How is a Drolet heat commander supposed to work?

[fields_mj]

I installed a new heat commander this fall. I'm trying to work through an issue with one of the servo motors on the grate draft with their tech support (great folks). Along the way though, I've learned more about the unit and now I'm wondering exactly how I'm supposed to use the unit. I have it feeding into the duct work in my central air system. According to the manual, I'm supposed to build a fire in it and then let it burn down to almost nothing before reloading. When the house thermostat calls for heat, and the unit has heat available, the blower is supposed to kick on at its lowest speed and supply heat to the house. The manual also says that when the little green light is flashing slow or on solid, the unit thinks it has heat that it can supply. What I learned today is that the green light is tied to a thermocouple in the stove, but the blower won't actually kick on until the RTD temp probe reads at least 130 deg F in the plenum. Even with a big fire, the unit seems to have a really hard time reaching, let alone maintaining this temperature in the plenum. With a BIG bed of red hot coals, the surface temp on the plenum is only about 110 deg F. The unit itself gets plenty hot. It has no problem self cleaning any creosote build up off the glass on the door (+450 deg according to tech support). I have a barometric damper, and I measured the draft to be about 0.05" WC. Another thing that I learned from tech support is that the furnace will take at least an hour to get up to temp and allow the blower to kick on, and could take a lot longer (up to 4 hours), and its expected to have to reload the furnace with wood before reaching temp when starting a new fire.

If the fire box is hotter than 450 deg, and the plenum isn't reaching the minimum 130 deg, how is the unit ever supposed to pump hot air through out the house? I'm half tempted to run a 6" duct with a damper over to my cold air return in order to actually get some heat moving through out the house. I know its not a Kumma, but the furnace does seem to have a good following so I must be missing something somewhere, or doing something wrong.

 

[Laynes6999]

Well....unfortunately I've been a member for years, however had to re-register. I have a Caddy Advanced and had the same issues as yourself. You can relocate the thermocouple for the blower and if the motherboard is the same, adjust the speed of the main blower. Id start with relocating the thermocouple on the back of the furnace just above the heat exchanger. I'm heating a hefty home so I've done few more with my furnace.

 

[sloeffle]

@Laynes6999 how does the new Caddy compare to the old one?

 

[fields_mj]

Well....unfortunately I've been a member for years, however had to re-register. I have a Caddy Advanced and had the same issues as yourself. You can relocate the thermocouple for the blower and if the motherboard is the same, adjust the speed of the main blower. Id start with relocating the thermocouple on the back of the furnace just above the heat exchanger. I'm heating a hefty home so I've done few more with my furnace.

That makes sense. Thinking more about my setup, I have a back draft damper on the connection to the hot air plenum for the central air system. I'm thinking that is basically stopping my air flow and not allowing the air in the plenum to pull heat off the fire box like it normally would. Having said that, when the blower DOES kick on (only once or twice max if at all during a burn) it only takes a couple minutes for the plenum temp to drop below the 105 deg shutoff. I think that may be mostly related to an issue I'm having with the grate damper, which SBI is helping me with. Maybe I'll add a small vent to the basement to create some air flow in the plenum and see what effect that has. I'm on the small side with regards to the surface area of my outlet anyway. Worse case, if I don't like the result, I take it off and put a plate over it.

 

[JRHAWK9]

Well....unfortunately I've been a member for years, however had to re-register. I have a Caddy Advanced and had the same issues as yourself. You can relocate the thermocouple for the blower and if the motherboard is the same, adjust the speed of the main blower. Id start with relocating the thermocouple on the back of the furnace just above the heat exchanger. I'm heating a hefty home so I've done few more with my furnace.

Why'd you have to re-register? That sucks, as you are a long time member!

 

[sloeffle]

Maybe I'll add a small vent to the basement to create some air flow in the plenum and see what effect that has. I'm on the small side with regards to the surface area of my outlet anyway. Worse case, if I don't like the result, I take it off and put a plate over it.

Have you checked the static pressure in your duct work? When I had my Caddy there were some guidelines for duct pressure. If it's not in the manual, I'm sure SBI would be able to answer the question.

 

[Citationls]

I believe the manual states static pressure in duct work should be at least .2 IWC. To measure accurately you put one line in the blower housing box (to account for air filter restrictions) and one line in your plenum or in the ductwork close to the plenum. I doubt that is your problem though. I've tempararily run my system at .1 IWC before without an issue.

