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First Post-Help with Custom HVAC System?

2K views 19 replies 5 participants last post by  beenthere 
#1 ·
Hey All, This is my first post on this site, so please be gentle:yes:

I Stumbled upon this forum while doing some research on a brainchild project I have in mind.
For starters A little background info:
I live in 120yr Old Farmhouse that my wife and I have renovated/are still renovating. One of our first projects we completed on the house was to install a hvac system as ALL of the 25 radiators in the house had blown up one winter while it was abandoned before we bought it. Along with that, the oil tank in the basement was wrecked (had holes in it) and the boiler was beyond repair.

Needing heat and also wanting AC we opted for a heat pump/AC unit with electric strip backup heat (our first choice was hydronic coil backup but as just mentioned the dead boiler put a damper on that)

anyways...Im sure some of you know where I'm coming from here with a drafty ol' farmhouse...they sure do look cool but MAN do they cost a fortune to heat!!! We recently installed some woodstoves and that seems to help a lot, however the layout of the house and fact that we aren't home for a lot of the day doesn't really help maintain the heat, which Finally leads me to my crazy idea...

I was looking at installing a wood fired boiler in our basement, and installing a hot water coil in the air handler plenum (or maybe return air side??) I want to still keep the electric backup heat though on the chance that I have to be away from the house for several days, however I want the hot water coil to be the main backup when the heatpump can't do it's thing.

A few of my comments/questions:
- Would most likely need glycol in the lines as the air handler is in the attic

- Is having a second backup system feasible/possible?

- Anyone have a setup similar to what Im describing?

- Any thoughts on controls? Would I need a second thermostat to control the wood boiler's circ pump and air handler blower and set the existing thermostat maybe 2-3 degrees lower so that it doesn't kick on while wood boilers going?

- Am I COMPLETELY Crazy!?! I do tend to get a little nuts with my ideas but love when I can get them to work...

Any input/info/help is GREATLY appreciated....I haven't done anything with this idea yet except try and lay it out in my mind

Thank you in advance

Dan
 
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#11 ·
I have researched a few indoor wood boiler units, I'm not sure what you mean by controlling the wood fire? I basically would have a wood boiler burning as often as possible, I know of a few with very large fire boxes so the burn time would be close to 10-12 hours constantly heating my water so I'm thinking I need to turn on a circ pump and the air handler when calling for heat. If the fire dies there's controls on the wood boiler unit to cut off the circ pump, and I'm guessing I either get a second thermostat or use my existing Honeywell prestige to kick on the heat pump/electric backup when the wood boiler gets too cold.


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#2 · (Edited)
It is an idea but a very difficult one to accomplish. My first concern is the extra coil will add resistance to the airflow thru the airhandler and if it is too much then the AC can freezeup and get damaged in the Summer. No way to find that out until the glycol coil is in and then it may be too late. The controls and thermostat required is not easy to do and rarely done so you may need to invent that system. Most airhandlers use a integrated circuit board and there are no provisions for homemade add on units later.

If you have space in the basement then I would get a wood furnace and run a few vents to the main floor and let it run on it's own thermostat. Need a couple return vents also. If you have a closet that can be used as a chase then they can run a duct upstairs.
 
#5 ·
If you have space in the basement then I would get a wood furnace and run a few vents to the main floor and let it run on it's own thermostat. Need a couple return vents also. If you have a closet that can be used as a chase then they can run a duct upstairs.
This was another Idea I was Kicking Around....The locating of the wood burning unit would be right below one of the main cold air returns to my air handler. Do you think I could duct into that? And when you say "run a duct upstairs" I'm assuming you mean on it's own and not into the air handler plenum. I've seen the latter done via wood furnace manuals, but they are almost always right next to the air handler which is not attainable in my situation
 
#3 ·
Your plan doesn't sound completely crazy. There are many similar type systems out there that are working to varying degrees of satisfaction. you can get 3 stage heating stats that could control all 3 heat sources at once if that is what you desire to do.

One thought would be to make sure the heat source coils and elements are in the proper configuration. Ideally you would want to have the HP coil first in the airstream, then the hydronic one and finally the electric heaters if you have the option.
 
#4 ·
It may be do-able but if you don't have enough airflow then later your electric elements can overheat and burnout. Not saying don't try but it all depends on the size of ducts and there is no scientific way to know the airflow issue ahead of time. These systems are custom built and later if the installer disappears or goes out of biz then you are stuck with no one who knows how or wants to service it. I run into all kinds of weird scenarios like that.
 
#6 ·
Agreed, airflow is key in this type of adaptation, one option there would be to get ahold of a fan coil unit which would then have the Hp coil built into the suction side of the fan instead of in the discharge airstream. Have seen that unit oversized by 1 coil size to accommodate higher airflow through the ducting system to compensate for added resistance.

Control can also be tricky, but is doable if you have an adaptable type of thermostat.
 
#15 ·
First off, $$$, I get a permit for $15/cord per household to cut my own wood. My father in law helps out and he only needs 1 cord himself...There's a 3 cord limit so i take my 3 and the other 2 from my father in law, I can heat the house for less than $100 in fuel...
Granted it's quite a bit of work, but I must be sick in the head or something...I kinda like it:wacko:

Plus, where I live Nat-Gas isn't available, and don't want to incur the cost of setting up a propane system.
 
#14 · (Edited)
A wood furnace will radiate the excess heat into the basement when the thermostat is satisfied. Not sure how well that wood work with a wood boiler in the basement and only one coil. Could put a radiator in the basement to help out.
 
#16 ·
I'm glad a lot of people brought up the problem of Air-FLow...didn't think about that one too much...What if I made some sort of Dampered bypass somewhere that I can open and close manually. Run it through my hydronic coil whenever I'm burning in the boiler, and If I do happen to go away for an extended period of time I'll turn over to what I'll Call "emergency" and run it on normal heat pump with electric backup? I have the Fiber-board plenum and return on the air handler now, think I could rig something like that up...Still going to need a slightly more than simple control scheme to run everything how I would like...

Anyone have any thoughts on this??
 
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