How Hot Should a Motor run?

Recently replaced the pump on the hot tub. The new motor seems to run very hot - too hot to touch even though it has a fan and cooling fins. Is this normal? It cuts out after about 3 hours running for about a minute and then starts up again. I'm not looking forward to taking it out again but it's got to be motor or maybe control panel but that has been OK or the last 16 years.
--
bert

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On Friday, 12 October 2018 16:31:18 UTC+1, bert wrote:

You need to check the current it's drawing and make sure it's not more than the rating plate. It's the only way to be certain that it's OK. A lot of cheap modern motors are very inefficient. The losses appear as heat.
Also check that the ventilation path is clear. If the ambient temperature where it lives is too high, it will overheat. There needs to be ventilation slots on your tub for an air circulation.
Some motors are only intended for intermittent use too & will overheat if used continuously.
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It's an Italian Electromeccanica same as the one it replaced

Will check that when I get it out.

There never has been and the other motor ran OK for 16 years.

Not much use for a hot tub.
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bert

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Will have a look on the plate.

So pretty hot then.

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On Saturday, 13 October 2018 10:51:27 UTC+1, bert wrote:

A motor whose case is hot enough to burn is usually running too hot. Chinese consumer goods do like cheap insulation.
NT
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snipped-for-privacy@gmail.com writes

This one is Italian.
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bert

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On 12/10/2018 22:57, bert wrote:

Yes, you can get a nasty surprise from touching a Class H that's running near its full rating.
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Well obviously the motor has a thermal cut out then. If its getting hot it sounds like its either under powered for the job or is faulty. Being as its allied with water and people I think I'd want a motor that was going to work like the original. MY shredder gets hotter and cuts out if overloaded so one other thing to say is that are we sure its not being overloaded by mis assembly of the device somehow?
Brian
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On 12/10/2018 16:24, bert wrote:

As others said, obvious first check is the voltage and HP rating along with the rated duty cycle to make sure you are actually replacing like for like.
Also, if this has a separate run cap have you checked whether that is ok and still matched (in value) to the new motor?
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writes

Voltage is correct. It's actually rated higher HP wise at high speed 2hp rather than 1.5. I raised this with the supplier (a hot tub specialist) and he said it would be OK.( he does stock the 1.5 motor also). The plan at the moment is to remove the motor and return for check/replace as it is under warranty. Current weather has temporarily halted the operation.
Duty cycle - I will have to get the model number off the plate[1] and check on manufacturers web site - they give lots of technical info. But no hot tub supplier who values their reputation would sell a motor that was not rated to run continuously.

Came with new run caps installed.
[1] Not as easy as you might think. I need to partially dismantle the gazebo built over the tub (it's outside) to get at the panels to see the motor. Two sides to actually get the motor out.
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On Sunday, 14 October 2018 16:07:58 UTC+1, bert wrote:

You can measure the motor current without all that. You can use your electricity meter if you ensure there is no other load connected.
Run it for a couple of hours & see what it consumes from meter reading.
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Pointless trying to estimate current from electric meter without knowing the power factor. The meter reads watts not VA. Borrow a tong tester if you haven't already got one.
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On 14/10/2018 16:02, bert wrote:
<snip> > Voltage is correct.

It was because you said it thermally tripped that I was wondering. But they do tend run quite hot anyway.
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Well that's my assumption, It restarts after about 1 minute then runs for while before tripping again. The underside of a Hot tub is a pretty crowded place and manufacturers got to some trouble to keep heat *in*.
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On 15/10/18 14:24, bert wrote:

A typical motor will start to be in trouble much over 60C case, because that means the windings are a deal hotter than that.
insulation and solder if there is any start to be a problem in the 100-200C range
shellac insulatin goes at 120-150C, and some modern insulatins that are 'solder through' at similar temps
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