHERS – CATALOG OF REPLACEMENT PARTS
In either case, I’ve no doubt that they’re both Parker valves. As such, you have the option of taking accurate data from the valve to check with your local Parker distributor in order to get a rebuild kit. Probably cheaper that way.
MemberNovember 28, 2017 at 5:44 am
In addition to the above, I would look at changing the hi limit on the rinse tank. it is located on the front of the tank and has a manual reset button. It may no longer be operating properly. This has nothing to do with the heater running too hot but should stop the heater from working when it gets too hot. If you are not using soft water for your machine, I would ask your tech about descaling the boiler. This too can cause the rinse to run too hot.
Final rinse should run about 185deg. Two hundred is a little high and, stream coming out of the spray arms would make it seem that it is even higher. Have a qualified tech look this machine over.
MemberNovember 28, 2017 at 7:41 am
I was referring to the solenoid valve for water. It stopped spraying after I cleaned it. It may not have shut off completely but it helped. I will rebuild the valve but it seems like the control board is the only thing limiting the booster temp as far as I can see. I’ve unhooked the resettable high limits which disabled the booster and running chemical sanitizer at the moment.
fixbear - ADK NYMemberNovember 28, 2017 at 7:52 am
He did not say that the high limit has been tripping. So why would one replace it? As for mineral build-up in the booster, Good point. If loaded like some I’ve seen, it would hold enough heat to keep heating the water after a call for heat long enough to boil the water but not trip the limit. As it is below the heaters and in a area that will always stay wet.. Even though the temp probe is fairly high in the booster, minerals will insulate it. Wish I had taken pictures of some of them I have come across. Full to the point one had to pry out the heaters and chisel the build up loose.
fixbear - ADK NYMemberNovember 28, 2017 at 8:22 am
genemattice, We are in a bit of a fog here without the ML number. I don’t know what options you have like a condenser or gas or drain tempering, or even which booster. Because the thermister is on a extension cable. Make sure to ohm it at the control board first, then at the booster. They should be the same, but cable failure is a possibility. If you do it the other way you may have scraped the plug terminals enough that it will not show you the resistance as operating.
fixbear - ADK NYMemberNovember 28, 2017 at 9:16 am
That will not clean the booster. The booster is fresh water that is added at the rinse phase. I really recommend getting a new booster gasket and removing the heat bundle. You’ll find a bunch of mineral buildup in the booster and a wet vac helps a lot with cleaning it. Also a good flashlight and a long screwdriver. Having fun on the floor.
MemberNovember 28, 2017 at 10:06 am
the ML # is 130039 with 3 phase 480 electric booster under the dishwasher. I just chased the sensor wire out of tank and back to control board and resistance was the same. Both kept climbing slowly while I was testing. Maybe the small current flow was causing heat. Something that I failed to mention is that the booster tank was changed about a year ago due to a pinhole in it. Now I’ve noticed that this tank is leaking also. well, not exactly leaking yet but there are signs of the tiniest pinhole where limescale and almost undetectable moisture is present . The more I look the worse it gets.
MemberNovember 28, 2017 at 10:16 am
The unit is around 6 years old and the booster tank was changed last year due to a pinhole. The Hobart Tech said he had never seen a stainless steel boster tank fail since he has worked on them (10 yrs). I see now that the tank seems to have an almost undetectable leak in it. If it weren’t for lime build up you wouldn’t see it. I had changed that rinse thermister arund a week before all this started and it worked fine for a week. The rinse temp has always been a little higher than normal as far as I know and the incoming water temp is not much over 110.
fixbear - ADK NYMemberNovember 28, 2017 at 10:45 am
That sounds like you have either a electrolysis problem or a water problem. Did Hobart replace it or someone else? Ohm out the thermister to ground to make sure there is no leakage. It should not climb.
MemberNovember 28, 2017 at 10:53 am
Hobart replaced the tank and acidic water or maybe a bit of both. it was around 6 Megaohms. maybe I could switch sensors. The sensor by the vacuum breaker is exactly the same one.
fixbear - ADK NYMemberNovember 28, 2017 at 12:20 pm
Where exactly are they developing. If near the mount or a weld area, it could also be influenced by pressure changes. Making the tank sidewalls expand and contract. You may want to verify the water supply for both pressure and line size. All the way back to the source for the 3/4 diameter.
Some years ago I had a customer that had run a 1/2 copper line to his dishwasher 170 ft. He didn’t think it would be a problem since line pressure was 120 psi. After replacing a few regulators and solenoid valves he finally re-plumbed with a PRV and 3/4 plex. Took a lot of drawings and all to get it threw to him. Yes we can get the volume thru the small pipe, but the speed of that water column is like a big ass hammer when you stop it. Ask anyone who has slammed shut a fire-hose on a long line. .
