wood stove hydronic combined w/ primary,secondary condensing

kaffinated

I am installing a stainless loop in the fire box of my wood stove and plan to pipe it into my existing system which is a primary secondary high efficiency. where should I tee in at. On a stand cast sectional its a no brainer. thx

Tim McElwain

How do you plan to

control the extremen temperature created by the wood stove. You better have a relief valve on that thing somewhere or it will blow you to kingdom come.



How about pushing some steam through the coil on your Mod/Con that should really make for some fun.

Mark Eatherton

Bad idea... I have had a personal experience...

I've blown coils on stoves before, and what you are proposing is not a good idea.



The ONLY way I'd recommend you even consider doing it is to pump the stove heat into a large buffer tank, and make certain that you have UPS that can power the extraction pump long enough to snuff the wood burner when you get hit by a power failure. AS TIM SAID, YOU ARE PLAYING WITH DYNAMITE HERE. Make sure you REALLY want to do this...



ME

zacmobile

heat it indirectly

DANGER WILL ROBINSON!! I would keep stuff out of the firebox itself. Like Tim says it can lead to much havoc and general hard times.



I have seen some success in this application by embedding copper tubing in masonry surrounding the firebox like a Russian style stove, anyway you do it I would employ a buffer tank with a differential temperature controller to ferry hot water to your heating system anytime the wood heat exchanger is hotter than your heating system temperature.

TonyS

Pipe it in a closed loop drainback configuration

similar to a solar system. This will protect you from pump failure and over heating.

Of course it is a big help if you have a basement under your wood stove.

hot_rod

hydro hearth

there were many of these products on the market in the 1980, a few can still be found at fireplace shops. Care needs to be taken to prevent overheating and possibly flashing to steam.



It's the same issue with wood fired boiler, really and there are hundreds of thousands of them in use. It can be done safely, some wood boilers use low pressure relief valves and 210F T&P valves for double protection.



Another option is to wrap an exchanger on the back, outside of the stove. This keeps it out of the intense heat and eliminates holes in your stove. Too much HX surface can lower the flue temperature and lead to creasote problems.



hr

TonyS

Here is a drainback tank

use the one with the exchanger and a Tekmar 157 control. Replace the solar panels in the drawing with your wood stove loop and tie the exchanger in to your closely spaced t's.

Fasten your loop in the firebox so it drains. As an extra safety you can add a high limit in series to shut down the pump. Gravity is pretty foolproof. Use a single loop coil if you have a modern EPA stove. I installed a new quadrafire this year and there isn't much heat left for the stack without a coil.

hot_rod

interesting idea

a drainback loop for the wood stove. The new solar controllers have high limit protection options built into them to prevent the pump from shoving fluid into a red hot coil.



Although the coil might be safer in a location where it could not get red hot. You would limit some of your harvest by locking out the loop when it was too hot, even if the tank was demanding heat, but it might be offset by eliminating the "closet bomb" potential.



A drainback loop outside or below the stove would solve that, but might be tough to install in a fireplace.



You see a lot of parlor boilers in Europe. They are basically a nice looking woodstove with a hot water coil. I think these are a couple Buderus parlor stoves.



Notice the drill rig in the background promoting GEO.



hr

TonyS

What controls would you recommend ?

You keep up to date on these latest controls Hot Rod.

Does Caleffi make a small drainback tank with a exchanger?

hot_rod

tanks and more

I think HTP, Heat Transfer Products had the best selection of drainback tanks, with or without HX coils, same selection from Solar Skies.



www.energylabsinc has some also but I think they discontinued the small sizes.



This Trendsetter is another interesting stack DB tank with a lot of coil inside.



There are a lot of nice digital solar controls on the market. In addition to being a differential control they will do a lot more, record pump hours, energy metering, timer functions, exercise programs, min and max temperature control, variable speed control, and a nice digital display screen that shows which pump, sensors and temperatures are being used. Very user friendly.



As you discovered solar controls work great for wood boiler applications where you want to switch pumps or valves on a differential instead of a setpoint, or a combination of delta T and setpoint or thermostatic function..



hr

WilliamLaurence

Wood Stove

I bought one of these from ChimneyHeaters.com . I installed and it works fine. Heats my 2000



square foot house. I have the pump connected to a UPS but I am not sure how long the pump



will run if the electric goes out. I had it installed all winter and did not have to turn on



my Electric heat once which saved me about 200 euro a month here in Romania.



The Electric is not stable here so I had to rush to take out the fire a couple of times



because the water pump had stopped and the pressure valves were going off. The UPS will



solve that but I don't know how long a UPS will keep my central pump going.  I will attach a



pic of what chimney heaters are in case you are not familiar with them. The pump is a



Grundfos and has three speeds.

zacmobile

pump run time

It should be fairly easy to figure out your pump runtime, do you know what the watt rating is on it? what speed do you normally run it in? what is the watt rating on your ups? I've been toying with the idea of getting one of these to run my boiler on during power outages, I figure I should get at least 8 hours out of it, seeing as they say you can run a refrigerator for 6. http://www.canadiantire.ca/AST/browse/4/Auto/SolarPortablePower/BackupPower/PRD~0111818P/Garrison+Back-up+Power+System%2C+1%2C800W.jsp?locale=en

Jean-David Beyer

My UPS

Mine is rated at 2200 Volt-Amperes; about 1600 watts. My load (my computer, mostly) is power factor corrected, so I might be able to actually get 2200 watts from it if my computer needed that. Right now it is drawing 396 watts, 396 VA. It calculates its remaining run-time continuously and is currently 1 hour 18 minutes.



So if your circulators, plus the control unit vent fan, gas valve in your boiler plus any control boxes plus your LWCO,  plus your thermostats plus your zone valves take about 400 watts, a new UPS like mine should run your system for a little over an hour. It would take 6 power supplies like mine or perhaps one Larger unit. I looked at the manufacturer's site for the UPS units I used, and they have several that would run a 400 watt load for 8 hours for between $3,250 to $3,275 (plus shipping). Those UPSs are pretty much like mine, but one has three auxiliary batteries, and the other has two larger auxiliary batteries.