Controls for Storage Circulator

[nbroyer]

Hello,

I finally have my new Eko 25 wood boiler and 500 gallon pressurized storage tank plumbed up and am ready to tackle the wiring. I thought I had this all figured out but realized today that I overlooked something. I plumbed the storage tank using the two port method. I have one circulator by the boiler on the return line from the tank and the other is on the supply side from the tank to the rest of the system. I think I want the boiler circulator to always be on when the wood boiler is hot. Then I was going to have the tank circulator on whenever the house was calling for heat and the tank temperature was hot enough. The thing I didn't consider is that if the tank is cold but the wood boiler is hot and the house is calling for heat, I want the tank circulator on to push the wood boiler hot water to the system. How can I control the tank circulator in these two different scenarios? I currently have a Tekmar 150, Tekmar 156, a 4 zone controller and a strap on aquastat that I'd like to be able to use, but obviously will buy something else if necessary. I have two temperature sensors coming out of the wood boiler and one off of the tank.

Thanks!
Nathan

 

[Bob Rohr]

Hello,

I finally have my new Eko 25 wood boiler and 500 gallon pressurized storage tank plumbed up and am ready to tackle the wiring. I thought I had this all figured out but realized today that I overlooked something. I plumbed the storage tank using the two port method. I have one circulator by the boiler on the return line from the tank and the other is on the supply side from the tank to the rest of the system. I think I want the boiler circulator to always be on when the wood boiler is hot. Then I was going to have the tank circulator on whenever the house was calling for heat and the tank temperature was hot enough. The thing I didn't consider is that if the tank is cold but the wood boiler is hot and the house is calling for heat, I want the tank circulator on to push the wood boiler hot water to the system. How can I control the tank circulator in these two different scenarios? I currently have a Tekmar 150, Tekmar 156, a 4 zone controller and a strap on aquastat that I'd like to be able to use, but obviously will buy something else if necessary. I have two temperature sensors coming out of the wood boiler and one off of the tank.

Thanks!
Nathan

Can you send a drawing of how it is piped? You have a boiler pump and a system pump? Is there a back up boiler also?

Basically the boiler pump should run when the boiler is warmer that the tank. Ideally the tekmar allows the load to be pulled via outdoor reset to best use the tanks energy.

In this Idronics we selected a few of the most common piping schematics. Along with an explanation of the control logic, and a ladder diagram for the wiring.

Read the entire issue to see the difference control logics that could be used.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_17_na.pdf

 

[nbroyer]

Hi Bob,

Thanks for your reply. Looking at the issue of Idronics you linked to, my system is closest to figure 8-6. It looks like to solve my problem, I should put the temperature sensors at the supply side tee out of the tank (point A in my drawing) and the return side of the zones (point B in my drawing) and use my Tekmar 156 delta T controller to control the tank circulator. Does that sound right?

I was originally going to use the Tekmar 150 to turn on the wood boiler circulator when it reached a certain temperature. I get why you mention needing a delta T controller comparing the wood boiler temperature to the tank temperature now. With a single stage setpoint controller once the tank was charged and the fire went out, the wood circulator could still run because it would be pulling in hot water from the tank. So in that case, I will need to pick up another delta T controller for the wood boiler circulator as all I have left on hand is two single stage setpoint controllers. Unless there's a way I can use the RK2001-UA controller on the boiler? Although that looks like it's also using a single stage setpoint to control the circulator output.

Thank you,
Nathan

 

[nbroyer]

Actually, could I use a single stage setpoint controller at point A and when it's hot and the house is calling for heat, turn on the tank circulator? When point A is not hot and the house is calling for heat, turn on the propane boiler. Then I can save the delta T controller for the wood circulator.

 

[maple1]

I don't think the Danfoss will work correctly in that diagram, in that location/orientation?

 

[nbroyer]

I don't think the Danfoss will work correctly in that diagram, in that location/orientation?

You're right, I drew it wrong. This is how it's plumbed.

Thanks!

 

[stee6043]

You may be over complicating this. If your boiler is warm enough to heat your loads the danfass/mixing valve will be open sufficiently to satisfy the draw from your "tank circ" when it is on, regardless of the temps of your tanks. Let your heat load control the tank circ, let the EKO control the boiler circ. If your tank isn't warm yet the load will be satisfied directly from the boiler.

If your boiler is not sufficiently warm to satisfy your load there is no amount of mixing, valves or controls that will solve the problem of no hot water to support the requirement of the tank circ. Until your boiler is up to temp and the danfass wide open there isn't a lot of heat to go around, whether its going to your tank or your load.

FWIW I had 1,000 gallons of storage plumbed almost exactly as you have drawn. And I had two circs. My "tank circ" was simply controlled by a thermostat on the wall in my home. The boiler circ was controlled by the EKO. Nothing fancier required.

