Storage with Econoburn Outdoor Model

Last night I finished setting up my 500 Gallon storage tank and began charging it/opened it to the entire system.

My plumbing is simple:
Supply Side: Wood boiler supply 150' underground to in basement T, one end goes to top of storage tank, the other goes through a 3-speed circ to a T on supply side of my propane boiler.
Return Side: Return on propane boiler T to T on bottom of storage tank, one end goes to tank and the other goes through a Danfoss 3-way mixing valve to the return side of the wood boiler.
- 150' x 1" dia. underground pex each way (from house to wood boiler and back)
- indoor propane boiler has zone valves for upstairs, downstairs, indirect domestic hot water tank (just another zone with mixed output on the potable side) and radiant loop for bathroom
- indoor propane boiler has 1 Grundfos circ pump
- Econoburn Outdoor 150 set to 178 degrees F


I'm not sure if this is the most efficient way to plumb everything, and there are a few questions I'm having since putting the storage online last night:

1) How do I know if my circulators running too fast or too slow? My Econoburn 150 Outdoor model came with a 3-speed Grundfos, so that is set to the middle speed. The Circ on the storage tank is also set to the middle speed. The circulator on my propane boiler is a one-speed Grundfos, so I'll have to look into model to determine speed/flow.

2) The Econoburn Outdoor models are different than the indoor models in that they continuously run the circulator as long as there is power to the boiler. There is a Honeywell aquastat that is set to 190 degrees F on the supply side that shuts the fan off if the temp is 190 or higher. This morning the storage tank felt good and hot, however the indoor boiler showed a temp of 148 degrees F. The outdoor boiler was around 150 degrees F and the fan wasn't on (idling), however the firebox was more than half full of dry white oak splits.
- I'm thinking that the boiler fan should have been cranking and gasifying since my delta T was >20 degrees.

I think I need to set the Honeywell aquastat to something higher than 190 degrees F when running with storage, but does anyone out there have experience with the outdoor econoburn models and storage?

Matt

Update: I just talked with Dale and he gave me some things to try, so tonight I will run through the programming of the controller on the boiler to verify that it's setup properly. He said that the boiler shouldn't have been idling at 152 degrees with my setpoint of 176 so something is not quite right. I will update this thread tomorrow with my findings.

Update: this sucks!

I woke up to a 75 degree boiler this morning. Yay! Inside the tank was around 150 so I'm not getting transfer from the boiler to the tank and tank to the rest of house. I'm shutting down storage until I can figure this out, and will post pictures and schematics tomorrow.

I really think the 1" pex lines that I have in the ground are killing my heat transfer from the boiler to the house: 150' per run (supply and return) 1" diameter Central Boiler non-oxygen barrier pex.

This spring I'll be replacing my main runs, so if you guys know where to get 1-1/4" or 1-1/2" oxygen barrier pex with waterproof insulation for direct burial please chime in!

Matt

Guys - thanks for the comments. My boiler schematic is below:

RobC said:

In the short run you should be able to get things to work. Think of your 500 gallon storage as a buffer tank. The 1" pipe could be a problem delivering heat. Given enough run time on boiler hopefully you can get tank charged even with the 1" pex.
Have you checked your head and flow rates with the circulator that is on the boiler since you are using the 1" pex ?
Your boiler shutting down ? Are you going into over temp shut down from not being able to pump away heat ?

Click to expand...

My boiler is not shutting down...that's part of the problem: once the wood is depleted, the fan continues to blast cold air into the firebox, effectively exchanging the heat out to the air. I'm looking into a simple way to solve this and may have it figured out, but I'll post more when I know more.

The boiler pump is on as long as there is power to the boiler - the circ never shuts down, so I have to think setting the speed as high as possible will be the best solution for now, regardless of head / flow.

Here are my thoughts and solution:

1) Timers are not a real solution for me, as I want the wood to burn completely out, leaving no chance for creosote.
2) My setpoint is 176 which seems to work well for now even with 500 gallons of pressurized storage.
3) I’m not getting the most efficient heat transfer due to my lines in the ground being 1†Central Boiler leftovers from my failed experience with Central Boiler’s junk OWB that failed with multiple weld problems in less than 6 years of ownership.

Solution:

1) Wire the pump to run continuously regardless of what the controller is doing. In my outdoor Econoburn 150, it’s wired directly to main power anyway, which facilitates using an ECM pump to make the system more efficient.

