Wood Boiler Controls (again :-))

hr

run the primary loop pump all the time. At least in the heating season. Insulate this loop and let it run! Nothing happens within the system unless that pump can move some energy.

Two 155's will accomplish what you are trying to do. One will load the buffer when the loop is hotter than the tank.

The other will "unload' the tank when it is hotter than the loop.

Piping wise, you will need protection from thermal migration IF you plan on piping like your drawing.

Any takoffs from the top of a loop will be prone to this.

Thermal drop loops (my least favorite) one loop and one check pump, or a check pump and a second check on the return.

The boiler and buffer pumps should also have protection. one side is sufficient on the lower side.

This tekmar drawing is how I do wood boiler/ buffers. I used a Miximiser as the boiler (return protection)protection mechanism.

This method is one of many, and while not the least expensive, it covers all the bases.

hot rod

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Kevin_30

Wood Boiler Controls (again :-))

Hi hotrod and everyone. I have been put off from doing this wood gasification job due to customer money problems and other things (never do work even for distant family)! Anyway, I think this is my final piping diagram for the wood system. Thanks to hotrod, I do understand the Tekmar diff. controls much better. I was always bad with controls because I try to make it too hard! :-) I chose the tekmar 155 setpoint diff. to control the charging of the storage tank. I plan on opperating the primary loop pump simply by means of an on/off switch. I thought about using just using a tekmar 150 or 152 to control the temp of the primary loop but: Let's say the primary loop falls below it's setpoint the relay will open and call on a pump for heat, but how can it choose to pull heat from the storage tank by starting that pump or directly from the boiler? Thanks for everyone's help. Have a great day!

Andrew Hagen (ALH)

Another Option

This is not a particularly inexpensive buildup but it does everything. It should be able to fit in a 3 ft x 4ft space on the wall. The wood boiler pump runs continuously. The gas boiler provides domestic hot water. The 363 automatically detects if the storage tank on the wood boiler side is hot enough to provide heat. it can run the storage down as low as possible to maximize its usage. Everything is automatic excapt of course stoking up that wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This is not a particularly inexpensive buildup but it does everything. It should be able to fit in a 3 ft x 4ft space on the wall. The wood boiler pump runs continuously. The gas boiler provides domestic hot water. The 363 automatically detects if the storage tank on the wood boiler side is hot enough to provide heat. it can run the storage down as low as possible to maximize its usage. Everything is automatic excapt of course stoking up that wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This is not a particularly inexpensive buildup but it does quite a bit. It should be able to fit in a 3 ft x 4ft space on the wall. The wood boiler pump runs continuously. The gas boiler provides domestic hot water. The 363 automatically detects if the storage tank on the wood boiler side is hot enough to provide heat. it can run the storage down as low as possible to maximize its usage. Everything is automatic excapt of course stoking up that wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This is not a particularly inexpensive buildup but it does quite a bit. It should be able to fit in a 3 ft x 4ft space on the wall. The wood boiler pump runs continuously. The gas boiler provides domestic hot water. The 363 automatically detects if the storage tank on the wood boiler side is hot enough to provide heat. it can run the storage down as low as possible to maximize its usage. Everything is automatic excapt of course stoking up that wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This is not a particularly inexpensive buildup but it does quite a bit. It should be able to fit in a 3 ft x 4ft space on the wall. The wood boiler pump runs continuously. The gas boiler provides domestic hot water. The 363 automatically detects if the storage tank on the wood boiler side is hot enough to provide heat. it can run the storage down as low as possible to maximize its usage. Everything is automatic excapt of course stoking up that wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This is not a particularly inexpensive buildup but it does quite a bit. It should be able to fit in a 3 ft x 4ft space on the wall. The wood boiler pump runs continuously. The gas boiler provides domestic hot water. The 363 automatically detects if the storage tank on the wood boiler side is hot enough to provide heat. it can run the storage down as low as possible to maximize its usage. Everything is automatic excapt of course stoking up that wood boiler.

