new daka wood burning furnace install questions

[markyrocks]

Hi, I'm new. Currently in the process of installing daka wood burning furnace. I think it's 521b. I got the forced draft kit as well as a separate draft inducer.

My first question is about getting my primary furnace to kick on when the daka furnace thermostat needs fulfilled. I'm planning to place the daka thermostat next to my existing one. Can I just add a jumper between the thermostats from green to green? Now that I typed that it just sounds bad. My concern would be if the fire burned out the Dstat would be calling for heat then my main stat would call and I'd have 2x 24v running to my furnace. Idk i may just have to leave the main furnace fan run 24/7 or my other option is installing a fan limit switch in the main furnace plenum but I was hoping to avoid that for the time being.

OK so question two.
Is about the ductwork. To simplify things and to save on cost I'm considering running one 8in round duct to the main furnace plenum. Would this be sufficient? My logic about this is the same amount of air will travel from daka to main plenum just would be under more pressure and traveling 2x as fast?

Also about the materials my ducts are made of temperature ect.

So my main runs in the house are thick metal but there is like no ctc. The manual says 6" over 1st 6'. I know most would say follow the manual but the daka furnace is not stock.
The stock furnace called for materials that handle 250 degrees, with the forced draft kit the Temps in the daka warm air system should never exceed 200 degrees and there is actually 2 safety features to make sure of this. Also I have a couple heating vents being supplied by flexible insulated pipe. I understand the manufacturer is trying to cover there behinds but these flexible pipes are rated for 200 degree air. I find it impossible to believe 200 degree air moving from daka to main plenum mixing with 68 degree air is actually going to leave the plenum higher than 125 -150 degrees. Even if the volume of air from the cold air return and the daka was 1-1 it would be 134 degrees and I'm pretty sure the blower on my main furnace would beat the pants off the daka blower. Idk. I guess it wouldn't be too crazy to replace them for insurance sake. Just this project budget is already blown out the window. Idk guys any help would be great.

Edit my house is 1000sqft. I guess I could add heat shield to main plenum to overcome ctc requirements

 

[Wisneaky]

most of us set our other furnace thermostat a few degrees lower than the wood furnace thermostat. I think of you hook two thermostats together it would ruin them or short out the circuits in your other furnace, but I could be wrong. I'd say follow the manufacture specs when it comes to duct work. Probably could use heat shields, but I wouldn't recommend it. I have my duct work fed into my LP furnace plenum from my wood furnace so it is okay to do, but you need a back drafter damper on the existing furnace to prevent the wood furnace from blowing down into it. One other thing you'd be surprised how high plenum temps can get with a wood furnace. I've had them up close to 200 degrees.

 

[laynes69]

I've boiled water droplets on ductwork from power outages, it happens. As far as the central furnace coming on to help, why? With a 1000 sqft home, the daka is likely oversized, unless it's build like swiss cheese. Just run your furnace in a parallel configuration and let the daka do the work. You'll likely find it will do the job, while 1 blower running will also help with the electric bill. Also a single 8" duct will only carry so many cfms. You don't want a reduction there, it will only aid in overheating the woodfurnace.

 

[markyrocks]

If the fan is running in my main furnace why would I need a back draft damper? Dont see how it would be possible to back feed also i pla to use a 90 to aim the airflow upwards inside the plenum.

 

[markyrocks]

I have backup generator, I'm not concerned about power outage situation. I want the normal furnace fan to come on bc that's how I have it planned out. The manual suggests it and I'm sure it will keep the ductwork cooler.

 

[Wisneaky]

I'm with laynes69 on this. I wouldn't run both fans.

 

[markyrocks]

I'm with laynes69 on this. I wouldn't run both fans.

Says right in the pic daka blower moves air to primary furnace, primary distributes to the rest of the house.

 

[Wisneaky]

interesting. Never seen it done that way.

 

[Wisneaky]

Hopefully someone can chime in on how you would wire the thermostats to work together.

 

[markyrocks]

Hopefully someone can chime in on how you would wire the thermostats to work together.