2) Install a normally closed relay in the fan circuit. The schematic shows the aquastat for high temp fan-kill already wired in the fan power circuit, so wiring an NC relay inline in the fan circuit will not cause undue stress to the Nimbus board since the aquastat opens the circuit when overtemp is reached.

3) Use the Alarm 1 on the TC33 controller to control energize the NC relay in the fan circuit at the Alarm 1 setpoint. The Alarm 1 contacts on the controller are wired to a pump relay and set at 110 from the factory for the indoor econoburn models. I’m simply setting it to 140, and when any temp lower than 140 is reached, the controller energizes the relay and opens the fan circuit.

I will wire a bypass and switch in the relay circuit, just to get fires started, but this solves my problem perfectly.

One last note: another option would be to put the NC relay in the Nimbus power circuit, effectively shutting down the nimbus board when the low setpoint is reached.

Manual for the Automation Direct TC33 is located here:
http://www.automationdirect.com/static/manuals/processctrlm/tc33_manual.pdf

“cooling Fan†problem solved!

Omron LY2-AC110/120 DPDT relay wired in the power supply to the Nimbus (terminals “N†and “Lâ€)
- opens circuit on the alarm 1 setpoint via terminals 9 and 10 on the TC33 controller
- You have to make sure the Function for alarm 1 is set to “Low Alarm†by setting “A1Fu†to “0â€
- pump must be wired directly to power and not controlled by the boiler controls

I'm HAPPY!

Note: the outdoor boilers are wired very differently than the indoor models, trust me: I tried to setup mine using the schematic from the manual and it’s nothing like the indoor units. Mainly, the pump is wired direct and always on.

When I installed the Omron L2Y DPDT relay (using alarm1 to energize the coil), I was able to use one side of one pole of the relay to open the power to the Nimbus module and kill the fan.
- The other side of the pole was used to light an LED switch that I wired in the coil side of the relay for a bypass to get a fire going past the alarm 1 setpoint.
- since this is a DPDT relay, I ran two additional wires from the other pole that I plan to use for pump flow control: one connected to the normally open side for low speed and one to the normally closed side for high speed.

These two modifications should make this boiler kick butt for use with storage tanks, for about $20 more for the relay, switch and some wire.

update: 128 degrees F at the boiler this morning and no fan running! Not perfect, but much better.

next step -use the alarm1 on the controller to reduce pump speed when fire is out...

Update: Thank God for the shoulder season!

It's been rough this winter, and I've got some improvements to make as I really dislike having to "babysit" this furnace and fill it every 4 to six hours, even with 500gallons of storage. I'm not sure about the rest of you, but I've gone through easily 36 face cord this winter with my 150k btu econoburn outdoor model.

1) Transfer Lines: I need to replace my 1" diameter non-O2 barrier lines with O2 barrier lines. Will 1-1/4" be adequate to transfer the heat I need to get to my house 150' away.

2) Heat Loss from the boiler being outdoors - I know they insulated it, but the doors and the entire front panel is a conductor to ambient air temperature, so I'm losing heat there. One idea is to extend my pole barn to cover the front face of the boiler, shielding it from the wind at least and gaining the benefit of heating the pole barn, albeit via parisitic heat loss from the front of the boiler.

3) The "eaves" of the boiler need something to take up the space between the sides and the eaves - there is not "soffitt" or anything blocking the wind from blowing through the outdoor boiler, which is another area of loss.

4) Controller - I'm almost finished building my own >$500.00 control system that uses an immersed, type-K thermocouple to accurately measure the temperature of the water and a flue-thermocouple to measure flue gas temps. This controller also has a web interface and data-logging capabilities and will control any pump (on/off) and any fan (on/off or 0-10V signal for the SmartFan Nimbus module). A backlit LCD and button panel

My biggest complaint with this boiler is the lack of an intelligently designed control system: If I'm out of fuel and the temp starts to drop, the controller should have a low setpoint and stop the fan from blowing effectively pulling heat out of the boiler while the fan is running! If this or any boiler is being sold to be used with thermal storage, there needs to be a low temp cutoff in the control loop.

afblue - I'm thinking that you are correct when you say the danfoss valve should be placed as close to the boiler as possible. I'm making this modification this weekend and will update as to how it works out.