New Furnace Day: Drolet Heat Commander

brenndatomu

Minister of Fire
Aug 21, 2013
5,530
NE Ohio
Blower needs an "ultra low" speed to keep a little heat coming to the house...something like 500-750 CFM when tstat is satisfied.
When the blower is not running you are still losing BTU's up the stack, but none is going to the house (unless you have a good gravity flow duct system)
That always drove me crazy, and is exactly what prompted the "invention" of the speed controller on my old T1...I expected it to help with heating the house better, but it exceeded my expectations...and got rid of that annoying cycling!
 
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Case1030

Feeling the Heat
Dec 12, 2017
304
Manitoba
So the blower is off if the tstat is satisfied? If so, wouldn't care for that either...
Kinda back to the wide open/ off except more precise:rolleyes:... not sure how well that would work in my house being I have a furnace on the same level and need the blower running to push heat into the living areas. It would be nice to utilize the idle while still moving air around a bit anyway...
 
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andym

Member
Feb 6, 2020
233
Hicksville, Ohio
So the blower is off if the tstat is satisfied? If so, wouldn't care for that either...
Sounds like they expect the thermostat to work well. I can see that allowing plenum temps to go that high would allow the fire to burn more slowly yet still be efficient, since less heat is being moved away form the firebox. Wouldnt work too well with a 165° heat dump though!
 

Case1030

Feeling the Heat
Dec 12, 2017
304
Manitoba
So the blower is off if the tstat is satisfied? If so, wouldn't care for that either...
I can see another "Tundra fourm" in the near future...
 
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brenndatomu

Minister of Fire
Aug 21, 2013
5,530
NE Ohio
Kinda back to the wide open/ off except more precise:rolleyes:... not sure how well that would work in my house being I have a furnace on the same level and need the blower running to push heat into the living areas. It would be nice to utilize the idle while still moving air around a bit anyway...
Yes, on some houses when it's really cold, or especially windy, BTU's must be pumped into the house non stop to keep from "falling behind"...I know that means you might need a bigger furnace, but I'm talking about a situation that would not be the norm, so the furnace is big enough 98% of the time.
Plus blower on/off would give that hot/cold feel that a forced air fossil fuel furnace has...lets the air stratisphy floor to ceiling...cold feet! !!!
 
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brenndatomu

Minister of Fire
Aug 21, 2013
5,530
NE Ohio
I can see another "Tundra fourm" in the near future...
Yup ;lol ...of course one of these guys will have to initiate it, since I'ma Kuuma boiy now ;lol...well, get to thinking about it, I didn't have a Tundra when I first started that thread though either! Must have just been a cold boring day or something. !!!;lol:p
 
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Case1030

Feeling the Heat
Dec 12, 2017
304
Manitoba
Yes, on some houses when it's really cold, or especially windy, BTU's must be pumped into the house non stop to keep from "falling behind"...I know that means you might need a bigger furnace, but I'm talking about a situation that would not be the norm, so the furnace is big enough 98% of the time.
Plus blower on/off would give that hot/cold feel that a forced air fossil fuel furnace has...lets the air stratisphy floor to ceiling...cold feet! !!!
Working on installing infloor heat in the crawlspace for the main floor. Just bought a 1 year old Heatmaster g100 for a good price. Thought I'd upgrade the Tundra to a Heat commander for a more controlled burn to help the boiler in times when it gets -40f.
 
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andym

Member
Feb 6, 2020
233
Hicksville, Ohio
If there is any fire burning it should not take real long to reach 190°. In my situation I think it would gravity flow quite a bit at those temps. If your ductwork creates a heat trap then the blower will no doubt cycle regularly. But I agree it would be better to have a super low speed instead. Evidentally they don't consider 190 to be dangerously high, that's good to know.
 

FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
Depending on which stat that is, they can be adjusted to stop frequent cycling.
Doesn't the jumper wire make it think the tstat is calling for heat non stop...run hot/burn fast/overheat the house in mild weather?
It's a basic low voltage t-stat. I didn't use the one that came with the furnace and instead used a battery powered, programmable t-stat with adjustable deltas each side of the set temp. Works great.
 
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FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
So the blower is off if the tstat is satisfied? If so, wouldn't care for that either...
It turns off the blower initially, meters the combustion air for a low output, long duration burn, and then goes to the higher set point for the fan cycling. Even though the higher set point is 190 for the RTD thermostat, the ducts and plenum surface temps only get up to about 130* F before the fan kicks on.

The furnace front temps on the heat exchanger door are around 240*F and the external single wall flue temp is about 200*F when it's in that mode, so it's not over firing or over heating the furnace.
 
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FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
Probably a little cooler in your basement now with the extra front cover and cover insulation. (Better delivery efficiency)?
Warmer! We added two registers in the basement, so we're getting heated air delivery in addition to the radiant heat from the furnace. :)
 
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brenndatomu

Minister of Fire
Aug 21, 2013
5,530
NE Ohio
If there is any fire burning it should not take real long to reach 190°. In my situation I think it would gravity flow quite a bit at those temps. If your ductwork creates a heat trap then the blower will no doubt cycle regularly. But I agree it would be better to have a super low speed instead. Evidentally they don't consider 190 to be dangerously high, that's good to know.
The funny thing is the T1 had a 200* (IIRC) high limit switch, and unless it fails closed (unlikely) it should open up if things get too hot, but when they first started cracking (and even later on) SBI was accusing people of over firing the T1, (leaving the manual switch on too long, etc) making them crack...but the HL switch should make "over firing" impossible (outside of propping the intake damper open or something stupid like that)...I guess where I'm going with this is it seems funny that 190* all day everyday is fine now, but 200* was over firing before? (I'm sure the firebox design has been improved, as far as longevity/durability)

You are right though, things should gravity flow at those temps, but even without a "heat trap" per say...some of these long/flat duct runs that ranch homes tend to have still aren't gonna gravity flow real great.
 
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FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
I guess where I'm going with this is it seems funny that 190* all day everyday is fine now, but 200* was over firing before? (I'm sure the firebox design has been improved, as far as longevity/durability)
I think the differentiator is that 200*F plenum/air jacket temps don't equal an over fire - the furnace body and face temps that drove T1 plenum temps that high with a fan running were the issue.

On the Heat Commander, the furnace face and flue temps are really mellow and it's in energy conservation burn mode when it's cycling at the 190*F point. The furnace is nowhere near an over fire in that situation.

In the T1, if you hit the 200*F limit switch in the air jacket with the fan running (which it always should have been at that temp), your furnace temps were WAY higher than the Heat Commander in fan-off, energy-saving mode.

Apples and oranges, in my opinion.

(Edit to add: It's worth noting that I don't think we ever hit the high limit on our Tundra.)
 
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FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
If there is any fire burning it should not take real long to reach 190°. In my situation I think it would gravity flow quite a bit at those temps. If your ductwork creates a heat trap then the blower will no doubt cycle regularly. But I agree it would be better to have a super low speed instead. Evidentally they don't consider 190 to be dangerously high, that's good to know.
We initially had no fan cycling and all of the heat was rising up the supply duct to our second floor while cold air gravity fed in through the first floor supply trunk in reverse of the normal air flow.

I used a one way damper in the second floor supply duct to stop the rising air from creating a siphon. It's technically trying to move in the proper direction for the damper flaps, but the weigh of the flaps is enough to hold the rising air back without a fan blowing.

Now, the fan cycles for about 60 seconds every 4 or 5 minutes and we get nice convective airflow on the first floor when the fan is off and the t-stat is satisfied.

