Harman PF120 installed - some questions on PF usage

[skidadil]

Hi all,

This is my first post on this forum, so a quick "hello" is in order. I spent a lot of time browsing this forum while I was making a decision on which pellet furnace to purchase. So, thanks to everyone who has contributed to this forum thus far!!

I ultimately decided on the Harman PF120 for several reasons. But, ultimately, it came down to the fact that it was the only PF that was sold by retailers in my area. Purchasing a PF of any other brand would have meant being 100 or more miles away from the retailer, and when it came down to considering future servicing needs that wasn't something I wanted to entertain.

My home has an oil furnace, which I decided to keep as a backup to my PF. My PF120 was installed just about a week ago. So far I'm super thrilled about the heat output I'm getting from the unit. It's nice to finally be able to turn the thermostat to where my family and I want it to be, and not having to fear seeing the oil truck come by and see my hard earned money go up in smoke. We were all so sick and tired of freezing our tails off during the winter due to having to keep the thermostat so low to be able to (barely) afford the oil. I estimate my annual heating costs will go from the $2500 - $3000 range burning oil to the $900 - $1200 range burning pellets.

For those of you that have experience running a pellet furnace, I have a couple of questions:

1. Is it normal for the furnace to run hours on end? Up until I moved into this home about three years ago, I've spent my entire life in homes that run on natural gas. Both gas and oil furnaces turn off once the thermostat's set temperature has been satisfied. The PF gets the house up to the desired temperature very fast, but then continues to run for several hours (usually 3 - 5 hours - some times longer, and some times shorter - but that's the typical range). The flame definitely quiets down during this time, and the retailer told me this is normal for a PF. But I wanted to double check that with all of you out there. It would be nice to hear that this is normal for the operation of the PF. I figure this is because of the amount of pellets it consumes as it's getting started, and by maintaining a smaller fire it'll ultimately use less pellets in the long run? While the fire was lit the fan was running continuously up until yesterday when the retailer changed settings on my fan/limit switch. Now it cycles on and off after the thermostat temp has been met, which I'm honestly not a fan of. I can hear the pellets being fed into the furnace, so my thinking is that I might as well have the fan blowing and get my monies worth rather than have it just make a nice little fire for no one to enjoy.
2. How much, if any, smoke/wood smell do you get throughout your house? We get quite a bit of smoke/wood smell throughout the house while the fire is going. It's particularly strong when the furnace first fires up, and then it scales back a bit and remains continuous while the fire is lit. I do not have any visible smoke anywhere (which is obviously a good thing), but I wasn't expecting to smell this much wood/smoke odor. I also cannot feel or see any exhaust coming out of the vent pipes, so my theory right now is that some smoke is making its way from the burn chamber and into the blower chamber. The other thing I'm theorizing about is the length of the fresh air intake pipe the contractors installed. The manual says to have a run no longer than 15 feet, and (after a rough measurement) mine is somewhere in the 18 - 20 foot range. I figure that would have more of an effect on the effectiveness of the fire itself, but can this possibly cause the burning to have other bad effects that might cause my smoke odor issue?

Here are a couple of pictures of my PF120:




(One of my kittens couldn't help but be in the picture )

 

[skidadil]

I have one more thought about the smoke smell. The vent had to be run horizontally out the side of my house, since it couldn't be combined with the vent up the chimney where the oil furnace exhaust goes. My other theory is that the smoke is seeping back into the house. My house was built in the 1930's, so it's rather porous. The windows were replaced about 13 years ago with vinyl double-hung windows, but they are rather drafty too. And now that I think about it, the odor is strongest on the side of the house where the vent is. The vent cap that was put on the exhaust pipe isn't the one the contractor wanted to put on. The one that's supposed to go there is on back order, so I'm holding out a little hope that the correct cap will help redirect the exhaust better.

 

[Delta-T]

-if the pipe adapter for the exhaust is pressed down all the way on top of the unit, there's probably a leak right at the seal, that allows smoke to get pulled directly into the distribution air. you wont see the smoke. need to move the adapter up about 1/4 inch, and reseal with silicone sealant.
-the unit really shouldn't run for hours at a time, the fan/limiter needs to be adjusted.
-is there a diverter/block off installed between the 2 furnaces so that the air cannot pass from 1 unit to the next?
-if the intake is 4" you shouldn't have a problem, but the dealer should have taken a reading of the internal pressure.