 

[nbroyer]

You may be over complicating this. If your boiler is warm enough to heat your loads the danfass/mixing valve will be open sufficiently to satisfy the draw from your "tank circ" when it is on, regardless of the temps of your tanks. Let your heat load control the tank circ, let the EKO control the boiler circ. If your tank isn't warm yet the load will be satisfied directly from the boiler.

If your boiler is not sufficiently warm to satisfy your load there is no amount of mixing, valves or controls that will solve the problem of no hot water to support the requirement of the tank circ. Until your boiler is up to temp and the danfass wide open there isn't a lot of heat to go around, whether its going to your tank or your load.

FWIW I had 1,000 gallons of storage plumbed almost exactly as you have drawn. And I had two circs. My "tank circ" was simply controlled by a thermostat on the wall in my home. The boiler circ was controlled by the EKO. Nothing fancier required.

stee6043,

Thanks for the reply. So you didn't have any trouble with the EKO controller keeping the boiler circulator running once the storage tank was up to temperature and the fire had gone out? I thought I had read in some older posts that once the fire went out, if the temperature of the water coming back from the storage tank was still above the EKO's setpoint, the pump would keep going.

Thanks!

 

[Bob Rohr]

Of course it depends on how much control you want and how automatic. My EKO has a pump output that keeps the pump off until it reaches 140 at the boiler, a simple but effective return temperature protection. So that pump could controlled from the EKO. Correct you do not want the boiler pump running when the fire is out, thats what a delta T controls offers more control. When ever the boiler has energy to add it can enable, even with the fire out, there may be energy to go to the tank and load.

On a call for heat both the tank circ and system circ need to run IF the tank is above your lowest temperature requirement, say 150.

Then a control also need to decide when the LP boiler kicks in in the event of no heat in the wood boiler or storage. The tank circ should not run when the lp boiler is firing so it needs to interface some how.

The LP boiler could be tied into the main loop because the primary secondary piping will cause some temperature blending. Is it a condensing boiler? Or does it need return protection also? Pump inside that boiler? It needs a separate pump when piped P/S.

A mixing device add would allow the tank to pull down to the lowest possible temperature based on outdoor rest. Less that 20% of a heating season are you at demand condition, so you may be able to pull the tank down to 130F and still cover the load on milder days. That does add more components and complexity.

I think Nofossils control could be built and programmed to run all this from one box, that would eliminate the interfacing of multiple control and may simplify things for you.

 

[nbroyer]

Of course it depends on how much control you want and how automatic. My EKO has a pump output that keeps the pump off until it reaches 140 at the boiler, a simple but effective return temperature protection. So that pump could controlled from the EKO. Correct you do not want the boiler pump running when the fire is out, thats what a delta T controls offers more control. When ever the boiler has energy to add it can enable, even with the fire out, there may be energy to go to the tank and load.

On a call for heat both the tank circ and system circ need to run IF the tank is above your lowest temperature requirement, say 150.

Then a control also need to decide when the LP boiler kicks in in the event of no heat in the wood boiler or storage. The tank circ should not run when the lp boiler is firing so it needs to interface some how.

The LP boiler could be tied into the main loop because the primary secondary piping will cause some temperature blending. Is it a condensing boiler? Or does it need return protection also? Pump inside that boiler? It needs a separate pump when piped P/S.

A mixing device add would allow the tank to pull down to the lowest possible temperature based on outdoor rest. Less that 20% of a heating season are you at demand condition, so you may be able to pull the tank down to 130F and still cover the load on milder days. That does add more components and complexity.

I think Nofossils control could be built and programmed to run all this from one box, that would eliminate the interfacing of multiple control and may simplify things for you.

I do like the ability to have things be a little more automatic. I built my own microprocessor based control system for my old boiler which did simplify things and gave me more flexibility, but it came with its own problems. I'm hoping to have this boiler run with more basic controls and use my microprocessor system to just monitor temperatures and not control anything.

I think my plan now is going to be to use the Tekmar 150 to monitor the temperature at the supply output tee of the tank (point A). If that temperature is > 130F and the house calls for heat, run the tank circulator. This should take care of both scenarios where the tank is hot and the wood boiler is not running, or the wood boiler is running and can satisfy the heat demand. If that temperature is not 130F, then I'm going to turn on the LP boiler, which is condensing and has an internal pump. The system circulator is going to run whenever there is a call for heat from the house.

I'm going to use the Tekmar 156 to monitor the temperatures of the wood boiler and the tank. If the wood boiler temperature is greater than the tank temperature, then the wood boiler circulator will run.

