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???
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!

[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?

[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