Woodboiler and a Buderus

Bob Forand

I have been asked to pipe a wood boiler, using a flat plate hx, to a Buderus G215 boiler. I need to wrap my head around how to pipe it and control it.

The scenario is this, he currently has two zones of radiant heat, set up with thermostatic mixing valves. He is not piped with a bypass or any type of primary/secondary. He comes out of the boiler into mixing valve, off to manifolds. And returns directly back to boiler.

He wants me to pipe in the wood boiler and add a zone of baseboard to the basement.

Can someone help me with how the piping arrangement should be and how to control the oil boiler so if the wood boiler was to go out the oil takes over.

Thanks,
Bob

Mark Custis

Bob

I'll give it a try 16 hours and 500 road miles into the day.

Are the theromsatic valves manual or computor controled?

I do not know the boiler, but your question about bypass points to CI.

Hot out of the boiler to the three ways then the loops provide the cooler water for the mix then the balance goes back to the boiler?

Have you taken temps on the system in action?

I concure with your feeling that this is not good design.

I do not know what gos on with wood fired boilers but give me a web site and I will go look.

To do what your customer wants done two ways come to mind: Primary/secondary piping or a hydroseperator.

Draw a cirlce, that is the primary loop. Take two lines, closly spaced, off the big circle and attatch the to the existing boiler. Take two more off the circle for the woodboiler. Pump each to the big cicle and ad a pump to the big circle going what ever direction you wish.

Now for heat emiters, just past the main pump a pair of tees to the base board, give it a pump and tie it to a thermostat. Next add your biggest radiant load with it's own set of tees and pump, with its own threeway. Next the other radiant loop and its mixer.

I hope this helps. If not get "Pumping Away" and "Primary/Secondary" from Dan H here.

Now on to hydroseperators. Go to Caleffi and down load Idronics 4 and we will learn it together.

hot_rod

an outdoor wood boiler or OWF?

If so I assume no additional buffer tank will be used?

A crude, late night drawing. The HX from the wood boiler is treated like any heat source or other boiler. The control could be as nice as a two stage tekmar boiler control or a setpoint control to fire the buderus when the primary loop temperature falls. Be sure to drop off the HX pump when the Buderus runs to keep from sending heat to the unfired OWF.

Pull high and mixed temperatures off the loop as needed.

hr

Mark Custis

Road trip

Hot Rod thats what I ment.

Do wone with a hydroseperator.

hot_rod

hydro separator

another rough drawing

hr

Bob Forand

Hot Rod

Hot Rod , why the second pump on the boiler side ? I think I understand the boiler piping, but not the reasoning behind the second pump. Is it to force flow through the heat exchanger ?

What would the model of the Tekmar control be, or what set point controller would you be thinking ?

It is a wood boiler, a classic, and will not have a buffer tank. I think that the wood boiler side will be constant circ with a 009 pump.

Thanks,

Bob

ScottRW

I have an OWB which is open loop, so probably thats why no buffer/expansion tank. Bob do you know if your OWB is open or closed loop? Should say somewhere on the tank...
Scott

Bob Forand

Closed loop

It will be closed loop, the wood boiler on one side of the plate exchanger, and the Buderus/radiant on the other side.

Joe_136

....something else that you could take into consideration. On my wood burner/munchkin system- I put a relay in the mix which shuts off the power to the pump on the wood burner when the fire has dwindled down and is not making enough heat. That way, I don't try to keep that mass of water warm with the Munchkin.

Jed_2

And how long

do you think it will take for the off-line OWF to start freezing? Unless you Intifreezed it.