Something I missed?

[Gary]

If the valve SH is sitting on the border of conflict with TD (fourth circuit (SH index circuit)) then there wouldn't actually be a whole lot of stroke left for it to open through.

Which would mean that it is running wide open.

[busman]

Well, I give you all credit, you've got your thinking caps on. I just got home from another family party, and it's waayyy too cold to be messin' around out there right now. Temps in the 20's F, with a 40mph wind gusts, near zero wind chill with snow to boot. I just locked out my heat pumps and I am firing on hydronic boiler at the moment.

The distributor tube lengths, are all exactly cut, and carefully measured. Now, as stated before, I could not find a distributor with the size tubing that Sporlan's software called for. They called for 3/16 tubing. Sporlan does not offer a 7 circuit 3/16, only in 1/4 inch. Using 1/4 tubing does not offer the pressure drop needed to properly distribute refrigerant. I used the 1/4 one, and used exactly and evenly cut 1/4 tube stubs to mount into the distributor, and then sweated the 3/16's into the 1/4 tubing. Unconventional, yes. Insertions were all at exact measurements, so that all would be even too. All 3/16's were debured, and inspected to allow even flow between all circuits. I'm starting to wonder here if maybe there is something going wrong in the distributor because of this "unconventional" usage of the distributor.

[Gary]

It is entirely possible that the increased delta-P from refrigerant overcharge is affecting the distribution also.

It seems to me that we are putting the cart before the horse. This system has multiple problems, and we need to identify and resolve them in the proper sequence. The frost pattern is likely to be the last problem on the list.

We need to start with a full list of temperature measurements.

We already know that the airflow needs to be reduced and the charge needs to be adjusted. Who knows what other problems a full list of temperature measurements will reveal?

[busman]

I'm not sure if we are going to be able to come up with the "perfect" conditions for this unit to work at and attain a "perfect" charge. The ambient temperatures that this unit will run at, is anywhere from +55°F to down to +15°F. With an outdoor coil half the size of the state of Georgia, it's going to be hard to find an extact charge. I've tinkered around with the thought of managing the liquid end somehow, but unsure how. Since this is a heat pump with a reversing valve. I could come up with a receiver, about 4 check valves, and create some kind of liquid "rectifier" of some sort, but thought that it maybe somewhat unpractical.

When I first put this unit online, I did have it overcharged. It shut off on high pressure late one night running in heat mode (mild evening). So I reduced the charge. Then last year, I added refrigerant because I opened up TXV, and it has run happly since, with the exception of the frost.

Little unsure about your delta P idea. Are you talking across the entire valve to evaporator inlet, or just post TXV across the distribution assembly?

Re-hashing some of the other ideas here too, not sure I've gotten the jist of the TXV superheat/full stroke open idea either. It seems as though this problem is persistant across most of it's operational temperatures, only just being more noticable when frosting occurs.

As for head pressures, it is mostly dependant again upon ambient temperatures it's operating at. It will varies from at the lowest ambient of operation about 200 psi to as high as 325 at it's warmest operation. Of course it's really nice in the summertime, because the head just barely even gets to about 200 on the hotest day, and bottoms out sometimes around 150 on the coolest of days.

[shogun7]

Busman in a heat pump the out side coil that is too big can act like it has an insufficient charge, liquid line restriction, or TXV problems which can generally cause what is called the ZEBRA EFFECT, which are bands of frost like you describe. Now, some physics and heat pump basics, the warmer the outside air, the more capacity it has for moisture. Heat pump coils generally run 20° colder than the outside air temperature to facilitate heat exchange. So if the outside air temp is 35, the coil is 15° or so - plenty cold to lower the air passing through to dewpoint temperature and then convert the condensation to frost. Moderate outdoor air temperatures accelerate the frosting phenomenon, other things being equal. Now of course the only way to prove the is by taking the proper readings as Gary suggested, but I suspect that unless you install a smaller condenser you will not do much to alleviate the present situation. It seems to be working in a fashon, but you can try to do some of the recommendations that have been brought up with out replacing it

[shogun7]

Which of course brings us all the way round back to the original question "Why the uneven frost pattern?"