One concern I have still is what to do in case the wood boiler is overheating and the tank is charged? I realize I should be able to avoid this based on when I start a fire and how large of one I make, but I feel like there might be a learning curve there. Should I just open my dump zone valve if the boiler temperature gets to 200F?

Thanks for all the help!

 

[maple1]

One concern I have still is what to do in case the wood boiler is overheating and the tank is charged? I realize I should be able to avoid this based on when I start a fire and how large of one I make, but I feel like there might be a learning curve there. Should I just open my dump zone valve if the boiler temperature gets to 200F?

That would seem to be the obvious thing to do.

Have you also considered a power outage overheat?

 

[nbroyer]

That would seem to be the obvious thing to do.

Have you also considered a power outage overheat?

I did try to design my dump zone in case of a power outage. The valve is normally open and I put about 40 feet of baseboard directly above the boiler. I'm hoping this will work. If it's not enough, I may add a UPS.

Thanks!

 

[stee6043]

stee6043,

Thanks for the reply. So you didn't have any trouble with the EKO controller keeping the boiler circulator running once the storage tank was up to temperature and the fire had gone out? I thought I had read in some older posts that once the fire went out, if the temperature of the water coming back from the storage tank was still above the EKO's setpoint, the pump would keep going.

Thanks!

I installed a $20 timer on my fan to turn it off after the burn was complete (overnight) but I never bother to shut down the circ. I'd simply walk downstairs before I left for work and turn the boiler off. There are more sophisticated ways to control the circ in that scenario, definitely.

 

[maple1]

I did try to design my dump zone in case of a power outage. The valve is normally open and I put about 40 feet of baseboard directly above the boiler. I'm hoping this will work. If it's not enough, I may add a UPS.

Thanks!

Sounds good then. So you should just have to have that >200° control open (break on rise) that NO zone valve & you should be good. If that zone valve has an end switch you could perhaps also tie that back into your boiler pump circ circuit to make sure that circ would run if it's a power-on overheat. I also added a UPS to my setup, I plug my loading unit circ into it if I have to go out mid-burn or the weather is looking wildish. Lots of redundancy is good to have for an overheat situation. Likely the biggest part of my overheat protection is that the timing of my burns rarely has me burning when nobody is home or we're asleep.

 

[maple1]

I installed a $20 timer on my fan to turn it off after the burn was complete (overnight) but I never bother to shut down the circ. I'd simply walk downstairs before I left for work and turn the boiler off. There are more sophisticated ways to control the circ in that scenario, definitely.

Could you also have wired your circ to the same timer?

 

[stee6043]

Could you also have wired your circ to the same timer?

Yeah...seemed a bit riskier than the fan. If the switch failed or I didn't spin it quite far enough the boiler would overheat if the circ shut down. If the fan shuts off for those reasons the fire just dies and I wake up laughing at myself for being an idiot.

Usually my circ would only be running for a few hours when it didn't really need to. So the amount of "undesirable" mixing I got from the circ running nonstop was pretty limited.

But yes....could be improved. There's always room for improvement!

 

[Bob Rohr]

I do like the ability to have things be a little more automatic. I built my own microprocessor based control system for my old boiler which did simplify things and gave me more flexibility, but it came with its own problems. I'm hoping to have this boiler run with more basic controls and use my microprocessor system to just monitor temperatures and not control anything.

I think my plan now is going to be to use the Tekmar 150 to monitor the temperature at the supply output tee of the tank (point A). If that temperature is > 130F and the house calls for heat, run the tank circulator. This should take care of both scenarios where the tank is hot and the wood boiler is not running, or the wood boiler is running and can satisfy the heat demand. If that temperature is not 130F, then I'm going to turn on the LP boiler, which is condensing and has an internal pump. The system circulator is going to run whenever there is a call for heat from the house.

I'm going to use the Tekmar 156 to monitor the temperatures of the wood boiler and the tank. If the wood boiler temperature is greater than the tank temperature, then the wood boiler circulator will run.

One concern I have still is what to do in case the wood boiler is overheating and the tank is charged? I realize I should be able to avoid this based on when I start a fire and how large of one I make, but I feel like there might be a learning curve there. Should I just open my dump zone valve if the boiler temperature gets to 200F?

Thanks for all the help!

You might look at the Caleffi solar controllers.

The I solar plus has two 120V relay outputs. Arr 2 for example is a delta T and a setpoint function. It may cost less than two controls and it has a lot of features, a nice display and some basis data logging.

The BX or MX LTE have up to 5 relay outputs and more functions. Th MX LTE has some virtual relays, you chose the function and then assign sensors, so it can be customized.

Here is the basic i solar Plus manual.

https://www.caleffi.com/sites/default/files/caleffi/uploads/files/49011111.pdf