Need help with wood furnace in Vermont

[kellygreen]

Question

Please recommend a professional who can help me fix and maintain my Caddy Advanced wood (primary heat) and Bosch propane (backup heat) forced hot air furnaces and related duct system. I am in central Vermont.

Background

For a long time, I heated my 1,600 sq. ft. circa 1955 cape with a Newmac wood/oil combination furnace (I have forced hot air). My house was always toasty warm and all it took was 3 - 4 cords of wood (a little oil when I was away). I never had any trouble getting the house to 75 degrees (and hotter) with just a load or two of wood. When I fired the furnace up, either the wood or oil side, hot air poured right out of my ducts, particularly into the kitchen where the duct is closest to the plenum. I loved everything about the system, but had to replace it when I cracked the heat exchanger last year.

I replaced the Newmac with a Caddy Advanced wood furnace, and this year I added a Bosch propane furnace for backup heat. Now, I cannot get the house above 66 or 67 degrees and I can only manage those temperatures if I am home filling the Caddy's fire box religiously from dawn until dusk. The air coming out of my ducts is tepid and I can barely feel it. The problem exists whether I am using the Caddy or the propane furnances.

I am frustrated and need to hire a professional who understands forced hot air heating systems, can maintain a wood furnance and related systems, and who loves wood heat. The guys who installed the furnaces are not an option. Any recommendations for someone who can get to central Vermont?

 

[Citationls]

I cant help you find a service technician, but so you have a barometric damper installed on your flues? Too much exhaust draft will send all your heat right out the flue.

 

[brenndatomu]

Something has to be way off with this install...

 

[NotScot]

I cant help you find a service technician, but so you have a barometric damper installed on your flues? Too much exhaust draft will send all your heat right out the flue.

There is a barometric flue installed and the basement is well sealed. The outside air kit (OAK) is installed which reliably keeps the flue damper closed.

The series connected upstream Bosch has a bigger circulation motor (3/4HP) and larger fan than the downstream Caddy. The coupling ducts between the two systems seem to be constricting flow, reducing flow, and abruptly changing flow direction 180 degrees. Bosch fan has appropriate static pressures and delta-T is good. It's 1320 CFM versus the Caddy 875 CFM, and the Caddy static pressures are way off. SP_in is -0.70. SP_out is +.04 w.c. Not sure if changing the coupling duct work between the Bosch and the Caddy will resolve, as last year, it was Caddy only and it did not perform well in terms of air flow. Anyway, am looking at it.

 

[Citationls]

.7iwc before the Caddy blower seems high. .04 after is low, but probably not the end of the world. If you can get the pressure before the blower down, the pressure after the blower should go up.

You either have a very restrictive air filter, or the return duct work going to the caddy air filter/blower box is restrictive.

And just to clarify, when you say "series connected" I'm assuming you are referring to motor wiring, not duct work? Meaning your Bosch blower isn't in the duct work that feeds into the Caddy?

 

[NotScot]

Thanks for the reply. Series connected furnaces... Bosch output = Caddy input. The ductwork between them is both restrictive and has sharp transitions. Filter present only on the Bosch, as the Caddy filter would be redundant and just make a bad situation worse.

Working on getting a better connection duct setup. Making zero changes to either furnace. Heating profile for user and installation constraints dictate this setup, which was formerly a dual fuel/parallel NewMac with a monster air circulation motor and seriously oversized for this dwelling, but extremely effective. Duct work was adequate for that machine. Sadly, the heat exchanger broke and the unit could not be repaired. The Caddy is from the era of well insulated dwellings, and the NewMac was from the era of cheap oil. Under ideal circumstances, the Caddy will do 875 CuFt/Min. The NewMac was 1300-2000 if you go by the specs in the manual. Firebox about 2.5 times the size and oil burner was 140K BTU/Hr in and 110K out.

In the current configuration, prior duct work seems adequate except for the inter-furnace hack. ( Professionals did this, but it is clearly a bottleneck. ) Working on getting interconnect with better geometry. Absent that, the Caddy may be surplussed and removed.

Note... last year, the Bosch was not here. The Caddy was it. BTU output and air flow were pretty anemic and again, the user profile was a little incompatible with the Caddy characteristics vis a vis heat delivery profile. She is often gone during the day and is the only operator, meaning that the Caddy is soon down to 15k BTU/hr from its peak of 45 or so. Bitter climate, so some super cold days, the heating load is high, and the dwelling cools rapidly. If she were there to maintain peak output, it was barely adequate on a cold day, and ok on a warmer day with good solar gain. There's nothing wrong with the Caddy. ( with the exception that I think there is a software error two in it ) but it's size and output characteristics might not be a great match for this dwelling.

 

[Citationls]

Ok, sounds like you have a good idea of what needs fixing then. I live in eastern CT in a 2400sq ft colonial built in 1997. I use my Heat Commander to heat about 2000sq ft of the house. Unless it stays below 30F outside I only run the HC for about 16hrs or else it gets too hot. That is with multiple small to medium reloads throughout the day to keep from overheating. Even when its been below 10F for a couple days the HC still ends up idling with the thermostat set to 70F.

I would think if the Caddy is similar to the HC it shouldnt have an issue keeping your house warm once you get everything sorted out.

 

[NotScot]

Thanks! This house is 1950's build, mediocre insulation, original double hung single pane windows, bad attic insulation. There's a lot of heat loss. I'm recording thermal performance to see what the nighttime energy leakage is... 2 days into a 7 day session.

Owner LOVES wood, so a larger unit might be good. Too soon to tell. It's close to zero many mornings up here for the last few weeks, so the marginal output really shows up. Glad your HC works well! Caddy looks lovely. The thing is pretty and good worksmanship. Might just be too small until the house is sealed up better ( or until i get the airflow issues resolved. )

Note: one of the problems with the old NewMac was that it would damn near melt the paint off the house. WAAAY too hot sometimes and not much way of moderating the output. That's why it broke, in fact. H/E got too hot. That thing was a monster!

 

[Citationls]

That will be interesting to see how much heat loss there is. Definitely nice to have wood heat as an option if there is that much heat required. Hopefully the Caddy will get the job done once its all squared away.

 

[brenndatomu]

was formerly a dual fuel/parallel NewMac with a monster air circulation motor and seriously oversized for this dwelling,

Belt drive? Many of those were turned WAY down...rarely actually needed blowers that big. Our place had an old coal coverted to oil furnace with a HUGE blower...had (4) 20x20" filters on it! It was so stinkin oversized!
But, that also means my ducts are oversized too...so then you have to play "whack a mole" balancing the registers to get the heat where you need it...a small adjustment here can mean a big change there type of thing.

 

[NotScot]

Belt drive? Many of those were turned WAY down...rarely actually needed blowers that big. Our place had an old coal coverted to oil furnace with a HUGE blower...had (4) 20x20" filters on it! It was so stinkin oversized!
But, that also means my ducts are oversized too...so then you have to play "whack a mole" balancing the registers to get the heat where you need it...a small adjustment here can mean a big change there type of thing.

I hear you! I'm anxious to get to that part of the troubleshoot. Balancing will be fun compared to the current issue. I'm fighting restriction at the moment. Fortunately, most days are not this cold and some days are sunny, so marginal performance is uncomfortable, not lethal. I'll get it figured out, just a matter of dealing with one thing at a time! Interconnect ductwork is the focus this week.