MemberNovember 28, 2017 at 12:30 pm
I get what you mean about the hammer. I’ve had problems with the hot water tanks in the basement and have put in an expansion tank to help. The kitchen is quite a ways from that and the sprayers which are as bad as solenoids slamming closed. The first pin hole was right in the front of the tank above the thermistor where the tank starts to bend. No weld there but I’m sure it is stretched when stamped out. The second hole seems to be in or near the weld on the side.
fixbear - ADK NYMemberNovember 28, 2017 at 1:30 pm
I have never needed to replace a tank. This is troubling to me. Was the removed tank examined for the cause?
Ohm driffting, pinholes? thinking electrolysis. With stainless, the first one may have a a undetected inclusion. It’s common in lower grades. But not a second one too.
MemberNovember 28, 2017 at 2:16 pm
I just switched rinse thermistors top to bottom and booster tank is no longer over heating . the final rinse temp is reading 108 which tells me that my one week old, ohm drifting ohm has gone bad. As far as the old tank, I kept it and am cleaning it up now. It looks more like a crack . will let you know. I will plug it and charge it with air.
My understanding of electrolysis is that it is caused by 2 dissimilar metals coming in contact causing corrosion. Or is this an electrical thing where a small current flow from stray voltage could cause it?
ectofix - NashvilleMemberNovember 28, 2017 at 5:59 pm
AH! I wanted to say “maybe a bad probe”. But, you said you’d replaced it. I “assumed” that it was good, then. You know what they say about when you “assume” something.
I sure wished I had a table to use for testing Hobart thermistors out of a service manual. I think they’re 100KΩ thermistors. Negative temperature coefficient ones.
Off the shelf, the best numbers I came up with through my own tests were:
That’s all I got. Did that a few years ago. I need to fire up a fryer in the shop with water in it and do more tests for 180° or so.
ectofix - NashvilleMemberNovember 28, 2017 at 6:29 pm
The only built-in boosters I’ve replaced were ones in a Jackson door-type machine (never identified the cause) and…in a Hobart undercounter LXi.
On the Hobart, I discovered that it wasn’t installed with a PRV. The LXi doesn’t have one built in and apparently was overlooked during installation. It just so happened that I ran a call on it some time after the tank was replaced. While running it, I saw that the rinse pressure was WAY too high, so looked at the plumbing…and found NO PRV to regulate incoming water pressure.
I don’t know how that would’ve been overlooked by the Hobart-trained technician who installed it.
That’s just testament to the fact that ANY technician who’s bearing that title and strives to live up to it, should KNOW the equipment and attentively observe EVERYTHING – from when it’s turned on, through ALL aspects of its operation…and when it’s turned off.
Every click, tick, hum, delay, rush of water, gush of steam, light, fan, control panel display, guage, drainage, VOM reading…or whatever. Every breath that machine takes.
fixbear - ADK NYMemberNovember 28, 2017 at 8:01 pm
It can be either/or or both. The latest frigate built for Australia is full of holes after 6 mouths. Someone hooked up the anode system with reverse polarity. Any time there is a current flow threw a metal object that has different dielectric ratings, there will be a transfer of metal. If you have a acidic or saline solution and a flow of current, electrolysis is happening. Water heaters have a magnesium rod or chain down the middle just for that reason. Sea water heat ex changers use zinc rods. I don’t believe that the dielectric strength of the Cal rods and the stainless are that far apart.
But back to your problem. Stainless is very prone to cracks. after all, that’s what sank the Thresher. It does not like pressure and heat change together. Technically the booster is under 20 to 25 lbs. But if the prv is set high or the rinse piping/wands are restricted it may see more. As I recall they are 2 spun cylinders that are welded together with a bracket. Stress would be at the bracket welds. Or the threaded taps. I would really examine the water supply to the machine and the prv setting.
MemberNovember 29, 2017 at 7:08 am
Okay, I just want to run this by you. It seems to me that there is never any actual pressure on the booster tank to speak of. There is no condenser on it. It has a hood so that solenoid in the rinse line is not there. Is this correct or am I missing something? It seems to only push water through the tank when it goes into rinse and the solenoid opens. I believe that is why when to booster wouldn’t shut off the water was pushing out the wash arm. Also, there couldn’t be any water hammer on the tank in any way so I’m thinking that it has to be electrolysis. Make sense ?
MemberNovember 29, 2017 at 7:16 am
Oh, something else I noticed when I was looking at the dishwasher was that the pressure reducer was set very high so I turned it down to 20 pounds right in the green area on the gage. The next morning the dishwasher wouldn’t fill and showed the EE code so I turned it back up and it worked just fine. Hobart technicians have been the only ones that have ever worked on this machine until now.
fixbear - ADK NYMemberNovember 29, 2017 at 8:40 am
That my fiend sounds like a blockage in the screen of the PRV or solenoid. Ir in the rinse piping/ nozzles. Verify gauge accuracy.
