Series Install Ductwork and Wiring / Cutting up new Hotblast

[nomorecold]

First off I want to thank everyone here that helped to get me this far! The Hotblast 1551E is installed in my unfinished (dirt floor/stone wall) basement. Chimney has been put up twice now after getting a bad ceiling support box and replacing it. The chimney is 34-35’ of actual height, through the house, of 6” Duraplus with one pair of 30 degree offsets in the attic. I added a flue damper directly to the back of the wood furnace with the Duravent DVL damper/stovepipe adapter piece. This put the damper in horizontal pipe instead of vertical like most I have seen but seems to be working ok. It is DVL from the furnace to the ceiling support box. No single wall at all was used. The auto draft doors damper control motor didn't work right out of the box. USSC sent a replacement and so far seems to be doing its job now by actually opening.

Onto the topic. I finally removed the two 8” 90’s and scabbed together ductwork I had to give me two temporary registers. I had a plenum made the size of the top of the Hotblast 32”x22”x15”H with 1” flanges. Currently one side has 15’ of 8”x 16” ductwork feeding three 6” takeoffs and one basement register I usually leave closed. The other side has just one 6” collar directly off the plenum to one 1st floor register about 7’ away. This was a definite improvement but now it seems like my factory blowers are really working to keep pressure in the new ductwork. I originally planned to run in series with my existing FO furnace so here we go!

My plan is to use the 8x18” ductwork I already have to go from the FO furnaces top exit hot side to Hotblast wood furnaces bottom rear cold side intake. So far I only have to buy a longway 90 and two shortway 90’s in 8x18”. The 8x18” will run horizontal 4’ from the fuel oil furnace into the longway 90, into a shortway 90, sending it down about 3.5’ to the second shortway 90, then about 4 ft horizontal to get into the back of the Hotblast. I plan to remove the HBs factory cold air filter box to reuse on the FO furnace cold side and remove the factory blowers and throw them in the corner. I want to make the HB and FO furnace both run the FO furnaces blower for heat distribution. Since the HB factory blower openings are so small for the blowers I am thinking I might have to cut out where they mount to the full 8x18” ductwork size feeding it to get rid of the bottleneck. I am also wondering if I might want to cut out the metal between the two 8” outputs on top of the furnace under the plenum as well?

Thoughts? Opinions? Did I already mess up besides getting the HB? Can anyone steer me in the right direction for wiring the HB to the FO furnace blower correctly? Specifically, laynes69 and brenndatomu, I am hoping for your input here! Haha, thanks again everyone and stay warm!

 

[nomorecold]

Here are some pics of what I have going on for the wiring and blower motor controls. I am guessing I might have to hook to certain wire screws in the first pic from the hotblast controls?

 

[nomorecold]

So what I am finding is my limit switch and blower on the FO furnace has a high and low speed 120V circuit where my HB has just a on/off style limit switch. I just called up a buddy in the field that thinks he has an extra high/low style like the fuel oil furnace has that I can cut my plenum for on the HB wood furnace and mount to have high/low speed fan operation from the wood heat as well as have the other one in the fuel oil furnace for when it is running.

Now I read somewhere that you don't want 120V signaling both the high and low wires on the blower at the same time or it will burn up. They must make a switch that if one of either high or low circuit sees power the opposite one will break. For tonight I am hoping maybe I can just run on either high or low speed only and I will cap the wires im not using for now out of the high/low limit switch and the blower.

 

[laynes69]

Unfortunately it's been too long since I had my old furnace in series. I did exactly what you want to do...I removed the jumper on the limit/control and ran 2 wires to the board of the central furnace. When the woodfurnace would get hot...the limit control would activate and charge the forced air blower. If the LP furnace would need to fire....the blower would shut off from the woodfurnace and kick back on when the LP would run, it worked well. It's an installation that I preferred if I wasnt going to use the LP much. What you want to do it possible.

