Need Small Buck/Boost Transformer

Status
Not open for further replies.
retirede said:
If the shaft load is 'X' horsepower, the motor doesn't know if it's a fan or something else.
Click to expand...

With fan type load, torque required decreases with speed and so horsepower. With constant torque loads, the reduction in horsepower is small.
 
JFletcher said:
golddigger, they are R-410 units, have been for many years. It seems to be as good as R-22.

electriclight, not installed to the letter of the manual, but none are and they all work fine. the air is plenty cold; the front fan just doesnt move it well enough.
Click to expand...

Well, this is a plausible symptom if the installation practice deviation from the manual is something that might affect the airflow. You could get a 120v to 240v travel transformer and run both fans from an outlet just to confirm if a transformer would do anything while letting the compressor run on original circuit. Since 200v under load is within the ANSI tolerance for 208v service, if this fixes the issue, it's a manufacturer's issue. This is assuming installation deviation doesn't affect air flow. (like clearance on the back, sides, proper placement in wall)
I don't know the specific piece of equipment but also check diagrams in the cabinet that there's no taps for 208 vs 230v. Such a tap is common in kitchen equipment.
 
Yes, 50 VA will be sufficient. 24 volt secondary passing 1 amp (actually .22 amps) is 24 VA.

This will bring voltage at the fan up to 223 volts. Give one a try and see if the speed picks up. Just wire it into the room fan circuit, nothing else.

I found Acme makes a 208 (and other taps) to 24 at 50 VA. Here is an example:

https://www.platt.com/platt-electri...-480-24/Acme/TB81321/product.aspx?zpid=654226

Is physical size the problem?
 
What other causes are there for the fan to turn too slowly? It is a two speed motor. When high speed is selected, the fan does in fact switch from low to high speed. The fan wheel is clean and the bearings lubricated. The run cap is a 2uf unit; changing this out yielded no results*. Would a 2.5 or 3uf cap make any difference? Is there a way with a stroboscope or something else to measure the speed the fan is turning?

The only other thing I can think of is a control board issue, yet everything else works fine, and if the boards were going bad, they'd fail in a variety of ways and probably more catastrophically than running the indoor fan slower than normal.

*Was changed from another unit. I spoke with Amana today; that cap is likely the culprit. Easy fix I should have caught before now.

Frank, if I need to install that I think there is enough room in the chassis for it.

eta: new PTACs are quiet. They achieve this in a variety of ways: better insulation, smaller compressors, and .... smaller fans that move hardly any air. There are 25 year old GE and Carrier units still going hard even with coils that are (were) nearly completely clogged. Yes, they arent whisper quiet, but a new unit that has no margins for anything being slightly out of whack is worthless when it's 95* outside. The units are sized correctly for the rooms, and even the 12k BTU units have the same identical front fan as the 9k ones.
 
Electric-Light said:
Well, this is a plausible symptom if the installation practice deviation from the manual is something that might affect the airflow. You could get a 120v to 240v travel transformer and run both fans from an outlet just to confirm if a transformer would do anything while letting the compressor run on original circuit. Since 200v under load is within the ANSI tolerance for 208v service, if this fixes the issue, it's a manufacturer's issue. This is assuming installation deviation doesn't affect air flow. (like clearance on the back, sides, proper placement in wall)
I don't know the specific piece of equipment but also check diagrams in the cabinet that there's no taps for 208 vs 230v. Such a tap is common in kitchen equipment.
Click to expand...

No such luck. The units have dual ratings on everything based on if they are 208V or 240V - heating output, cooling output, everything, is lower at 208 than 240V.

I have checked the wall sleeves and grills as well as other possible airflow restrictions. The front coil and filter are clean, the cover is installed correctly, no drapes in the way, and so on.
 
Hi, JF, have you checked the rated CFM for the air conditioner with an air flow meter? It may be given in the unit manual. A thumb rule is 400 CFM/TR.
 
Sahib said:
Hi, JF, have you checked the rated CFM for the air conditioner with an air flow meter? It may be given in the unit manual. A thumb rule is 400 CFM/TR.
Click to expand...

I have not tho I know it's low. I believe factory specs are 280/340 CFM for low/high speed. The opening is roughly 2" x 2', and due to the design of the fan, airflow is uniform across that opening. 340CFM/.4 ft2 = 850ft/min, or 14.2fps, or 9.7mph. I'll need exact duct measurements of course. Standing 5' in front of the unit, you cannot feel the air coming out. I've also tried orienting the grill both ways (more out vs up and vice-versa).

