Help with hooking up wood boiler to two forced air furnaces

[FreezinginPA]

I have read and re-read this site and found so much useful info. How to properly hook up the exchangers, underground piping, etc. but have afew questions and any help would be appreciated.
Boiler 6480 Central Boiler
Two Furnaces
One Basement 125kbtu
One Attic 100kBtu
Total Sq. Ft 3200 +-
Should these be run in series, with a manifold, or a secondary loop to the attic boiler.
My furnace is 125' from the foundation and then an additional 40' to the basement furnace.
Basement Furnace is 8' below OWB elevation
Attic furnace is above the basement furnace 22' higher. (or 14' above furnace level) +-
I plan to use thermopex or similar pipe - even though it is expensive I read not to skimp on the underground pipe)
Here are my questions.
Is 1" supply enough - 1 1/4" is much more $$
Once inside I plan to run all 1" where possible. (oxygen barrier necessary?)
Should I run in series and not worry so much. I was told to run in series and another said to run a loop off of the supply run to go to the second floor with another pump. Keeping a 4" or less space between the out and in of the run.
Where should the pump or pumps be located and how do I figure sizes easily. I was told use a Taco 007, 009, 014 to the point of confusion. I was told that placing the pump in the basement could make it burn up ??? Elevation supposedly determines this??
Recommendations on exchangers and what to watch out for (inlet /outlet sizes, number of rows of coils, etc.)

I never thought I would be so confused but local plumbers I attempted to hire just run everything in series no matter what the application and throw a pump on the line. Please note there are no licenses to be a plumber or electrician around here. Just go to Staples and get some cards printed up and voila you are now a plumber, electrician, etc.

I would believe that the lift of the pump, as well as friction loss, are important in calculating the proper GPM needed for the exchanger. I would think that this is also based on the CFM of the furnace and the water temp but everyone I ask seems to just throw out a pump number and say youll probably be alright with that.
With the cost of the OWB and accessories I would really like to be sure I hook everything up in the most efficient manner.
Help Please

 

[FreezinginPA]

Anyone?
Even an opinion on how to hook up - would help, manifold or series, or secondary loop?
Please - its gettin cold here.

 

[700renegade]

use a Taco 007 as your primary circulator at the boiler.

Tap off the feed to the attic furnace in the basement using the arrangement of the two close-coupled tees. Use a Taco 009 to feed up to the attic, a 007 will dead-head and never fill the system the first time. Max head on the 007 is only about 11'. The 009 runs up to 34'. ( 014 is only good to 22' and has way too much GPM capacity for what you want.)

Easiest is to get the 009 equipped w/ the zoning option so you can just trigger it with the 24v thermostat to turn on. If your outside piping enters at the rafters, keep the 009 up there - the closer to the attic the better.

If the furnace is a down-draft you may want a flo-check valve on the loop to the attic to prevent ghost flow. ( ghost flow in traditional up-draft furnace is usually a good thing, but not down draft ).

 

[700renegade]

Oh yea - you are running an open boiler - O2 barrier is not necessary as it gets in at the OWB anyways.

1" PEX is plenty - you should get about 5 to 10 GPM flow in your main loop which is great plenty to transfer the BTUs you will use.

Never put that 009 pump much above the level of the loop feeding it - it must always have a good supply at the inlet or it cavitates and pump is shot.

 

[FreezinginPA]

Renegade- thank you for the reply. Exactly the info I needed. Thanks for the heads up on the 014 GPM - everyone is recommending that one but I had a gut feeling that no one was considering the GPM flow. I would assume that the GPM flow is one of the most important factors to capture heat from the H2O. THANKS THANKS THANKS.

 

[pybyr]

it sounds to me like you have an awful lot of furnace capacity for a 3200 square foot house, unless it is virtually uninsulated and way draftier than even the ordinary old house - so trying to replicate what is there may not be the best point of reference. if it is really that uninsulated and drafty, put some $ into insulation and air sealing instead of trying to design a system to heat the great outdoors...

don't assume that whoever came before selected the necessary or optimum size(s) for furnaces

a 125 btu furnace has generally sufficed with my old farmhouse in VT, at 2500+ sq ft, which had nearly no insulation at all when I started

I really doubt that 1" pex can really push 225+/- btu -hour at any flow rate that a Taco 007 can push through a long line (but, again, you may not really need to

you really want to start by considering what the heat loss/ demand is for the structure, and then go from there

that will then let you figure out how many BTUs/ hour you need, which will dicate the GPM flow that you need to move that many BTUs with a reasonable temp drop through the loop, and then, from that, you use that to look at and balance sube size and circulator size

 

[FreezinginPA]

I am back to being confused. The home is fairly tight since it is only 6 years old. Two Story - It is a modular and that is why we put the split system in. One for floor two 1430 sq.ft and one for the first floor 1800 sq ft. The second floor unit was likely sized a bit large since finishing the attic in the future may be an option. It seems as if it would be easier to move to a warmer climate. I would love to just run more pex lines in the ground but the $$$ is too high. I read that foaming in trench is not good and it is good - another confusing part. Locally I can get a foam company to foam my trench 125' for around 500.00.

 

[700renegade]

What's confusing? Your existing furnaces have too much BTU capacity for your needs is all. Just ingnore their ratings. If your boiler coil can't keep up on a super cold night and your 'backup' furnace kicks on, what's the big deal?

Here is the shortcut formula for heat flow:

q = h / ( 1000 * dt )

where q = water flow rate in gpm
h = heat flow rate in BTU/Hr
dt = temp difference in *F

In this example, I'd guess freezingcold is going to get a flow of about 8 gpm based on what he told us.