 

[brenndatomu]

First off I want to thank everyone here that helped to get me this far! The Hotblast 1551E is installed in my unfinished (dirt floor/stone wall) basement. Chimney has been put up twice now after getting a bad ceiling support box and replacing it. The chimney is 34-35’ of actual height, through the house, of 6” Duraplus with one pair of 30 degree offsets in the attic. I added a flue damper directly to the back of the wood furnace with the Duravent DVL damper/stovepipe adapter piece. This put the damper in horizontal pipe instead of vertical like most I have seen but seems to be working ok. It is DVL from the furnace to the ceiling support box. No single wall at all was used. The auto draft doors damper control motor didn't work right out of the box. USSC sent a replacement and so far seems to be doing its job now by actually opening.

Onto the topic. I finally removed the two 8” 90’s and scabbed together ductwork I had to give me two temporary registers. I had a plenum made the size of the top of the Hotblast 32”x22”x15”H with 1” flanges. Currently one side has 15’ of 8”x 16” ductwork feeding three 6” takeoffs and one basement register I usually leave closed. The other side has just one 6” collar directly off the plenum to one 1st floor register about 7’ away. This was a definite improvement but now it seems like my factory blowers are really working to keep pressure in the new ductwork. I originally planned to run in series with my existing FO furnace so here we go!

My plan is to use the 8x18” ductwork I already have to go from the FO furnaces top exit hot side to Hotblast wood furnaces bottom rear cold side intake. So far I only have to buy a longway 90 and two shortway 90’s in 8x18”. The 8x18” will run horizontal 4’ from the fuel oil furnace into the longway 90, into a shortway 90, sending it down about 3.5’ to the second shortway 90, then about 4 ft horizontal to get into the back of the Hotblast. I plan to remove the HBs factory cold air filter box to reuse on the FO furnace cold side and remove the factory blowers and throw them in the corner. I want to make the HB and FO furnace both run the FO furnaces blower for heat distribution. Since the HB factory blower openings are so small for the blowers I am thinking I might have to cut out where they mount to the full 8x18” ductwork size feeding it to get rid of the bottleneck. I am also wondering if I might want to cut out the metal between the two 8” outputs on top of the furnace under the plenum as well?

Thoughts? Opinions? Did I already mess up besides getting the HB? Can anyone steer me in the right direction for wiring the HB to the FO furnace blower correctly? Specifically, laynes69 and brenndatomu, I am hoping for your input here! Haha, thanks again everyone and stay warm!

I seen this when I was at work yesterday but forgot to reply last night, sorry.
Did you mess up buying a HB?...well, since you asked...if you asked here before buying it, I think you would not have much support for that decision...but you have it already, so lets make it heat.
As far as your current duct arrangement...it should work, just need to damper down the ones that are close, open the ones that are further away...adjust it so you are getting the air flow/heat where you want it most.
Many people have complained about the weak blowers on the HB and have upsized them...some even put a full sized furnace blower on that was bought used on CL for cheap. Not sure if that will be "too much" air for the HB or not? (drive the duct temps too low) You may have the same issue with using the oil FO furnace blower too...I dunno, never ran a HB.
If you'd rather do the series install...may want to have your buddy look at the best way to wire it up...sometimes it can be tricky to wire stuff like this properly "over the internet"...I know I personally find it difficult to do when I'm not actually there, at least unless it is something that I'm very familiar with...and every individual install can be a bit different.

 

[nomorecold]

Thanks to both of you for chiming in on this. I understand how you feel with wiring over the internet just thought maybe the solution was simpler than I was making it out to be. When I took it apart and started looking at how it is wired myself it made alot more sense.

Seems to me if I put both the HB and FO furnace on one circuit/breaker, I could easily enough make one speed, just high or just low work with both furnaces in series. Reason I'm seeing to be on one circuit is unless you knew for sure your two separate breakers were on the same main lug in the main panel I believe you would have a 50/50 chance (depending which lug your breakers are on in the panel box) to be accidentally sending 240V through the blowers one wire. This would happen if both furnaces were sending 120V each for the blower to turn on at the same time in a three way splice with the blower hot wire, either low or high speed. (120V from two separate lugs in the main panel) Someone correct me if I'm wrong here.

The tricky part seems to be having both speeds. For example, if the fuel oil furnace limit wants low speed and sends 120V for that and meanwhile the HB wants high speed and sends 120V for that then both high and low speed wires of the blower would be powered at the same time which I read burns them up. Should I give running them both on low speed only or high speed only a try for now? I guess what I am asking is can I use just high speed with the fuel oil furnace or is there a good reason it needs low speed as well on the safety/function end of things?

