If the blowers' HP match - are they the same?

[psuskeels]

I have a Amana 80% Commando GUIC140_50. The blower needed replacing, and the service person replaced it with a 3 speed DL1076. The previous blower was 4 speed. Are these the same -are they pushing the same amount of air?

My temp rise is 60F when the fan speed is on high - the specification sheet for this furnace shows less than 49F temp rise on high.

[4l530]

Eh, three speed, four speed...how many do you need??? :D
In addition to horsepower there is also RPM and rotation to consider.
I suppose he could have it rotating the wrong direction maybe, there's other variables to consider also, if you're not satisfied that it's running like it ought to, call the guy back.

edit: If the temperature rise is too high, there could be another issue besides the blower.

[fixitmanmc]

What was the rise before the motor change?

[psuskeels]

not sure what the rise was, i guess i'm more concerned if they put a substandard fan in (as it was an emergency repair and they didn't have time to order the exact replacement)?

[dngtig]

It is very common to install a 3 speed motor in place of 4 speed motor. But the motor need to be rated the same. A 4 speed 1/2hp motor that draws 2.1 amps on high speed @ 1075 rpms could be replaced by a 3 speed 1/2 hp motor that draws the same. Your only using one speed at a time. You probably had 3 unused speeds now you have 2 unused speeds. The temperture rise could be caused by many different things. Did you call the contractor to ask him about this?

[mark beiser]

In addition to the HP, RPM, rotation and voltage, one thing that is very often overlooked is the winding stack height, which is reflected in the amperage.
The new motor may move significantly less air, and possibly overamp and overheat, if its amperage rating is significantly lower than the OEM motor.

Matching the amperage rating of the new motor to that of the OEM motor is often more important than matching the HP.

[Mr Bill]

Lots of different things can cause heat rise above factory specs. besides the blower motor or speeds it's set at, like someone said above if your not happy call them back and show them the specs. for your furnace, but get ready to pay extra if your coil is dirty or duct system is not sufficient or WC on gas valve set to high or return is not sufficient among other things. Installing a three speed motor or a 10 speed motor don't really matter, what matters is that they installed the right Hp. and right RPM motor and if they did you probably have others issues not related to the new motor.

[amtec services]

What Mark said! Learned that lesson very well. Fool me once, shame on you. Fool me twice, shame on me!:o

[sadlier]

In addition to the HP, RPM, rotation and voltage, one thing that is very often overlooked is the winding stack height, which is reflected in the amperage.
The new motor may move significantly less air, and possibly overamp and overheat, if its amperage rating is significantly lower than the OEM motor.Expound on this, please. How would a given HP and RPM result in reduced airflow from one motor to the next irrespective of amps? Isn't a HP at a given RPM going to be the same regardless of amp draw provided the amp draw is below the nameplate rating?:confused:

[markwolf]

The easiest way to explain it for me would be this.The manufacturers lie is why.Read this it is lengthy but will explain. http://users.goldengate.net/~kbrady/motors.pdf

[sadlier]

Thanks for the link. It was interesting and an eyeopener on those tool ratings we usually don't think about. He got ohms law wrong - I wonder why.

Anyhow, he admitted that there are different efficiencies in "the real deal" motors. So if an older 1/4 HP 65% efficient motor is replaced with a newer 1/4 HP 70% efficient motor then can't we presume that the new motor will have a lower amp rating than the old motor?

[Milk man]

All of the above and where are you taking the temprature rise. It needs to be out of sight from the heat exchanger. IOW, down the trunk a little so the radiant heat off the HX is not read.

Are all your resiter open?

[sadlier]

Wrong thread, milkman:D :D :D

[dec]

I use to buy pallets of the ACE motors for replacements. Now I only remember 1 time that I really had a problem with using them as a replacement.

This was probably back about 20 years ago and I was replacing a motor on a Rheem . It was probably about a 160,000 btuh standing pilot furnace with a 4 speed blower.

All I know is I replaced the motor in the winter with the 3 speed Ace motor. Worked fine for heating but when it came to summer ......... the a/c was always icing up.

It took quite a while to figure to figure out what was wrong being the motor was replaced in the winter and all was pretty much forgotten about it.

If you looked at the motor specs you would have never thought there would be much differance being it was real close as far as RPM and the same horsepower.

