installing a wood boiler 2 zone

Randy-Lee Braman

We use a aquastat in a well that makes on rise,set at 195
with a 5 deg diff.to control dump zones.The grocery store boiler will be piped right to the header manifolds with 2"blk iron and the manifolds are all blk iron.After that
its all 1" Pex.
Randy

oil-2-4-6-gas

woodburning boiler 2-zone

i might be changing my sign-in oil-2-4-6-gas-wood , anyway my brother-in-law bought a wood boiler and wants to know if i can pipe it and control it --its a Thermo-control mod#500 idealy he would like to pipe it to 2 zones ,the apartment upstairs and the first floor where he resides, leaving the basement as a dump zone --the boiler will be shut off. running the existing thermostats, for the pumps does anyone have any experience with the piping ,wiring of such a system? - he is a treeman so he has plenty of wood -and plenty of time in the winter to tend this system, i would like to help him out while maintaining a safe system with safeties

hot_rod

Plenty of relief valve capacity!

if it's a closed pressurized vessel A HX isolation if it's an open system.

Really the piping is not unlike any hydronic system. An air scoop in the best location, size the expansion tank carefully, some of those wood fired units hold hundreds of gallons of water.

How close is the rated output to the building load? Overfiring to the load is by far the biggest problem. Yes a dump zone or buffer tank helps. i'd prefer a buffer to store those BTU's instead of dumping energy. You'll soon see even wood heat is not completely free!

Hooking two boilers gets a little more involved. P/s is one way, parallel another. Just don't flow through an un-fired boiler in either direction.

Two stage t-stats are a simple control. wood goes till the fire dies, gas or oil takes over.

Combustion air and CO detector if the wood fired is inside. I put a single fire sprinkler head above mine for extra piece of mind.

Might check with the insurance carrier, some forbid solid fueled appliances, others don't bat an eye. either way they should know and acknowledge the installation and use.

hot rod

oil-2-4-6-gas

yeah i know very well that wood heat is not "free" the labor involved --myself i would not attempt, but my brother-in-law has always heated with wood before this house ---anyway -he has a burnham-with 3 zones argo panel using seperate circulators the plan is to keep the 2 circulators on the argo just valve for the oil boiler or the wood ,keeping the feeder and expansion tank tied in, but i still am not sure how to safely wire and pipe this ---of course there will be a relief valve on the wood boiler --but how do i wire and pipe a buffer tank or the dump zone ? and i'm thinking of a zone valve --tied to a temperature control --as an emergency dump and drop out side ( of course in a safe location) --are there any examples of piping for this type of a system ? the house is roughly 150,000 btu heat-loss the wood boiler is rated 125,000-- though the basement zone is not an issue -as far as being a regulated temp --honestly depending on the efficiency of the wood boiler i feel it can handle the 2 zones for 95% of the winter

hot_rod

A 3 way zone valve is one simple way.

I'd pipe it with large diameter pipe so a power outage could gravity feed a dump zone. select a zone valve operator that opens to the dump port with power off. Caleffi offers ZV's in either version and a high cV 3 way.

Finding a large insulated (affordable) buffer tank has been my biggest problem. This company builds some nice ones that double as DHW and radiant HXers. I think it is the brand that Tarm sends with their wood boilers.

www.stsscoinc.com/AboutUs.aspx

The Nichols boys at Team Tarm up NH way have some nice piping drawings at their site. I've installed 2 of their systems here in Missouri. They work great. Didn't like their brand of 3 way thermostatic and I would add some better purge points.

www.woodboilers.com/piping-layouts.asp


As you know I used an old 500 gallon LP tank for my buffer. Not the easiest thing to move around and insulate. The price was right.

I'll get you some piping options if you can wait a day or so.

Grab some scrap paper and draw some loops with connection points. It will become clear as you start adding direction arrows. I tried to make mine as simple as possible. While not exactly as controlled as i would like I did it with a few setpoint controls and some Taco pump relay boxes.

hot rod

oil-2-4-6-gas

i didn't even think of the 3-way zone valve - i was trying to do it electrically with a relay or something --but i know at some point something will fail --and i need to have an emergency safety --to close the intake damper(its a manual 1)and a way to drop some temp/pressure

Mike2

piping

Attached is a diagram of how I'm piping my system. I'm not an expert so feel free to critique, disagree or totally disregard.

