Furnace Motor Took A Dump

[dunedog]

Never going to have a furnace crap out on me,....... ever,Peter





(now my boiler......always on a cold arse Sunday!)

[Southern]

Thanks for the explanation Peter and the offer to fly down here on my expense. Believe me you would be bored with my furnace. It is very basic, no circuit boards or computers, just some components (temp switches) hard wired together. My digital thermometer is more complex and it isn't programmable.

Any suggestions on my eventual furnace/air conditioner replacement, which brands do you recommend or which brands to avoid?

[peter]

Depends on what you're lookin' fer, Southern.

I've been dead against heat pumps my whole life. When they came out here in Quebec, they were prone to breakdowns quite often and replacing a compressor just before or after the 5 yr warranty period was the norm rather than the exception. Remember now, this ain't Florida. Below freezing temps are quite normal here, and back then the manufacturers were touting that their heat pumps were good to around +5F. At temps lower than this, the heat pump just doesn't have the technology to absorb whatever heat is outside so that it can release it indoors (theoretically, there is heat in the air at temps down to -460*F. Good luck getting at it, though ).

Problem was that even at temps around freezing or slightly below, these older heat pumps just weren't reliable. They'd freeze up on the outside coil quite often, defrost boards would crap out with regularity. And compressors would fry. If you were lucky, the compressor would die just before the 5 yr warranty period. Which meant that you could get another compressor free. But you'd still have to dish out for labour, refrigerant, solders, filter-drier etc..

Another thing that most homeowners don't know is that almost all manufacturers insist on the 3-way valve being replaced whenever a compressor is changed out. This valve (also known as a reversing valve) simply reverses the flow of refrigerant so that in summer, the indoor coil absorbs heat & rejects it outside thru the outdoor coil. In the winter it does the opposite. Anyways, this valve will sometimes become "leaky", which means that the two separate circuits within the valve become exposed to each other. Sorta like a leaky heart valve. Nothing leaks out, but it can still be a problem. That leak can cause the compressor to run much hotter than it's supposed to, therefore leading to premature compressor failure.

This valve is a royal PITA to replace. Just the thought of having to change one out has me crouched in the corner of a dark room, whimpering like a little girl. You've gotta hold a three-pronged oxy-acetylene torch in a certain position and carefully un-solder the old valve. That's the easy part. You then have to install the new valve in it's place, all the while being careful not to overheat the myriad of heat-sensitive Teflon O-rings within this valve. It's a nightmare.

This $600+ valve isn't usually covered by the extended warranty. The techs rarely change it because it's such a nightmare to replace, plus they're scared to incur the wrath of the homeowner who bought the darn heat pump to save money, not spend more of it.

Fast-forward to 2008. Heat pumps are more efficient than ever, and breakdowns are now a rarity. I installed a Bard heat pump package unit at my friends house in Florida this past spring. This unit was the same brand and dimensions as his old 11 SEER cool-only unit which had electric elements for heating, which made duct connections a snap. The new unit has an efficiency rating (SEER) of 13 and uses the compressor to heat. For Florida, it makes perfect sense. It's impossible for him to NOT see a decrease in electrical consumption. And even up here in Mtl, I would maybe think of going heat pump in my own home due to advanced technology in this field.

Finally, I suggest one of the Big Four. Lennox, Carrier, York or Trane. There are many other brands out there and I'm not saying they're no good. But up here, whenever one of our commercial clients has a breakdown on one of their little-known brands, getting parts is always a slower process. And some of the designs being cranked out by some of these lesser-known manufacturers....you wonder if they even tried to work on their own equipment after building it....

PS: Nice to see I can still write short stories and novels.....

[Southern]

Thanks for the novel Peter, it was very helpful. I'm not a big fan of heat pumps being that I live near Chicago but I don't know how efficient a gas furnace to consider. I suppose it will come down to price. My main concern is reliability and availability of parts (circuit boards) 20 years later. My other main concern is how much electricity does it take to run. The new blower motor I ordered (not here yet) uses less amps then the original motor 5.1A vs. 3.9A, not a huge difference but it will add up. Since my existing 22 year old Borg-Warner furnace has no circuit boards the only thing I replaced has been the thermocouple (several times) which is a true low cost to own furnace. What do you think about Goodman products?

