I have a box heater in my garage. It’s 220VAC, on a 30 Amp circuit.
My problem is, the 220 4-speed fan motor is now stuck on high. On high, the air around the edges doesn’t get heated much or at all, so it blows both hot and cold. Takes much longer to heat the shop.
Is it possible to get this motor fixed?
Info: It’s a 1/5 HP motor driving a 16-18″ dia fan. There is a 5 pin connector on the back of the motor. To change speeds, you rotate the square plug. Every 90 degrees gets you a different motor speed, well it used to. Sorry, forget the motor brand and rpms.
I have found, if I block of part of the front grill, forcing the air to blow past the coils, it works ok, but would still work better at a lower fan speed. I can and do use it as is, but if it is fixable, for a reasonable price, I’ll take it in to the motor shop. If it’s not, I won’t waste the time disassembling things to get the motor out.
Thanks
Billy
Replies
Get the information off of the motor name plate, and call an electrical supply company. Give them all the info, and they will likely have one in stock or be able to oder one for you. My guess is a cost of $150.00 to $220.00. Multi-speed motors of that hp are not in great demand, thus the cost is higher than a compareable single speed unit.
Davr
Thanks, I'll take your suggestion. I'll get the number and see what one costs. Found a good site where I may be able to buy one: http://shop.emotorstore.com.
I was thinking more after I posted this, and I may just take it out and put a smaller fan blade on it. A 10-12" fan would reduce total airflow and blow most air past the coils and possibly accomplish the same thing at a lot less cost.
Right now it's in a box about 24" square. The heating coils only cover about a 18" square in the center of the front grill. Forcing most of the air to go through this area may have the desired effect. I picked this up used at a thrift store for $10. Even though it doesn't work real well, if I block off the edges of the grill, I can heat up the garage more in an hour then all day with my tank top propane heater. Won't heat things above 70 degrees no matter how long it runs.
Maybe this is too old a post to matter, but is this heater recirculating air, or bringing in outside air? If it's all recirculated air, and you can't heat the garage the way you want, the problem is not the flow, it's the capacity of the heating coil.
There is a separate comfort issue relating to the temperature of the air that is blowing down your neck. For example a lot of 80F air won't feel as comfortable as a smaller volume of 120F air, but the heat that's going into the room is the same.
Also, look up the BTU/hr rating of the propane heater you are comparing to the electric heater. Multiply by 0.293 to get Watts. I wouldn't be surprised if the heating capacity of the propane heater is way beyond the rating of the electric heater.
Edited 4/23/2003 5:54:01 PM ET by alecs
Thanks for posting. The heater is a metal cube that hangs from the ceiling, so it just recirculates the air in the garage.
You are right that it is really a heating coil issue. The coil simply doesn't get hot enough to heat the volume of air the fan shoots past it. When the fan motor had 4 speeds I'm sure that wasn't an issue, as at lower speeds, I'm sure the coil could easily keep up.
I have found that just by blocking part of the exhaust grill, which is about 2' square, to restrict the fan output, it works much better. I still plan to put a smaller diameter fan blade on it as the cheapest solution to the issue. Not much sense in working the motor hard to push a maximum amount of air then restricting the air it pushes. For a few dollars I can reduce both the airflow and the load on the motor. Before blocking part of the exhaust I could only heat the garage to 70 degrees with this heater. With the grill partially blocked I can heat it to 80 degrees.
As far as the propane heater, it's just a small tank top unit. 12 or 15,000 BTU/hr if I remember right. Multiplying by 0.293 gets me 3516-4395 watt output. The electric heater has a 60 amp 220 breaker on the back, but is plugged into a 30 amp 220 outlet. No idea how much power it's actually drawing, but it works fine, and both heating coils are working. Grainer shows a 24 Amp 220VAC heater putting out 17,100 BTU/hr, not much of an increase over the propane unit.
Ok, you surprised me, the electric heater puts out not much more total heat then the propane unit. The biggest heating problem with the tank top unit has always been not having a good way to disperse the heat. Putting a small fan on a stool behind the heater helps, but it still takes hours to acheive the heat gain I get in 20 minutes with the electric heater.
Biggest safety problem is my kids get too close and set things too close to the propane unit. Gonna have a fire or burns with that thing someday. Just can't seem to get them to respect it.
I drew a simple front view of the heater, hope it makes more sense then I've made so far.
Thanks
Billy
Billy,
I misread your original post, I thought you could heat the garage with the propane heater where the electric heater was not up to snuff.
Changing the fan diameter should definitely reduce the airflow. I am not sure why reducing the airflow has the effect of heating the garage faster, though. It would seem to me that the output of the heating coil would be the same if not greater the more air you moved by it. Also, it's surprising that the coil doesn't seem to be sized for the full airflow of the fan. Are you sure that all sections of the coil are working properly? If you have an ammeter, see how much the draw is compared to the nameplate rating.
of course, soon it will be warm enough that you won't need the heater, and you'll forget about the problem until it gets cold again!
Well, it's an old pig. Don't know why the coils aren't sized for the entire airflow, but they're not. Don't have an ammeter, and there isn't any nameplate, so I don't know who built it, or what it is rated for. I picked it up used for $10.
