Condenser motors overheating.

[edward301]

Have several singer refer units, some 20hp, some
10hp units where some of the condenser fan motors
have gone bad. Replace motors with same specs,
and new motors get hot and thermal shutdown. Cool
down and do same all over again.

Motors were 1/3hp, and went up to 1/2hp but still
having same problem, just not as much. Caps are
new, and proper value. Not sure what to think.
Voltages are correct also.

Fan blades are 22 inch, and 27 pitch. Do not
know it fan blades are correct, since they were
there when I took over. They fit correctly so
the 22" diameter is good, but 27 pitch may be a
bit much. Motors are 1075 rpm, should I drop to
say 850 rpm. Motors I took out were 1075 rpm.

Any ideas.

Are motors today over-rated

[frozensolid]

Check you supply voltage. If it is low you could be over amping those motors.

[jhd1234]

I ran into a similar problem on Hill units a number of years ago. Amp draw on the replacement motors was ok but they would overheat and shut off on the thermal protector. They were horizontally mounted and out of the weather underneath the hood on the cabinet. I took the ends bells off the air inlet side of the motor and punched out the stampings so that air could flow thru the motor from that side. It solved the problem. When selecting a replacement motor, you have to make sure the amperage draw of the replacement meets the specs of the failed motor, irregardless of the horsepower. However, be careful about replacing with a motor that is too large. An underloaded motor will overheat. If you change to 850 rpm motors, you might reduce the condensor airflow too much. You didn't mention if you checked the amp draw of the new motors.

[refer dude 2479]

Check the condenser and make sure it is clean. HP requirements for a prop fan increase as the static across the fan increases. Plugged condenser increases static. Have you measured the amp draw. how does it compare to name plate. Also motor reliys on air flow to cool. Air flow loss also could be dirty condenser.

Good luck

[frozensolid]

Amp draw? Do you have other motors without problems, with the same blade?

If it’s an airflow problem, you should be able to see that with your head pressure.

You may want to check your volt drop across any switches, relays or contactors.

[edward301]

Voltage is 230. Amps are good, relays are good.

While air flow is good, a few units are running
high head pressure, 300-325. If I put some water
on coils head pressure drops to 225-250, as
would be expected. I am going to give the
coils a good cleaning, and see if condenser
motors do better. Units running with R409a
should not have that high a head pressure.

I can only go with the dirty coil possibility,
as 2 unit have no fan problems, with the same
motors. As some unit have 3 condenser fans,
and others have 2, I can only feel part of the
condenser coils are dirty, and sometimes only
one fan of the 3 will thermal out.

Do any of you have thoughts about putting water
misters in front of the coils during the summer
months. Only put out a fine mist, not large
amounts of water.

These units are on a gravel roof, and it gets
very hot, with no air movement. They all run
full time, and get very hot, even the cabinet
is very hot to the touch.

[jhd1234]

My thought is misting water onto the condensors will scale them up making the situation worse.

[refer dude 2479]

Originally posted by edward301
Voltage is 230. Amps are good, relays are good.

Do any of you have thoughts about putting water
misters in front of the coils during the summer
months. Only put out a fine mist, not large
amounts of water.

These units are on a gravel roof, and it gets
very hot, with no air movement. They all run
full time, and get very hot, even the cabinet
is very hot to the touch.

I would not recommend water on the condenser. The water evaps and leaves all the crap in the water behind. Just keep the condensers clean and you should be fine.

[icemeister]

If you've got Singer condensing units, they've got to be at least 25 years old. The Singer name disappeared when Dick Snyder bought everything up and formed Snyder General.

Those units were a little short of condenser from the git-go (especially the MT units running 25 Deg F evap temps)and if they're dirty, just cleaning should help. If they're badly corroded enough so you've lost the mechanical bond between the fins and the copper tube in the coil, you're done for.

