JFletcher
Senior Member
- Location
- Williamsburg, VA
Need Small Buck/Boost Transformer
- Thread starter JFletcher
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
I don't waste time figuring these things out by myself. I just call Acme Tech Support and tell them what I need and ask them what Transformer they have that will do that. They have a bazillion diagrams on how to wire up Transformers to do just about anything that they can email you.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
170904-0900 EDT
JFletcher:
Ballpark you want about 40 to 50 V output at 0.3 A or at least 15 VA.
Stancor has some moderately small transformers with variable input taps to get different output voltages. But I don't know if there are any 240 V input units.
Signal Transformer makes a lot of different dual input voltage transformers (120 or 240) with many different input to output ratios. You need about a 40 or 50 to 200 ratio. So possibly 240 to 60 V.
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JFletcher:
Ballpark you want about 40 to 50 V output at 0.3 A or at least 15 VA.
Stancor has some moderately small transformers with variable input taps to get different output voltages. But I don't know if there are any 240 V input units.
Signal Transformer makes a lot of different dual input voltage transformers (120 or 240) with many different input to output ratios. You need about a 40 or 50 to 200 ratio. So possibly 240 to 60 V.
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- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
The motor says right on the nameplate that it accepts 208V, you are wasting your time. Just hook it up. All motor voltages are designed for at least +-10%, on 230V motors under 5HP they are generally built as capable of 200-240V for this very reason.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Thanks all. I'm at my whit's end trying to fix these units. They simply suck, and I think it's a design flaw. A nearly brand new 9k BTU unit in tip-top shape cannot cool a small hotel room on even a moderately warm day. Amana has been no help. Grasping at straws here.... heck, 20 year old (which is ancient by PTAC standards) GE 7k units work better...
smartmoney: they are 208 1ph units that are running around 200V at the receptacle.
smartmoney: they are 208 1ph units that are running around 200V at the receptacle.
Seems to be a conflict with your original post saying a 0.22A motor. Don't see how 0.22A is realistic for a PTAC. Perhaps 22A? What's the voltage at the service? What size wire was run to the receptacles?
- Occupation
- Licensed Electrician
That's well within reasonable tolerance for voltage. Buck/boost ain't gonna do nothing for you.
JFletcher
Senior Member
- Location
- Williamsburg, VA
0.22A is the front fan only. The service is 208Y/120. The compressor draws ~3.5-6A depending on model. Back fan draws maybe 0.5A. 12/2 with reduced ground wire (60s or 70s original wiring). Those GE units I mentioned before are supposed to be on 15A OCPD but all the PTACs in the building are on double 20s. :happysad:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
I wonder how much, if any, of the difference is ozone friendly refrigerant compared to the classic Freon?
Could the performance coefficient for an optimized design be that different?
Sent from my XT1585 using Tapatalk
Could the performance coefficient for an optimized design be that different?
Sent from my XT1585 using Tapatalk
Electric-Light
Senior Member
Is it installed correctly to the letter per the installation manual?
I would check for proper exterior intake and exhaust and absence of inappropriate recirculation.
I would check for proper exterior intake and exhaust and absence of inappropriate recirculation.
Without sufficient amount of refrigerant in the system also, there will be poor cooling.
In addition to others' queries, is this one unit or many?
Draw down to 200 volts seems a bit unrealistic on 12/2 with a 7A load. A boost trannie may improve your efficiency a bit, but I don't think it will be significant enough to notice by physical observation.
Draw down to 200 volts seems a bit unrealistic on 12/2 with a 7A load. A boost trannie may improve your efficiency a bit, but I don't think it will be significant enough to notice by physical observation.
JFletcher
Senior Member
- Location
- Williamsburg, VA
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. If you put a small fan on top of the PTAC, the room gets cold very quickly. This is not an acceptable solution tho.
smart$ - many units. there are 96 rooms in the main building.
sahib - these units have 5 thermistors and all have been checked and bad ones replaced. indoor air varies of course but cant go lower than 60*. indoor coil is around 35, indoor duct 40-45, outdoor air varies of course, outdoor coil usually a few degrees higher.
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. If you put a small fan on top of the PTAC, the room gets cold very quickly. This is not an acceptable solution tho.
smart$ - many units. there are 96 rooms in the main building.
sahib - these units have 5 thermistors and all have been checked and bad ones replaced. indoor air varies of course but cant go lower than 60*. indoor coil is around 35, indoor duct 40-45, outdoor air varies of course, outdoor coil usually a few degrees higher.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
I recently did some research on this subject and the information I read disputes this. I am not presenting the veracity of this information, but it made sense when I read it. It drew the conclusion that a nominal voltage of 208 should be using a 200 volt motor, just as motors are not rated 240, they are rated 230 and that rating is applicable to a 240 volt system. I believe it was a Baldor paper that had that information. It went on to state that a 208/230 motor will have a lower life when run at 208 that has voltage dips.
- Occupation
- Licensed Electrician
There are gobs of 230V motors that say "usable at 208V" on the nameplate.
Usable is rather ambiguous - a marketing term. It may have reduced life under ideal conditions, will have lower starting torque, less able to tolerate voltage imbalance, etc. when used at 208.
When I was in the air compressor industry, our motor specs did not allow the manufacturer to supply a tri-voltage (208/230-460) for our 200V applications even though the manufacturers tried to get us to use them. We even got to the point that we quit accepting tri-voltage altogether because customers would get a 230V unit and hook it up to 208 thinking it was acceptable based on the motor nameplate. The motors frequently failed within the warranty period.
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