Note that we disconnected the second floor duct with the T1 because we don't want it to be very warm up there. We're happy if it's 10 degrees or so cooler for better sleeping. :)
 
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Mrpelletburner

Minister of Fire
Jan 20, 2011
622
Maine
What does the furnace do when you reload and press the button? Does it burn wide open for a period to 'fire' the load as the manuals recommend for the older models? I always feel like that process is unduly long and is the main culprit of the heat surge from a new load. If the Heat Commander can minimize that time and spread that heat out through the rest of the burn, it will definitely be an improvement.
I don’t recall seeing an answer to this question.

Eric can you comment on this?

Also, is there any smoke that exits the door when you start the unit? If I read correctly, the door has to stay opened when reloading?
 
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trx250r87

Member
Nov 30, 2012
80
NE Wisconsin
I don’t recall seeing an answer to this question.

Eric can you comment on this?

Also, is there any smoke that exits the door when you start the unit? If I read correctly, the door has to stay opened when reloading?
Maybe @SBI_Nick can answer this as I'm not sure what is supposed to happen vs what is happening with my furnace.
I'm still trying to finalize some plenum/duct connections as my basement is getting way too warm with most of the plenum air not making it up stairs.

Eric
 

FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
I don’t recall seeing an answer to this question.

Eric can you comment on this?

Also, is there any smoke that exits the door when you start the unit? If I read correctly, the door has to stay opened when reloading?
Yes, when you press the reload button, the primary shutter opens fully and thr grill shutter opens about 30%. They remain open for a period of time to char and fire the wood, then close for optimal burn.

You only need to leave the door cracked for a minute or two while ensuring that the flames engage the wood (on a reload) or your kindling catches (on a cold start).
 

andym

Member
Feb 6, 2020
233
Hicksville, Ohio
Yes, when you press the reload button, the primary shutter opens fully and thr grill shutter opens about 30%. They remain open for a period of time to char and fire the wood, then close for optimal burn.

You only need to leave the door cracked for a minute or two while ensuring that the flames engage the wood (on a reload) or your kindling catches (on a cold start).
So basically an automated version of how the older tundras worked. Does the air control adjust often?
 

FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
So basically an automated version of how the older tundras worked. Does the air control adjust often?
It's the same heat exhanger, but a different firebox with what I'd call "three-stage" combustion: metered "boost" air through the floor grill, metered primary air, and unmetered secondary air.

The shutters on the grill and primary openings adjust in real time, based on fire gas thermocouple readings. I've seen them make small adjustments every 10 or 15 seconds, but it's smart enough to wait a bit most of the time to let the adjustment stabilize before making another one.
 

SBI_Nick

New Member
Oct 15, 2020
2
Quebec city, Canada
Hello, here few answers to more concerns:

  • What do you think about hooking the plenum up direct to a main supply (trunk) duct, by-passing using all the little 6" pipes?
Modifying the supply duct might affect the furnace performance. If this is your only option, we recommended to keep the outlet surface area between the minimum (170 sq in) and maximum (285 sq in) allowed. If you do that, it is important to keep a proper static pressure and keep the plenum temperature probe at the same place. At the end of the day, the easiest and best way to do that is to use our air supply adapter kit (AC01396). Using the adapter kit will ensure that the furnace will perform properly. http://files.drolet.ca/upload/images/accessoires/manuels/triple-hot-air-supply-adapter-kit_Manual_001.pdf?_ga=2.183931366.1956502533.1605710370-687149352.1579267598


  • Power consumption?
The power consumption on the web site is the average from an EPA test. As some of you mention, static pressure has a big impact on power consumption. If your power consumption is higher, it’s probably because your static pressure is lower and the blower moves more air.

  • Blower speed
The blower speed is fixed, we don’t use other speed like in the Tundra. The fan will stay at the same speed and switch only if the furnace is overheating. What you will noticed is that the blower will start and stop at the different temperature according to the thermostat state to increase comfort. The main reason why we did that change was to meet the emission standard.

