Hi
I have a 4 years old York Diamond-80 furnace/ac unit. Its blower motor went bad and was replaced under warranty by contractor who installed the unit when the home was build.
When the mechanic was replacing the motor I noticed he pulled a little probe type rod (about 5" long and .150" thick) from the old motor casing and when he tried to slide it into new motor casing he had hard time. He then decided to connect the ground wire to a stud on motor casing instead of the rod where it was connected before. System operates and works fine but I like to know,
Is it safe or I should call them to put the rod back?
Is that rod/probe is only for ground or it works as temperature sensor too? (I'm concerned about overheating)
Any help will be greatly appreciated.
Thanks
Dhaniyal

As long as the motor is grounded that is all that matters. Many untrained HVAC service people simply do not connect the dedicated ground and this can be a problem.

Feel lucky you got a good service person to do your motor change.


BTW I have never seen a motor temp sensor directly connected on a residential HVAC system motor. They are used on motors in commercial or industrial variable speed applications where the temp is monitored along with speed to prevent damage.

Thanks for your reply havc1000
I forgot to mention that motor is 1HP and I wasn't sure about that probe wither it's for ground or temp sensing (I don't know much about A/C systems).
So what I understand from your reply that probe was for dedicated ground terminal and I'm okay as long as motor is grounded?

Yes to the ground

One HP is a large motor on a residential unit. You must have a large duct system and a lot of square feet to cover.

I would like to add that you said your unit was only 4 years old. If it was running at hight speed and the supply and return duct is not designed for it the one horsepower motor on high speed can draw to many amps and die a early death. It does not have to draw enough to trip the over load in the motor just enough to slowly cook the windings. I hope the service person used a amprobe to set the speed of the motor to a safe level/speed.

We live in a single story 2650sq ft unit.
The a/c unit is only 4 tons but 14seer and I was told by the inspector and these a/c guys also that this size is okay for these new energy efficient homes. I started noticing almost from beginning when we move in this brand new house 4 years ago that whenever heater is running I could hear a rough sound from above kitchen ceiling area where unit is located also motor used to make rattling type of sound. May be this was a bad motor from the beginning but I'm concerned now just like you mentioned “it not draw too much power to trip just slow cook the windings” I think this exactly what happened we turned heater on one day and little burned smell and system stop working. Technician told us motor is not burned but its getting overheated, capacitor was okay. I ask him about one of the rooms not getting hot or cold enough because is the farthest in the home (but it has an air return) Technician told me it could be the type of filters I'm using it’s over loading the motor (I use pleated filters with 1050 micron filtration 3M).
Can you help me figure out what killed my motor, was that the filter or my ducting or just the bad motor.
Motor runs quite now no rattling

I hate to tell you this but from where I am at I cannot help to find the problem that really caused your motor to go out.

What really needs to happen is a service person with a amprobe needs to take a reading on the motor that is installed now and compare it to the maximum draw that is on the motor label. We are now concerned with the motor you have now not with the old burnt one.

The only correct way to set up a blower with the correct speed so the motor lives is to use the tool I mentioned above then is the reading is below the rated draw of the new motor all is OK.

If you are worried I would get it tested before you loose another motor and have to pay for it down the road.

If you express your concerns to the shop that replaced the motor and act knowledgeable they might come out and let you watch the meter and read the motor label so you know for sure. Many times the maximum draw is also on the motor box so they may not have to remove the motor from the blower to find out the draw.

I might add that this test needs to be done with the air filter you are using installed and the blower door closed. The motor power legs can be accessed in the main furnace wiring area for testing. It is imperative the filter and the blower door is on or you will not get a true reading.

My company service sheets always contained the draw of all motors on every service call so that we could tell the customer if they might be facing future repairs. That bit of extra work sold many a motor for us because most of our commercial customers did not want a breakdown to deal with and they would just replace marginal motors and other parts as preventative maintenance.

Thanks for your detailed answer.
You are absolutely right my concern s/b about new motor and that’s what I meant when I said what killed my old motor so we can trouble shoot the cause.
I'll try to contact the company who installed the system and all the ducting to check if they are willing to work with me to avoid any future warranty service calls.
I also like to post pictures of some of the ducting and furnace so you can get an idea and give some expert opinion about that installation if it is correct or can cause system to over load.
I also like to know if I get a third party (with you recommendations) to come and check how much this will cost me.
Zafar

You can post some pictures but what really needs to be done is a manual D if you suspect duct/air flow problems.

Answer this question? Does the unit heat and cool the house with in reason?

Is the air distribution OK (but not exactly perfect) in all the rooms?

Yes, unit works overall very well. On/Off cycles/intervals are very well matched.
Distribution also is very good when the system is running I can feel the air flow almost same in all areas of home except one room. Witch is less hot or cold than the rest of the home, this room which is master b/d has very high ceiling and too less gap between ceiling and roof and also this room is farthest from a/c unit. That is the only problem area.
Thanks
Zafar

Hi,
As you suggested I was finally able to get load test on my blower motor.
Motor is 3 speeds 1hp, 1075 rpm and 12.2 amps.
Current draw with full load is between 9 and 9.15 amps


Note: I posted above info in another thread but posting it here to keep all related info at one place.

9 to 9.15 looks good.