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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by The MG Pony
Over time I have learnt that after a point there is no reason to continue fixing it up. FYI I didn't say swap out I said flat out replace the whole lot, I'd re-assemble the old one just to figure it out, sell of what was worth any thing.
And what may be that point for you? Seems that searching too long or dmaking some efforts is the main reason.
For me, the decission to replace an item is when it can't be repaired or a repair will cost more then a new one.
"By now I'd have had the system teared out and a new one put in" is exactly what you said, teare it out.
So many replaces parts without knowing why they replace it. "We will change this part and we will see if it's beter, if not, then we will change another part and left the previous part of course and see if this helps"
I have to admit, that's the reason why I hate to service nowadays airconditioning, you have to replace a whole PCB, without knowing what defective part you're changing. On these PCB's, the part that's broken cost mostly not more then a few cents.
But it's the only way to solve the problem.
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Re: MP66 & Compressor Overheating
You said that the valve has a number 1 behind the type.
According to the Sporlan literature, this '1' means that you have a capacity of 1TR, or +/- 3500 Watt.
A 1.5 HP LBP gives +/- 1200 Watt at -20°C, so your present valve is far too large.
Isn't it possible that this valve was placed by the previous tech and that he had turned on the needle so many turns, trying to achieve an acceptable SH that he closed it almost completely?
But if this valve is turned almost completely in closed position, then there's no possibility that it can inject sufficient refrigerant.
You need at least a valve of 1/2 TR or +/- 1700 Watt.
But still the sudden Sh botters me and you have somewhere a point saying that the readings don't support the replacement of the suction line. There should be also an accompanying pressure drop which there isn't.:confused:
But a HE can add heat without changing the pressure.
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Re: MP66 & Compressor Overheating
Quote:
But if this valve is turned almost completely in closed position, then there's no possibility that it can inject sufficient refrigerant. You need at least a valve of 1/2 TR or +/- 1700 Watt.
The valve I have available is 1/2 ton, will work with 401B, and low temp bulb charge. It's externally equalized, just have to put in equalization connection. Should be trying it today.
Quote:
But still the sudden Sh botters me and you have somewhere a point saying that the readings don't support the replacement of the suction line. There should be also an accompanying pressure drop which there isn't.:confused:
But a HE can add heat without changing the pressure
The heat exchanger is only adding around 20F to the total superheat of 100F. So I don't think this is the problem, surely not helping things thought. Customer said he will allow me to "do some playing" with the system after I get it working. Want to see the difference with/without HE. By the way, took Peter's suggestion and printed out a slightly edited version of this thread and gave it to the customer. He was VERY IMPRESSED. Good idea Peter!! Guess you're OK no matter what everyone else says.
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by Intermez
The heat exchanger is only adding around 20F to the total superheat of 100F.
Yes but... The heat exchanger and whatever is happening between the last plate and the heat exchanger is contributing about half of the superheat that you have.
Quote:
Originally Posted by Intermez
Guess you're OK no matter what everyone else says.
Peter is a great guy and I defy anyone to say otherwise.:D
Quote:
Originally Posted by Peter
But still the sudden Sh botters me and you have somewhere a point saying that the readings don't support the replacement of the suction line. There should be also an accompanying pressure drop which there isn't.:confused:
This is the part of the problem I don't like. Pictures would really help for us to see what is going on. The data provided supports Peter's comment above quite well.
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by Peter_1
And what may be that point for you? Seems that searching too long or dmaking some efforts is the main reason.
For me, the decission to replace an item is when it can't be repaired or a repair will cost more then a new one.
"By now I'd have had the system teared out and a new one put in" is exactly what you said, teare it out.
So many replaces parts without knowing why they replace it. "We will change this part and we will see if it's beter, if not, then we will change another part and left the previous part of course and see if this helps"
I have to admit, that's the reason why I hate to service nowadays airconditioning, you have to replace a whole PCB, without knowing what defective part you're changing. On these PCB's, the part that's broken cost mostly not more then a few cents.
But it's the only way to solve the problem.