 

[nomorecold]

Unfortunately it's been too long since I had my old furnace in series. I did exactly what you want to do...I removed the jumper on the limit/control and ran 2 wires to the board of the central furnace. When the woodfurnace would get hot...the limit control would activate and charge the forced air blower. If the LP furnace would need to fire....the blower would shut off from the woodfurnace and kick back on when the LP would run, it worked well. It's an installation that I preferred if I wasnt going to use the LP much. What you want to do it possible.

So you are saying you made your limit switch in the LP furnace 120V by breaking out the jumper (mine already is) and ran two wires (high and low speed off the switch?) to somewhere on the primary controls terminals that are marked with letters? Were you using two separate limit switches on each furnace and high and low speeds for both?

I noticed what I was reading was pretty dated afterwards. I believe it was actually one of your posts somewhere I read that basically said the change from parallel to series was well worth it in your case of a big old house and made me want to go that route. I appreciate the help in trying to get me there!

 

[nomorecold]

So looking at it again I believe I was mistaken. The limit switch appears to have 120 hot in, 120 out to Beckett FO gun and 120 out to the control board back side. How the heck does it know which speed to use? Im guessing varying voltage/resistance from limit to control board? The back side of the control board is where the other end of the acrual blower motor wires attach. Blue and black.

 

[brenndatomu]

I have never seen a Honeywell fan/limit switch with lo/hi speed...are you sure it is not the standard lo/hi temp switch?
It turns the fan on/off...and then cuts the burner off if the plenum temp gets too high...

 

[nomorecold]

Yes, I tried to correct myself in the last post, I was mistaken just giving it a quick look. It is a Honeywell L4064 as is the one I just got for the Hotblast plenum. At first glance I thought they were low and high out but I noticed just one of the two goes to the primary/secondary relay and both fan speeds come out of it. The guy I got the extra switch from says yeah, it is a limit switch. It has a temp LIMIT, haha. He explained how it works and the wiring end of it to me and after a little more research I understand what it does now a bit better. I think ill just try running on high only for now since he didn't seem to think there would be any problem with it.

Im still trying to think how to make them not call for fan at the same time when trying to run just the fuel oil furnace and the fires still dying out. I don't think I should have the problem the other way around though because the fuel oil furnace plenum temp should never be high enough to kick the fan on when the wood furnace is running downstream 12’ and FO thermostat is set lower.

 

[brenndatomu]

I think ill just try running on high only for now since he didn't seem to think there would be any problem with it.

My experience has been that low works better on a wood furnace...otherwise the fan cycles on off on off on off on off...…….…….all day/night!

Im still trying to think how to make them not call for fan at the same time when trying to run just the fuel oil furnace and the fires still dying out. I don't think I should have the problem the other way around though because the fuel oil furnace plenum temp should never be high enough to kick the fan on when the wood furnace is running downstream 12’ and FO thermostat is set lower.

Use a "lockout" relay...I need to install one on my Kuuma blower to keep it from trying to run when the FO kicks on...the FO furnace plenum ties directly into the Kuuma's plenum.
I will just wire a commonly available DPDT 120v coil relay in to kill power to the Kuuma's blower when the FO blower kicks on...I would think you can make some variation of the same thing work for you too...

 

[JRHAWK9]

I will just wire a commonly available DPDT 120v coil relay in to kill power to the Kuuma's blower when the FO blower kicks on...I would think you can make some variation of the same thing work for you too...

I'm not so sure I would like that. What if there is a fire going in the Kuuma when somebody happens to flip the furnace on and it calls for heat? With women and kids around anything is possible. LOL

 

[brenndatomu]

I'm not so sure I would like that. What if there is a fire going in the Kuuma when somebody happens to flip the furnace on and it calls for heat? With women and kids around anything is possible. LOL

I was wondering if anyone was paying attention...
Since the FO furnace discharges into the Kuuma's plenum...if the FO blower kicks on, it will push the FO heat out...and take the Kuuma's heat with it. If things gets too hot, the Kuuma's high limit should kick in and shut the damper down too. Plus I still have my old Yukon emergency heat dump door on the Kuuma plenum too so...

