Help Needed Plumbing System

[heat4steve]

I am plumbing into an existing propane boiler system with an econoburn 150 and wish to keep the existing setup as much as possible. Below is the concept I am considering for achieving this. It is essentially a parallel flow setup. During wood heating or thermal storage discharge, pump p-1 (controlled by boiler) and pump p-2 (thermostat/aquastat controlled) will be used. I expect it to work as follows:

1) Zone Heating and DHW
P-1 and P-2 are operating with most of the flow directed towards the zone valves. However some flow will go to the thermal storage tanks.

2) Thermal Storage Charging
P-1 is operating and P-2 is off. All flow will go to the thermal storage tank. Check valves and zone valves will prevent flow into the rest of the system.

3) Thermal Storage Discharging to zone valves and DHW
P-2 is operating and P-1 is off (no boiler heat) . Flow will reverse through the tanks and flow through to the zone valves.

4) Propane Backup
Operates as it presently does when thermal storage and wood heating are not available

I would appreciate any recommendations on how to improve this system.

 

[ewdudley]

I am plumbing into an existing propane boiler system with an econoburn 150 and wish to keep the existing setup as much as possible. Below is the concept I am considering for achieving this. It is essentially a parallel flow setup. During wood heating or thermal storage discharge, pump p-1 (controlled by boiler) and pump p-2 (thermostat/aquastat controlled) will be used. I expect it to work as follows:

1) Zone Heating and DHW
P-1 and P-2 are operating with most of the flow directed towards the zone valves. However some flow will go to the thermal storage tanks.

2) Thermal Storage Charging
P-1 is operating and P-2 is off. All flow will go to the thermal storage tank. Check valves and zone valves will prevent flow into the rest of the system.

3) Thermal Storage Discharging to zone valves and DHW
P-2 is operating and P-1 is off (no boiler heat) . Flow will reverse through the tanks and flow through to the zone valves.

4) Propane Backup
Operates as it presently does when thermal storage and wood heating are not available

I would appreciate any recommendations on how to improve this system.

It looks like there is a sixth zone valve to the left of zone valve 1. If we call the three circ pumps at noon, three o'clock, and six o'clock on the left side P-3, P-4, and P5, does the existing system open the sixth zone valve when P-4 is injecting hot water into the P-3 loop? If so will you need to open the sixth zone valve in order to let P-2 pump back through the DHW coil when there is a DHW call for heat?

Is there a flow-check as well as a check-valve on the outlet of P-5? I think there needs to be in order to prevent some flow through the propane boiler when P-2 is active.

Cheers --ewd

 

[heat4steve]

Sorry for the confusion. The sixth valve is a new valve and is not part of the existing system. I plan to use this valve for provide wood/storage heat to the indirect hot water tank – Note I need a check valve on the hot water tank to prevent bypass. Pumps 3,4,5 will never be in operation unless the wood boiler is off and the thermal storage is below set point. From a control standpoint I was trying not to add P-2 but use just P-3 having it directly controlled by the zone valves. However, my plumbing layout would require the addition of a three way valve to achieve this. My planned control logic is as follows giving DHW priority:

If DHW Aquastat request heat then
If Wood Boiler is On (Flow Switch or Boiler Aquastat) or Thermal Storage Temp (Aquastat is Above Low Limit)
• Open Zone Valve for DHW
• Close Zone all other zone valves
• Turn On P-1
Else Then
• Send Request to Propane Boiler – Which fires and turns on P-5
End
End when DHW Aquastat request is off.

If Thermostats request heat then
• Continue if no request for DHW
• Open Zone Valves
If Wood Boiler is On (Flow Switch or Boiler Aquastat) or Thermal Storage Temp (Aquastat is Above Low Limit)
• Turn On P-1
Else Then
• Send Request to Propane Boiler – Which fires and turns on P-3 and P-5.
End
End When request is off.

Now I just have to translate this into a reliable relay circuit.

Thanks for your help.

 

[ewdudley]

Sorry for the confusion. The sixth valve is a new valve and is not part of the existing system. I plan to use this valve for provide wood/storage heat to the indirect hot water tank – Note I need a check valve on the hot water tank to prevent bypass. Pumps 3,4,5 will never be in operation unless the wood boiler is off and the thermal storage is below set point. From a control standpoint I was trying not to add P-2 but use just P-3 having it directly controlled by the zone valves. However, my plumbing layout would require the addition of a three way valve to achieve this. My planned control logic is as follows giving DHW priority:

If DHW Aquastat request heat then
If Wood Boiler is On (Flow Switch or Boiler Aquastat) or Thermal Storage Temp (Aquastat is Above Low Limit)
• Open Zone Valve for DHW
• Close Zone all other zone valves
• Turn On P-1
Else Then
• Send Request to Propane Boiler – Which fires and turns on P-5
End
End when DHW Aquastat request is off.

If Thermostats request heat then
• Continue if no request for DHW
• Open Zone Valves
If Wood Boiler is On (Flow Switch or Boiler Aquastat) or Thermal Storage Temp (Aquastat is Above Low Limit)
• Turn On P-1
Else Then
• Send Request to Propane Boiler – Which fires and turns on P-3 and P-5.
End
End When request is off.

Now I just have to translate this into a reliable relay circuit.

Thanks for your help.

When P-2 is running and ZV6 is closed there is a parallel path back to the WB/storage where return water from the zones can go in the hot side of the DHW loop and back out the cold side. Depending on the relative resistances it might or might not cause enough flow to be a problem. If you have a plan to deal with it you could wait and see if it's a real problem, else looks like you need another check valve where hot water from the PB enters the P-3 load loop. Again I'm calling the pump at noon of the left side P-3. The pump at three o-clock is P-4, and the pump at 6 o-clock is P-5.

Regarding control logic, it seems to me you don't need to get the wood boiler or P-1 involved with the load-side of the system. I believe typically the wood boiler has a jumper across its T-T terminals and the boiler controls P-1 to get rid of heat as fast as it needs to. The flow can go to storage or it can be drawn off by P-2, the boiler doesn't know or care.

Likewise P-2 doesn't need to know if the boiler is running or not. If it is running there will be plenty of hot water at the top of storage soon enough, so all you need is an aquastat at the top of storage to enable P-2 along the lines of the logic described in the 'Simplest Pressurized' sticky.

--ewd