Regarding air conditioners is it better to go with the new refrigerant R410 or stay with the R22? I've read that R22 is being phased out which may make it more expensive down the road if I need a charge.

BTW I my house is a two story 1800 sq ft with a full basement with newer Pella windows. I plan on living here for another 20 years but according to the wife we have moved several years ago.

[peter]

WHAT? That makes no sense. Yes, new motors are more efficient than older ones. But going from 5.1 amps down to 3.9? That's like a 20% drop in amperage, which means an equiv. drop in consumption (volts X amps = watts, which is what you're bill is based on). Too good to be true?
While the drop in electrical consumption is fantastic, I have a nasty feeling that the motor you ordered may be under-rated. Possibly a 1/4 hp instead of a 1/3, or something to that effect. If that's the case, then your new motor ain't gonna last too long.....If this is not the case, please lemme know. I'd be interested to learn that the hp ratings are identical, but with that great a drop in energy consumption.

Gas furnases are up to 94% efficiency, up from 70-80% in the past. That means that you now get 94 cents worth of heat from $1.00 worth of gas, as compared to the 70-80 cents you're getting now. Is it worth it? I think so, especially in colder regions where you use a lot more heat than in, say Florida.
We have Goodman up here now. I'm not very familiar with the line, but I know that their prices are hard to beat. I do believe that you get what you pay for, though. And if your furnace is to last the typical 15-25 yrs, I'd think you'd wanna spend a few extra $$ to ensure that Lady Luck is playing for you rather than against you


I'm not sure you can even buy R-22 systems anymore. But I can promise you that either R-22 or direct drop-in replacement will be around for yrs afterwards, just as is the case for R-12.

Don't make yourself sick with worries about electronics. Just as with cars, manufacturers have pretty well ironed out the sensitivities associated with circuitry. And if you're gonna have trouble, you're gonna have trouble. Spend a few extra dollars striving to get quality equipment and buy both the equip. and extended warranty thru a long-time, established HVAC contractor in you area. You should be fine!

[Southern]

Thanks again Peter. When I get the new motor I will let you know the details regarding the amps. I have a clamp type ammeter that I measured the existing motor draw with the blower attached (6.2A running 11.0A starting current). I assume that since the blower was attached it draws more current then the motor nameplate plus since the bearings are going on it doesn't help lower the current draw.

[peter]

Not true. The stated amperage draw is the maximum full-load amperage (FLA) rating for that particular motor.

You're usually allowed a 10% overdraw from the FLA rating. If you ever see an SF (service factor rating), that's usually the absolute, positively max amperage that this motor can handle before flaming. And it's usually indicated in SFA (service factor amps) or SF (service factor). Service factor amps is stated as the absolute max. Service factor is usually 1.1 or 1.15.
Meaning that you multiply the service factor by your FLA to get the absolute maximum amps your motor can tolerate.

Having stated the above, your motor is pulling little more than FLA. If you had the blower motor access panel off while measuring the amperage, then that's the reason for the over-amps. By removing the access door, you allow the motor (and therefore the squirrel cage) to "see" the air coming into it alot easier. It therefore ends up handling more air than it normally would. Hence the over-amps.

Tune in next week as I go into details on how to kick-start your woman on a cold wintry day

[LiftedAWDAstro]

Tune in next week as I go into details on how to kick-start your woman on a cold wintry day

Ohhh Ohhhh I can't wait Uncle Petey...I've always wanted to know the answer to this!!!!!!

[Kabey's Van]

I'm sure you have Lifted; I'm sure you have.

[Southern]

Yes I had the access panel off while measuring the motor current. That would explain why I was drawing 5.8A measured at electrical junction box feeding the furnace. I figure the 40VA transformer is drawing a max of 1/3A which feeds the motor relay and gas valve coil but I also believe that the humidifier was on which draws 3/4A. I believe that with the furnace on Heat (instead of AC) I am running the motor at medium speed instead of high speed. What does this do to the motor amps? Nothing was stated on the motor nameplate.

