Harman P68 - 4 RPM or 6 RPM Feed Motor - Which is better?

Hello

I have worked on 4s and 6s installed in P68s but what is the difference? Does the 6 RPM put out more heat?

Four of the Dip switches on the Circuit Board sets the feed motor for the correct charge of pellets to the burn pot and other differences at startup but is there any real advantage to either setup?

What is your experience if you tried both setups?

See pics

 

?? They are 2 completely different feeder units,not interchangeable parts.Old style,that sometimes gummed up,and updated style.

 

I did not realize they are interchangeable. The P43 came with a 4rpm and the P68 came with a 6rpm. I just bought a replacement for the P68 and went out of my way to buy the same 6rpm motor that came on it. Assume this is an engineering design decision on the appropriate motor for the unit, based on overall design, and paired with other components like burnpot size, heat output specs, etc?

 

not interchangeable,2 different feeder units,early and late

 

In dons case there is an early and late feeder assembly.Now about the p43,it has a way different burn pot.I think the 68 is much bigger?

 

Hello

Thanks guys

The auger is different for the old 4 RPM feeder motor than the new auger for the 6 RPM motor - see different part #s below.
So why does the shorter auger have a faster motor ? ? ?
It is only 1 inch shorter, just does not make sense?

Are the fins on the 6 RPM stove father apart than the 4 RPM stove?

Looks like the
Newer 6 RPM motor part #3-20-60906 is for:
Harman P68 (After serial # 008280309)

Harman Auger part # 3-50-00565 This part measures roughly 9 1/2" from end to end.
P68 (After serial # 008280309)
------------------------------------------------------------------------------------------------------------------
Older 4 RPM Part # 3-20-40904 motor is for:
Harman P68 (Pre serial # 008280309)

Harman Auger part # 3-50-00465 This part measures roughly 10 1/2" from end to end
P68 (Pre serial # 008280309)

 

Don't know Don,other than an improvement.The newer auger fits all the newer stoves,that have the newer feeder assembly,yet use the same 4 rpm motor,except the p68.The length of the auger means nothing.A p68 has much larger burn pot,as the stove is rated something like 20k more btu's more.As the older p68 has same burnpot,it would appear it never saw its true potential,and may be improved by putting 6 rpm motor on it.However it could also be that the older firbox could not handle the load.Just some thoughts.

 

Good point Bob about the augers being the same on all newer stoves. The user still has control of the heat range so that would mean that the difference is the 6 RPM auger motor would put out more heat at the high heat levels?
Thanks guys for the help to analyze this!

 

the old 4 rpm units had the larger (longer) feeding gate above the slide plate, whereas the UL units were about an inch narrow (see why the auger is different now?).....so, in the UL units, since the feed gate is smaller, you would need more rpm's out of the motor the get the same amount of pellets to the fire, ergo, 6 rpms. Be mindful though, the feeder never runs constantly (limited by the feed adjuster setting). So, even though the motor CAN run more rpm's, doesn't mean it will.
As for the auger, the pitch is the same....the bearing is different. if you look at both, you will see that the "old" style auger/bearing buries into the feed assembly about 3.4" of an inch or so, where the "new" style buries into the feeder only maybe 3/16" of an inch......
P68 serials numbers prior to 00820309 will be 4 rpm. Although sometimes folks have no idea what the serial number is, the stumble in and just ask for a P68 gearmotor, and might end up with the wrong one!

 

I thought about that,LW,but had no way to check.As the newer stoves still use old rpm motors and programming,I still see it as somewhat of a design flaw?I really would like to see Don put a newer motor on older stove and post results.

 

The newer stoves use 6 rpm motors (in the P68 anyways, not the other models...they are 4 rpm).....Since these units run off the ESP and the circuitboard, I would think that the 4 rpm motor would simply run more (making the feed adjuster setting VERY important!)......in other words, there would be fewer pellets delivered in the same amount of time, causing the ESP not to be satisfied as quickly, and cause the feeder to run more to satisfy the heat demand, as calculated by the CB and the ESP. A newer 6 rpm motor on an older, non-ultralight stove would likely just result in the motor running less.
And you cant put the old auger in a newer stove, and vice versa.

 

In theory,as the reaction time is slow(esp change) and is covered by a program in the chip,a 6rpm on a older stove will put more pellets in eyerytime it runs,probably causing stove to flare up and down(hey like a top feed!) but may,over a period of time,put out more heat.

 

Hello
Thanks LW
Putting a new 6 RPM motor in an older stove may not make too much of a difference but it may give a little more heat on the high levels. One of my other Harman dealer friends said it did not seem to make much difference so I may try doing it to see for myself