OK so upon further contemplation I think I have figured it out. OK just to specify my furnace has forced draft kit so it has a thermostat that when temp drops will kick on and tell the forced draft blower to dump air on the fire, causing it to roar up , blower in the daka kicks on and subsequently I'm trying to make my main furnace blower kick on too.

For whatever reason I kept thinking each thermostat needed it's own 24v positive or R wire coming from separate sources. (The daka has a fan control center with R,G,Y,C,W connection) but it dawned on me 2 thermostats can share the same 24v connection and common and fan circuit as well. So check it out its so simple I can't believe it took me so long to figure it out.

Also I want to add that most standard programmable thermostats are probably capable of doing this on one unit but since I have electric furnace, heatpump with 20kw emergency heat backup, just too much stuff to coordinate.

Also I would like to add that the only down side to this is after the fire burns down or out the fan on the main furnace will run 24/7 until the fire is tended to or the Dstat is turned down lower than main stat.

Edit this answers my question about using one 8" duct from daka to main vs 2
https://en.m.wikipedia.org/wiki/Venturi_effect

 

[brenndatomu]

Aye aye aye, where to start with this?! Hope you are paid up on your insurance because you are just begging for problems!
I'm almost hesitant to try to help here because I feel like you have a couple problems that are major dis-qualifiers and you are probably not going to spend the time and/or money to fix, hope I'm wrong.

As for the tstat issue, yeah, I'll hafta think about this a liI bit, but right off the bat I'd say you need to just have two separate stats.
As for the blower issue, I'd wire in a relay for the existing duct blower that the Daka limit switch controls, that way DLS (Daka Limit Switch) can kick on both duct blowers but not vise versa. (you will need a backdraft damper in the Daka lines to stop back feeding air when you are running the A/C or the other furnace solo) If you have central A/C then there is likely already a relay there. But I believe running the blowers together is going to cause a static pressure night mare...I'm think I'm just gonna ping @STIHLY DAN , see what he thinks about all this mess. In the mean time, I'm gonna look up your Daka manual to read up on the duct tie in your are referring to since I can't read your screen shot (too small and I can't seem to blow it up)

Anyways, one 8" duct WILL NOT work, (why do that anyways?) as was posted earlier, one 8" duct will only carry so many CFM and the real issue is, only so many BTUs, especially when the power goes out. I know you said you have a genny, but are you ALWAYS gonna be home and AWAKE when you are burning? I think not. Therefore, your duct work needs to be big enough to safely handle gravity heating chores for an unknown period of time...which means you need to upsize or multiply the number of 8" ducts, and you really need to fix that CTC issue...or at the very least install an emergency heat dump. And that flex duct has gotta go, period!
There are reasons the manual is stating to not do all these things you are trying to do...I would guess that each one of these things they mention has caused a fire(s) and possibly death(s) somewhere in the past. Kind of like the OSHA manual...I'm told each and every one of the rules in those thick manuals is "written in blood"
You said the Mfgr is just trying to cover their butts...yeah, and yours, and your family's...

 

[markyrocks]

Yes I hear you. I'm going do what I got to do to fix the issues. I'm going to put in a heat sheild on the first 6 feet of main ductwork. Kinda sux bc it goes in 2 directions. Fixing the couple of registers that are flexible duct is not that big of a deal. I've already invested too much to stop now. I'm sure the thermostat setup would work. A t stat is just a 24v switch that send signal down different paths. Running circuit through one stat or two should make no difference.

As far as one 8" pipe goes. Have you ever put ur thumb on the end of a garden hose? The water shoots farther faster.... the water in the hose is under more pressure but the actual amount coming out of the hose over a given time period is exactly the same as if ur thumb wasn't there....

 

[brenndatomu]

Good to hear you are willing to fix your duct CTC issues, etc.

What is the advantage of using one 8" supply duct, besides saving a couple dollars?

Have you ever put ur thumb on the end of a garden hose?

Yep

The water shoots farther faster....

Yep

the water in the hose is under more pressure but the actual amount coming out of the hose over a given time period is exactly the same as if ur thumb wasn't there....