Please tell me that the answer to your riddle isn't a diamond.

[Smiliesafari]

Oh Petey..............If you use KICK and WOMAN in the same sentence you're not likely to reach middle age. Be very careful young man.

[peter]

Yes I had the access panel off while measuring the motor current. That would explain why I was drawing 5.8A measured at electrical junction box feeding the furnace. I figure the 40VA transformer is drawing a max of 1/3A which feeds the motor relay and gas valve coil but I also believe that the humidifier was on which draws 3/4A. I believe that with the furnace on Heat (instead of AC) I am running the motor at medium speed instead of high speed. What does this do to the motor amps? Nothing was stated on the motor nameplate.

Please tell me that the answer to your riddle isn't a diamond.

Whoa. All of my above literary spewage was based on the assumption you were running on high speed. Yes, furnaces are usually wired to run on medium speed for heating and high speed for cooling. The amperage rating is always based on high speed unless the amp rating for every speed is indicated. Which is rare.

Medium speed is a lower hp rating, but at a lower rpm. So yes, amperage would be lower. And yes, BTW. You were right about worn bearings affecting amperage to a point. If the bearings have excessive clearance in them, this allows the rotor/stator clearances to change. Sometimes, the clearance is so great that the rotor actually "sticks" to the stator, causing the rotor to seize magnetically. In this case, you'd get LRA, or locked rotor amps.

Start the fan on high speed by putting the "fan" switch on your t-stat to "on". Then check the amperage inside the control box and on the power feed wire to the motor itself, but the blower panel should be in place as mentioned earlier. Oh, and keep your clamp-type ammeter at least 2-3" away from any transformer, it can affect your ammeter readings.
Lemme know what you find....

PS: Where exactly am I sending the invoice for all this info, BTW?

[Southern]

OK Peter, here is the results:

I measured the furnace amps at the junction box as the furnace was running. After unplugging the humidifier and booster fan (which combined drew 1A) the furnace was drawing 4.0A.

After the furnace was done heating I pulled off the access panel and measured the rear bearing cap temp (27 Deg C) and the motor winding temp (36 Deg C) with my temp gun. Before I put oil in the bearings the motor got so hot it shut down on overtemp. There is some play in the motor shaft which is evident when it is running (I can hear a slight rattle) due to worn motor bearings.

Then I placed the t-stat to "ON" to measure the motor amps at high speed. At the junction box I measured 4.6A, at the motor I measured 5.1A. The higher amps at the motor was because I had to pull the furnace filter to see my meter (excessive air flow).

PS: Where exactly am I sending the invoice for all this info, BTW?
Merry Christmas Peter and to your better half. I know how much you like giving people a warm fuzzy during the winter.

[tbhager94]

i bought a fan motor for my furnace from a elec motor shop i think it was $80 and i installed it my self ,that was 3 yrs ago and it still humm's along.

hey ,peter have you heard of fairbanks-morse furnaces ??

[peter]

OK Peter, here is the results:

I measured the furnace amps at the junction box as the furnace was running. After unplugging the humidifier and booster fan (which combined drew 1A) the furnace was drawing 4.0A.

After the furnace was done heating I pulled off the access panel and measured the rear bearing cap temp (27 Deg C) and the motor winding temp (36 Deg C) with my temp gun. Before I put oil in the bearings the motor got so hot it shut down on overtemp. There is some play in the motor shaft which is evident when it is running (I can hear a slight rattle) due to worn motor bearings.

Then I placed the t-stat to "ON" to measure the motor amps at high speed. At the junction box I measured 4.6A, at the motor I measured 5.1A. The higher amps at the motor was because I had to pull the furnace filter to see my meter (excessive air flow).

Well, if the bearings are shot, then you definitely called this one correctly. The motor's not over-amping, but it still must be replaced. Again though, I'm dying to see what the hp rating of your replacment motor will be.


"Merry Christmas Peter and to your better half. I know how much you like giving people a warm fuzzy during the winter. "