Draft test results on P43

Figured after all this time, we should find out what the draft readings look like on the stoves, so picked up a magnehelic on ebay. It came in today, so I tested the P43 after work. According to the Harman manual:

The high draft should be in the -.50 to -.60 range. The P43 high draft is -.58.
The low draft should be in the -.35 to -.45 range. The P43 low draft is -.52.

Manual suggests turning the low draft voltage adjustment screw down until it gets into the -.35 to -.45 range, or if it won't go that low, just adjust it down as far as it will go. Never touched that screw before on either of my stoves. Will try it soon and report back what it does (if anything, lol).

Always had a feeling the P43 draft was a bit on the high side. It burns super clean, meaning there is virtually nothing left in the base of the burnpot at the end of the shutdown cycle. No un-burned pellets, and little to no ash. Also when the stove is running, we see a fair amount of embers flying out of the pot. Really nothing to complain about, like how it burns - super clean. Will still try to adjust it down to the manual specs and see what happens.

 

Thanks TT will have to have another look at the manual . Great Information thanks Man !

 

by turning that potentiometer, you're just lowering the voltage to the combustion fan. It comes factory preset to max (turned all the way clockwise). The newer boards have much more adjust-ability than before....used to be like 10 volts min/max difference, whereas now, I think its about 25 volts min/max. As per the folks at Harman though, they have been suggesting not to turn it lower than 10 volts. Remember, this is on a CLEAN stove! A dirty stove will read less typically, but if its dirty on the upstream side, it will read more.....dirty on the downstream side, it will read less. Since your vac switch shuts down the igniter and feeder around -.15 inches water, you dont really want to be anywhere near that.
Of course, with too high a draft, you can be putting heat up the chimney. You cant really set your high draft well, only low draft.

 

Yeah, figure we'll try to adjust it according to the manual and see hat happens. Worst case, we can adjust it back to where it has been all along.

 

Reduced the low draft to -.45 on the P43 a couple days ago. So far, not noticing a difference.

Also checked the draft on the P68.

High draft on P68 was -.61
Low draft on P68 was -.55

Per the manual, used the low draft voltage adjustment screw to get the low draft reading to be at or close to -.35 the -.45 range. Turned the screw as far counter-clockwise as it would go, and ended up at -.49. That's as good as it's gonna get with the P68. Again, not really noticing any difference yet.

 

As we talked about... I had a lot of fireworks going on... so I did a draft reduction on mine..
Just kept turning it down till most of the sparks didn't look like Roman candles..
I DID notice a difference... stove temp went up considerably... had to crank mine down to the stop...
I guess when you do it by the book... your chimney is not warm..
After it is warm, I suppose your natural draft pulls a lot more..
(My stove dumps into a clay lined real chimney...)

Dan

 

yep, thats the reason to attempt to set the low draft....Ive found the fireworks are usually more a function of the amount of fines in the pellet rather than the draft, but your results may differ

 

Not so much that they differ.. I agree with that.
However, when you set the combustion fan to a lower voltage, I should think
that means it is running slower... therefore, not throwing so much
air into the pot... which does have a relationship to how many sparks are flying as well...
And the size.. ? I also notice that the flame looks different... (not so much forced air..)?

Dan

 

mostly being familiar with the Harman, yes, turning the potentiometer adjustment screw counterclockwise lowers the voltage across the motor and slows it down. The motor pulls air through the burnpot, and in doing so you could change the airflow characteristics somewhat. The idea being that there isn't so much draft that you're pulling an excessive amount of heat into your exhaust (rather than against your heat exchanger). Oftentimes, as folks are seeing, even at a maximum adjustment, you still cant get that low draft to where the instructions say it should be. Note that the draft adjustment is done on a COLD and CLEAN stove, as with a fire, you might get some component of natural draft, messing with your numbers.

 

Very interesting info.....