Caddy Annexe Add-on?

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Jerkzack

New Member
Nov 22, 2021
17
Canada
So I've had my brain set on finding an Englander 28-3500 to supplement our heat pump, mainly for ease of installation.

But just a few minutes ago a 12ish year old Caddy Annexe Add-on furnace was listed somewhat locally for <$500. I know there will be a lot more reworking of ductwork to get this to work, but should I be leaning more towards the Caddy? The money saved in getting a better furnace will be quickly eaten up by installation costs I'm afraid. Is it even feasible given my current setup?
I will post pics, but the wood furnace will be placed where the yellow bucket currently is (in second photo) as the chimney is kind of visible between it and the water heater.
I'm assuming water heater will also have to be moved? It's electric so shouldn't be too difficult.

Also, we're in eastern Canada, 2500sqft all one level (plus basement), with a 4 ton Bosch Bova Heat pump with 20kw electric backup as our current source of heat/AC.

Thoughts or advice?

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sloeffle

Minister of Fire
Mar 1, 2012
1,072
Central Ohio
I've had a similar looking green model Caddy for the last 11 or so years. It has never given me a drop of problems and sips dry wood. It will definitely be more efficient than what you are burning now. In the U.S. we didn't have a Caddy model called the Annexe.

Does this model have a fan ?
 

Jerkzack

New Member
Nov 22, 2021
17
Canada
Does this model have a fan ?
No, it doesn't. Currently it uses the electric furnace fan to circulate the air.

For the life of me I cannot find any information on adding a wood furnace in series and downstream of a heat pump. Is this not a common installation?
 

LogCabinFever

New Member
May 24, 2021
59
CT, USA
Series installation is not legal in the US. Only in Canada. I don’t see why it can’t be done although it may void your heat pump warranty. Not sure though. The heat pump installation guide doesn’t show series as an option?
 

sloeffle

Minister of Fire
Mar 1, 2012
1,072
Central Ohio
For the life of me I cannot find any information on adding a wood furnace in series and downstream of a heat pump. Is this not a common installation?
The documentation for the furnace on PSG's web site has information on how to set it up in series. As @LogCabinFever said, it might void the warranty on your heat pump because the hot air passing over the A coil all of the time is probably not a good idea.

The Caddy that I have, has its own fan. I have a damper on top of my furnace that keeps the hot air off of the heat pump coil.
 

Jerkzack

New Member
Nov 22, 2021
17
Canada
Series installation is not legal in the US. Only in Canada. I don’t see why it can’t be done although it may void your heat pump warranty. Not sure though. The heat pump installation guide doesn’t show series as an option?
I spoke with Bosch and as long as I don't alter any of their equipment, it won't void the warranty. Or so they say. But where the Caddy doesn't have a fan, I need to put it downstream of the air handler. So the return air goes through the handler, heated or cooled as per thermostat setting, then through Caddy, then into ductwork. This is also per Caddy installation manual.

I also spoke with a gentleman named Martin at PSG (who was VERY helpful) and it's against code in Canada to have two fans forcing air into the same ductwork, so having the Caddy plumbed in parallel to the heat pump and using dampers to open and close which one I want is out of the question. Their newer furnaces are optioned to install in series with a heat pump. He said I could make an older green one work, but it would take some finagling of electrical stuff to get the air handler to turn on when the Caddy senses heat, etc. Doable but not what I'm looking to delve into at this point.

What started as a small wood stove in our basement for emergency power outages kind of snowballed into this conundrum. My plan was never to have a wood furnace as primary heat source. I liked the idea of an add-on for power outages as the fan could be run by battery backup, or easily by generator and extension cord. Or if it's a -20f day and we're home, build a fire to take the chill off.

I think my best option is still an Englander. I can have a couple lengths of ductwork installed quite easily, it'll heat the basement to keep pipes from freezing, no thermostat or air handler to have to wire into, no dampers to open or close seasonally.
 
Last edited:

laynes69

Minister of Fire
Oct 2, 2006
2,671
Ashland OH
Correct....series is legal in both the US and Canada as long as the manual lists so. Parallel is illegal in Canada. Honestly, I preferred series when I had the old woodfurnace hooked up. You would just add a bypass damper for summer and winter (as I wouldn't want AC air sitting in the furnace). Disconnecting the furnace in the summer and adding a dessicant only helps. Even the Max Caddy has reference for systems with A/C. With a series install, the furnace and woodfurnace can run at the same time. No dampers to worry about and a nice simple setup. On my old woodfurnace, there were 2 wires coming from the limit control to the board on the furnace. If the LP furnace was to fire, the blower would stop and when the LP furnace hit temp, the blower would start. Super easy.
 
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