Hot Blower Motor

[Coenraads]

A friend who has a 12 rank pipe organ in his house is concerned that the blower motor may be running too hot.
The motor is rated at 3.5 amps and is drawing 3.3 amps which suggests it is operating normally.
Still, after one hour the temperature is 70 degrees C and after two hours it is at 100 degrees C.
For industrial motors, we understand this is normal, but for a blower motor?
John

[tpappano]

100C is pretty hot if this is the temp of the motor housing. Is this perhaps a "permanent split" capacitor motor? If so, the capacitor may be failing which can cause higher current draw and heating.

[Nutball]

Maybe oil the bearings too. Bearings can generate heat and friction will increase the amp draw.

[Pipeorganbuilder]

The older blower motors run extremely hot to the touch. The two blowers on my pipe organs run hot like this. Since the motor current is in the normal range, I wouldn't be that concerned.

Michael

[Coenraads]

Follow up:
The original problem was that the 0.8 hp Meidinger motor was slow in starting and tripped the 1 hp breaker on the blower.
My friend took the blower to a motor shop where they replaced the 30 ufd cap with a 50 ufd unit. Bad idea! Although the motor now reached running speed more promptly, it also reached 100C after extended running, whereas Meidinger indicates that 65C is the maximum housing temperature.

The motor is rated for 3.5 A and that is why we did not understand why it was overheating when it was only drawing 3.1 A.
Putting the 30 ufd cap back, resulted in a current reading of 2.0 A! Clearly the larger cap was pushing too much current to the secondary winding.

We also did not appreciate that this is a permanent split capacitor motor, as pointed out by trappano (thank you) and that therefore there is no centrifugal switch that disconnects the capacitor once running speed is reached. If it had such a switch, installing a larger cap would do little harm, and maybe the motor shop operated on that assumption.

Yes, Meidingers are slow in starting but we now understand 15 seconds is normal. But with the breaker being so closely rated, it was always on the verge of tripping. A slightly larger breaker is the answer.

The lesson? Don't alter the cap value on a permanent split cap motor. It also needs to be a paper capacitor and not electrolytic.

Too soon old, too late smart.

[tpappano]

Great news, glad you got it sorted out!

[KC9UDX]

The original breaker was maybe weak. I would install a new one of the same rating, not a larger one.

[myorgan]

KC9UDX,

Good point to make. I used to think circuit breakers were multi-use devices, but when starting the electricity for my garage, I discovered that technically, GFI and circuit breakers are only warrantied the first time they trip. If one resets the breaker, it isn't warrantied for subsequent trips. That was a shock to my system! (pun intended).

Michael

[KC9UDX]

Yep. This is another reason why fuses are superior.

Fuses open faster, more predictably, and you never have to wonder if they're really going to work the second time. A circuit breaker (at least all the ones I'm familiar with) should be replaced the first time they trip. I don't know that I've ever heard of anyone doing it. I've replaced many that would trip too soon, and some that would trip too late, or even not at all. (Some adjustable ones will never trip if they're turned up too high. This is really scary: you'd think that going a quarter turn more than 10A is 12A but it's really 1000A (or worse).)

Installing a larger one is almost always a really bad idea. Unless you know for sure that everything downstream is rated higher than the new breaker, don't do it. Even then, unless you know that the system was mis-engineered, the smaller one is probably there for a good reason.

[VaPipeorgantuner]

This is a Meidinger blower? ALL meidinger motors are 3-phase motors and require the correct capacitor to run. Because the motor uses a capacitor to supply a "ghost" phase, it will run hotter than if it were on 3-phase current to begin with. Also the motor will run slightly slower (but not detectable without a tachometer that can measure rpm's). If the original capacitor that came with the blower uses a certain value, ONLY that value should be used when a new capacitor is installed. The capacitor value will depend on the input voltage (110 v.a.c. will use a different value than a 220 v.a.c supply).

[Opie56]

Agreed! All the Meidinger's on organs I service run hotter on single-phase than 3-phase - mainly due to the inefficiency of the "ghost" phase. Changed one a couple years ago from single-phase to 3-phase - - it's starts fast, current draw is lower, and the runs a *lot* cooler.

[sh)ck44]

As an electrician I was asked to trouble shoot a Motor used for a pipe organ. It is an open faced Motor with older worn out brushes,commentator is pretty much carboned up.They tell me the air flow is lower than normal the pipes were just tuned up. The Motor was made by Century Electric Co.,
single phase [email protected] Amp (1hp) no.5 6567 patented MAR.7,1899/JAN.13,1903.This Blower is installed for a M.P. MOLLER-HAGERSTOWN,MARYLAND (OPUS 6449)-----1936. Hoping to find some info on Motor,or maybe just install a newer type motor.

[KC9UDX]

Has someone determined that the motor is really the source of the problem? What RPM is the motor running? Is it running hot?

[VaPipeorgantuner]

the blowers on M P Moller organs was built either by Kinetic Engineering or later on by Moller using the Kinetic name. The earlier Kinetic blowers are large wooden green boxes, and used (mostly) Century Induction/repulsion type motors. The brushes lift after the motor reaches about 70% of the rated speed, which was typically 1165 r.p.m.. You could use a more modern motor >BUT< finding one with the correct speed may be a challenge. What has been done if the motor can not be rebuilt/brushes replaced is to use a 1760 rpm motor and reduce the shaft speed by using a 5-to-4 pulley ratio which will get the blower fans spinning at slightly faster speed.
HOWEVER -- an organ technician should check for OTHER reasons why the wind supply is lacking if it has been sufficient in the past. That should be done FIRST before any action is taken with the motor.
Those Century motors are built like tanks. You may need to find an "old time" motor shop that has experience with these older Century motors so they know how to replace the brushes and re-set the throw-out mechanism correctly.
RickInVA

[tpappano]

Sounds like a repulsion-induction motor, the brushes and commutator are engaged during startup, then disengaged by a centrifugal device when running speed is reached. I would think a good motor shop could clean it up and replace the brushes. Does the nameplate specify the rpm? Is it drawing excessive current? Is there radial play in the bearings?