TCD150B300BD blower motor overheating
ok guys, here I am again....
I went to one of my clients the other day, this rooftop trane unit presented the blower motor overheating, and consecuently, the motor was turned off by the thermal protector, the coil was also ice blocked at that time.
I assumed that the motor was bad. And I proposed to change it. They agreed and I bought a replacement from the American Standartdealer down here.
The description between both motors, the old and the new one, were the same (but different brand, the old one was the original motor taht came with the unit from factory , I think "motortech" and the replacement they told me is the correct one is a marathon) as follows:
After I replaced the motor, I spent 1 hr checking the correct function of the a/c unit and it was fine but today, two days later...I receive a call from my client complaining obut the unit...it was not working fine.
Actually, it presented the same symptoms as he first motor did. Overheating and the protector turning the motor off.
As a method for trying to find an answwer,,I measured the voltage/amps in other unit, same model and everything and the motor was using 6.2 Amps (9.3A said the mfg data)instead of 9.6A wich is using the new motor installed and 211V.
Then I found tat the contactor was not good, it showed like a shortcicuit at one of the terminals. I replaced it with a similar T-square 24V coil contactor.
The new motor installed continued using 9.6A @ 211V.
Any ideas? why is the new motor using 9.6A instead of 6.3A
The blower's axe seems to be fine...is in similar shape than the one in the other a/c unit where the motor is using 6.3A ...so I don't now what to do...maybe the contactor was the problem...but I am not sure....I think he is gonna call me tomorrow complaining again.
What to do? wait?
I'm wondering if the iceing has anything to do with it? do you suppose a return is blocked? Or maybe liner blocking inside the duct. If you dont get the airflow, you will increase your amp draw. With a multivolt motor like that one, it's easy to have it wired incorrectly. I'd check all those things as early as tommorrow, and dont make the customer call you. I am assuming this is a direct drive motor, but if wired right it should pull the correct amps.
Look at it this way, The unit HAS been running and now that the coil froze, it's pulling high amps. Or if it suddenly pulls high amps, the coil will freeze when off on overload....you will have to decide which of these it's doing. If both motors react the same, i doubt it's a motor problem.
the icing is a reaction b/c of the motor being disconected by the thernal protector...it doen not have to do with the motor high amps. The motor uses 9.6A all the time, and in all conditions.
Is the blower a belt drive with the motor sheave at the same pitch diameter as the unit that is running the 6.2 A load? Is the supply duct static low and the return duct static high allowing the motor to run into the over amperage range. Is the voltage balanced between all three phases. Are there any bad spots in the wire or any connections that could cause the motor to single phase? extremly worn sheaves can bind up the belt and over heat a motor.
firsd excuse my english, OK first I don't like that 211 volt. the original motor may be, but the new nooo. # 2 clean coil very very good. # 3check dampers #4how you see the fan ran low or fast. #5 locked the blade very close and compared with the other unit.#6 check dirt or oxid in wire,and put very hard.#7 elementary rotation. OK the you has low and discharge pressure ok.good luck
This is a Voyager
Did you check the belt and all pulleys for wear? How much tension is on the belt? Is everything properly aligned? I have run across idler pullers that will seize up after running for awhile then turn freely. I believe this unit has a 2 pole contactor for the blower motor with the third leg wired direct. The contactor may have been a partial problem.
you said this is a tcd150 how old is the unit /filters clean /if blower is pulling high amps all the time check the pulley sheaves probably spun all the way in that will increase amp draw on motor also make sure belt is not overtightened and straight listen for bearings may get resistive when hot causing amp draw
Just a couple of dumb questions. Do you have the motor wired right, the right capacitor for the new motor, & the right speed tap? Did you replace the capacitor when you replaced the motor? Old trane motors had different wiring hook ups for 230 volt & 208 volt power input. Also if you had a frozen coil the amps would go down due to lower air flow if the fan is after the coil. But low airflow also could cause the motor to get hot do to lack of cooling over the motor. Is the new motor an open type frame?
Here we go....
-The blower uses a belt drive motor sheave at the same pitch diameter as motor.
-The static low/high pressures (how to measure them?)
-The three phases are balanced +-5% between each other.
-No bad spots....the motor is using 9.6A all the time with 211V between each phase.
-sheaves ar normal wear, you can turn it with ur hand, turn it manually for 3 or 4 cycles and when you leave it, it wil only run for one full cycle.
-The belt is new B-62 and the tension is correct (not too much tension applied)
-There are 211V comming from the Panel. Same voltage is applied to the motors/compressors. The new motor's plate says 208-230V/460V-3ph
-Coil is clean.
-Dampers?...the air is moving fine across the ducts and running out from all the registers.
-The blower motor seems to be running fine, like 1750rpm
-Blades, are similar...same unit...unit was working 3 days ago, nobody changed the blades.
-belt is new, pulleys are fine.
-tension is fine.
-pulleys are aligned.
-yes, there is a two pole contactor (blue-red wires) and the black (common) wire is wired directly to the motor.
The amps between each other is almos the same.
-Today, I replaced the contactor which was damaged.
-Air filters are new.coil is clean.
-bearings are not like new...but it seem they are working, they dont presented movement when I tryed moving the axe.
-belt is fine and new.
-motor is wired right. It has a switch where you select from 230V (LO) or 460V (HI) inside the case. Of course I selected the "LO" position...then the wires go to 1, 2, & 3...easy connection. Used same wires that the old motor used. The new motor didn't come with the wires.
-NO capacitor, this is a 3-phase motor.
-Only LO or HI setting.
-I am thinking about the case you mentioned:
What if the freon charge (2 compressors) is not correct...and that causes the coil to froze, then the air flow will decrease, and the motor overheats???!!!
- The new motor is totally enclosed. Old motor was open frame.
Please continue with the replies....you are great guys!
is the new motor TEFC (totally enclosed, fan cooled) or TENV. If it's the latter then wrong motor is installed. Usually blower motors are open frame, but you can use a TEFC in a dirty/wet environment & if the motor is TEFC then check the winding type ( a, b or f)
other than that if amps are 9.6 unless you are using a true rms amprobe more than likely your amps are 10 to 11. Amps are too high if pulleys same size as an identical unit then the fan is trying to push too much air= possible broken supply & or return duct inside the buildind near the unit. How much outside air are you running at?
I will check tomorrow if this is a true replacement they gave me.
-I am using a Fluke 370 true rms clamp meter.
-pardon me...the pulleys are not the same size, the shafts are...pulleys seem to be:
(blower) 3:1 (motor) or more. They are the original pulleys. I checked the other unit.
Air flow seem to be fine.
I meant are the pulleys the same size as the pulleys in the other unit. If so like I said earlier look for a broken supply duct.