frozen evaporator on military a/c

[hardtime$]

i am a marine on active duty in a foriegn country under combat conditions unfortunately im not allowed to say which one. i am also a refrigeration mechanic working on a/c's that keep communication gear cold. i am having a problem with the evaporator coils freezing on my a/c's. my modern refrigeration and air conditioning book tells me about something called a "baffle". i would like to fabricate one for the a/c's but i have two questions first. 1) does the evaporator have to hanging vertically or can it be horizontal. 2) does any one have any idea on how to make one of these baffles.

not trying to insult anyones intellegance, but a baffle is a bunch of drain pans used to catch condesation before the evaporator coil freezes over. i'm not sure if it is placed before or after the evaporator. all i have is a picture with an evaporator attached to a "baffle".

thank you, hardtime$

[dash]

Your "baffle" sounds like what I'd call a drip eliminator,it catches water driing off the coil,that doesn't track poperly to the drain.

Coil freezing ,would be due to other causes,low charge,dirty filter,coil,blower wheel,lack of airflow.etc..


Model numbers,tonage,etc. may help,if you post them.

[air of honesty]

If your nighttime temps drop much below 60 while your load stays constant, you might be freezing due to low freon pressure. Do you have a head pressure fan cycling switch on the high side?

Very common in communication/computer applications.

[hardtime$]

i do apologize but im afraid i dont even know what a head pressure cycling fan switch is.

as to the first reply i got already thought of all those basic troubleshooting still have same problem. thought i had a possible leak but system checks out ok on vacuum. and elec leak detector, soap solution and halogen leak detect.
as for information on a/c itself. not authorized to post due to the fact the nationals can intercept sat signals. my apologies.

[cdp3]

Originally posted by hardtime$
i do apologize but im afraid i dont even know what a head pressure cycling fan switch is.

as to the first reply i got already thought of all those basic troubleshooting still have same problem. thought i had a possible leak but system checks out ok on vacuum. and elec leak detector, soap solution and halogen leak detect.
as for information on a/c itself. not authorized to post due to the fact the nationals can intercept sat signals. my apologies.

Hardtime,

Check into "Motormasters" and head pressure cycling switches. ICM makes a nice little unit that wires in fairly simply. All it does is slow down the condensor fan to allow the head pressure to build up. The perfect solution for low outdoor ambients and A/C.

If filters, coils are clean, charge is correct, and fans are running properly (amp draw?) I would step up to these.

Good Luck and keep your head down!

cdp3

[Dad]

Straight talk...

If it is cold at night (60 or below) try this

Put your gauge set on one of the units. Take a light weight blanket, cardboard, plastic sheet or alike and cover about 1/2 of the outdoor unit but do not block the discharge air only the coil. If you block too much of the coil you will over amp the outdoor fan motor and burn it out so be careful.

Keep your head pressure over 230 and under 275. Not the best way but if you don't have the fan cycle controls you need it is better than a nothing.

Your problem may be caused by outside low ambient conditions and interior high temperatures. Blocking the outside air flow will raise the head pressure. If this works then you will know the cause and the cure.

Call supply and have them send a refrigeration pressure fan cycle control with 1/4" flare connection fitting and 48” cap tube, a 1/4” flare Schrader tee and a couple feet of #12 thnn wire for each unit you service. Adjust the fan cycle to cut out at 225 with a differential of 35. Put the Schrader tee on the high side valve of the outdoor unit and install the fan cycle on the tee (be sure to remove the Schrader core so the control will see pressure).

After you install that run some wire from the fan cycle control and interrupt your outdoor fan power leg. Be sure to leave the high side valve cracked open so the fan cycle control can be pressurized. You should be able to use your gauges on the other side of the tee and see pressure. Trust me you will know what to do.

If the blanket doesn’t do it you will not need the fan cycle controls.

Your problem may also be too cold interior temps or undersized system too. If your system runs constantly even with good airflow you are going to freeze up sooner or later.

Good luck and let us hear from you.

[troyorr]

Why don't you use the equipment repair manuals that should be provided? You don't have to be so vague about the equipment or your location. Just because a piece of equipment is used in a "Military" application, the operation is the same. Get your gunny or someone else that knows what they are doing to work on the equipment. Either it isn't a critical piece of equipment or you have caused a site to go down unnecessarily.

[maxster]

if the unit had none before and is icing up now its either the air across dirty coil,or your charge on the suction side reacting to a possible low ambient outside.the other techs can see what this baffle idea is from the bookhttp://ww2.imagewiz.net/images/hvac/141766_usmcbaffles.JPG

[hardtime$]

well thank you everyone for your advice ill get back to you on whether or not it probably will.
oh and to troyorr thanks for telling me to check my manuels or ask someone else. i never thought of that man, i should have asked you what to do 9 months ago when i first got here. oh and dont get upset if i cant tell you where im at or what kind of a/c it is. just because your anti coalition.


there is no such thing as a stupid question, only a confused person.

