# 2 HP motor or 12 inch impeller?



## Elden Cozort (Oct 30, 2018)

I have a 2 HP blower with a 9 inch impeller, I recently picked up a 1 1/2 HP blower with a 12 inch impeller. 

I thought it would be a simple task to remove the 9 in impeller and put the 12 in one on for a simple upgrade.

Problem is that with the 12 inch impeller on the 2 HP blower as soon as it starts to get up to speed it blows the 20 AMP breaker. No hoses connected, just the motor and impeller. I did all sorts of testing and put the 9 inch back on. It works with no problem. So I guess the 12 inch is just causing the motor to pull to much juice.

So,... my question is which would you rather have: a 2 HP blower with a 9 in impeller or a 1 1/2 HP blower with a 12 inch impeller??

Note: I have a top hat type dust separator.


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## woodnthings (Jan 24, 2009)

That relationship is inverse! The lower HP motor has the larger impeller and works fine? Somethin ain't right here. Both motor's RPMs the same? Both run on same voltage? Sometimes a blower will need a restriction on the intake or it will over rev, but I'm no expert on that, so check it out. Duct work in and out the same size? 
Who knows?


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## HoytC (Dec 30, 2019)

The top hat has a lot of pressure loss. You want the fan with the highest pressure. That's the 12" fan. Fan static pressure varies with the square of the fan diameter, so the 12" fan has about 1.8 time the pressure of the 9" fan.

It's unlikely that the 9" fan will draw anywhere close to 2HP. Where did you come up with that number?

With the top hat separator I doubt that the 12" fan will get close to 2HP either.


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## _Ogre (Feb 1, 2013)

Elden Cozort said:


> So,... my question is which would you rather have: a 2 HP blower with a 9 in impeller or a 1 1/2 HP blower with a 12 inch impeller??


you sound like some of the guys over on the gearhead forums i hang out on
woodnthings nailed it, rpms & voltage.
plus you run into mathamagics, like a 6hp shop vac, 
no, i do not want a 6hp shop vac motor on my table saw


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## Elden Cozort (Oct 30, 2018)

woodnthings said:


> That relationship is inverse! The lower HP motor has the larger impeller and works fine? Somethin ain't right here. Both motor's RPMs the same? Both run on same voltage? Sometimes a blower will need a restriction on the intake or it will over rev, but I'm no expert on that, so check it out. Duct work in and out the same size?
> Who knows?


Yep the 1.5 with the 12 inch impeller runs fine on the 20 AMP circuit and the 2 with the 9 in impeller runs fine on the 20 AMP circuit, but putting the 12 inch impeller on the 2 HP motor blows the circuit. 

The 1.5 is 3450, not sure about the 2 HP motor but I think it is 3450 also. It is a harbor freight unit.


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## Elden Cozort (Oct 30, 2018)

HoytC said:


> The top hat has a lot of pressure loss. You want the fan with the highest pressure. That's the 12" fan. Fan static pressure varies with the square of the fan diameter, so the 12" fan has about 1.8 time the pressure of the 9" fan.
> 
> It's unlikely that the 9" fan will draw anywhere close to 2HP. Where did you come up with that number?
> 
> With the top hat separator I doubt that the 12" fan will get close to 2HP either.


The 2 HP 9 inch impeller unit is from Harbor Freight. The test i did was with nothing attached to the blower unit.


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## HoytC (Dec 30, 2019)

Elden Cozort said:


> The 2 HP 9 inch impeller unit is from Harbor Freight. The test i did was with nothing attached to the blower unit.


Ah, the HFDC. I've done some testing of that unit with a 12' fan, see the gory details here.

The original fan is 10". not 9". The motor will overheat above maybe 1.4 HP, which is about what it draws in it's standard configuration with the inlet open.

At startup, with a 12" steel fan, it will draw 60+ A for at least 4 seconds, longer with the inlet open than with it closed. Your breaker needs to tolerate that.

If you have both inlet and outlet open (that is, disconnect the hose on the blower outlet) the running load is about 2 HP with the 12" fan. 18 A or so. The HF motor won't last long with that load.


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## Elden Cozort (Oct 30, 2018)

HoytC said:


> Ah, the HFDC. I've done some testing of that unit with a 12' fan, see the gory details here.
> 
> The original fan is 10". not 9". The motor will overheat above maybe 1.4 HP, which is about what it draws in it's standard configuration with the inlet open.
> 
> ...


Thanks--so what would you recommend? Should I do the 1.5 HP with 12 inch impeller or the 2 HP with 10 inch impeller (I must have been using a bad ruler when I measured it) By the way my longest run is about 12 feet but it with flexible duct.


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## Elden Cozort (Oct 30, 2018)

woodnthings said:


> That relationship is inverse! The lower HP motor has the larger impeller and works fine? Somethin ain't right here. Both motor's RPMs the same? Both run on same voltage? Sometimes a blower will need a restriction on the intake or it will over rev, but I'm no expert on that, so check it out. Duct work in and out the same size?
> Who knows?


Thanks for the info about restriction. I hooked it up to the top hat and it only blew the breaker 3 times out of 5. Obviously, I won't be able to use that setup. 

So--what is your input regarding which blower I should use:
1/5 HP with 12 inch blower
2 HP with 10 inch blower (Hoyt corrected my 9 inch error)


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## HoytC (Dec 30, 2019)

Elden Cozort said:


> Thanks--so what would you recommend? Should I do the 1.5 HP with 12 inch impeller or the 2 HP with 10 inch impeller (I must have been using a bad ruler when I measured it) By the way my longest run is about 12 feet but it with flexible duct.


The top hat separator will limit the flow enough that you probably won't overload either motor so I would just go with the 12". The greater CFM will help with dust pickup.

