Urgently need some help on a MH Coleman-evcon furnace model# DGRT070AUA...

Old 07-18-03, 01:10 PM
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Urgently need some help on a MH Coleman-evcon furnace model# DGRT070AUA...

I have a manufactured home with a coleman-Evcon furnace Model #DGRT070AUA. The furnace is equipped with a 1/6hp blower motor that shows 1000rpm. I'm wanting to increase the cfm's and noticed on the furnace data sheet that a 1/2hp motor was an option for the furnace (part# 7900-6051). I called around to several places in town and one individual told me that the furnace I have does not offer a bigger blower motor housing/assembly but they do carry the 1/2hp motor. They sent a tech out and he wanted to know if I wanted to have it installed saying it would increase the CFM's. Well I talked to another company and they are saying it will not make a difference on the hp or rpms for that matter, basically the hp rating is for bigger blower wheels. I've tried to call evcon-coleman several times but no luck. Now in speaking with the original tech and voicing my concerns he basically says the other company is wrong and laughed that I would believe someone else over him (I also mentioned that I asked this question on another internet based HVAC site (not this one) and they said it would not make a difference either) and really laughed that I would take the word of someone on the net). I'm really confused. He said that the 1/2 hp motor has an rpm of around 1200 but when I asked him again today when he called he said to beleive whatever I want. Kind of pisses me off that this guy is being an a-hole. Bottom line - will a bigger hp blower motor with same size wheel and assembly increase cfm? Thanks for the help. -Shawn

One more thing - why would the manufacturer have different hp blower motors listed on the data sheet, with my 1/6hp motor being checked, if you can't get a bigger assembly and the hp doesn't make a difference on cfm???
Old 07-18-03, 03:00 PM
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The main reason is that if your furnace has a/c installed, it will take more power to move the cold dense air. That is where the more powerful motor comes in. Not to move more air, but to move the same amount without over working the motor. Don't pay for a motor with a higher hp rating just to get more air. It won't happen. You are correct about increasing the size of the blower wheel to get more air flow. You will need to replace the whole blower because the blower housing is a match for the blower wheel.

I think you may be approaching this problem from the wrong perspective. If you need more airflow, you might just redice the static pressure. Larger duct, or a more efficient duct system. Less sharp turns and restrictions. If you just increase airflow the system may get noisy.

It may pay to find someone who can really look over the system and make logical recommendations for modifications.

Get rid of the guy who was looking for the fast buck.

The information you will get on this site is offered by professionals who work in the hvac field and have tons of experience. They also know their recommendations will be checked by many other professionals who frequent this site. If I didn't think this site gave straightforward honest info to homeowners and contractors alike, I would never return. It is however a serious threat to contractors who prey on the ignorance of their customers. A free second opinion or double-check of the facts has saved many people from wasting their money.

Good luck fixing your problem.

Old 07-18-03, 04:30 PM
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Ken is correct. It's the rpm and blower wheel design that determines air volume and pressure.
The hp rating of the motor is to match the motor to the amount of work the blower wheel has to do.

The attitude of your serviceman shows someone who is likely not familiar with the internet as a research tool.
I personally do not widely broadcast that information I use is from the web. There are a lot of people who are distrustfull and some who don't understand how to properly separate the good from the bad.

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