  • Thermostat requirements
The furnace has been designed and certified to be operated with a t-stat, if you don’t the furnace will always be burning at the lowest burn rate possible. This will also affect the furnace efficiency, adapting your load to the heat demand is probably the smartest thing to do. Having a thermostat will improve homeowner’s comfort and optimize the furnace combustion and heat transfer efficiency. The heat Commander as what we called a coal burning function, at the end of a load it will produced more heat then the Tundra and reduce the coal build up which is a big advantage over the Tundra. To take advantage of this, it needs to be hook to a thermostat. By passing the t-stat could decrease the lifetime of the furnace even if the design has been improved. For sure, the smart controlled should also prevent overfiring but if you have to do that to heat your house, it probably means that the furnace is too small or something else is wrong. Yes, you should hook the furnace to a thermostat.


  • Thermostat Delta
On some t-stat you can change the delta T, I think for most of them you can choose 1 or 2 degrees. With the one supplied with the furnace you can’t do that, but you can set the number of heating cycle from 1 to 6 cycle an hour. I’ve personally never experienced it but can be an interesting feature to try.


  • Plenum overheating temperature
The plenum overheating temperature are set during the safety testing (shall not affect emission under any circumstances). The standard state that the plenum temperature shall never exceed 250F during normal operation (which is not such normal for a user when you see the test, it is extreme). So, we set a temperature that is far enough from normal temperature and also far enough from safety limit. If someone continuously hit the overheating, it means that there is probably something wrong with the plenum set-up, static pressure, air return, filter or blower. Comparing the temperature between the Tundra 1( 2x 8’’ duct) and the Heat Commander is like comparing orange and apple, the overall jacket temperature of the Tundra was much higher than the Heat commander, the air volume was much smaller. This is the main reason why we switched to a rectangular plenum in the Tundra II, to be able to run the furnace cooler. Also, it’s not because you read 200 F at a specific point, that it is the same in the air jacket. The overheating temperature is calibrated between the sensor location and the 250 F safety limit while testing.


  • Button
Every time you start a fire or reload the furnace we recommend to press the button. Depending if the furnace is cold or warm it won’t react exactly the same way. Basically, you tell the furnace that you have add wood. According to the firebox temperature, it will open the air inlet and increase the amount of air to the firebox until clean combustion is achieved. The main purpose of that, is to reduced smoldering, emission, to simplify starts-up, reloads and improve efficiency. You will probably have a heat boost for the first few minutes, but it will ensure you have a good fire going and as soon as the combustion is set and clean the burn rate will reduce as much as possible (depending of t-stat input) to save wood.



Thanks,



Nicolas
 

FixedGearFlyer

Burning Hunk
Oct 8, 2010
143
Michigan's Upper Peninsula
A Heat Commander update:

It's a properly chilly November day in Michigan's Upper Peninsula. The temp was 23*F at dawn and it's about 27*F with a stiff wind and flurries at 3:00pm.

When I came downstairs this morning, it was 60*F on the first floor. I flipped on the pellet stove while I made coffee, answered emails, had breakfast, and planned out my day. That brought the downstairs to about 65*F at the center, and a bit cooler away from the pellet stove.

Around 9am, I turned off the pellet stove and ducked into the basement (with a fresh cuppa) and made a small fire in the Heat Commander. "Small" means about 8 or 10 wrist-size splits of maple, which is about 1/3 of what the furnace can take.

The thermostat is set to 70* and it's been between 70 and 73 since about 9:45am. As I type (and, actually, what made me think to make this post), the furnace is in "energy conservation, no call for heat" mode with a nice bed of coals that's still cycling the fan on and off.

So, just over 6 hours of good heat on a small load of small maple splits. It's 71*F on the first floor, 67*F on the second floor, and 62*F in the basement.

Of major note, I literally didn't touch the Heat Commander or the thermostat after lighting it this morning - we let the Heat Commander's computer manage the burn while we spent the day out in our family's shop, sewing and filling orders while our kiddos were in the house.

If things continue like this, it's going to be the easiest, warmest winter in the 10 years that we've lived here. :cool: