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JRMN 08-19-2009 09:58 AM

New Attic Fan Didn't last a day
The roof mounted attic fan went out in my house. The motor is made by Lomanco with a 12Ē blade. My brother who is a electrician told me to go pass Drexel , however, they didnít have a replacement motor and suggested I go to Grainger. Seeing as though I only needed a motor I ended up buying a gable unit with the exact same motor because it was cheap. We installed the new motor and new thermostat with the old blade and everything worked great. However, the next day I went back up in the attic to make sure it was still working and noticed the fan wasnít running. So I turned down the temperature on the thermostat and it still didnít come on. To make a long story short, somehow the motor went out again. We know that because we bypassed the thermostat and it didnít work. Thinking it was a fluke, I exchanged it for another; however, this time I also bought a replacement blade from Amazon because the old blade looked a little bent.
Iím thinking about hooking it up myself because my brother is only available on the weekends. I watched him hook it up the first time and I believe its straight forward. However, I was wondering if something else could be causing the motor to burn out. Any thoughts on what that can be?
Oh and I should also mention the old motor wasnít hooked up to the thermostat.

J. V. 08-19-2009 01:26 PM

You must use the original fan blade or one exactly like the original. If it is not exact you probably are moving to much air, thus pulling to much current and overheating and eventually burning up the motor. It may not be enough to trip the breaker, but enough to ruin the motor. Does this motor have an internal overload. This should have protected the motor. Check that you have the correct blade first!!!!!!!!

Same goes for the motor speed. It must be the same as before and the same blade as before. The motor speed (RPM) and blade must match. (designed to run together). If you are buying these parts separately, that might be whats wrong. Why not buy the complete assembly. Motor, blade and housing. Thats how you do it.

Get the information off the motor and post it. All of it.

JRMN 08-19-2009 07:07 PM

I wouldn't feel comfortable installing the complete housing myself. I've called around and it seems to pretty expensive to have it install by a professional.The new motor and blade are replacement parts for the old motor.

The motor is a Lomanco FO510B2944:
3.4 Amps
1/10 hp
1100 R.P.M
120 Volts

J. V. 08-20-2009 11:28 AM


Originally Posted by JRMN (Post 316660)
I wouldn't feel comfortable installing the complete housing myself. I've called around and it seems to pretty expensive to have it install by a professional.The new motor and blade are replacement parts for the old motor.

The motor is a Lomanco FO510B2944:
3.4 Amps
1/10 hp
1100 R.P.M
120 Volts

Is the old motor 1100 RPM? Are you 100% sure the blade is exactly like the original? (this bothers me the most!) Did you check the voltage (at the motor) when the motor was running? Did you have to reset the breaker each time?
If the motor is the exact replacement and the fan blade is the exact replacement and you have the correct voltage going to the motor when it is running, it has to be a bad motor or a bad internal overload in the motor. Do you still have the first one, second one that quit? Can you hook a cord to the motor and plug it into a receptacle to test it? Did you allow the motor to cool down to see if it would start again?
I will Google your motor and see if I can help you. In the meantime answer all my questions please.

J. V. 08-20-2009 11:33 AM

Okay I found your motor. I see you have the correct fan blade and motor. It has to be the internal overload or the motor itself if you have the correct voltage to the motor. Is the breaker tripped in the panel? Do you have a meter to measure voltage?

JRMN 08-21-2009 08:40 AM

I don't know if the original motor failure tripped the break the first time because it didn't work when I bought the house, however, the motor that my brother and I installed didn't trip the breaker. My brother measured the voltage at the switch and he got back 122 volts. Could that be it?

J. V. 08-21-2009 11:35 AM

122 volts is what you want to see. You really need to check the voltage at the motor when it is running. This will tell you if it's the motor or something else. Can't you run a temporary cord up there and see if it works on another power source?
Can you wait until your brother comes back. That would be the best thing for you to do, unless you have a meter.

JRMN 08-21-2009 11:40 AM

I guess it can wait another day until my brother can help. I'll have him measure the voltage at the motor and report back. thanks.

J. V. 08-21-2009 01:15 PM

If your brother is an electrician you will be fixed the same day he gets there. Unless he has to order parts. Good Luck. Let me know what you find. I would hate for you to get it fixed and not tell us what was wrong. Thanks John

Wildie 08-21-2009 09:37 PM

One thing that needs to be remembered, is that supply ventilation must be in place and be of such size to supply the air being drawn out by the fan!
If there is no supply ventilation the attic will develop a negative pressure (a vaccuum), relative to atmospheric pressure!
Outside air will try to flow back against the fan, and increase its load. It will run hotter and could easily burn out!

JRMN 08-24-2009 07:08 AM

@J.V., well my brother wasn't able to help, but he did allow me to use his tools. Everything was working fine last night; however, I plan to check to make sure everything is still working when I get home from work.

@Wildie, when you say supply ventilation, you mean other vents in the attic to allow air to flow in right? If that's the case then I believe I have 3 other shutters/vents.

JRMN 08-25-2009 07:09 AM

Bad news, when I got home yesterday I went back into the attic to make sure the fan was still working and it wasn’t. I also lowered the temperature on the thermostat down to 70 and it still didn’t come on. This is the second motor that has burnout in less than a day.

My brother said it could be a number of things (bad wiring, circuit over loaded, fan could be drawing too many amps), does anyone have any other ideas on what could be cause the motors to burnout? I am thinking about calling a professional out to take a look.

J. V. 08-25-2009 02:00 PM

First you say it was not working and now you say you went up there to see if it was STILL working? What's up with you? If this fan quits and comes back on by itself, it is overheating and the thermal cutout switch (inside the motor) is whats causing it to shut down. The thermal switch inside the motor does just what it's name implies (thermal cutoff). If the motor gets to hot it shuts down. Then when the motor cools off it starts again by itself. Is this whats happening? If this motor runs when you first installed it and then it stops, wait until it cools off and see if it starts by itself. NOTE: Some small fan motors have a reset button on them you must push to reset the switch. Does yours have a resettable button? If it does, push it. Reset it.

You may have two good motors that just need to be reset, or you have burned up two motors? Once we figure out what you have, then we can try to find out why the fan quits. I am having a hard time believing you can correct this. As simple as it is. I also, believe the motors are okay. The thermal cutoffs should have protected them.

Did your brother by any chance leave you an Amp meter or Voltage tester? If not, call a professional.

One more thing. Did you put the fan blade on the same way the original one was. If you put it on backwards, this could be your problem. Try it. Turn it around/over. It could have been backwards the whole time. Even before you started with it.

If you have an amp meter we can verify this in minutes.

JRMN 08-25-2009 02:30 PM

Sunday I installed the fan and external thermostat, everything worked fine. About an hour and half later I went back into the attic to make sure it was work ok. The fan wasnít on, but it was a lot cooler in the attic, so I checked the fan by turning down the temperature on the thermostat to around 80 to make sure it was working. The fan came on. I cut the temperature back up to around 110.

Yesterday when I got home, I went back in the attic and the fan wasnít running, so I turned the thermostat down again to make sure it was still working. Well this time it didnít turn back on, which leads me to believe it burnt out somehow.

Iím pretty sure I installed the fan blade correctly because itís only one way to install the blade. And as far as I can see there is no reset switch on the motor. My brother is supposed to check the amp/voltage this afternoon when I get home. I think he said something about testing the amp load (???) at the breaker box.

It was my plan to have a professional come out tomorrow, but Iíll let my brother have a-look-see to see if he can figure out whatís going on. If he canít figure it out, then I will call the professionals.

J. V. 08-26-2009 11:22 AM

You are confused about the thermostat. You have one that tells the fan to come on when it reaches the predetermined temp in your attic. This is the one you are adjusting. The motor has one inside it that shuts off the motor when it over heats. This one is not a so called thermostat. It is a switch that shuts off the motor internally if the motor over heats. This is why I think you have two good motors. I bet if you put them back in they will work until they over heat and shut off. This has nothing to do with your adjustable T-Stat. Your brother should be able to find your problem.

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