No I do not do that, I replace total system and log it very well, so next time it needs work there is no guessing you read the log you know the exact age of the parts last opperation don, I am very neurotic about having things tightly organised and loged
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by The MG Pony
No I do not do that, I replace total system and log it very well, so next time it needs work there is no guessing you read the log you know the exact age of the parts last opperation don, I am very neurotic about having things tightly organised and loged
Replacing the whole system just for a faulty TEV? Even better!
Keepings logs, running parameters and a sheet of the used material is of course very good, it's even mandatory in Belgium to do this.
Each intervention on the system must be clearly described in the same booklet and when you had a refrigerant loss, then you must describe where, reason and what you have done to prevent it happens again.
But that's not my point.
Nevertheless, you have your way to solve a problem, I have mine.
And there must be a difference, otherwise there should be no competition.
But, we still have a system functioning not properly that needs to be repaired. ;)
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by Peter
Replacing the whole system just for a faulty TEV? Even better!
This is just too funny.:D :D
And to think... I wasted all of those years sitting in school and listening to the old guys trying to tell me something.
I have not laughed that hard in a while!
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by US Iceman
This is just too funny.:D :D
And to think... I wasted all of those years sitting in school and listening to the old guys trying to tell me something.
I have not laughed that hard in a while!
Lol now come on now, if it where this simple on the system in question I'd imagine he'd be don by now, but long term issues?
I am indeed keen on seeing what the problem is my self.
(As for the old guys I spend nearly ever minute of the day chatting with them ;) when I can; how do you think I've learnt this much? I'm on a 2 year waiting list for my entry course to start)
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Re: MP66 & Compressor Overheating
Quote:
...but long term issues?
Then Kevin will have a life long customer. He tried to fix the system without just changing parts, which by the way, owners begin to notice after the second or third attempt. It does not take them too long before they begin to see what kind of tech is working on their system.
Once you loose your credibility with them, you could solve the problem the next day, and they will think you are guessing again.
Ripping out systems to "fix" problems is an easy way out. I hope the school you go to, does not condone this type of ethic?
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Re: MP66 & Compressor Overheating
you all seem to be jumping to conclusions about my methodology, I would not resort to that right off and oft take times to work away the problem and oft do (Only on computers currently) but if the system has a history of issues and has an odd one then one must consider upgrading. I have a system on my bench in such a state I have worked on it multiple times and have it repaired and this is the 5thed time it needs work (More to it then just that but I'll leave the life story out of it) so I will recommend it is time for them to get a new one. that's what I was stating about this since he said it was having issues be for and if it is a time critical job.
Ripping out and replacing IS NOT THE DEFAULT! you all seemed to assume this is what I was saying when I wasn't.
We all have our own methodologies of doing things (and judging by the loyal customer base for Computer work I have I must be doing some thing right)
either I said it wrong or you miss understood either way we are all way off base as to the thread topic.
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Re: MP66 & Compressor Overheating
In the computer repairs, it's of course something different:
1. it's impossible to pinpoint the faulty piece on a PCB, and even if it should be possible, these pieces can't be found.
2. PCB's and all replacement parts are rather cheap, very cheap compared to pieces in refrigeration.
3. These replacements parts are made to replace, not to repair
4. Swapping pieces in a computer takes sometimes less then a minute. Removing a HE is a work of hours.
If it's not the default, well, I only can agree with you.
Perhaps I misunderstood you, but you must be aware that things can be understood different from what you mean, especially by those where English isn't there mother-tongue. :D
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Re: MP66 & Compressor Overheating
Not to familiar with this system at all guys.
But from a layman s point of view I would at this stage replace the tev and orrifice together (remove faulty tev from equation) also check cappacity of tev and orrifice is correct for system.
Ive pulled my hair out for daus before now because an engineer before me changed the tev for the size he happened to have in the van. (different to the one required)
Also I dont know the system but is their any way to reduce the load in order to test the system?
Has the load changed in recent times and is now too great for the system to opperate.
One last thing R49i is the replacement i use, Maybe the replacement gas your using is the problem, Perhaps try another replacement gas that is a better drop in.
Hope some of that is of use.
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Re: MP66 & Compressor Overheating
MG Pony,
Well, English is my native language and I understood you to say,
Quote:
By now I'd have had the system teared out and a new one put in...
If we assumed too much, then why did you suggest tearing out the system as your second post to this thread?
If I'm coming across too harsh, I aplogize in advance for that, but I do not like the suggestion of tearing out systems, just because the problems are too diffficult to solve.
The important part of this (besides fixing the system) is to keep the owner fully aware of what you are doing to the system.
It is better to explain to the customer you are having some difficulty in finding the problem and then proceed to solve the issues. Most of them will appreciate the honesty and the willingness to carefully review the system before spending money on various parts.
One of the hardest things to learn when you are getting started in this business is... patience. Do not be in a big hurry to solve things.
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by US Iceman
The important part of this (besides fixing the system) is to keep the owner fully aware of what you are doing to the system.
It is better to explain to the customer you are having some difficulty in finding the problem and then proceed to solve the issues. Most of them will appreciate the honesty and the willingness to carefully review the system before spending money on various parts.
I would like to add USIceman: I allways explain my customers what I'm doin and why I'm doing something.
When I'm not sure it's reapaired for 100%, then I also tell client that he can expect troubles and try to predict what troubles we could expect.
Example: there was moisture in the system and the TEV was blocked. I replace the dryer but I tell the client that he has to monitor the sight glassand that the problem can come back.
I learned through the years that if you lie or don't tell everything, that everything will be thrown sooner or later in you face if truth comes above water or another tech comes on site and tells the customer his vision of the problem.
If a customer doesn't or won't understand that a problem can't allways immediately be fixed and that it can take some time before it's fixed, well, then I have happily the opportunity to walk away and he never had to come back to me.
That's the advantage of having too many work ;)
I once had a client who called me at 05 AM on a Sunday morning (in fact night for me :) )
I hadn't hear the phone and the answering machine took up the line in the office.
He made a second call around 06 AM and we heard someone giving an explanation.
So, I thought, I will see when I wake up at 08:00 AM.
At 07 Am, a 3th call and shouting realy loud through the telephone. I stood up and listened to the recorded tape: that this wasn't the proper way of servicing, that his coldroom already had problems since Thursday(!!!) and that it now on a Sunday morning completely had stopped and it was full of meat.
So I decided to go, I was anyway ready to start my Sunday with a croissant.
I told my wife that I should go first to help him before giving him my view and return with the croissanst so that we could eat together.
I entered at 07:20 his shop and he told me something like: "Well, you came walking I suppose, it's more then 2 hours I called you. You can see that' my fridge will be arranged within minutes " I stood their with my toolcase in my hand and in the other the doorknob and replied "Repeat that once again and I will even not place my toolbox on the ground for you. You can shout to your wife like a dog but not to me. If you don't appologise, then I will leave immediately"
His wife appologised for him and I repaired his coldroom. He's still a client but his attitude is changed since then.
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by Peter
I allways explain my customers what I'm doing and why I'm doing something.
When I'm not sure it's repaired for 100%, then I also tell client that he can expect troubles and try to predict what troubles we could expect.
Well said.
This is the reason why I also believe this...
Quote:
I learned through the years that if you lie or don't tell everything, that everything will be thrown sooner or later in you face if truth comes above water or another tech comes on site and tells the customer his vision of the problem.
This is not the type of advertising you want for your reputation...to have people talking about you badly.
I once had a person similar to Peter's story (I'm sure everyone has a story like this;) ). He called at midnight with problems on an ice cream case. He knew about the problem at 6PM, but waited until midnight (after he quit trying to fix it himself??). I told him I could be there early in the morning (sunday morning again).
When I arrived, there was another service tech working on the system. He called every company until someone came right out.
He screamed and cursed at me and said it was my fault! I said OK, sorry you feel that way, and good luck with the new tech and went back home to enjoy the day.
Yes, we are off the topic, but these lessons can be just as valuable as learning refrigeration.
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Re: MP66 & Compressor Overheating
Quote:
Most of them will appreciate the honesty and the willingness to carefully review the system before spending money on various parts.
That would be my first operation would be to solve it, how ever the mentality of this area I live in they'd be at this point wanting it to work, hence by several weeks of looking and geting no where then I'd replace the whole system given that they said it was having issues befor hand.
Then I'd rebuild it at Home and find the problem, becuase I would like to know, but it is what the person wants. It is great the guy wants the old system repaired that is very rare now days (Or at least so it seems in thees parts again)
for some reason I thought this was a time criticle job. and when dealing with old systems with a history of having issues (This is what I got the jist of) it is best to properly build a very well documented one that will give years of truble free service. As the old dock saying goes: you can only patch the haul so many times befor your in a paper boat.
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Re: MP66 & Compressor Overheating
I would not ever lie, that defeats the whole reason to talk, if the info you give is not right then best not waste the air to say it is my saying, no idea how we got on that line of thought, this is what I do, I all ways explain why and what in any field it is the only right thing to do.
Good business is repeat business, and honesty, quality and precision should all ways be the only acceptable out come, and so far I have maintained that stance and methodology and all ways will
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Re: MP66 & Compressor Overheating
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Re: MP66 & Compressor Overheating
Peter, it seems we have lost our little project???:confused:
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Re: MP66 & Compressor Overheating
Hi
It is 12:30 am and I cant read to the end of the thread, not certain if anyone else has posted this...
I have in front of me a publication from Honeywell on retrofitting from R12 to MP66. They state that excessive discharge temperatures and capacity reduction may occur in situations where you have high compression ratios. It can be seen at honeywell website
I am also looking at an article entitled
Compressor overheating Todays's Most Serious Field Problem from Aug 1981 RSC. Without reprinting it here, the author explains the impact of a LL to suction heat exchanger. Adding such a HE to a system with insulated suction line contributes to compressor failures by elevating suction return temperatures.
There is a direct correlation between the discharge temperature and the return gas temperature. The author recommends installation of a desuperheating valve within 6 feet of the compressor.
I am looking at this as a problem of refrigerants gone bad to worse.
If this is a copeland semi-hermetic, I would add cooling water coil around compressor body, or change to different refrigerant. My research is showing that the latest and greatest drop in refrigerant to replace R12, compatible with all oils is RS24. The only issue with it is low temp applications require PE oil, but you dont have to be anal about it. The PT chart for it is almost identical to R12 and minimal glide.
I am going to use this refrigerant on all my changeovers. I would suggest trying it here.
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Re: MP66 & Compressor Overheating
Can you provide us a link to this Honeywell website?
Couldn't find it.
Quote:
There is a direct correlation between the discharge temperature and the return gas temperature.
This is of course true because but where is the big Sh coming from.
What does the author mean with a 'de-superheating valve'?
I could imagine what he's trying to explain but how must this be doen in practice? You simply can't inject refrigerant in the sution line without taking certain precautions.
If the system is well designed, then you don't need fancy tricks to protect the compressor from high discharge temperatures. http://www.refrigeration-engineer.co...ead.php?t=5203
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Re: MP66 & Compressor Overheating
Sorry everyone, the thread is not lost. Was called away due to an unexpected death in the family.
Here's where things are at. Replaced the 7/8 suction line with 5/8 with new insulation. Removed the heat exchanger and suction accumulator. New liquid line and suction line filter/dryers installed. New TEV (externally equalized). I do not have a complete set of readings as of yet but will get them today.
I am now able to keep the system running without it going supernova.
With the factory TEV super heat setting I was seeing about 15F of superheat which gradually decreased to around 2F as the system ran for the first 20 minutes, however I was still seeing the discharge temperature climbing up to about 240F (and still climbing) when I shut things down. Suction temperature at the compressor was around 60F. To me, the problem is still there. At this point I assumed that the large amount of superheat added by the suction line could only be due to low flow.
I decided to forget about the superheat setting at the plate outlet. Decided instead to set the superheat only by the superheat at the suction inlet at the compressor. Took a stab, opened up the TEV by 1.5 turns. Suction superheat at compressor now around 20F. Discharge temperature around 210F. At the plate outlet the readings now are: 6psi and temperature of -13F. This equates to -7F superheat at the plate outlet (negative superheat). This was after 30 minutes of running. Plates seem to be pulling down nicely, but this is where I stopped. Will get a detailed set of readings today.
Is this at all normal in cold plate operation? Obviously there is liquid evaporation in the suction line, but I still have low temps at the plate outlet. The amount of heat added by the suction line is down considerably, running about 30F (not the 100F I was seeing before). I'm not yet sure what happens with these settings as the plates pull down. I also don't know yet if the suction superheat will remain stable as the plates pull down (worried about liquid slugging). Should find out today.
Thanks again guys!, Kevin
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Re: MP66 & Compressor Overheating
possibly not enough refrigerant to do the job?
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Re: MP66 & Compressor Overheating
PROBLEM SOLVED!!!!!
Peter and Iceman and everyone else, thanks for all your help! I know you all thought I was nuts with the symptons/readings I was getting, but they were real.
It was the contactor. The relay/contactor on this system was a solid state one, not a mechanical one. One of the first things I checked on this system was the voltage at the compressor at startup when the current is the highest. It was around 210 volts, just fine. What was happening is that the solid state contactor was heating up and after 5 or 10 minutes the voltage at the compressor had dropped to 190 volts. All AC motors generate excess heat when operating at lower than normal voltage. This excess heat is what was causing the high exhaust temps. Replaced the contactor with a good old mechanical type and can now adjust things as they should be. It's now working fine. Will have to do some fine tuning but everything is now operating as it should.
By the way, if any of you recall somewhere near the beginning of this thing, I mentioned that the system had both a temperature and suction pressure shut down for some reason. Don't like a temperature shutdown, so I disabled it by setting it to -10F. The system shutdown because with a lot of tweaking I got it down to -10F. When it shut down, I figured I had locked up the compressor, as I had totally forgot about the temp shutdown. Started taking voltage readings to figure out what was going on. That's when I discovered the low voltage problem. So I can take no credit for solving this, it was just dumb luck!
Thanks again everyone, Kevin
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Re: MP66 & Compressor Overheating
Kevin, congratulations.
I should never had thought on this propable cause.
This was really a very, very difficult one.
I think that you have learned a lot with this s...y thing.
And this is also something I will try never to forget.
I was wrong with my diagnosis.
A SSR is indeed not the best option for this kind of application. I only use a SSR when there's a need for very fast switching.
Anyway, these service calls will make you every time a better tech then already are.;)
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Re: MP66 & Compressor Overheating
Well, well... If someone were to say we got our knickers in a knot over this project I would have to agree.
It still doesn't explain the high superheat out of the last plate and through the wall though:confused: .
If it works, I am not going to kick a sleeping dog.;)
In any event, I hope all of this was worth something to you Kevin.
Quote:
Originally Posted by Peter
Anyway, these service calls will make you every time a better tech then already are.;)
Amen brother...
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by
US Iceman
If it works, I am not going to kick a sleeping dog.;)
Should this be posted in the other thread :D ?
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Re: MP66 & Compressor Overheating
I'll add that minor contribution to the other thread Frank.
Do you want to guess how many kicks it takes?
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Re: MP66 & Compressor Overheating
Thanks again everyone!
Quote:
It still doesn't explain the high superheat out of the last plate and through the wall though:confused: .
This problem and all the other weird readings were because of low ***** flow, not enough gas flow to keep the temperatures from rising quickly.......just the way I had to set the TEV to keep things running without the compressor temp going over 250F. All the readings make sense now that I have a compressor that is acting normally. Oh yeah, remember the low ultimate suction with no flow....I'll bet it is higher now that the compressor is running with full voltage.
Finally :p , Enough school for now, Kevin
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Re: MP66 & Compressor Overheating
Quote:
Originally Posted by Intermez
This problem and all the other weird readings were because of low ***** flow, not enough gas flow to keep the temperatures from rising quickly
I'm not sure if I buy that. The contactor had nothing to do with the mass flow, other than the fact the compressor shut off.
50 degrees of superheat increase within a few feet of pipe is not an answer of low mass flow.
But, if you are happy with the results then I won't argue about it.
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Re: MP66 & Compressor Overheating
it seems the compressor capacity is insufficient or compressor inefficient.
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Re: MP66 & Compressor Overheating
Still sounds like a compressor capacity problem