Installation Of Hot Air Coal Furnace With Propane Back Up

My home came with a propane furnace of decent efficiency (92%) and good insulation. However, with propane prices not showing much tendency to return to cheaper I was resolved to find a cheaper way to heat my home. Luckily I had plenty of experience using coal since I had heated a similarly sized home in PA for ten years with a hand fed Surdiac. I looked around for a suitable hot-air coal furnace that I could tie into my existing propane unit. The idea was to use the propane unit mainly as a back up and to provide heat during the late days of spring/early days of fall when it wasn't practical to fire up the coal unit. Since I am heating a 2,500 sqft, 2 story home with a full sized basement I quickly narrowed the choices down to a Hyfire II or an Alaska 140. I eventually chose the Alaska unit because it came with it's own heat jacket right from the factory whereas the Hyfire II requires an add-on jacket which I felt would not be as suitable or efficient as one which is built-in. At this point I contracted my local Alaska dealer to install the Alaska 140 auger in my basement and tie it into the existing propane unit with the ability to run either the propane unit or the coal unit and to have the propane unit kick in if the coal unit should stop heating by itself.

The first picture shows both thermostats side by side. The one on the left is the one for the propane unit while the one on the right is the optional unit for the Alaska 140.


The next picture shows the general installation. At the bottom left is the cold air intake for the air circulation blower which is encased in sheet metal. Up above is the hot air plenum which was installed on top of the furnace. This ties into the cold air intake of the propane blower.


The next picture shows the tie-in to the cold air return from the air intakes in the house. There is a valve near the top which allows the furnace intake to be isolated.


This is a close up of the box for the air circulation blower.


Here is the tie in to the intake for the air circulation blower for the propane unit. There is a valve just above the tie-in to force the air flow into the blower. The device in the upper center is the controller for the in-line humidifier.


Here is a close up of the Aprilaire whole house humidifier. Installed in the hot air feed to the rest of the house.


The next two pictures show the vent line with baro and the power vent outlet outside the house (under the deck).





Feel free to ask any questions.

Will

Hi Will, did you tie in the 140's cold air return from the propane's return or it's a separate return? Is the Aprilaire in the propane or the 140? If it's in the propane's, how do you activate it without triggering the propane furnace? My Aprilaire is in the propane and it's ties to the circuit board. It goes on when it's needed, how would this work with the 140?

The 149's air return is tied into the cold air return for the propane unit. It ties in just before the downcomer segment which goes into the propane hot air circulation fan. The Aprilaire unit is tied into the propane side on the hot air riser per standard installation (after the filter). The propane circulation fan is tied into the circuit which controls the 140 air circulation fan. When the plenum gets up to temperature both fans kick in. The Aprilaire unit is triggered by the control unit and the circulation fan. If the control unit is calling for more moisture then it also kicks in when the propane fan is on. Since both units share the same circulation fan it works well. The only problem with this is the propane fan has a higher air flow than the 140 fan so the air coming out of the registers is rarely more than slightly warm.

Nice install wlape3, you will be nice and cozy this winter.

One thing I noticed is your baro wide open indicating excessive draft, if you install a rheostat on the power vent you can control the speed to prevent this, with this mod I would also recommend a manometer to monitor the draft and verify correct setup. Usually the Alaska powervent set up uses the damper that comes in the Field Controls 4HD SS to limit draft, however it might collect fly ash and clog up as the season progresses.

Enjoy your new set up!

Thanks for the tips Matthaus.

On the evening when the photos were taken it was quite warm outside so the furnace was running very low which is why the baro was open so much. Draft according to my manometer is 0.02-0.04 which means the baro is doing it's job but I would like to see it open less in general. Any recommendations for the rheostat? The internal damper is already adjusted to near closed and I share your concern about ash building up should I close it more.

Will

wlape3 wrote:snip... Any recommendations for the rheostat? The internal damper is already adjusted to near closed and I share your concern about ash building up should I close it more. Will

I personally have used this one: 2.5, 115, K177-1002 $18.80 from these guys: http://www.electricmotorwarehouse.com/kbwc.htm

But there are many out there, we use a different brand we buy in bulk for the LL Power Vents. Also the internal damper can be removed if you install the rheostat since you will no longer need to physically restrict the flow to control draft.

Thanks again Matthaus. My Alaska vent is a squirrel cage blower. Any potential issues with slowing down this constant speed blower? Are the leisure line blowers similar? It's been a while since I studied motors.

From the picture I can see you have a Field Controls 4HD SS this is the same unit we use, speed control with a proper controller (no dimmer switches please ) will work very well.

wlape3 wrote:The 140's air return is tied into the cold air return for the propane unit. It ties in just before the downcomer segment which goes into the propane hot air circulation fan. The only problem with this is the propane fan has a higher air flow than the 140 fan so the air coming out of the registers is rarely more than slightly warm.

I've been thinking about your statement and want to share with you a way you may be able to improve on your air temperature.
When we installed our Koker last year we also ran the heat duct into the propane furnace cold air return duct just ahead of the air filter, so the propane furnace blower was pulling the heated air from the Koker and moving it upstairs.
Here's what may help you: my propane blower has a circuit board that allows me to set different motor speeds. We used the "cooling" mode to run with the Koker and turned it down to match the Koker 1500 CFM. So when we ran the propane furnace to heat the house, the blower motor ran at normal speed. When we heated with the Koker the motor ran at 1600 CFM to match the Koker.
The only drawback to this modification is that in the spring, I needed to reset the circuit board to run the motor at full speed for the A/C (2000 CFM).
Since you have a high efficiency propane furnace, you may also have the ability to slow your motor down.
Just a thought.
-Len

Thanks again Matthaus. I will do some more research and give it a try.

Coalen, thanks for the tip on the blower motor. My brother-in-law installs furnaces as a side-line so I can ask him what the possibilities are with my unit. I fix his computers and he helps me fix everything else

Thanks Will, It's a good start. Like I said tonight I should have some nice clear picks of everything the "boiler tech" installed (hopefully by 6PM) and I can try and get a handle on this. You guys are great, and I do actually appreciate this. These days, finding people willing to help one another is sadly, getting rarer and rarer.

You've come to the right place. A lot of good people always willing to lend a hand.....