Non related, is the dairy still in operation?
MemberNovember 29, 2017 at 9:04 am
Okay, I can look into the rinse piping. I just noticed rinse pressure is 25 pounds on the top gage. So that makes sense that something is clogged . What Dairy do you mean ?
fixbear - ADK NYMemberNovember 29, 2017 at 10:21 am
MemberNovember 29, 2017 at 11:06 am
Its not open. It was when I was a kid. I think it was called Prospect Dairy ? The last sign on it might say Hi-Health. Not sure how long it has been closed. Maybe over 30 years ? My father-in-Law used to work there I think.
fixbear - ADK NYMemberNovember 29, 2017 at 11:12 am
I was there weekly in 1970. We had a repair shop in it and every tuesday I had a route from Albany to wassaic, wingdale, Stamford, Johnstown and Glens falls. Never got home before 2 AM
MemberNovember 29, 2017 at 11:16 am
That was a while ago. In 1970 I lived right across from the train station. I could see the dairy from my porch. I was around 9 though
fixbear - ADK NYMemberNovember 29, 2017 at 11:27 am
Gene, Olivero reminded me of something I had forgotten. And it sounds like it may be related to your problem. After all, I have worked with assisted housing before. Check this out.
Chlorine in contact with water and as a dissolved gas, sometimes found in water treatment applications, is potentially aggressive to stainless steels.
Localised crevice & pitting corrosion attack is a hazard in water and stress corrosion cracking (SCC) can be an additional hazard in damp chlorine gas, if the temperature is high enough.
Condensates formed over chlorinated water in storage tanks have been known to result in staining or pitting to stainless steels. Improvements to ventilation in such situations should help reduce the risk of attack.
For more there is a linc in the steam generator thread.
MemberNovember 30, 2017 at 1:01 pm
I just cleaned up the tank we changed last year and it is exactly as you described. It has an actual crack and several pinholes. I put 40 pounds or air pressure to it and found that it had other leaks than the one we saw. The booster had been running quite hot for months too. Below where it says improvements to ventilation should help. I take that to mean for the outside of the unit. ? I’m not sure how I would ventilate a tank. I will look at that steam generator thread. I really appreciate your help.
fixbear - ADK NYMemberNovember 30, 2017 at 2:30 pm
So— what is your action plan. Did you find the blockage? I’m betting on teflon tape in the strainer or one of the valves. As for the tank stress cracks and pinholes, Measure your chlorine and ph. I know that the dish machine uses a lot of water a day, but you may have to do something to remove or lower the chlorine level. That or spend a thousand a year replacing.
fixbear - ADK NYMemberDecember 2, 2017 at 1:21 pm
Ok, so I’ve done a bit of research on stainless corrosion and stress fracturing. And it seems that it is usually accelerated by high frequency radiation or magnetic field. Being 480 volt I certain that the the motor field magnetism reaches out that far But more a concern would be a harmonic in your power system. Usually 4th or 7th generation. They are common today with electronic ballast on lighting and computer systems. If you have that problem, it would create a radiation from the heating coils. Also excessive motor heat.
MemberDecember 4, 2017 at 7:14 am
Wow, what in the world could be done about something like that ?
fixbear - ADK NYMemberDecember 4, 2017 at 9:56 am
Find the source of harmonic if it exists. 60 cycle isn’t that bad, It’s when it is around 400 cycle radiation that it gets extreme. The easiest way is to get/ borrow a oscilloscope if you have the background to use it. Today there are power quality analyzers out there, but they are pricey. like Flukes 40, 400, and 900 series.. Some test equipment like this is available to rent from GE test systems rental pool. Or you could find a company to come in a test for it. I don’t know the age of your facillity, to to see a assisted living running 480 is rare. That means a lot of transformers to get down to 115/208 V with their related losses. You can always ask your local electrical house. They would know who has the capability..
On another item with this. Take a magnet and check your tank for any magnetism. If there is any it mans the tank is a 400 stainless, not a 300. That will also increase the ability for it to corrode.
MemberDecember 7, 2017 at 5:20 am
The dishwasher and the booster are 480 volt so that is straight off the power company transformer. I’m not really following how this works I guess
fixbear - ADK NYMemberDecember 7, 2017 at 8:16 am
Gene, Wiki does a good job of explaining them. Google power harmonics.
Generally they are Harmonic voltages and currents in an electric power system are a result of non-linear electric loads. Harmonic frequencies in the power grid are a frequent cause of power quality problems. Harmonics in power systems result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors. Examples of non-linear loads include common office equipment such as computers and printers, Fluorescent lighting, battery chargers and also variable-speed drives. In your case, how much of the buildings are using 277 for lighting? Improperly built transformers or anything with a rectifier circuit will cause them. I had to install a 50KVA square wave power tamer in one customers building.
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