These units have a local (unit mounted) thermostat. It'll be 60* at the PTAC and 80* across the room. Units simply dont blow air far or hard enough away to cool the room uniformly. I'll have some new 2uf caps in the morning, will see if that solves the issue.
 
Do not try to oversize the capacitor lest it should increase the current in the winding beyond its capacity.
 
Sahib said:
Do not try to oversize the capacitor lest it should increase the current in the winding beyond its capacity.
Click to expand...

Yeah the Amana guy said to not go with a 2.5 or 3uf cap, tho I will not be using Amana caps to replace the 2uf ones in there; I prefer the metal caps to the tiny printed circuit board looking things that are in there. Fortunately that cap is not attached to the board.
 
Oh. I didn't think of this earlier. Get 240 out of a CWA metal halide ballast that has both 208 and 240 taps. Give it to 208 and feed the 240 from the 240 tap to the fan. Set the whole thing up outside the unit on the floor. You don't connect anything on the secondary side where lamp goes.

Interconnect into the cabinet with a lamp cord and use a 3-way switch as a SPDT so you can switch it back and forth between 208 and 240v. Don't touch any part of it while energized and don't place it into actual service.

This is a test set up just to prove or disprove your theory. The fans will have a bit more oomph and you'll hear it but I doubt it will solve the issue. But in the slim chance it does, you'll have to figure out how to deal with the remaining 95 or so units
 
JFletcher said:
I have not tho I know it's low. I believe factory specs are 280/340 CFM for low/high speed. The opening is roughly 2" x 2', and due to the design of the fan, airflow is uniform across that opening. 340CFM/.4 ft2 = 850ft/min, or 14.2fps, or 9.7mph. I'll need exact duct measurements of course. Standing 5' in front of the unit, you cannot feel the air coming out. I've also tried orienting the grill both ways (more out vs up and vice-versa).

These units have a local (unit mounted) thermostat. It'll be 60* at the PTAC and 80* across the room. Units simply dont blow air far or hard enough away to cool the room uniformly. I'll have some new 2uf caps in the morning, will see if that solves the issue.
Click to expand...
That is what I have noticed in hotel rooms. Turn the unit down and it will be cool near the unit, cool enough the thermostat isn't calling for cooling, but not sufficient enough air flow to mix the air throughout the room. Given enough time the other end of the room will cool down, this sort of works if you leave the temp set and don't adjust it constantly. In hotel room housekeeping likely changes it back to wherever they are told to set it whenever guests check out, and the room never really stabilizes in temperature.

Window shakers aren't really much different - cool near the unit warm across the room.

Discharge air and return air are so close to one another you mostly recirculate the same air through the unit, especially when mounted close to the floor as colder discharge air will tend to fall to the floor and that is the air taken back through the return.

You need ceiling fans to stir the air up and even the room temp.
 
kwired said:
That is what I have noticed in hotel rooms. Turn the unit down and it will be cool near the unit, cool enough the thermostat isn't calling for cooling, but not sufficient enough air flow to mix the air throughout the room. Given enough time the other end of the room will cool down, this sort of works if you leave the temp set and don't adjust it constantly. In hotel room housekeeping likely changes it back to wherever they are told to set it whenever guests check out, and the room never really stabilizes in temperature.

Window shakers aren't really much different - cool near the unit warm across the room.

Discharge air and return air are so close to one another you mostly recirculate the same air through the unit, especially when mounted close to the floor as colder discharge air will tend to fall to the floor and that is the air taken back through the return.

You need ceiling fans to stir the air up and even the room temp.
Click to expand...

Nope, I need old PTACs that are loud and blow air like a hurricane, not these new prissy, quiet, energy saver POS models. Some people complain about noise; this place has block walls and is low enough budget you WANT some 'white noise' in the background to block out the other sounds you're going to hear, like the local train passing by every 30 minutes, gunfire, and yocals gettin' 'good and ****** up!'

As much as I'm not liking this PTAC side project, I can tell you that surface mounting EMT and boxes for ceiling fans here and then tying into the existing FPE panels seems markedly less fun, tho at the rate new units are going, every hotel room in the future may very well have a ceiling fan to help the crappy PTAC out.
 
Status
Not open for further replies.
Top