The HFDC is NOT a 2 HP blower. That's just what they call it. That's not what it does.

What are you doing on the outlet? Do you have a make and model number for the "1.5 HP" unit? What are the inlet and outlet sizes? Picture of your top hat separator and approximate dimensions?


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## Elden Cozort (Oct 30, 2018)

HoytC said:


> The top hat separator will limit the flow enough that you probably won't overload either motor so I would just go with the 12". The greater CFM will help with dust pickup.
> 
> The HFDC is NOT a 2 HP blower. That's just what they call it. That's not what it does.
> 
> What are you doing on the outlet? Do you have a make and model number for the "1.5 HP" unit? What are the inlet and outlet sizes? Picture of your top hat separator and approximate dimensions?


For the outlet, I have a 10 foot 5 inch flex ducting that I generally just lay on the ground outside my garage, sometimes I hook it up to the original HF bags. No make or model for the 1.5, just the blower with a tag on the motor. The tophat is
approximately 22 inch diameter.


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## Elden Cozort (Oct 30, 2018)

Not sure why the pictures are there so many times


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## HoytC (Dec 30, 2019)

Elden Cozort said:


> For the outlet, I have a 10 foot 5 inch flex ducting that I generally just lay on the ground outside my garage, sometimes I hook it up to the original HF bags. No make or model for the 1.5, just the blower with a tag on the motor. The tophat is approximately 22 inch diameter.


Ok, you have enough restriction on the inlet side that either motor will stay fairly cool. Use the 12". You should have more flow with it.


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## Elden Cozort (Oct 30, 2018)

While cleaning up the 1.5 hp blower that has the 12 inch impeller, I found a warning label that basically said not to operate with first reading the manual and said that if you can't find the manual call ShopFox--so this unit was sold by ShopFox-it is just the blower, no bags.


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## Elden Cozort (Oct 30, 2018)

Here are pictures of the two blowers. Left picture is the 1/5 HP ShopFox with 12 inch impeller, Right picture is the 2 HP Harbor Freight with 10 inch impeller. 

Both are almost identical housings

I am curious though that the vanes on the impellers are in opposite directions. Does the direction make any difference?


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## JayArr (Sep 18, 2018)

Do the motors run in opposite directions?


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## woodnthings (Jan 24, 2009)

They have "discovered" that reverse direction vanes that "push" the air are more efficient than cupped vanes ..... IF I remember correctly? Understanding moving air is a bit like a magic show.... it's hard to know what's really going on. Just a bit less mystical than watching electricity flow through wires.... LOL. Like why does the motor run better when it's restricted? Who knows? 

You can go back and remove those duplicate photos using the 3 small buttons at the upper right side of the text. Click on that and you'll find EDIT and REPORT, choose edit and wait a few seconds it will allow you to "edit". I use it all the time.


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## HoytC (Dec 30, 2019)

Elden Cozort said:


> I am curious though that the vanes on the impellers are in opposite directions. Does the direction make any difference?


It makes some difference. At the same flow rate _and the same size fan_ a backward curved blade will produce less pressure than a forward curved blade. It also requires less power at that flow rate. The difference increases with increasing flow.

Backward curves generate a bit less noise and are less prone to build up when used with dusty air.

In the blog I linked in a previous post I tested the two fans you have (assuming the Rikon and Shop Fox are the same fan, and they sure look the same), both using the HF housing and motor. You can see the differences, both in flow rate and current drain.








The flow vs pressure curves are with the stock components on the outlet. The fans without those restrictions will of course will do much more than that chart shows. See this post.

Note on the flow/pressure chart that the two curves converge around 650 CFM. That's the difference in blade angle. If the two fans had the same blade angle the curves would remain separated at higher flows. There would also be more separation in the current curves.


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## Jar944_2 (Oct 30, 2020)

Both motors are 16A. Ignore the "hp" number on the Hf


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## Elden Cozort (Oct 30, 2018)

JayArr said:


> Do the motors run in opposite directions?


No, both run the same


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## Elden Cozort (Oct 30, 2018)

My thanks to everyone that gave me input. I really appreciate it. 

Dave (HoytC) I certainly appreciate the time and effort you spent testing and writing your experience with replacing the impeller on the HF unit. Amazing information. 

Jar944_2 is probably correct that they are both 16 AMP motors and that the ShopFox is called 1.5 HP and HF calls theirs 2 HP. I have seen other 16 AMP motors called 2 HP. Wen, for example.

I remain curious why the HF trips the breaker with the 12 inch impeller is installed, but oh well. 

I haven't been very disappointed with the dust collection of the HF unit but had read about upgrading to a 12 inch impeller and when I got the ShopFox blower, I thought I would try. I didn't research the true HP of the motors.

My current guess is that simply using the ShopFox blower instead of the HF blower would yield the same results as trying to install the 12 inch impeller on the HF blower (without the problem of tripping the breaker).

I plan to install the ShopFox blower today and use it for a while and see if I notice a difference. If I don't then I'll put the HF back in place. 

I'll update if I find something. Thanks again.


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## Elden Cozort (Oct 30, 2018)

Update: (Final?)

I decided to just experiment. Keep in mind that I have a small shop and only run one piece of equipment at a time.

I had the HF blower (supposedly 2 HP w/10 inch impeller) installed so I did some very un-scientific tests to see how well it operated and then I removed it and installed the ShopFox blower (1/5 HP w/12 inch impeller) and performed the same tests. I thought the ShopFox worked marginally better so I left it installed.

One note: the HF blower has a 5 inch inlet and outlet, the ShopFox has a 6 inch inlet and 5 inch outlet.


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