 

[skidadil]

-if the pipe adapter for the exhaust is pressed down all the way on top of the unit, there's probably a leak right at the seal, that allows smoke to get pulled directly into the distribution air. you wont see the smoke. need to move the adapter up about 1/4 inch, and reseal with silicone sealant.
-the unit really shouldn't run for hours at a time, the fan/limiter needs to be adjusted.
-is there a diverter/block off installed between the 2 furnaces so that the air cannot pass from 1 unit to the next?
-if the intake is 4" you shouldn't have a problem, but the dealer should have taken a reading of the internal pressure.

Thanks for the reply. I'll check on the exhaust pipe when I get home tonight, but I'm pretty certain it's pressed all the way down.

As for the unit running for hours ... this is becoming a bigger concern. The installer stopped by briefly last Saturday and adjusted the fan/limit switch. This definitely helped prevent the blower from running for hours on end, but now that I'm not hearing the blower noise I can hear that pellets continue to get fed for the same duration. So the furnace continues to call for fire even for hours on end, even though the thermostat is satisfied. When I came home last night I could hear pellets being fed. About three hours later the pellets continued to be fed, and the fan never turned on. The furnace just kept maintaining a relatively small flame throughout, and I don't understand why. I'm chewing through pellets like crazy. In reading another post in this forum, I read that the PF maintains a small fire for about 45 minutes after the thermostat is satisfied. And if there are no further calls for heat, it lets the fire die off. That's not the case here. It just keeps the fire going and going, seemingly endlessly.

As to the block off, there was one installed at the fresh air intake side of the other furnace rather than at the plenum.

 

[Delta-T]

if the exhaust collar is pressed all the way down that's where the smoke is coming from, seen it about 100 times. the beige sheet metal is not welded to the exhaust flange. the flange is welded about 1 inch below the sheet metal and that sheet metal makes up the air chamber for the heat exchange. the fan limit "on" might be set too high, preventing the fan from turning on at the right temp, and/or the shutoff temp is too high, which keeps the unit from dissipating its internal temp to get to shut down temp.the recommended temps are in the manual, just take a look and see how they compare. if the installer is a Harman Cert tech, he should have the DDM (diagnostic box) and should be able to watch the internal temp change during operation.

 

[skidadil]

if the exhaust collar is pressed all the way down that's where the smoke is coming from, seen it about 100 times. the beige sheet metal is not welded to the exhaust flange. the flange is welded about 1 inch below the sheet metal and that sheet metal makes up the air chamber for the heat exchange. the fan limit "on" might be set too high, preventing the fan from turning on at the right temp, and/or the shutoff temp is too high, which keeps the unit from dissipating its internal temp to get to shut down temp.the recommended temps are in the manual, just take a look and see how they compare. if the installer is a Harman Cert tech, he should have the DDM (diagnostic box) and should be able to watch the internal temp change during operation.

-if the pipe adapter for the exhaust is pressed down all the way on top of the unit, there's probably a leak right at the seal, that allows smoke to get pulled directly into the distribution air. you wont see the smoke. need to move the adapter up about 1/4 inch, and reseal with silicone sealant.
-if the intake is 4" you shouldn't have a problem, but the dealer should have taken a reading of the internal pressure.

The exhaust pipe is pressed all the way down, but I don't know if they used the specially made duravent collar for Harmen appliances. Perhaps that's meant to be pushed all the way down? I'll have to ask the installer which part they used there.

As to the intake, it's a 3" pipe. So I'm going to go ahead and reroute that a bit to shorten the length.

I set my fan/limit to 80/150 which helped keep the fan on while pellets were still being fed. However, even just today the furnace has been running for about 5 hours. It's keeping the temp right at my set temperature, which is great. But I don't see the need for it to run for so long. It reaches the set temp very fast, and then just keeps a small flame going for hours and hours. It feels to me like it's just needlessly burning through pellets. I'm going to try a much higher quality pellet to see what difference that makes. The content of the one I have seems to vary quite a bit from bag to bag, and some pellets even has corn in it. :-\