When purchased, the heater coils had been disconnected and it was being used just as a fan. If the fan is unplugged, the coils will heat to a bright red color, then shut off when the thermal switch triggers. Each coil has a thermal switch on it to prevent overheating. Both coils and both switches work perfectly.
>>It would seem to me that the output of the heating coil would be the same if not greater the more air you moved by it.
I assume you're right that the heating coil output is the same, but the amount of temperature increase imparted to the airflow is directly related to the coil temperature, and the temperature differential between the coil and the incoming air.
My theory is that so much air moves past the coils that they never have a chance to truely heat up. The coils are cooled too quickly. The reality is that so much air blows past the coils, cooling them so quickly, that the coils are unable to do their job. The coils never pick up any hint of color even in pitch black conditions. Holding a thermometer in front of various parts of the airflow I found a variance from about 60 degrees (ambiant temperature) at the edges, to about 120 degrees near the center. Covering the 3 sides greatly increases the temperature of the air coming out the front, though I didn't measure it.
>>of course, soon it will be warm enough that you won't need the heater, and you'll forget about the problem until it gets cold again!
Actually, I won't forget it. Right now it's sitting on my floor in the way, so I need to fix it and build a mount on the ceiling for it, then run some wires to it. I intend to put a smaller fan blade on it, add air filters on the intake side, and get a 110VAC/220VAC relay. I'll hook the relay to a 30 minute mechanical timer I have so I can't accidentally leave the heater running. It won't be used too often, so that makes more sense then a thermostat. I'll probably put bypass switches on the heater coils so I can use it just to move and filter air in warmer months. Just got to find time to pull the motor back out and measure the shaft size and see what the max rpm rating is so I can order a fan blade. Wasn't smart enough to do this when I had it out cleaning and lubricating the motor.<G>
Just had a thought, maybe I'll drill some new holes and stagger the coils, so they aren't sitting directly next to each other. Pehaps shifting one to each side of the box opening, and covering just the bottom would improve things.
Coils now: ------------- Directly in Front Of Each Other.
{ }
{ }
{________}
-------------
Coils staggered: ------------- Shifted to box edges.
{ { } }
{ { } }
{__{____}__}
-------------
Someday I'll learn brevity. Too late here.
Thanks
Bill
Modine?
Whatever kind of heater I'd first try hitting Google for a replacement motor. Secondarily I'd hit a local rewind shop. Look under motors in the yellow pages. If you do that look at your wiring clearly and make notes for rewiring the motor. I am very uncertain but I'd bet you've got a multi winding motor that is rewired by the plug connection. You've probably burned out some of the windings and they need to be rewired. The motor people will be able to tell you what is up.
I suppose you're right, when I take the motor out I'll drop it at the motor shop. I drive past them an average of 4 times a day. Nice guys.
I'm sure it's a multi-winding motor. I read somewhere once that windings can short together so you end up with a single speed motor. Not sure this is true.
Won't be any trouble to rewire. There are only two wires going to the motor, and they're hooked to a connector.
The plug is kind of cool. It's square, there's a power socket in the center that is connected to one leg, then 4 holes in the outside, one of which is connected to the other leg. There are 5 pins sticking out of the back of the motor. You plug it in, it connects two pins, each time you rotate it, you send power to a different pin. Supposed to be 4 speeds. Only get one no matter how you plug it in.
Guess I need to quit talking and take the motor back out. I lost my notes, but when I looked up the motor number once, I could buy a replacement for $220 off the web.
Could be as simple as some mechanical device inside the motor housing hopefully. The windings are "varnish" coated then wound in a standard pattern around the core.
From my work selling servo and 4 quadrant controls for motors I got to see the inside of a motor manufacturer. Surprisingly low tech. They take the spool of wire used in the windings and run it thru a grooved pair of maple blocks with a wing nut hooked up to the pair to create friction / tension for the winding. This is production mind you! Ugly. I was selling servo's on the supply reel to provide controlled resistance for the automatic winder.
In the field, heat, dirt, (frequency) vibrations, voltage spikes, and solvents eat up the varnish in the motor and soon the windings short to the core or to each other. That is how we get to temperature rated insulations in motors and transformers. Tight winding is important for noise and energy efficiency. Too tight and you ruin the insulation.
The core never seems affected so rewinding will be a great solution. Best of luck.Jack of all trades and master of none - you got a problem with that?
Interesting. I have only a dim idea of how motors work. But, what you're saying makes sense. I'll bet the motor has 3 coils, and they've all shorted together. So, only one speed is now available as all the coils are powered when the motor is plugged in. I wonder if a motor shop could reseperate the coils.
I took the motor out and cleaned it real good, took it apart, but didn't really look at the windings closely at that point. Next time I take it out I'll look it over much closer.
Anyone know of a good site with some graphics showing how motors work? I've seen such things, but it was years ago.
Just for anyone's future reference. The motor shop told me that when a multispeed motor turns into a single speed motor, you have two choices. Replace it, or live with the one speed ya got.
A motor's a couple hundred bucks, so I'll live with this speed. They didn't have a smaller fan blade that'd work. I have some filter material I'm gonna put on the intake side of the heater. I'll also put some baffles in to direct all the airflow past the coils.
Time to reassemble hang and wire this thing. Get this pig up out of my way. I found a high voltage thermostat, so I'll wire it on that. Then I can't accidentally leave it running, or at least it'll stop when the garage is warm instead of running non-stop until I notice.