Kool-a-matic fan replacement

[mrkane]

Recent experience in Q and Senator's Wash in California, while boondocking in warm weather, re-established the need for a 12V, whole-house exhaust fan. My Kool-a-matic fan motor needs to be reconditioned, but no reliable shop has been found.

A number of owners have recently replaced their generator radiator squirrel-cage fans with 12V flat electric units usually found in compact cars. The throat of the Kool-a-matic fan is ~12 inches on my coach. I have found 10" diameter flat fans rated at 650 cfm @ 5.3A, to 950 cfm @ 7.9A costing from $60-$110.

The Kool-a-matic motor is about 1/10 hp, therefore around 8 A. I haven't found a published flow rate, for comparison.

Anyone try this? Other suggestions?

Thanks--

M.R.Kane
1987 PT40 'Sleipnir'
currently near Wills Point, TX

[csprenger]

(04-03-2014 00:54)mrkane Wrote:  Recent experience in Q and Senator's Wash in California, while boondocking in warm weather, re-established the need for a 12V, whole-house exhaust fan. My Kool-a-matic fan motor needs to be reconditioned, but no reliable shop has been found.

A number of owners have recently replaced their generator radiator squirrel-cage fans with 12V flat electric units usually found in compact cars. The throat of the Kool-a-matic fan is ~12 inches on my coach. I have found 10" diameter flat fans rated at 650 cfm @ 5.3A, to 950 cfm @ 7.9A costing from $60-$110.

The Kool-a-matic motor is about 1/10 hp, therefore around 8 A. I haven't found a published flow rate, for comparison.

Anyone try this? Other suggestions?

Thanks--

M.R.Kane
1987 PT40 'Sleipnir'
currently near Wills Point, TX

I replaced our Kool-a-Matic with a Fantastic Fan so I'm no help with the motor. I'm wondering if a 14" Hayden fan would fit up into the ceiling cavity. Reason I bring this up is I have a Hayden 14" fan sitting here in the garage. It's looking for a home. Fan is free for the shipping cost.

[mrkane]

Curt:

I would like to keep the existing duct, in case I can eventually get the original motor repaired. The opening on mine is about 12 inches, so I don't think there is space to mount a 14" unit above the BB louvers, as I planned. The larger Hayden fans also tend to pull 3x more current than the K-o-M, as do the available NAPA replacement DC motors.

Thanks--

M.R.Kane
1987 PT40 'Sleipnir'
currently near Wills Point, TX

[davidbrady]

Hi Mrkane,

If you go to our search page and do a Google Custom Search on "Kool o matic" you'll get many hits.

Some folks replaced it with a Fantastic Fan, some bought components from JC Whitney, some were able to get components form Kool-o-matic, which does seem to still be in business.

There's 3 pages of hits from our Google Custom Search.

[mrkane]

(04-05-2014 11:19)davidbrady Wrote:  Hi Mrkane,

If you go to our search page and do a Google Custom Search on "Kool o matic" you'll get many hits.

Some folks replaced it with a Fantastic Fan, some bought components from JC Whitney, some were able to get components form Kool-o-matic, which does seem to still be in business.

There's 3 pages of hits from our Google Custom Search.

Most recent entries returned by the search date from 2009, and describe unsuccessful attempts to obtain equivalent parts.

IMO, the suggested NAPA motor draws more current than the wiring will support. Indeed, low current draw would also be best in a boondocking context.

The optimal solution would be to repair my original motor, but finding a competent shop in the areas where I travel has not been successful--"Oh, yeah, we had a great repair shop, but it closed when the owner old Bob Jones passed." An outcome of our aging population, I guess. (I've been retired 10 years this week, so I'm in that group of 'used-to-be' too.)

The interior volume of my coach is roughly 2000 cuft. I suppose a fan rated to move that much air in 2-3 minutes would be adequate.

Thanks--

M.R.Kane
1987 PT40 'Sleipnir'
currently near Wills Point, TX

[davidbrady]

Hi Mrkane,

Is this the motor: Four Seasons 35502, ebay item: 350933892758

[mrkane]

(04-05-2014 12:43)davidbrady Wrote:  Hi Mrkane,

Is this the motor: Four Seasons 35502, ebay item: 350933892758

Can't find hp, rpm, current specs?

This appears similar to NAPA motors 655-2012 and 655-2378 suggested in other postings. However current draw is reported to be over 16 A for those. The Kool-o-matic motor is only marked with an in-house number, but the sticker on the duct states 8.5 A maximum current.


---
M.R.Kane
1987 PT40 'Sleipnir'
currently near Wills Point, TX

[davidbrady]

What kind of speed control do you have on the Kool-o-matic; i.e., potentiometer, rheostat, solid state, none, etc?

I ask because the speed control should drop the voltage going to the motor and the current going into it. My guess is that the Kool-o-matic uses a rheostat. If so then you should check to see if the rheostat offers resistance at the high speed setting. It could be that the rheostat is the current limiting factor in your motor circuit, in other words, choose a multi-position rheostat that limits the max current to your wiring specifications.

[mrkane]

(04-05-2014 14:22)davidbrady Wrote:  What kind of speed control do you have on the Kool-o-matic; i.e., potentiometer, rheostat, solid state, none, etc?

I ask because the speed control should drop the voltage going to the motor and the current going into it. My guess is that the Kool-o-matic uses a rheostat. If so then you should check to see if the rheostat offers resistance at the high speed setting. It could be that the rheostat is the current limiting factor in your motor circuit, in other words, choose a multi-position rheostat that limits the max current to your wiring specifications.

Speed control was with wire-wound resistors, but it burned up when the bearings froze. (Max speed was full voltage: ie 1/10 hp * 746 w/hp ~= 7.5 A)

Previous postings stated the NAPA motor burned up the relay due to excessive current. I wouldn't trust the present wiring or thermostat to handle that much power, either.

---
M.R.Kane
1987 PT40 'Sleipnir'
currently near Wills Point, TX

[davidbrady]

If the NAPA is 1/3 hp at 3000 rpm's and draw's 18 amps, I'm saying use a larger rheostat inline to control the speed to a maximum of 1000 rpm's which will cut your power to 1/10 hp and your current to 6 amps. (Approximate numbers). IOW's, the rheostat (or wire wound resistor) will drop the voltage that the motor sees, but it has to be rated to handle the power dissipated across the rheostat/wire-wound resistor.

A quick search shows that the wire-wound resistor values are something like:
0.46 ohms, 50W
0.6 ohms, 22W
1 ohms, 16W

IOW's, don't run it at full speed!