IT just didnt pack it. IN cases anymore if its a large btuh furnace or bigger tonage air conditioner ....... I really try putting the exact same thing back in.

They just have to pay the extra trips or the cost of time installing a temporary motor to get them by.

Hell i dont drive a semi so dont expect me to carry every part that you could possibly need.

[Milk man]

Wrong thread, milkman:D :D :D


I was addressing his 60º temprature rise.

[mark beiser]

Expound on this, please. How would a given HP and RPM result in reduced airflow from one motor to the next irrespective of amps? Isn't a HP at a given RPM going to be the same regardless of amp draw provided the amp draw is below the nameplate rating?:confused:

For good explanations of how the various ratings affect the performance of the motor, and great info on how motors work, diagnosing problems, and selecting replacement motors, check out the Fasco Facts booklet.

http://www.fasco.com/pdf3/fasfacts.pdf

Page 33 and 34 have specific info on selecting by amperage.


2 motors with the same HP, RPM, voltage and rotation can have very different performance when used to turn the same exact fan.

[RoBoTeq]

Line voltage electricity being my weak point, this is a great thread. Thanks for the links guys.

While I have always known most of what is being stated about matching all characteristics of motors, I really was a bit shy of knowing why.

[thatguy]

Before you blame the service tech though do keep in mind that there could also be a valid reason for why it was not checked or adjusted that I am unaware of. Keeping that in mind...
He should have checked the temp rise after he installed the motor. Too high of a temp rise can lead to premature failure of the heat exchanger. It doesn't take long to diagnose and fix a temp rise problem when he is already there but now he needs to go back and get set up again. There is no reason that you should have to pay for him to come back and adjust the gas valve or make an adjustment when he failed to do that when he was there the first time. Installing a new motor and checking the temp rise is standard practice. If he cant get the temp rise within the specs than he needs to get a motor that will blow enough air. It would be crazy for someone to install a motor that is going to damage your equipment.



Things to check before you call him back:

Did you upgrade your air filter to a high efficient at the same time?
- High efficient air filters will block return air causing higher temp rises.


Is your air filter dirty?
-A dirty air filter blocks airflow creating a greater temp rise

Did you close any registers or block any grills?
-Blocking airflow will create slower air movement across the heat exchanger creating higher temp rise.

[PrestonPierce]

Expound on this, please. How would a given HP and RPM result in reduced airflow from one motor to the next irrespective of amps? Isn't a HP at a given RPM going to be the same regardless of amp draw provided the amp draw is below the nameplate rating?:confused:


I would liketo see an example of that myself.

[PrestonPierce]

For good explanations of how the various ratings affect the performance of the motor, and great info on how motors work, diagnosing problems, and selecting replacement motors, check out the Fasco Facts booklet.

http://www.fasco.com/pdf3/fasfacts.pdf

Page 33 and 34 have specific info on selecting by amperage.


2 motors with the same HP, RPM, voltage and rotation can have very different performance when used to turn the same exact fan.



It doesn't say that anywhere I can find.

[mark beiser]

It doesn't say that anywhere I can find.

What specifically are you looking for it to say?
If you read the whole thing, there are several parts of it that support what I said.

Over the years I have personally experienced many situations where a generic replacement motor didn't work well, or at all, as a replacement for an OEM motor that had the same HP, voltage and RPM, but had a higher amperage rating.
Most of the time in those situations, the OEM motor has significantly more iron in the winding stacks.
I have seen on Lennox equipment, but run into it on most of the name brands with blower motors and condenser fan motors.
If you are ever replacing the condenser fan motor on a unit and it has an Emmerson motor that has a HP rating of something like "1/4b", you can bank on a generic 1/4hp motor not being up to the task as a replacement. ;)

[PrestonPierce]

""2 motors with the same HP, RPM, voltage and rotation can have very different performance when used to turn the same exact fan.""


I didn't see that there.

You wrote "1/4b" does the b mean design, brake HP or something else?

[kurpie]

1. High efficiency motor draw less current.

[PrestonPierce]

1. High efficiency motor draw less current.

Thats what the "b" means ?

[Mr Bill]

I have never went into a supply house and bought a motor according to amps "unless" I could not read the Hp rating on the motor and I could read the rpm's. If I can't read either I try my best to get the info from the mfg. of the unit.
And I have never witnessed someone else in a supply house in my life buying a motor were the Hp. and RPM's can be read buying it by amps.

