Harman PF 100 distribution blower wiring and advice?

[Don2222]

Hello

Working on a 6 year old Harman PF100. The distribution blower is a really big! LOL
However it only works on high. I see only 2 wires connected to the 3 position toggle switch and only two wires connected to the starting capacitor. There are 3 wires just hanging there?

2 Questions

1. Any idea how these 3 wires (Red, Blue and Yellow) should be connected?
On the 1638 CFM blower the Yellow wire is the Blue Medium speed! See below:

2. Does the Harman Circuit Board turn this blower on and off in Automatic Mode?

See pics below

Click pics to enlarge:

 

[dhall28]

if i remember correctly the blower is being sent power all the time, even when the control board is off, as long as the red switch on the junction box below the hopper is on then i think power is being sent to the fan control in the hot air plenum

 

[dhall28]

I think I once wired one of these a long time ago, it is a four speed blower so you hook up the low speed and high speed wires and then you can go with either blue or yellow, I dont know which is which but it is basically deciding between medium low or medium high if i remember correctly.

and I double checked the wiring diagram and yeah the power to the fan control is independent of the board.

 

[Don2222]

I think I once wired one of these a long time ago, it is a four speed blower so you hook up the low speed and high speed wires and then you can go with either blue or yellow, I dont know which is which but it is basically deciding between medium low or medium high if i remember correctly.

and I double checked the wiring diagram and yeah the power to the fan control is independent of the board.

There are different size blowers that come with these units. I just learned the Yellow wire on the 1638 CFM blower is the medium speed which is a blue wire on the other size blowers!

 

[dhall28]

correct, i was referring to this specific blower being a four speed blower and the two smaller more common ones are only three speed, if i remember correctly you can use either of the two medium speed wires one is just slightly faster than the other, at least that is how i remember it.

 

[Don2222]

Yes

For this machine, it looks like

Black=High
Yellow=Medium
Red=Low

Since the switch currently only makes the fan run on high, the problem is not only the violet and black are on the wrong post!
The fix is this:
1. shut off power to the furnace
2. Remove the black wire and move the purple wire to that post.
3. Put the black wire on the post directly behind the purple wire
4. Put the Red wire where the black wire was attached
5. Put the Blue wire on the last open post in the back

 

[Don2222]

Just got the answer to the second question!

"Now, the circuit board INDIRECTLY turns the fan on. It does this by lighting the fire when the probe calls for heat, stove lights, which heats up the heat exchanger, which heats up the air in the air jacket, and the hot air rises to the limit switch in the plenum above the stove....this limit switch (Harman part #3-20-23139) in turn switches on and powers the fan. This big fan does not connect at all to the circuit board though."

Thanks LW