My Heat Commander blower turns on about 10 minutes after starting a fire with a cold start. If I do a terrible job building a fire it might take a half hour for the blower to kick on. No idea where they pulled the 1-4hr warm up time from, unless they are accounting for a poorly built fire that just smolders for 4 hours.

I have the most heat available while the fire is actively burning and there are visible flames. As long as there are active flames I always have heat available. There is less heat available once it gets to coaling stages. Assuming the thermostat is calling for heat, the blower will remain on until probably the last hour or so of the burn. During the last hour the blower will have to cycle on/off due to lack of available heat. If my thermostat was calling for heat the entire duration of the burn, from a cold start, 20lbs of oak would probably last 3 hours.

Something isn't adding up if you have a hot fire and your plenum is not getting up to temp. Either something is blocking the heat from reaching the plenum, or the hot air in the plenum is being moved elsewhere before it has time to reach the desired temp. Does your ductwork have a natural draft to it? Does air come out the registers when the blower is off but the furnace is hot?

Also, make sure your baffle plates above the secondary air injection tubes are in the right spot and seated properly. I seemed to lose a lot of heat when mine were pushed all the way forward by accident.

 

[trx250r87]

My usage and behavior mimics @Citationls as well.

Eric

 

[Laynes6999]

Why'd you have to re-register? That sucks, as you are a long time member!

Because of my e-mail changing. I e-mailed hearth and never got a reply.

 

[Burnin Since 1991]

Because of my e-mail changing. I e-mailed hearth and never got a reply.

send a dm to @webfish

 

[Laynes6999]

@Laynes6999 how does the new Caddy compare to the old one?

Ehhh....I'm still on the fence. Relocating the blower thermocouple and turning up the speed improved things drastically. I think the older model burned longer and produced more heat, but that's due to no under fire air. When it gets much colder, ill close off the air intakes by a 1/3rd or so and it helps not to push all heat out the chimney. I used to be picky about it, but life is too busy to worry.

 

[travis8352]

Something definately does not seem right. With my heat commander i can turn the thermostat off and load it up and have blower cycling for 7-10 hours depending on wood type followed by 6-8 more of coals with heat radiating through my vents. I like burning that way if the temps are warm enough as i like to just load it up and let it heat rather than load for temp, yes i use more wood this way but i dont mind. I can get 12-14 hours straight of blower run time with the thermostat on and i get obviously more heat that way for colder weather. Is it the right way to do things? Probabaly not but life is hectic and it keeps a fire going and i never have to cold start it

 

[JRHAWK9]

Because of my e-mail changing. I e-mailed hearth and never got a reply.

send a dm to @webfish

yeah, I'd think it would be easy for them to fix that.

 

[brenndatomu]

That makes sense. Thinking more about my setup, I have a back draft damper on the connection to the hot air plenum for the central air system. I'm thinking that is basically stopping my air flow and not allowing the air in the plenum to pull heat off the fire box like it normally would. Having said that, when the blower DOES kick on (only once or twice max if at all during a burn) it only takes a couple minutes for the plenum temp to drop below the 105 deg shutoff. I think that may be mostly related to an issue I'm having with the grate damper, which SBI is helping me with. Maybe I'll add a small vent to the basement to create some air flow in the plenum and see what effect that has. I'm on the small side with regards to the surface area of my outlet anyway. Worse case, if I don't like the result, I take it off and put a plate over it.

That doesn't sound right at all...it might cycle on/off a few times after a cold start, but once the fire is stabile, the blower should run non stop pretty much until the house thermostat is satisfied, or the plenum temp drops too far.
And even when the Tstat is satisfied, the blower still cycles on/off at about a 50/50 ratio, depending on wood load size/wood left.
Just FYI, there are 2 thermocouples in the firebox, 1 in the firebox (behind that shield in the LR corner, and another right above it, but above the baffle board. (which those should be cleaned every now and again too...just brushed off)
If the grate damper is not working right I bet that can affect things a lot...although I think its only open when the fire is building up (new load) and then again once the load is getting pretty well burnt down (coal burn down)
I don't worry about that whole thing they say with loading log cabin style, then burn down completely before reloads...that's just for people that don't know how to run a modern wood stove properly...load it however you want that takes off and builds a nice fire, then reload when there is just enough coals to relight the load without messing with it much. If there are too many coals left you should be able to rake them onto the grate and get some heat from them while they burn up...then do your load. Or, if you don't need to load a huge load, just throw a few splits in on the ("too large") coal pile and be on your way...it shouldn't "go nuclear" with a small load like that, especially since you have a baro damper.