Ahh, no. When pressure goes up, volume goes down, that's a scientific fact. Look up a water (or air) pipe flow chart and play with pressures, restrictions, etc. Heck, even the smoothness of the inside of the pipe affects flow...as does how many elbows you have, degrees of the elbows, length of the line. Doesn't matter if it is water or air, the science is very similar.
Air movement in a duct is even more sensitive to pressure changes, volume changes pretty rapidly with pressure change. Restrict things too much and you'll overheat the blower motor not to mention the firebox.

You mention that the furnace is not stock...how so?

I'm almost afraid to ask, but what do you have for a chimney?

 

[markyrocks]

I have duravent class a tripple wall chimney installed with all ctc 2".

Yes the volume does go down some but it doesn't get cut in half.

My furnace is not stock bc it doesn't come with the forced draft kit which I have. I only say that in regards to temperature regulation. Once the air box hits 190 the forced draft blower cuts out effectively choke fire of oxygen so it dies down.

Edit. They sell a twin blower kit that adds a second blower using the same two 8" warm air outlets.... that kinda sounds like 1 to 1.

Edit. The reason besides money I don't want to install 2x8" pipes is bc my daka is probably 20 ft or more away from my primary furnace and I was trying to avoid having a labyrinth of pipes running all over. With the ctc req. The pipes are going to be a head bonking hazard. The extra room the other pipe would take up. Plus I'm trying to keep it from being a major eye sore. My basement kinda nice. I'd like to keep it that way

 

[Davej_07]

Assuming that your Daka is putting out the 'normal' 550-600 cfm from the blower, you would need a 12" round duct to do the job. I agree that you should eliminate all flex as it increases friction loss 10x.
Too small of a duct from the plenum to your main duct runs will potentially cause problems with the blower. The motor is air cooled and with that much head it would most likely get insufficient air flow for cooling.

You could get away with 2 8" ducts feeding the main.

Dave

 

[brenndatomu]

Yes the volume does go down some but it doesn't get cut in half.

Dang near!

Once the air box hits 190 the forced draft blower cuts out effectively choke fire of oxygen so it dies down.

That would be the high limit switch. It is not supposed to be activated normally if everything is set up and working correctly. It's more of a last ditch safety feature to keep you from testing your insurance policy.

Hey, this is your home and your party...sounds like you are in for "some school of hard knocks" edumacation.
No worries though, no hard feelings here, when you wanna make it work right, come on back, we'll help ya sort it out.

 

[brenndatomu]

You could get away with 2 8" ducts feeding the main.

Winner winner chicken dinner for the new guy! (That's why the furnace has two 8" duct connections on top...but don't tell marky that) Welcome Dave!
Oh, guess I never said welcome to Marky...welcome to hearth marky!

 

[Davej_07]

Winner winner chicken dinner for the new guy! (That's why the furnace has two 8" duct connections on top...but don't tell marky that) Welcome Dave!
Oh, guess I never said welcome to Marky...welcome to hearth marky!

22 years as a sheet metal worker so this was no biggie to me
I've been a lurker here for a long time but I finally decided to chime in on something.

Dave

 

[brenndatomu]

Here is the manual for this machine if anybody wants to read along. https://store.dakacorp.com/v/vspfiles/documents/DAKA_521FB_Furnace_Manual_BW_7-15.pdf
Like @Wisneaky said, never seen a duct tie in/blower set up like this before...

 

[markyrocks]

Here is the manual for this machine if anybody wants to read along. https://store.dakacorp.com/v/vspfiles/documents/DAKA_521FB_Furnace_Manual_BW_7-15.pdf
Like @Wisneaky said, never seen a duct tie in/blower set up like this before...

How is it normally done?

Ok So heat sheild check, replace flex pipe check, as much as I don't wanna, I'll use 2x 8" pipe check.

Has anyone looked at the thermostat plan? Thoughts opinions?

 

[brenndatomu]

How is it normally done?

Most furnaces don't use the blower of the primary furnace, just the wood furnace blower. Then you have to install a damper so as to not back
feed the primary furnace.
I'm thinking the extra cool air is going to dilute the warm air from the Daka too much, but hey Daka is calling for that, so gotta try that first I suppose

Ok So heat sheild check, replace flex pipe check, as much as I don't wanna, I'll use 2x 8" pipe check.

Perfect! What was the aversion to using two 8" supply lines anyways?