Running the equation at 225,000 btu, the temp difference calculates out at 28*F. Not too bad - 175* in - 147* returned to the boiler. Seems liveable to me but I'm no expert at this - just a hobbyist who cares.

I've never checked other people's opinion on this, but I assume you want to run the least velocity ( thus GPM ) in the circulation loop that will get the job done. Velocity is the killer of piping systems at fittings, etc. in terms of eroding the internals - especially in an open OWB system w/ O2 floating around.

If you can keep acceptable return water temps, throttle down the circulation pump by turning down the ball valve on it's discharge side. Your flow rate will go down, plus you have the bonus of using less electricity in the circulation pump than if it is pumping full GPM. If you look at the pump curve for the Taco 009 you will see why that is such a great choice for most systems - high head capability for the initial fill but will never pump more than 8 gpm EVER. A 007 will pump up to 20 gpm if you have little headloss. 8 gpm in 1" pex is 7.2 feet per second - that is SCREAMING. 2 or 3 feet per second would be much better.

Something interesting to realize is that in this guy's example layout you ONLY need the high head pump to fill the system the first time. Once it is filled and the air is bled out of the top of the loop it circulates with the same headloss as if the loop were laid out horizontal across his basement versus vertical up into his attic. Also he could only go up a total of 28' above his boiler water level before he would run into a funky vapor locked system at the coil when he shuts down the furnace for the year.

 

[pybyr]

I also wish that I cold be more help, but I also am not a pro, just an avid DIY-er who has learned a lot from others and tries to pass it on

I have no experience with OWBs and am puzzled as to how one could have a water-air HX above an unpressurized OWB, so don't want to give you bad advice based on things that I do not have first-hand experience with

 

[FreezinginPA]

Thanks a million. You saved me endless nights of sleep. I wish someone would write a dummies guide. Everything is finally making sense and if I would have listened to the clowns that sold me the wood stove I would have had an 014 on there and the gpm would have been WAAAYYY to high. I had a gut feeling that more had to be taken into account when hooking up my boiler. Thanks again. I appreciate you helping me very much. I am making my list of parts and hope to have it all hooked up by thanksgiving.

 

[700renegade]

freezingcold, are you going to use a zoning version of the 009, or just a plain one? If it's not a big deal to pull a piece of 14/2 romex along with the pex upstairs, you could just power the 009 with a tap off the terminals that feed your furnace fan.

Another thought that comes up is that you should put a ball valve on the return line from the attic right at the pair of tees in the basement. When you fill the first time keep the return valve closed so you can fill that pipe column up with water. Also I assume you know how important it is to have an air bleed at the tippy-top of that coil in the attic. Gotta get every bubble of air out of it up there when you first start up or you will have continual problems. Note that you could do this system with the 009 as your circulator at the boiler and just run the attic system in series. You would have to put in a host of ball valves and bleeders to get this to work on startup though.

A trapped air bubble at any spot in your lines is just like having a valve at that spot partially closed. A bubble that takes up the top half of the pipe is just like a gate valve 1/2 way shut. A lot of folks ignore the problems that can arise if you can't bleed them out.

 

[FreezinginPA]

RENEGADE
I hope to let the 007 circulate at all times and place an 009 that has a zone option for the second floor. Relaying it with the fan when a call for heat from the thermostat occurs. I will need to have a switch to turn it off - if I ever go back to propane for a vacation. I have seen the separate zone valves in some of the CB booklets and assume they open and close based on voltage to them but what happens to the circ pump - does it become restricted because it pushes against a closed zone valve? I am going to take everything I have learned (THANK YOU) and put it to paper and see what is left to figure out. I think you are right that my HVAC is oversized - that is where I plan to start. I am going to figure out a complete setup down to the fittings this weekend. Mark

 

[FreezinginPA]

Renegade,

I was afraid to simply run in series - probably since it is easier. My main concern was to hook it up right and I assumed that hooking up in series was not the most efficient way to assemble everything. Around here there is no license to be a plumber and they run everything in series and put an 014 on it. You could have radiant floor heat, DHW, two furnaces, and ten baseboards and they would run it all on 1" outdoor in series. If I run the secondary loop to the attic - the 009 should be located at which position. I read that I should keep it as close to the supply line as possible in the basement. Is that correct? Thanks again and I wont bug you any more - I highly appreciate your help.
MArk

 

[700renegade]

Why not just feed a plain 009 ( no zoning controls ) with 110v tapped off the attic fan? put a $0.49 light switch next to it to disconnect it when on vacation if it bothers you. Personally I'd leave the whole system run while on vacation so you can assure you are dumping heat from your gas furnace into the system to keep it from freezing ( you aren't running glycol are you? ). You mention a zone valve - where does that come into play? Put the 009 directly off the tees in the basement.

pm me for a sketch of what I am imagining if you want - you are not bugging me.

 

[FreezinginPA]

Sorry it has taken me so long to reply. I am actually in a financial piclkle. Was supposed to start 4 homes this winter and now down to one. Oh well - Gotta love the economy. I hope to get things sorted out the next few weeks and then I can afford the piping, hx, etc.
No glycol and I think I will run as you mentioned with no zone valves - just let-em circulate. With my current $$ problem I now wont have to worry about setting it up for any vacations. Thanks again - Ill post soon.

 

[pybyr]

hang in- if misery loves company, there are abundant signs that you've got company; at least you, like lots of us, are started down a path to stem the hemmorage of cash to things that won't work in the long run

but

running several circulators continuously 24/7 just in case is going to slowly kill you on electric costs unless your electric rates are a lot cheaper than mine.

do a search on "dimmer switch" here for a recent mention of a device which can pulse circulators periodically to keep some fluid and heat moving