This is the theory of operation I have come up with for my diagram. I am looking for you seasoned professionals to review it and tell me how it will work.
The storage tank is 500 gallons pressurized.
I will be programing a PLC with thermocouple at the locations given in the diagram. I am an electrician, not a heating tech. Let me know if my diagram and controls seem they will work correctly.
Theory of operation: If the wood boiler is at temp and house isn’t calling for heat, send the heat to the tank. If the wood boiler is at temp and the house calls for heat, send the heat to the load. If the house calls for heat the tank is at temp but wood boiler isn’t, send heat from the tank to the load (this will depend on whether it is a radiant (low temp) call or a DHW (high temp) call. If the wood boiler or the storage is not hot enough the oil boiler will fire.
Anytime the tank is feeding the heat load Valves at location G and A are closed and valve at location E is open.
Anytime the Wood Boiler is feeding the heat load the valves at location G and C are closed and valve A is open.
I will have a toggle switch on the control box that will either:
I am relying on an automatic standby generator for power loss issues.
The storage tank is 500 gallons pressurized.
I will be programing a PLC with thermocouple at the locations given in the diagram. I am an electrician, not a heating tech. Let me know if my diagram and controls seem they will work correctly.
Theory of operation: If the wood boiler is at temp and house isn’t calling for heat, send the heat to the tank. If the wood boiler is at temp and the house calls for heat, send the heat to the load. If the house calls for heat the tank is at temp but wood boiler isn’t, send heat from the tank to the load (this will depend on whether it is a radiant (low temp) call or a DHW (high temp) call. If the wood boiler or the storage is not hot enough the oil boiler will fire.
- -If the temperature at location “A” is above 100 degrees and there is at least a 10 degree difference between Location A and location B the circulator at location B turns on and the valve at location A opens
- If the boiler return (Location B) is over 150 and the boiler output (location A) is hotter than Location D, and the house is NOT calling for heat the tank valve at location C opens.
- If the boiler return (Location B) is over 160 and the boiler output (location A) is hotter than Location B and the house calls for heat, the valve at location C closes, the valve at location E opens, and circulator at location F energizes. (all valves/ circulators resume back to operation as in step #3)
- If the boiler return (Location B) is NOT over 160 or the boiler output (location A) is NOT hotter than location B and the house calls for heat:
- Valve at location A closes and Circulator at location B deenergizes. This holds true until the temperature at location A exceeds 160.
- If zone calling for heat is radiant and the tank temperature at location H is above 100 the valves at location C & E opens, and the valve at location G closes. If the temp is not above 100 the valve at location G opens, Oil boiler is fired, and valve E is closed.
- If zone calling for heat is DHW and the tank at location H is above 140 the valves at location C & E, and the valve at location G closes. If the temp is not above 100 the valve at location G opens, Oil boiler is fired, and valve E is closed.
- If the tank rises above 200 it forces valves at locations A, C and E open and energizes circulators at location B. It also forces on the basement radiant zone which is 2600 of slab radiant. If the tank doesn’t drop below 200 for 5 minutes it triggers a trouble alarm output on my security system
here are more ways of saying the same theory of operation
Anytime the oil boiler is operating the valve at location G is open. Valve at location E is closed.
Anytime the tank is feeding the heat load Valves at location G and A are closed and valve at location E is open.
Anytime the Wood Boiler is feeding the heat load the valves at location G and C are closed and valve A is open.
I will have a toggle switch on the control box that will either:
- In normal position/operation Connect the zone controller end switch with the PLC input and the oil boiler control will be operated via a relay controlled by a PLC output.
- In Emergency Bypass position it will allow all function of the PLC to perform normally EXCEPT: It connects the zone controller end switch directly with the oil boiler control. This will allow the oil boiler to operate as a complete standalone system if there are any issues with controls/components.
I am relying on an automatic standby generator for power loss issues.