Or were you hoping that you could hide the fact that you have no idea of whats going on by merely giving the symptoms an exotic name? Intellectual camouflage.

Well of course your just jelous because you didn.t think up the term EH bumbkin? Boy are you thick! the reason has already been explaned ...the outside coil is too big for the application!!!
DID YOU HEAR THAT? peanut brain? now if you want the exact cause then it's because of uneven refrigerant mass flow. You
see I don't need all the double talk to make me sound like you that is state many various reasons and hope I hit the right coard. By the way what are you afraid of? That I might be right?

[shogun7]

In what way is the coil too big?

You see, it's like asking the officer at the scene of an accident (officer shogun):
"what caused the accident, officer?"
and officer shogun answers:
"well, accidents occur when things go wrong."
And so you persist:
"what went wrong here, officer"
and officer shogun answers:
"Well, can't you see, dummy, there's been an accident"

Perfectly logical...What I hope I'm not keeping you up too late Listen I have to go work out now so why don't you get some sleep youv got a big day tomorrow ...Right!

[Gary]

I'm not sure if we are going to be able to come up with the "perfect" conditions for this unit to work at and attain a "perfect" charge. The ambient temperatures that this unit will run at, is anywhere from +55°F to down to +15°F. With an outdoor coil half the size of the state of Georgia, it's going to be hard to find an extact charge. I've tinkered around with the thought of managing the liquid end somehow, but unsure how. Since this is a heat pump with a reversing valve. I could come up with a receiver, about 4 check valves, and create some kind of liquid "rectifier" of some sort, but thought that it maybe somewhat unpractical.

OR... You could flip the fan blade over and get me a full set of temperature readings.

When I first put this unit online, I did have it overcharged. It shut off on high pressure late one night running in heat mode (mild evening). So I reduced the charge. Then last year, I added refrigerant because I opened up TXV, and it has run happly since, with the exception of the frost.

It's running, but it isn't happy and it certainly isn't efficient.

Little unsure about your delta P idea. Are you talking across the entire valve to evaporator inlet, or just post TXV across the distribution assembly?

Re-hashing some of the other ideas here too, not sure I've gotten the jist of the TXV superheat/full stroke open idea either. It seems as though this problem is persistant across most of it's operational temperatures, only just being more noticable when frosting occurs.

As for head pressures, it is mostly dependant again upon ambient temperatures it's operating at. It will varies from at the lowest ambient of operation about 200 psi to as high as 325 at it's warmest operation. Of course it's really nice in the summertime, because the head just barely even gets to about 200 on the hotest day, and bottoms out sometimes around 150 on the coolest of days.

Pressures and temperatures by themselves don't mean a thing. As you hinted by relating high side pressures to ambient temperatures, it is combinations of temperatures that tell us what we need to know. In this particular case, subtracting the ambient from the SCT gives us the condenser TD.

Given a full set of temperatures, we can combine them in various ways to tell us everything about the system.

My books would greatly improve your skills.

[busman]

Yes, I know, get the numbers. Wife is out shoppin' at the moment, I could only steal away long enough to read replies. If I don't get my honey-do list done before her arrival, then I may have some explainin' to do about my time and where it was spent. . . don't want to have to do dat.

Will keep you posted. More company coming over tommorrow night. I guess they don't call it the 12 days of Christmas for nutin'.

[Temprite]

My books would greatly improve your skills.

Gary I am interested in purchasing your books,but when I go to the payment section of the site,no window comes up telling me that it is a secured site.Normally if I am on a secured site this window appears.

Rick.

[Gary]

Gary I am interested in purchasing your books,but when I go to the payment section of the site,no window comes up telling me that it is a secured site.Normally if I am on a secured site this window appears.

Rick.

The site shows "secure" for me, indicated by a closed lock at the bottom. Is anyone else having this problem?

[Temprite]

I have gone in there and seen the closed lock.But when I used to run windows 98 as an operating system it used to bring up a window indicating a secure site.I presume my current operating system (windows xp) is the same.Sorry to be a pain but you can't be careful enough when you are giving credit card details over the net.

[Gary]

Given that I am still on Win98, I don't know if XP has the same features. And quite possibly the window you refer to is an optional function of your browser, which may not be currently activated.

I can only assure you that your transaction will be secure.

[Gary]

If the lock is locked.

Exactly so. The closed lock is the universal symbol for a secure site.

[shogun7]

You'd have to be either an NT or a freak to get that one.



Indeed, according to the data so far available, the problem can only be uneven refrigerant distribution. Until that is sorted you likely can't start making any ultra-efficient adjustments to the refrigerant charge. Unless of course you throw another NT into the pot

Indead you twit that's what I have been saying all along, NOW you decide to come in from the cold All I can do is feel sorry for you dip sh*t! I will pray that you recover from being constipated of the cerebril

[Temprite]

Given that I am still on Win98, I don't know if XP has the same features. And quite possibly the window you refer to is an optional function of your browser, which may not be currently activated.

I can only assure you that your transaction will be secure.

Gary
You were right.
I enabled the function and as soon as I went into the products section it informed me that it was a secure site.
Thanks.

[Gary]

Gary
You were right.
I enabled the function and as soon as I went into the products section it informed me that it was a secure site.
Thanks.

I get so tired of being right. It's a curse.

[busman]

Well, now as the holiday schedule has calmed down a bit, I went to tinker about the unit this afternoon. Went to gather all the info that I could, and my thermocouple thermometer was not being co-operative. Seems that as the temperature of the instrument drops, it's reading increases. So, unless there's something new going on here with frost froming at 45°F, I'm going to have to hunt down a new instrument.

[busman]

Well, it's so nice to be in company of so many "cursed" and "blessed" people in this forum. Hopefully after 12 pages and over 100+ posts we'll all be right about something here!

[Gary]

Did you turn that fan blade over yet?

[Superheatman]

Just browsing and caught this posting of yours...if you havnt got around to sorting the problem yet then it is because you have your thermocouple plugged in back to front...just reverse the pins by 180 degrees and the thermometer should work fine,,,,

[busman]

Thermocouple is plugged in correctly. I have made that mistake before. It is an instrumentation problem. I keep forgetting to borrow the other instrument to do the test. I thought that after the holidays things would quiet down enough to go and piddle around with this thing again, but still seems to be a struggle.

I tried slowing down the fan blade to see what would happen, and it didn't seem to make much difference at all.

I talked to one of my fellow techs around here about the problem. Question after question, and answer after answer to no avail. Finally came to the conculsion that if all else fails, you could always crimp down on the lines that are over feeding. Not the best answer in the world, but starting to look very enticing after all this.

[frank]

I got called out to a Toshiba 13kw RAS unit in the week and noticed a similar sort of zebra frosting pattern when the unit had been running for 20 minutes or so. The system running amps were a little low and it may be a little short of charge. The problem was not related to the defrost and I'll leave the charge question until better weather.

[busman]

When you say "zebra" are you talking about an un-even frosting pattern between circuits, or are you talking about just even frosting between circuits leaving you with stripes of frost on the coil?

Now that you mention it, we've had a case one other time with this un-even refrigerant flow thing before. It was a Bohn evaporator in a walkin cooler. Cooler held about +37° (sorry, just a bit above zero for you Celius chaps) If I remember correctly, it had three circuits. Bottom circuit froze up very badly. Big ice ball on the bottom of the coil. Someone along the way put a big drain pan under the factory drain pan to catch the dripping off of the ice that grew out from the coil. Thought, "hey must be no nozzle in the distributor" or something along that line. Guess what, everything was "textbook." Correct orifice size, TXV, charge was good, distributor orientation, on and on and on. . . Still to this day it does the same thing.

[frank]

When you say "zebra" are you talking about an un-even frosting pattern between circuits, or are you talking about just even frosting between circuits leaving you with stripes of frost on the coil?

Even frosting between circuits

[Gary]

I tried slowing down the fan blade to see what would happen, and it didn't seem to make much difference at all.

Did you flip the fan blade over? How do you know if it made a difference or not? Did you measure temperatures before and after? Without temperature measurements, this is meaningless.

You are looking for a single problem, with a single solution; A single magic bullet cure. Sorry, it doesn't work that way.