 

[nomorecold]

My experience has been that low works better on a wood furnace...otherwise the fan cycles on off on off on off on off...…….…….all day/night!

Use a "lockout" relay...I need to install one on my Kuuma blower to keep it from trying to run when the FO kicks on...the FO furnace plenum ties directly into the Kuuma's plenum.
I will just wire a commonly available DPDT 120v coil relay in to kill power to the Kuuma's blower when the FO blower kicks on...I would think you can make some variation of the same thing work for you too...

Yes! This sounds like exactly what I need, thank you again! Ill be sure to check it out when Im done playing around with this 8x18 ductwork. I don’t know if I want to let the fire die down any to connect it tonight. It was 5 degrees out a little bit ago but it’s keeping up so far.

As for the fan on low for the HB was thinking that might be better too from reading. The guy I got the part from mostly does fuel oil furnace repair, maybe gas too but I don’t think he messes with much like my setup normally. The only other reason I was thinking of using high was to force some better pressure/heat out of the registers through the long runs of rectangular ductwork. Also I should be able to better adjust the fan on temp with this Honeywell unit I would think. If that lockout relay does the job I don’t see why I couldn’t run wood on low, fuel oil on high. Maybe even FO like it was with low and high and the HB as well.

 

[JRHAWK9]

I was wondering if anyone was paying attention...
Since the FO furnace discharges into the Kuuma's plenum...if the FO blower kicks on, it will push the FO heat out...and take the Kuuma's heat with it. If things gets too hot, the Kuuma's high limit should kick in and shut the damper down too. Plus I still have my old Yukon emergency heat dump door on the Kuuma plenum too so...

Very good. As I was typing that I was trying to recall how you had yours setup exactly. Figured you would have your bases covered.

 

[laynes69]

The more I think about it....I think I took the power away from the limit/control. The 2 wires would complete the circuit and trigger the control board on the central furnace to run.

I do have a 2 speed limit control on my woodfurnace...however with the low speed running it's hard to get enough heat to trigger in the second speed. It has a tap for low and on. With low on the blower I get zero heat in the house. I run speed 3 of 4 .

 

[JRHAWK9]

With low on the blower I get zero heat in the house. I run speed 3 of 4 .

Interesting how different house/setups can lead to such different results. As you are aware, I am the complete opposite.

I run my blower so slow that when I took this picture of coals yesterday I was still seeing 110° plenum temps and a delta T of 32°. The blower shuts off around 96°, so it still had 14° more to go before the blower would shut off.....and the more the temp drops the more the blower slows down.

 

[nomorecold]

Well heres what I picked up today, hopefully what I was after! LOL I was told its an “Ice Cube” relay and the other part is the base for the relay to plug into and wire. Hopefully10A is enough? Im thinking so for the one FO furnace blower.

.

I haven’t made it home yet to figure it all out but just one more stop to get another 8x18 piece of ductwork to save me scabbing together a small extension I need to the back of the furnace. I plan to cut the back of the HB out to accept the full 8x18 ductwork.

 

[brenndatomu]

Should work...

 

[nomorecold]

Got it all together. I feel like there was probably a better way to do it but what I did was run the fuel oils fan signal wire on one side of the relay and the wood furnaces fan signal wire coming from the HB Honeywell fan/limit switch on the other side of the relay. I made it so the Honeywell unit on the HB doesn’t see power until the factory fan switch sends it through. I came off the factory switch and tied into two wires in the mc cable, one going to signal coil power in the ice cube relay back in the fuel oil furnace and the other to line in on the Honeywell switch in the HB plenum. N/C the FO furnaces fan switch will kick on the fan. When the HB factory fan switch sends power through to the relay AND the fan switch in the plenum of the HB signal for it, then the wood furnace is running the fan. I wonder if I could have just made the Honeywell fan switch on the Hotblast output run the ice cubes solenoid and give power through the relay for N/O or N/C just jumped at the relay.

Basically I was trying to make it so either furnace could run the same fan but trying to make them not send power at once. In hindsight I wonder if it would have mattered as long as they were on the same circuit breaker, just twisting the fan wire out of each Honeywell switch together with the wire that runs into the fuel oil furnaces control box for the fan. Oh well. Its been working pretty good for a few days in the single digits and I will change something if there is a problem.