Bob Gagnon plumbing and heating

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Bob Gagnon plumbing and heating

wood boiler piping

I repiped a wood boiler like this and it worked out good. It was pretty much the piping diagram from the manufacturer. Bob Gagnon


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hot_rod

A question Bob

How do you control the temperature to the first floor zone? it looks like if either of the other zones calls flow goes through the first floor. Is there another zone valve downstream somewhere?

How does the zone valve above the wood boiler function. If it's closed zones would get flow. When it opens doesn't flow just loop through the wood boiler and not the zones?

hot rod

hot_rod

The \"low temperature\" bridge

between the supply and return? What's it's purpose? Does it have a balance valve or something to adjust the amount of flow? Perhaps for return temperature protection.

Are the heating zones low mass like baseboards or panel radiators. You want to be sure a high mass radiant slab, or even a bunch of cast iron rads, couldn't keep either boiler in prolonged "cold return" modes.

hot rod

Randy-Lee Braman

piping

We've been doing alot of thies this fall,and have used everything from old cast radiators to a radiant zone in
a garage that was never hooked up for dump zones.
we are doing a large outdoor coal boiler now that will use three modine fan units for dump zones at a grocery store,boiler is 500,000 btu(owners sick of his gas bill)he also plans to burn pallets and wood.
Randy

hot_rod

Use and control dump zones carefully

run them with a setpoint control and a tight differential. If not the dump zones start to boss around the boiler cycles. Looks a lot like a dog chasing his tail.


As long as you don't have any pex in the mix you could run that boiler up to 200F or so, and dump until the temperature fell 5 degrees below that high setting.

Is the boiler that grossly oversized to require so much dump capacity?

Be careful with pallet wood it burns hot, hot, hot, not unlike cardboard. Nothing warps a wood stove door like a load of fast, hot, wood

hot rod

Rob_25

low temp

The low temp is for return protection. I have a taco ebv tied to an aquastat. I think in this position it should function for either boiler.

The heating zones are about 110 feet of cast iron base board and 800 sq ft of under floor radiant.

hot_rod

low temperature

really you need to "read' the temperature right at the return piping to the boiler. Ii'm not sure one control could watch both boiler return connections? does the Bio boiler have a built in return protection? Most have a simple 140 stat that cycles off the circ to the boiler should the temperature drop below 140f they work well. The taco sensor could move to the other boiler return to protect it.

I'd worry more about the buffer tank keeping the return too low for too long.

Do you have a means to pull from the buffer tank when it is hot, without either boiler being involved?

I don't see which 3 way zone valve position would allow that to happen.

hot rod

Rob_25

I don't believe the Bio control accounts for return protection, but I'll take another look. I planned on placing the aquastat in the return line, between the low temp tee and the oil return tee. I'm counting on the aquastat to see a low temp and open the EBV to allow hot supply water into the return.

The supply from the buffer will tee in just above the 3-way.

If the wood is burning I will use it first. If the wood shuts down, I will power the buffer tank. If the tekmar 422 sees that the supply temp is insufficient it will fire the oil boiler, which will shut off the buffer pump and power the oil boiler pump.

As I said before, I don't claim to be an expert and I appreciate your input and your questions.

Attached is a sketch of how I see the control logic and a description is as follows:

When Wood Boiler fires, Wood Pump is on, which closes coil on R1.
A heat demand (from tekmar 422) will power Primary Loop Pump. This will power R1-6, which directs wood boiler water to the primary loop through a 3-way valve.
No heat demand means no power to R1-6, which will direct boiler water to storage tank through same 3-way.

When no Wood Boiler fire, Wood Pump is off, which opens coil on R1.
A heat demand will power Primary Loop Pump. This will power R1-5, which will initially power Storage Tank Pump through R2-5. Also at this time the Tekmar 422 will be sensing the temperature of the storage tank through R2-4.
If 422 sees low temp it will close boiler contacts to fire oil boiler. This will close the coil on R2, which will power the oil boiler pump, R2-6 and switch the 422 temp sensor to the primary loop, R2-3.

Rob_25

Controller

After further review, I see that the control will allow me to set a minimum temperature that will shut off the circulator. I guess this would be meant to provide low temp protection. Wouldn't this cause the pump to start and stop frequently until the entire system water comes up to temp?

By the way, the EKO and BioMax have the same controller, though I think they are a slightly different model. Mine is an RK-2001U.