[Red-z]

The furnace is natural gas. The old one is still working as we speak undamaged. It appears too risky to guess at the orifice and flame characteristic even with a photo if I send one. Maybe I should just leave it alone.

What's the risk of continuing to use a 30 yr old pilot burner?

[hvac1000]

What's the risk of continuing to use a 30 yr old pilot burner?

None

[Red-z]

Then, I think I'm done. Thanks again for your help. It's much appreciated.

[hvac1000]

Glad you got it going. Stay warm.

[Red-z]

Do you think I should replace the limit switch with a universal replacement? Its 30 years old. The insertion length is 10-3/16"

[hvac1000]

If the limit is defective replace with the same basic temperature cutoff.

[Red-z]

How can I tell if it is defective?

[hvac1000]

Test it and see when it operates. Then look on the furnace for the operating temps. You just asked if you should replace it cause it was 30 years old. I guess it must be working since you were only going to replace it because of age.

[Red-z]

Its working. I was just thinking of preventive maintenance.

[Missouri Bound]

Red, I'm sorry if I missed the post on these 5 pages, but did you ever get the proper rotation blower wheel or are you running the wrong one backwards? Because of the blower housing design, running the wrong wheel in the right direction still won't be as efficient as the proper wheel. You will get turbulance at the blower outlet. I think that would have been the first fix I tried before increasing the blower speed.

[Red-z]

Missouri:
I bought a ccw wheel and was shipped a cw. I reversed the motor rotation.

If I understand you correctly, by reversing the motor rotation you're saying that I am going against the design of the blower housing, and won't get the proper cfm. Is this correct?

[Missouri Bound]

Yes. You have diminished air flow because of this, how diminished would depend on the blower output design... the more open the output of the blower, the less the effect would be.

[Red-z]

I would agree with you, except that the blower housing is symmetrical, typically u-shaped from the side view, but rectangular at the top interface with the inlet. So there are no indications from the housing design that air blowing cw or ccw would make any differences as long as it passes upward over the heat tubes.
What do you think?

[Missouri Bound]

If your description is accurate, then I tend to agree with you. If blower housing design doesn't dictate the air flow direction, you are correct. Duly noted.

[Red-z]

My take is the replacement blower has less blower blade surface area and so it is not "paddling" as much CFM as the original.

Thanks anyway. I'm always open to ideas.

[Missouri Bound]

That's probably accurate. And if the blower wheel doesn't fill the opening completely, there is an issue with turbulance at the edges of the wheel.

[Red-z]

The blower wheel is the same width as the original, but the diameter is 1/2" larger. I couldn't find an exact universal fit.

[wmproop]

I've rebalanced the ducts. The net result so far is I've lost some blowing power with the new blower wheel. It has 12.5% less blade surface area than the original. If I need more blower power I may need to replace the new electric motor (1075rpm) with a high speed motor (1625rpm).

I would be very careful of replacing blower motor with a higher RPM motor,, the fast it blows the cooler the needed air will be by the time it gets to your living area

[Red-z]

It was deliberate. The air was too hot at the register. I've replace the motor and it's now ranging between 100-120 F.

But I will have to see how it performs at the coldest day in January.

Thanks for the thought.

[MarkwithaK]

I would be most concerned about the life span of the blower motor. If the blower motor is not sized to the blower wheel you can cause the motor to over amp which can lead to failure.