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Old 06-17-2011, 05:55 PM   #31
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PTAC On-Off is in the Breaker Box...


that wiper is called C(common ) becuase it feeds the speed wires within on the selector fan switch,and it has no power in the heating season "IF" the klixon senses hot water so it can supply the stat at 2 remove one end of the jumper tell us whats working or not

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Old 06-22-2011, 11:30 AM   #32
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PTAC On-Off is in the Breaker Box...


At the moment the rotary switch in the control box is bypassed. The blower fan is wired direct from the junction box.

I found a replacement rotary switch, made by the same manufacturer, also intended for A/C, but I noticed there is a difference in the specs.

The old rotary switch was rated for 15A at 120V. The candidate replacement switch is rated at 10A at 125V.

So the amperage rating is lower. On the other hand, the motor in my unit is 1/10 hp, and the new switch is supposed to handle 1/4 hp.

My shaded pole motor draws 1.55 A, according to the plate.

The relay in the system (which draws current though the switch) is rated at 8A.

Two of these Fan Coil Heating/Cooling units (living room and bedroom) plus the wall outlets on one LR wall and one BR wall, are all wired to a single 15A breaker in breaker box.

Is it okay to install the new 10A rotary switch in place of the old 15A rotary switch?

In other words, what does the amperage rating on a switch really mean? It is the typical usage current? Or is it the "Never Exceed" amperage?

Thank you for your insights.

John

Last edited by John Harris; 06-22-2011 at 03:30 PM.
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Old 06-22-2011, 06:03 PM   #33
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PTAC On-Off is in the Breaker Box...


that amp rating on the new selector is OK the switch might of been a generic one used when they might of also pulled a compressor load thru it or a bigger fan motor on the bigger sized unit....that is the MAXd rating but not a constant load thru it especially with a minut 1.55A as tagged...i worked on Trumps HI-rise condos in NYC he had 8000/10,000/12,000 BTU PTACS most of the controls were all the same ratings just in one condo.you load even totaled up with all three could go thru that switch...for reference...thats why its a 15A breaker.any motor draws 10X its rating on start for milli-seconds (called Locked Rotor in the indusrty) either it be a fan motor and or compressor its the run amps that a CB or switch needs to hold...
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Old 06-22-2011, 09:12 PM   #34
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PTAC On-Off is in the Breaker Box...


Thanks Biggles, that's good.

I would like to install the new rotary switch for motor speed control only (Off, High, Normal and Low) and leave everything else out of the circuit.

The wires from the switch are already color coded (Red, Blue, Black for Hi, Normal and Low), so this should be a straightforward wiring job.

The motor return (white) is already wired to normal in the junction box.

At present the "hot" wire is connected directly to the red wire from the motor. I would undo this (hacked) connection. Then I would connect the red line from the motor to the red line from the rotary switch. The hot line would then be connected to the switch wiper.

This should give me control of the fan on/off (and speeds) at the unit, instead of at the breaker box.

Then, over time, I can remove, study and troubleshoot the thermostat, the relay, and the Klixon.

Thank you again for your excellent analysis and help on this problem.

John
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Old 06-23-2011, 07:42 AM   #35
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PTAC On-Off is in the Breaker Box...


anytime...your definitly on top of it with your info here...just to verify the hot in the cooling mode goes to the fan speed selector switch and feeds the selected speed and in the heating mode seems it is a dedicated speed with that relay because the hot to the selector is aced thru the stat and klixon swing into heating pipe temp....if you already realized this just ignore my babbling...
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Old 06-23-2011, 08:45 AM   #36
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PTAC On-Off is in the Breaker Box...


Yes, I understand from the wiring diagram that the cooling and heating modes are intended to be different.

But I suspect the Klixon may be fused in one position or the other, and I know from measurement with the VOM that the relay shows an odd value (5000 ohms) across the contacts. Seems to me it should Closed or Open, not something in between. Net of it: I suspect both the Klixon and the relay are bad. I want to cut them both (and the thermostat) out of the circuit.

What I have in mind is a simple fan-speed rotary switch circuit that works in the same way summer and winter.

Basically that's what I have right now, in the hacked system. I flip on the breaker, and the fan runs full blast -- summer or winter.

By installing the new rotary switch I hope to 1) move the on/off to the unit, so that I don't have to keep visiting the breaker box and 2) add the refinement of High, Normal and Low fan speeds.

Would this create a problem, in winter operation for example?

Thank you for your insights.

John
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Old 06-23-2011, 09:01 AM   #37
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PTAC On-Off is in the Breaker Box...


the Kloixon swings the 115Vs to the stat and then the stat swings it to the relay/heating fan speed or selector/cooling...the action the klixon does allows the stat to change from summer/winter the klixon is the pipe stat and the unit stat is your control.might consider removing the relay and give yourself all the fan speeds in the heating mode just like cooling....let the unit mounted stat control cycle the fan in heating or cooling at any speed....sounds easy from hear typing away

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