As for the thermostat, like I said before, the Daka will need its own tstat to control the combustion fan. Controlling the duct fan is a whole separate issue. Daka seems to allude to the primary furnace fan kicking on after its limit switch warms due to backfeeding, but I think that will just lead to a lot of cycling on/off of the blower. I'd wire from the fan control switch of the Daka to the relay of the primary furnace blower so that they both engage when the Daka blower comes on.

 

[markyrocks]

Most furnaces don't use the blower of the primary furnace, just the wood furnace blower. Then you have to install a damper so as to not back
feed the primary furnace.
I'm thinking the extra cool air is going to dilute the warm air from the Daka too much, but hey Daka is calling for that, so gotta try that first I suppose
Perfect! What was the aversion to using two 8" supply lines anyways?

As for the thermostat, like I said before, the Daka will need its own tstat to control the combustion fan. Controlling the duct fan is a whole separate issue. Daka seems to allude to the primary furnace fan kicking on after its limit switch warms due to backfeeding, but I think that will just lead to a lot of cycling on/off of the blower. I'd wire from the fan control switch of the Daka to the relay of the primary furnace blower so that they both engage when the Daka blower comes on.

As far as the daka duct blower I'm going to leave that to function as its designed. I don't see any benefit of messing with it. I may add a second fan limit switch in the daka that have to be set

Most furnaces don't use the blower of the primary furnace, just the wood furnace blower. Then you have to install a damper so as to not back
feed the primary furnace.
I'm thinking the extra cool air is going to dilute the warm air from the Daka too much, but hey Daka is calling for that, so gotta try that first I suppose
Perfect! What was the aversion to using two 8" supply lines anyways?

As for the thermostat, like I said before, the Daka will need its own tstat to control the combustion fan. Controlling the duct fan is a whole separate issue. Daka seems to allude to the primary furnace fan kicking on after its limit switch warms due to backfeeding, but I think that will just lead to a lot of cycling on/off of the blower. I'd wire from the fan control switch of the Daka to the relay of the primary furnace blower so that they both engage when the Daka blower comes on.

Like I said before not trying to turn my basement into a labyrinth of pipes. I spend alot of time down there didn't want to be hitting my head all the time off of them. But whatever I'll do what I got 2 do.

The "diluted " extra cold air is circulating from the living space of the house. I'd assume this is how any regular gas or oil furnace works. Just taking cooler air from house , heating it up, then redistributing it. I'd like to hook the daka filter box into the cold return but idk if I'm going to be able to get to that. Been working 6-7 days a week. Trying to get this thing operational by winter.

 

[STIHLY DAN]

Thanks @brenndatomu, by the way can I/we just call you tom? Its much shorter and easier to spell. Marky, no need to worry about hitting your head on pipes because your situation will not work. I suggest you call Daka and ask them about your plans. I think in your situation your only choice is to run your unit as a stand alone. There is no way 20 ft away from supply plenum is ok. Also at only 1,000 sq ft this would be the best anyhow.

 

[markyrocks]

Thanks @brenndatomu, by the way can I/we just call you tom? Its much shorter and easier to spell. Marky, no need to worry about hitting your head on pipes because your situation will not work. I suggest you call Daka and ask them about your plans. I think in your situation your only choice is to run your unit as a stand alone. There is no way 20 ft away from supply plenum is ok. Also at only 1,000 sq ft this would be the best anyhow.

.

I chose my placement to have the shortest run of chimney to outside of the house.

Why exactly would you say this would not work? As long as I maintain proper ctc really don't see what the problem would be. it's 7 ft from floor to bottom of the joists. I just measured tonight and even maintaining 6" from joist I can still walk under without hitting

 

[STIHLY DAN]

If you look at the instructions it shows the Daka next to the furnace. This is for 2 reasons, for the furnace fan help pull a venture effect on the daka, also so when power goes out the unit dumps right into the plenum and up the duct work. A 20 ft run of the daka to a plenum will not allow this to happen. Especially when not tied into the same return plenum.
P.S there is a reason Daka states in the manual to have a professional with experience with solid fuel units to o the install. These are more difficult with a different set of rules than installing a conventional unit. Much more dangerous as well.