You have multiple problems, and the only way to solve them is to take a full set of temperature measurements and solve problem #1, then take a full set of temperature measurements and solve problem #2, etc., etc., etc., following a logical sequence.

Now you are going to start pinching tubes and make the system worse not better. You can then add pinched tubes to the list of problems.

Multiple sequential problem solving is what separates the techs from the wannabe's, and what it takes to follow the wannabe's around fixing their screwups.

[Peter_1]

http://www.climaticcontrol.com/info/jjzgate/Infotec/Info-Tecs1-10/Infotec_7(rev1).htm

http://www.outokumpu.com/pages/Page____18588.aspx

[Gary]

If the TEV and distributor dP exists with at least more than approximately 4K subcool then the problem indeed lies with the distributor and so something mechanically associated with the distributor would have to be changed to adjust the ballance of distribution. Right now, poor distributor performance is the only logical explanation for the uneven distribution. Crimping distributor tubes is logically a potentially pragmatic solution though not necessarily practical.

We don't know what the subcooling is, nor the delta-P or anything else, because we don't have the proper temperature measurements. If the refrigerant is completely boiled off before it reaches the coil outlet tubes, then all of those tubes will be at the same temperature, making it near impossible to adjust flow by crimping tubes.

Clearly the first step is to reduce load by reducing airflow. And we need full sets of temperature measurements to see what the system is doing each step of the way.

[busman]

Well, the cobbler's kids have no shoes. Preach to everyone about maintaining their own systems, and yet I go three months without cleaning my own air filters.

Some success has just been scored this week. I just got a Fluke16 meter for buying some guys some lunch. Not too bad, $14 dollars later walkin' out with a $140 meter. Time has been crunched here lately with some other more important projects. I will hopefully be able to sneak outside sometime here soon.

Looking back here, you keep saying turn over the fan blade. How in de heck is this going to make any difference? I don't follow your train of thought. You would only be changing air flow. Air flow may change, but how will that effect uneven refrigerant feeds to the circuits? The TXV may open and close, but already on previous occaisions, with different refrigerant charges, and superheat settings on the TXV, and same results.

I will experiment and give a full suite of numbers when time allows . . . more sooner than later I hope.

[Gary]

Well, the cobbler's kids have no shoes. Preach to everyone about maintaining their own systems, and yet I go three months without cleaning my own air filters.

Some success has just been scored this week. I just got a Fluke16 meter for buying some guys some lunch. Not too bad, $14 dollars later walkin' out with a $140 meter. Time has been crunched here lately with some other more important projects. I will hopefully be able to sneak outside sometime here soon.

Looking back here, you keep saying turn over the fan blade. How in de heck is this going to make any difference? I don't follow your train of thought. You would only be changing air flow. Air flow may change, but how will that effect uneven refrigerant feeds to the circuits? The TXV may open and close, but already on previous occaisions, with different refrigerant charges, and superheat settings on the TXV, and same results.

I will experiment and give a full suite of numbers when time allows . . . more sooner than later I hope.

You should never use the word "only" when referring to airflow. Proper airflow through both coils is critical on all systems.

In this particular case, you have a 3 ton TXV trying to control flow through a 10 ton coil. You have derated the coil by going to a smaller fan motor running at a lower speed, but it isn't enough.

Until the airflow is reduced to derate the coil enough to allow the TXV to modulate, the TXV cannot be adjusted properly.

When the TXV can be adjusted down to about 7F superheat, then you will find that you have WAY too much refrigerant in the system.

When the refrigerant charge is adjusted (to the proper subcooling) then you will find that the indoor coil is more efficient, as well as the compressor, the operating costs will be reduced and the whole system will have a longer lifespan.

And oh yeah... you also have a distribution problem.

[busman]

Really quick here guys, I was able to take a quick reading the other morning. I didn't write down all the numbers, but a quick summary for ya: Suction line temp at just before the accumulator was 2°F colder than ambient (23°F) I took a reading off of one of the non-frosting lines, and I had similar reading. Frosting line was reading 19°F at the outlet of the coil. I think we can call that a distribution problem.