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Bard V. Marvair and Bard's Economizer?

T

TomZ

I'm struggling to keep a BE 25T happy during the heatwave in Kansas.

Here's what's happening:
The 'shack' is a nice Cell box with two Bard wall AC units. One has an 'Economizer' that won't completely close and it's been hot-wired to let the compressor pump. These are either the 20WA1 or the 24WA2 models. I can't find the model plate but I have an 8th generation photo copy of the installation instructions that doesn't define much about either unit.

OK; back to the other foolery; The other side of the cell box hosts two Marvair Compact 2 series AC units. These units have been a disaster since installation about three years ago because the won't do a hard start. The need a human hand to switch the little lever from cool to off to cool after they have faulted due to high pressure.

At this moment, I have a level of balance that should hold the BE 25T in good specs overnight; but the morning promises more heat............ so, I need to clean the condenser coils on the Marvair boxes but this horse pasture holds no water.... could a leaf blower push any debris back-through the condenser coils or should I go find a guy with a mobile car wash platform and do this right?

I believe they are max-engineer'd to perform at their peak.
 
I see I forgot to address the Economizer.

It's trash but I can't see how it controls the rest of the box. I tied the yellow and blue together and now the compressor work but I can't seem to understand the black and red wires....

Surely the red powers the damper actuator and the black holds it's hand.... right?
 
My HVAC techs use a tank of nitrogen with a high-pressure regulator (not your usual line-pressurization 0-20 pound regulator) to clean the coils on indoor condensers where we can't flood the floor with water. Keep in mind that nitrogen is a rapid asphyxiant. I would not use it in any enclosed space that could not be very well ventilated and I would have someone else outside just in case. It does work - I've seen the high side pressure drop by 100 lbs with a single B tank blown through the coils of a 3.5 ton system.

The hard-start failure is more likely an issue with a low-head cutout. This should be bypassed on startup by a bypass timer until the compressor has had 15-20 seconds to develop pressure. Not sure what Marvair installs but a conventional AC unit has a small three-terminal plastic timer box with a rotary knob. A high head trip is more likely after extended operation, when it's extremely hot outside, or with clogged coils.

I'll also use a pump-type garden sprayer for routine cleanups, but they don't develop enough pressure to do much worthwhile.

Not sure on the economizer wiring but a failed economizer should be able to be blocked in the full-open position mechanically.
 
I've got eleven Bards of various vintage and two Compacs scattered about in the Georgia heat. We maintain them religiously, otherwise they will fail in the heat. You need to find someone who is familiar with them (Not always the easiect thing to do), and set up regular maintenance a couple of times a year. We clean coils after the annual dandelion seson... otherwise they simply pack back up with dandelion fluff. I have the tech show up with a LARGE tank of water in his van and a pump. He uses this to clean the coils with commercial coil detergent exactly the same as he does the ones with water in a hose available. We don't run the economizer. In our climate, easily a third of the load is apparent cooling, it makes little sense for us to pull humid air into the plant and then pay handsomely for the electricity to throw the water back overboard. Once the box is dehumidified, there's little infiltration of heat or moisture, all the A/C has to do is throw the transmitter waste heat overboard. We stick the HD injector waster loads outside as well, it saves 5 - 7KW of waste heat to the A/C units.

Keep them maintained, they will take care of you. Let them go to rack and ruin, and you'll spned a lot of time fixing ovrtemped equipment. It's cheaper in the long run to maintain them.
 
Thanks guys for your replies. As of this morning, I plan on taking a good leaf blower out to the pasture to see if I can push some of the Kansas dust back into the air.

I'm hoping this will give me a few more hours to find a guy with a mobile wash trailer.
 
Mention something, it give trouble. As of last night, one Bard that takes the breaker out on compressor engage, one which pciks up the blower but no compressor. Sigh. This is the second compressor I've lost in the facility in sbout six months.
 
Not that this has anything to do with anything, but Marvair is based in my hometown of Cordele, Georgia. I worked there for a very brief period of time in the mid 80's.
 
One thing I noticed while moving the leaf blower wand over the condenser coils is that the aluminium is extremely flexible. I'm off the idea of high pressure washing the coils.

The vendor is now in charge of this and I'm watching from the sidelines.

I believe the devil is in this detail:

High Pressure Switch
The high pressure switch is mounted on the compressor discharge line. It is electrically connected to a lockout relay which shuts down the system if the refrigerant pressure rises to 625 PSIG. This protects the unit if airflow through the condenser is blocked or if the outdoor fan motor fails.
Although the contacts of the high pressure switch close when the refrigerant pressure falls to approximately
450 PSIG, the system must be manually reset once the lockout relay is activated. A manual reset is necessary to prevent harmful short-cycling. To reset switch, turn primary power off, then back on or turn thermostat system switch off, then back on.

Found in the manual: http://69.33.187.224/marvair/pdfs/ComPacIOMan411.pdf
 
What a crappy design. While I agree that a high pressure cut-out is needed, timers are not that expensive and an anti-recycle timer would be a big help here. Oh well live and learn.

I've got a completely different problem here with aluminum fin deterioration on the coil of a 60 ton chiller.

Bob
 
At an AM site have a 2-ton Trane that was installed in 1968. Only major thing that's ever been done to it was the outside fan motor was replaced last year. Bearings finally gave up. Runs on 440V.
 
1968? Surely the year is wrong.

I always see Trane units providing bone chilling cold. The experts over sized a unit in Indy a few years back. 10 Ton unit w 10kw transmitter running at 4kw. (24 x 24 building) It was all I could do to keep it warm enough to service the transmitter in the summer.

A Church near here (Kennard) has a Trane, looks to be a 7 to 10 ton unit, ac for their Church. Older people (sigh me too) like cold rather than hot. It runs well with not a lot of pampering.

The simple design and apparent good design make these wonderful units to deal with.

My AC guy used a sprayer with some heavy duty cleaner to service all our units. (We had many varieties in the 15 units.) Once the soap was on the fins and was soaked in he had another sprayer (or the hose) just to spray this off. He carried a fin straightener too and shook his head at the high pressure sprayers. He claimed they did more damage. I could jsut schedule him yearly with that many units and usually did this in the spring. We had cottonwood that would clog the units regardless of our attempts.
 
1968? Surely the year is wrong.
Click to expand...
Found the manual for it with that date.
It's always been there since I first saw the transmitter site around 1972 or 1973 tagging along with the CE.
The electric heat is 8-stage 3-phase 480V ! Uses a Honeywell Modultrol damper motor to rotate cams that turn on microswitches in sequence. That turns on each stage as needed.

It is showing signs of EOL. CAP-Ex is in the works to replace it.
 
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