-Andrew

Andrew Hagen (ALH)

Kevin_30

Hi

Yes, I plan to simply leave the primary loop run all winter long. I will just turn it off during the summer. Yes, I am planning thermal loops and checks where they are needed. With the two 155's, I understand what they will do but still a little confused with how they will do it. I want to set up the system so that the buffer is not only a buffer for excess heat but also a heat storage tank. This way, a constant fire is not required, especially in the fall and spring when the temp. is mild. So basically, I need one control to keep the primary loop at a set temp for the rads. and Indirect for DHW. Then I need other controls to charge the tank while the wood boiler is hot but not charge the boiler when it is cold. Then, the primary loop heat control should always "chose" to take heat from the wood boiler unless it is below a certain temp, then it should draw from the tank. So, how could two 155's do all of that? Maybe I'm missing something. Thanks a lot. :-)

hr

Gosh Kevin

I'm running out of ways to explain this You might want to get a local control guy to help?

The boiler must, should, probably does have an aquastat and pump relay yes or no? This relay will kick on the boiler pump when the boiler gets up to whatever temperature you set it. I'd suggest 160- 180. If not a simple aquastat or setpoint control needs to be added to trigger the boiler pump to unload the boiler input to the loop.

When this control energizes the boiler will feed hotter water into the primary loop.

Whatever load is calling home, dhw, or buffer will get this input.

The DHW tank should also have an aquastat. This will control the pump that supplies hw from the primary loop to the tank anytime there is a demand.

One 155 will charge the buffer when the primary loop is hotter than the tank. IF you locate the sensors in the correct place and adjust the control properly.

The other 155 will drop off the buffer tank when the tank cools below the loop temperature.

This is in that tekmar drawing and wiring schematic. Mike from tekmar could e mail it to you if it is not readable. He would also draw up the rest of the controls for the boiler and indirect so it is all in one big schematic.

Unless you have a very large buffer, say 500 gallons or so, don't count on a long heat cycle without a boiler needing to be fired.

If you know the load of the home from the heat loss calc, and the tank capacity and temperature you can calculate that draw down period of time.

Hope this clears it up.

hot rod

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Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Andrew Hagen (ALH)

Another Option

This isn't a particularly inexpensive buildup, but if does quite a bit. DHW is handled by the gas boiler. The wood boiler storage tank is used as much as possible. The wood boiler circulator runs continuously. It's pretty much automatic except for stoking up the wood boiler.

-Andrew

Kevin_30

Yes, but Kevin,

where is the heat storage system and the controls for it. I understand the piping fine but I'm not very skilled in controls. I like what hotrod says but I still don't understand it completly. I understand that the two 155's will put the buffer "online" when the primary loop is hotter than it and the other will take it "offline" when the buffer is hotter than the loop. But, what will keep the Primary loop up to temp and control whether the heat comes from the wood boiler, if it is hot, or the tank?

thp_7

???

How big is the storage tank?

Andrew Hagen (ALH)

The heat

always comes from the tank. The wood boiler is not in the loop in the diagram I posted. I recommend finding someone who has done this before to set it up for you. It's worth it so you know it will work correctly.

-Andrew

hr

What I think you will find

is that you end up firing the boiler to the heat load. Really the BEST place to store your BTUs is in the firewood!

Once you burn the wood and turn it into hot water, besides taking the efficiency hit,now you have to store it (the energy) as hot water, and pump it around. So your energy is slowly slipping away.

I've found wood burner owner/ operators, learn to find the sweet spot. They build the fire to weather conditions and don't end up useing the buffer tank all that much.

I don't recall your load, but that 85K boiler will need to be fired pretty hard to maintain that 85K output. I think that number may be a bit optimistic, and under ideal conditions.

The primary loop will need to get it's heat input from somewhere. Either the wood fired boiler when it's running, or the buffer if it is charged.

Ideally a wood boiler should have an aquastat that turns the circ off if the return falls below 140. Some come feature. No sense in running the boiler pump if the boiler is not fired or hotter than the loop of buffer. A setpoint control would know this and fire the boiler circ accordingly.

If you do (run the boiler pump) without a fire hotter than the loop or buffer, you will be sucking the heat energy backwards and expelling it to the cold winter sky.

This is why you need to trigger all the various components at the right time and temperature. All these setpoints, aquastats, and diff controls are just on/off switches! They just work by temperature instead of someone toggleing them on and off by hand

hot rod

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thp_7

Simplify

Thats why I asked the tank size. He would be better off to dump a couple of the pumps. Use the house pump and circ the house loop through the storage tank and zone valve the rest.