[Red-z]

The blower wheel is rated to 1750 rpm and the motor is running 1625. The 1625 rpm motor amp is 5.4. The 1075 rpm motor is 7.4 amps.

[Red-z]

I do have a question for everybody between an old blower wheel and a new one: If the blower wheel diameter and width is the same, the number of blades the same, the rotation the same, and the motor shaft is long enough to mount the blower wheel, what difference would there be if the new blower wheel has a convex hub if the original has a concave hub?

[hvac1000]

I do have a question for everybody between an old blower wheel and a new one: If the blower wheel diameter and width is the same, the number of blades the same, the rotation the same, and the motor shaft is long enough to mount the blower wheel, what difference would there be if the new blower wheel has a convex hub if the original has a concave hub?

Every blower wheel has a rate of transfer. This rate is based upon testing by the manufacturer at various speeds in various style housings. One wheel can have many listed rates of air movement and safe speeds depending upon the load imposed by the cage it is placed in. Cage manufactures if different from the blower wheel manufacturers will also post this type of information or have it available for end users like major equipment manufacturer and there engineers. In order to find that information you will need to contact the manufacturer of the wheel/cage combination or visit there website if a website is available.

Engineers design equipment for a specific purpose and with specific goals in mind. Any modifications especially with HVAC equipment usually end in disaster by reducing the life of the equipment or creating a hazard. Heat exchangers are especially prone to damage as we have proven in our testing at the university. Manufactures have us test the equipment for failures under stress. Usually there is a 15 to 25% safety margin built into equipment till damage starts to occur. If for example a heat exchanger is taxed at 125% of its rated value for 5 minutes with 5 minutes cool down time no damage may occur but is taxed 15 times at this value some damage is noticeable (usually warping out of spec.) If the initial testing is at 125% for a 15 minute cycle at 15 times for this value the damage becomes much more severe and this goes on and on testing wise till total failure. This way if some idiot decides to modify there equipment to over fire for example they can cover there boxer shorts in a court of law. Even if the unit is returned to all stock parts before the investigation a
metallurgist can tell the values at the time of failure so there can be no coverup. Modern science is a wonderful thing and matching that with computers just makes it awesome.

It is a dangerous game we sometime play and in many respects just plain stupid since common sense tells us better. I try to follow the Do NO Harm policy. Try to repair as best as possible but Do NO Harm to the equipment that could cost human life.

The John Wayne attitude towards repair can be dangerous.

[Red-z]

Actually there is no difference in air flow, all else being equal. Concave positions the hub closer to the motor. Convex positions the hub further from the motor.

That's it.

Thanks for your help.

[Red-z]

hvac1000:
Why didn't you just say "I don't know". We're not addressing heat transfer gradients across the heating tubes, nor harmonic frequencies of blower wheel blades. This IS common sense.

I think you're twisted in your shorts again.

[hvac1000]

Since you are such a professional on air flow why did you ask the question to start with. In all your posts which started with blower running backwards till now you were the one with the cocky answers not me.

Example

I wouldn't be surprised if the rear wheels on my car were running backwards, too. I'll see if the supplier shipped me a CW instead of a CCW blower wheel.

To help you all I mentioned was the possibility of the unit running in reverse. Looks like that upset you because you could not figure out the problem yourself.

Example

You were right about something being backwards.

Looks like I helped you there. But that first cocky answer was a tip off to me exactly what type of personallity you have.

Example

I reversed the rotation on the electric motor to coincide with the wrong wheel, and its working much better.

I also mentioned that possibility in my post back to you.

It continues on and on with you asking questions and getting the best answers possible but you do not want to hear the truth all you want to hear is people agreeing with you and the methods you are using to modify your furnace.

If you are unhappy that is a shame. If you do not want to listen to the many helpers we have on this board that is OK in my book also. The John Wayne attitude you show towards the correct answers you have been given is a prime example of a person who always has to have his own way and that is probably how you try and run your life. That is just wonderful also but my last message to you was meant to make you think about what you are doing or have already done to your furnace. If the furnace was working correctly you would not have posted here to start with.

Good luck with your furnace since I believe you will need it when the real cold weather hits.