ReplyI would try tech support as long as you are a contractor they will help you.
If not try a Diamond Dealer and see if they will assist you.
Regular Guest
I have been working on a Mitsu for the last 2 days trying to figure out why it's not shutting off when the unit when temp has been met. I had to have the electricians come out and change their wire because they used 12awg and it needs to be 14awg so that these systems can communicate properly. Did that and the thing still isnt working. I went there today and customer has a wet bed and shows me pics of ice chunks on his bed. Thermisters? Can anyone help?
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I would try tech support as long as you are a contractor they will help you.
If not try a Diamond Dealer and see if they will assist you.
Quality and Value Service and Repair
Professional Member*
bigger wire will not cause communication problems.Originally Posted by bgymn2002
Now, ice chunks on the bed????
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Is it a single or a multi?
Regular Guest
It is a three system outdoor unit with only 2 connected. I was told my a tech at one of our supply companies and he told me to add ref. 1.62oz per every 5 foot over 25 foot of lineset. Still didnt work. Then found out that this three system or heads supposidly doesnt need any additional ref. unless the lineset exceeds I think it said 131ft or more add 1.3 or 1.6 oz.
Professional Member*
[QUOTE=bgymn2002;11284492]It is a three system outdoor unit with only 2 connected. I was told my a tech at one of our supply companies and he told me to add ref. 1.62oz per every 5 foot over 25 foot of lineset. Still didnt work. Then found out that this three system or heads supposidly doesnt need any additional ref. unless the lineset exceeds I think it said 131ft or more add 1.3 or 1.6 oz.[
I would check the wiring. I'm betting it's crossed so the other unit is energizing the wrong lineset.
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[QUOTE=Dr.phil;11284612]
Regular Guest
Is that the s1,s2 or s3 you are referring to? Could it be the freeze protection on the indoor because it maybe stuck open and cant close to turn the system off?
Professional Member*
What happens is on startup, the tech turns on all of the zones. If the wiring is crossed, he would never know because all linesets would be energized. If the wiring is crossed, when one zone is satisfied, it shuts off. The other zone energizes it's lineset, continuing to freeze the evap, taking any safety out of play. Making a great ice maker. The tech is already gone, and never knows, until he gets the ol WTF, from the next guy. That's why I recommend starting each zone individually.
Professional Member
The change from 12 to 14g wire was unnecessary. Sorry to say, but you should have known that. Larger wire merely entails less resistance, which can almost never cause a problem...
I wonder about the crossed wiring possibility, but presumably you would have traced that? Would only take a few minutes. I'm not really familiar with the Mr. Slim systems, I do Fujitsu, but I'm actually surprised if it wouldn't catch that error itself? The Fujitsu would, I believe, because it diagnoses coil temps etc: you would turn on a unit, and it would notice that the coil temps aren't changing as expected. At least I think it would catch that.
My bet is on a bad temp sensor. Does this happen in both the zones, or only one? Can you duplicate it while you're there? Ice on the bed? I have trouble believing that... So what, water condensed on what, the ceiling? and then turned to ice, and fell on the bed? Are you sure you trust this client to tell you the truth? How big were the ice chunks? The entire room got cold enough to form ice, when it was presumably hot enough outside to be running an air conditioner... I hereby register myself as doubtful.
Regular Guest
I changed the sensor and problem solved. I want to thank everyone for the advice.
Professional Member*
LOL
Just a guess, but don't you think the unit must be mounted above the bed?
Professional Member
Haha, I had a picture in my head and I didn't let go. It just sounded so ridiculous. Right, it was frost falling off the coil. That's funny.
Never mind....
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lol I actually had the same thoughts as you at first....
A question.... Would it actually matter if you had the unit "a" wired to the unit "b" terminals?
Professional Member
I'm mostly familiar with the Fujitsus, but you'd just get an error code telling you as much and it wouldn't run, I believe. I could look up the error code. Same thing happens if you miswire the communication wire with one of the power leads, for example... I can't vouch for how the Mitsus handle it.
Professional Member
Actually, every service school I've ever been to has said larger wire can cause communication problems. Due to the skin effect, the signals tend to travel on the outside of the wire, not straight through it. Larger wire can lead to distorted signals. I've never saw it myself in the field, but that's info straight from the manufacturer.
Professional Member
Interesting point. But I believe the communication line still functions at or less than 60hz, and the skin effect is a feature of AC and a function of frequency. In which case the skin depth is over 8mm, which is thicker than the wires of either 14 or 12 gauge. In other words, there isn't really a skin effect at 60 hz in those wires. But I might be wrong on the frequency (though it would have to be quite a bit higher to expect a problem).
If we were talking about high-frequency signals that were expected to be on 18g wire, I'd have an easier time believing a jump to 12g could be a problem, though like you said I've never seen anything like this in the field. Then again, I haven't really thought about it, so maybe I wouldn't have noticed! Thanks for drawing attention to it. I faintly remember talk about this, but haven't looked at it for a LOOONNNGGGG time.
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Code in NYC calls for #12 on the ductless units. The local Fujitsu reps have emphisised it at the F.A.S.T training. Never had a problem yet Mitsu or fujitsu.
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