I've got a C-Store customer with a 5 HP R12 Singer MT unit on the walk-in cooler. It's still got the original 1978 Copeland thumping away and surprisingly since it's only 100 yds or so from the Beach, the condenser is still mostly intact. I've found this puppy running as high as 350# on R401A (MP39) but with a good coil washdown it settles out to around 240-250# on a 95 Deg F day.....still pretty high, but doing the job.

I had to replace the condenser fan motor maybe 6-7 years ago and as I recall it had a 1/3 HP resilient mount motor but I had to go to a 1/2 HP replacement to get the power and amps right. It has a 27 Deg pitch 4-blade fan that should be moving a LOT of air. If you're not getting the airflow, you'll get high heads like what you're seeing.

Clean that coil.

[R12rules]

Did you say Austin? I work in Austin. Wanna have lunch?


I'll let ya borrow my latest amp clamp.

[edward301]

R12rules:

I thought someone said you worked in Austin.

I will get back with you last week of June,
Out of town next week.

[skunky]

Voltage is 230. Amps are good, relays are good.

While air flow is good, a few units are running
high head pressure, 300-325. If I put some water
on coils head pressure drops to 225-250, as
would be expected. I am going to give the
coils a good cleaning, and see if condenser
motors do better. Units running with R409a
should not have that high a head pressure.

I can only go with the dirty coil possibility,
as 2 unit have no fan problems, with the same
motors. As some unit have 3 condenser fans,
and others have 2, I can only feel part of the
condenser coils are dirty, and sometimes only
one fan of the 3 will thermal out.

Do any of you have thoughts about putting water
misters in front of the coils during the summer
months. Only put out a fine mist, not large
amounts of water.

These units are on a gravel roof, and it gets
very hot, with no air movement. They all run
full time, and get very hot, even the cabinet
is very hot to the touch.

Is your head Pressure than it Should be In Hot Weather?
I am in Texas and If you have a unit on the roof with 105 Degree ambient and 112 Degree heat index Due to Humidity Then It will Run Very Hot but That is Normal in very Hot weather Just make sure your coils are Clean and your charge is Good to cool the Compressor and you should be ok if your head Pressure is not too high I have had Rooftops Where the Units Were Surrounded By other units like AC Units Exhaust fans and have a 6ft Skirt around the roof With no airflow and Recirculating the heat from the other Units and That can cause some really bad Problems

[crackertech]

Is your head Pressure than it Should be In Hot Weather?
I am in Texas and If you have a unit on the roof with 105 Degree ambient and 112 Degree heat index Due to Humidity Then It will Run Very Hot but That is Normal in very Hot weather Just make sure your coils are Clean and your charge is Good to cool the Compressor and you should be ok if your head Pressure is not too high I have had Rooftops Where the Units Were Surrounded By other units like AC Units Exhaust fans and have a 6ft Skirt around the roof With no airflow and Recirculating the heat from the other Units and That can cause some really bad Problems

skunky you do know that this post is from 2004 right.:)

[tjc76]

skunky you do know that this post is from 2004 right.:)

it must be the phosgene crackertech:D

[crackertech]

it must be the phosgene crackertech:D

phosgene I................like it.:cool::D:D

[fl_dude]

Have several singer refer units, some 20hp, some
10hp units where some of the condenser fan motors
have gone bad. Replace motors with same specs,
and new motors get hot and thermal shutdown. Cool
down and do same all over again.

Motors were 1/3hp, and went up to 1/2hp but still
having same problem, just not as much. Caps are
new, and proper value. Not sure what to think.
Voltages are correct also.

Fan blades are 22 inch, and 27 pitch. Do not
know it fan blades are correct, since they were
there when I took over. They fit correctly so
the 22" diameter is good, but 27 pitch may be a
bit much. Motors are 1075 rpm, should I drop to
say 850 rpm. Motors I took out were 1075 rpm.

Any ideas.

Are motors today over-rated

Today I have had sized a 24" diameter blade, with 27 degree pitch, and 3 blades at 1100rpm, on a 35f box. To run these we was advised to use a 3/4hp motor. So knowing your working on the condenser which will be much warmer than my 35f box, your 1/2 hp motor seems to small to me.