I will say I have been burned twice in my 30 years replacing a factory 1/6 hp with an 1/6 oem, I always step it up a notch to the next hp maybe it's just been my luck but I will never take a factory motor out and put the identical oem in Hp back in.

I am not saying anything I said above is facts what I have stated was just my personal experiences. I will say I buy fasco motors only and I can't even remember the last time I had to go back and replace one I installed, so I am sticking to what has worked for me for 30 years.

As I have said here on the forum many times in the past you will not find a more opinionated bunch of folks than A/C and Heating folks and I think we can all agree on this, but I also think a lot of the opinions can also be developed from experiences. :D

[PrestonPierce]

I have never ordered a motor where I was even asked what the amperage was,thats why I am curious as to why he has had all these problems with motors. I don't buy all the scientific winding stack heights and stuff. We are talking about residential furnace blower motors they are fairly interchangeable unless they are variable speed.I don't beleive I have ever put an OEM motor in we carried a couple motors that covered almost all the furnaces out there. Why would you care about the amperage unless you were worried protecting the motor.

[mark beiser]

Maybe you guys have just been lucky...

I mostly have seen the problems when replacing blower motors in electric air handlers and outdoor fan motors on condensers and heat pumps, not so much on gas furnaces.
Lennox used to be bit notorious for having blower motors built to custom specs, and I worked for Lennox dealers for 8 years in an area that used to be dominated by Lennox, so that probably exposed me to more interesting situations than is normal. ;)

At any rate, just be sure your replacement motor is at least the same amperage as the old one and you will be fine. On blower motors, the regular generic motors are fine almost every time. Outdoor fan motors is where the most problems are to be had, with a number of manufacturers. I do far more chasing after OEM outdoor fan motors than I do OEM blower motors.

[thatguy]

Lennox is notorious for having specific part requirements. They are the only brand that I would never consider putting in a "generic" replacement motor. A coworker put in a replacement motor into a roof top and it caught on fire 2 days later. I wish I had the specs of the replacement motor and the original but he is gone for holidays (im not even sure if he would have them anymore as it was almost a year ago). I know that the office was looking everywhere for a replacement and that was the closest that they could get. I'm sure they make there parts slightly different just so they can charge more for them (and that would be ok, That's business) but it takes 6 weeks for there parts to get brought in and they don't stock anything in there store. Were always stuck telling the customer that they have no heat for 6 weeks.

[PrestonPierce]

I wouldn't be so sure that just because it wasn't an OEM motor that it caught fire there may have been other problems that he didn't notice. Why would it catch fire if it were the wrong motor if he had the HP correct and rpm correct. I think it would behard to intentionally catch a motor on fire even if you were trying to.

[thatguy]

I'll ask around and see if anybody knows the whole story. It sounds weird with the little amount of info that I have right now so hopefully someone will know more details than me.

[sadlier]

I'm not sure what to make of Fasco's following statements in their FasFacts publication:

pg 19: "Some energy-efficient motors will have matching horsepower but lower amps."
pg 20: "Do not use a replacement motor whose nameplate ampere rating is less than the defective motor."

So are they saying you should never replace a motor with an energy efficient motor?

Pg 20: "When replacing motors, the horsepower of the defective and the replacement motor should be the same."
pg 34:"Matching ampere rating is usually more accurate than matching horsepower."
pg 19: "Some energy-efficient motors will have matching horsepower but lower amps."

Sounds like a big circle. Same HP motors may draw less amps because they are more efficient(pg 19); Match the HP(pg 20); No, Match the amps(pg 34); Amps may be less on efficient motor which means matching amps will give larger HP (pg 19); Do not use larger HP because the motor will be underloaded (pg 19); Match the HP(pg 20); No, match the amps.....

[psuskeels]

So i talked to the contractor who installed the new motor - they believe it to be the same motor - same qualified by the same 3/4 HP and both running at 1075 RPM (so i guess the only possible difference would be the fan blade length - but he didn't mention that).

I measured the heat rise inside the small duct leading to the humidifer, which is coming off the main trunk, I would say a reasonable distance from the heat exchanger.

I did upgrade to a more efficient (merv 11) filter, but tested merv 6 and didn't see a difference.

I'm installing a new cold-air return as a contractor mentioned I need more return for the size house (?). I guess i'll post my results later.