I just replaced my pool pump motor and the new one seems to be running real hot (140f or so measured on the case)
I don't remember old one running that hot.
1HP single phase 240v
It is pulling 4.8a or so.
Input voltage is 251+ but that is normal here.

A little follow up. I checked my neighbor's pump, on the same transformer as me, he is running 140 too. The guy down the street is 131 or so but I am not sure what his voltage is.

New motors tend to run a lot hotter than the older ones.

To cut costs, manufacturers put less iron and wire into motors nowadays. Some also wind with aluminum rather than copper. They can get away with this to some extent because modern insulation materials can operate at high temperatures better than old varnish/fishpaper could.

The motor nameplate may provide Temp Rise and/or insulation class ratings. These may provide a clue whether "hot" is "too hot". The temp rise listed is above ambient, so some motors can operate quite hot under normal use.

I am sure the ambient is part of the problem. This was sitting at 88-89 before I turned it on.

Yeah that the part of issue and is the sun is " beating " on the motor like sun is shining on the motor ?

If so that can raise some of the tempture a bit.

I know the tempture rise will start at the ambenit tempture plus the nameplate for tempture rise so that you add them together it get pretty hot side.

Merci,Marc

This is on the south side of the house but it does get some shade right over the motor.

This is all I have

That is good picture there Greg.,

50°C = 122°F

so it mean it have 50°C rise above the ambiment tempture so what you got now is roughly 80 degress {F} now then add 122F result 202°F now that is very warm it the same idea with transfomers but the motors that something you have to watch little more closer and with your area., Greg I know how hot it get down in Floridie { I been there pretty often so I am famuir with hot weather ( Alabama is little more hotter due I have one home I used live there for short while and it do get very hot in summer }

Did you ever make a little roof or dog house roof above the pump motour ? if not maybe try that idea that will help a bit there.

Merci,Marc

The motor is in the shade. I have pan roof over the whole thing.
The insulation Class B says internal temp can be up to 130C.
I am still not sure how that translates to the case temperature since there is some cooling going on. Unfortunately these are 3R rated motors so there are no vents on the top of the case. Since my neighbor's motor runs at virtually the same temp I assume it is normal but I am wondering how much money I am wasting. I bet a high efficiency motor runs cooler. This was the one the pool store stocks. If I had more time I would have shopped around at a real motor supplier but it was dead.

I don't see any "rise" or hot spot allowance listed on there, merely a note that it's rated to 50C ambient temp, which is awfully hot, even for Florida. Class B insulation should not be exposed to temperatures over 130C (To clarify for anyone skimming: that's not 130F, but 130C). 140F operating temperature is not an issue; you could fry an egg on the motor, and it would still be OK.

So I guess it is safe, even if not all that efficient.
Thanks to all

Yes it is. If the motor is not overloaded. Have you checked the current? Rolled steel motors like yours get hot. They are supposed too. The thin rolled steel gets much hotter than a cast iron frame. Marathon makes a good motor. Have a beer and enjoy your pool.

What makes you think your motor is not efficient?

It can't be that efficient in pumping water if that much energy is coming put as heat.

Current is around 4.8 @ 251v

Greg, don't confuse the motor casing temperature with electrical losses due to inefficiency. The emissivity of a smooth-drawn steel motor casing will be very low, so that the amount of heat energy actually radiated will also be low. Small motors have proportionally much lower surface areas per hp than larger models, leading to higher surface temperatures as the motor sheds the inevitable electrical and mechanical losses as heat. Cast-iron shells do run slightly cooler because the surface is rougher, emits better and can have cooling fins easily cast-in. At 1 hp brake, on a pump = near constant torque, you should be getting losses of around 40-75W, perhaps 90-95% efficient. 4.8A at 250v looks about right/a tad high for a 1 hp motor, and I'd expect a sealed type [ no venting] to be fitted in a pump application, for obvious reasons.

The thing to look out for is that the water flow through the system is not restricted unduly, such as by partly closed valves, choked filters etc., as this can overload the motor and damage the turbine by cavitation.

The best test is to use your nose. If it ain't stinking of burning plastic, don't fix it!

Alan

Several irrigation pumps I have (5 hp - 240V) all run 190F in enclosures baking in the sun.

I replaced the filter and balanced the system again. That improved the head and I may have actually dropped the temp a degree or two but I still don't like things running that hot.

Greg, a friend of mine in Jacksonville contacted me two weeks ago with a similar problem. The motor ran OK, but was so hot to the touch that he burned himself. He had recently replaced the motor and it turns out that it had a shorted winding to ground, right out of the box. Half of the field became a great big heating element while there still managed to be enough of a field to allow it to run.

I'd check for continuity from L1 and L2 to the frame ground with everything disconnected. Depending upon where the shorted winding is, it may not offer enough resistance to overload the circuit. It might provide for a nice heater though. Of course, an Amprobe on each leg should tell you the story as well. If both readings aren't identical, then you have a leaking winding.

My friend took his motor back to the pool supply place and they replaced it promptly and stated that they've had quite a few of these returns lately. Maybe you got one of these outdoor heaters too?

That should trip the GFCI but I will still look.

There was no current on the EGC or the pool bonding wire.