[hardtime$]

well thank you everyone for your advice ill get back to you on whether or not it probably will.
oh and to troyorr thanks for telling me to check my manuels or ask someone else. i never thought of that man, i should have asked you what to do 9 months ago when i first got here. oh and dont get upset if i cant tell you where im at or what kind of a/c it is. just because your anti coalition.


there is no such thing as a stupid person, only someone in need of guidance.

[troyorr]

hardtimes, get over yourself. Where you are and what you are working on has no bearing in what I posted. If you don't even understand the nomenclature of the industry, you shouldn't be attempting to work on the equipment. You are obviously young and inexperienced so you need to ask someone there that is physically standing in front of you. Ask someone of a higher rank or experience. Please don't try and play the patriot card by stating I am anti coalition. Step back and let the skilled veterans do the work.

[maxster]

hardtime$...if you have to run the unit and the temps outside drop to below 60F overnight,take a garbage can top with a brick on top of it and put it on top of the condenser.this will act so as to stack the heat off the condenser within the coil area and give you a better head pressure.the liquid line should be just a little warm going into the wall from the condenser if it is hot slide the cover off the top slightly to let some of the condenser to top discharge,and the liquid line will drop a little in temp but you don't want it cold going in.you can do the same with newspaper/plastic wrap/cardboard on the outside of the condenser and wrap it around cover half 360 degees around and adjust it again to liquid line temp.i am taking you have a round condenser if any other style either restrict the air into or discharging out.if you have a belt on the evaporator and an adjustable sheave...close it in to get more air changes over that evap(flush up the top of the belt to the top of the sheave)

[Short Circuit]

Your mechanical issues are far from "classified", and the pro's on this site couldn't care less your specific "position" on this earth; you yourself stated you're in a "coalition" area. Duh! You mean Iraq? That's probably more than we needed to know here, BTW. Jeez.

Posting mechanical numbers and pressures, and just talking technical, is in no way classified. Some folks on this site are veterans, and they want to help you. Your AC needs are also not needed, perse, other than perhaps stating (if true) that you have a need to cool down 24x7 hot equipment.

My suspicion is that you are in over your head in fixing this problem, and that is why some Pro's stated, very eloquently I thought, for you to seek assistance. Nothing wrong with that, you know. If you solve this issue, that equipment will be happy-happy, and folks you haven't the faintest clue of whom use that equipment will not have problems down the line with their comm or CPU equipment. Think of the bigger picture, soldier. Get help.

[ham&egger]

Lets give you the benifit of the doubt. Still you are a MARINE. Stop your whining

[lcimpala65]

This whole post sounded a little fishy to me from the start. If this individual is a refrigeration mechanic, he either is not one for the US Marines or he is very new to the job. If he were trained by the Marines, he would have been trained to an extent that he could easily troubleshoot this problem. Could be he is a communications tech trying to fix something he was never trained by the Marines to do. The A/C in question is more than likely an enclosure air conditioning unit, these units usually employ a hot gas bypass valve to keep the evaportor pressure from dropping too low under low load conditions. Either way I wish him luck and that he stay safe where ever he is.

[highlimit]

[QUOTE]Originally posted by lcimpala65
[B]This whole post sounded a little fishy to me from the start.

Yea, he could even have been an Iraqi.
Answering his question might be treason.

[resolutetech]

Worse yet, he could be working on John Kerry's campain bus's ac system and trying not to admit that to the vetrans on this sight. hehehe

[leander]

I totally sympathize with this Marine. He deserves more respect. When I was in Vietnam the 1st Sgt asked if anyone has an air conditioner at home. Several of us said yes. The next day we were designated refrigeration specialists. Our main job was to replace the dirty ice as it melted.

[Edmund Forsthe]

where's kbr when you need them?

[troyorr]

leander, no one is disrespect him. Since he has been trying to fix this problem fo over 9 months, anyone can see tht the problem is above his abilities. Get help from someone that knows.

[troyorr]

lmtd, your post made absolutly no sense.

[Dad]

It made perfect sense..


He said, go get help to pull out the panties. :D

just kidding....

[hvac_tech_en3]

I know what you mean by government equipment i was in the navy and hafe of the crap i worked on didnt have tech manuals had to shoot from the hip...... thanks for serving and come home safe maybe you all ready have but anyways thank you ..

[Mod2]

Short Circuit:

If you are at where I think you are, see the special tech at FSSG, headquarters.

[Special Ed]

Something's fishy here. First & foremost, nothing about the design & operation of an A/C is classified. Heck, he gave us its purpose but he can't give us model/serial #? I can understand not giving us his exact location; however, in most cases there is a rep from KBR to take care of the A/C. Lastly, if he's where he says he's at then parts aren't so easy to come by & may take longer than he has left in-country to get to him.

In short, Hardtime$, you may have to rig something up for now to cure your problem.

[2hot2coolme]

Ha Ha Ha... That was funny! You guys been bamboozled, I knew this guy was a hoax after reading the first couple posts, you've been had...Ha Ha Ha.

By the way, I'm a Captain of the USS Lexington and the boilers' not working properly what should I do...