I've redone my control logic a half dozen times. I think I now have a completely hands free logic.
I may eliminate the tekmar 155 differential when I learn a bit more about the Watts. the Watts Solar (differential) control has 3 separate outputs and 6 sensor inputs. It allows two separate differential functions and a thermostat function. currently I am using one differential, and the thermostat function.
I added an isolation relay to P1 as it is powered from two different controls. One to load the tank, the other to onload. I'm told triac relays can be back fed without a problem, but decided not to risk it for an inexpensive RIB double throw relay.
My DHW, and radiant via a FP HX, feed from the Phoenix which also has solar input, but that piping and wiring is not shown to keep the wood side drawing cleaner.
On a cold start boiler, building calling for heat, the boiler reaches 145F and P3 circulates water through the boiler. This snap stat came on my EKO from the dealer. This is the cold return protection device and much simpler to install and use than a 3 way thermostatic.
P4 moves heat from the boiler loop to the primary loop, when the boiler is 10F warmer than the loop. The sensor is at P2 on the loop.
So on first start up, with a call for heat or DHW the boiler is heating directly to the load, none to the storage.
When the loop temperature rises to 140, which indicates it has, or is keeping up with the radiant floor loads, and DHW via the Phoenix tank capacity, then P1 starts charging the 500 gallon storage. It can run to 180F. I adjust the firein the EKO to the outdoor temperature as best as possible and have not seen any overshooting. The EKO idles if the tank does reach setpoint.
If and when the fire dies out, boiler cools both pumps P3 and P4 shut down.
as long as the 500 gallon storage tank is 150F or more, the thermostat function on the Watts will allow P1 to "unload" the tank. If there is no call for heat or DHW, the loop temperature rises and P1 shuts down.
So far this has been working well. Still moving sensor locations a bit to fine tune but the logic seems correct. Ideally I could get this down to two fairly simple, and readily available controls. One setpiont, and the triple function Watts or equivelent.
The Watts Solar control is a prototype, but I see Steca and a few others offer 3 output solar (differential) controls.
The Watts Solar control reads out all sensor location temperatures and even has a simple data logger and graph display function. It also keeps track of run hours on the outputs and does some simplistic BTU monitoring if you know nd plug in the flow rates.
This is a bit more pump intensive than other wood boiler piping, but pumps can be had cheap on e-bay and it really gives you nice control with every pump sized to its load exactly. With ECM circs, electrical consumption could be cut back to well under 200W for all pumps at design load.
I've played with some Grundfos Alpha ECM circs and P3 and P4 can move their loads with 17- 20W consumption! I'm told those Alphas will be available here in 120V 2nd quarter 2009. They can be purchased online at numerous UK websites, in 230V, however. Mine have inexpensive 120 to 230v inverters to run them. Wilo and Laing have ECM pumps on the market, currently.
I'll try to post a wiring diagram also.
hr
I may eliminate the tekmar 155 differential when I learn a bit more about the Watts. the Watts Solar (differential) control has 3 separate outputs and 6 sensor inputs. It allows two separate differential functions and a thermostat function. currently I am using one differential, and the thermostat function.
I added an isolation relay to P1 as it is powered from two different controls. One to load the tank, the other to onload. I'm told triac relays can be back fed without a problem, but decided not to risk it for an inexpensive RIB double throw relay.
My DHW, and radiant via a FP HX, feed from the Phoenix which also has solar input, but that piping and wiring is not shown to keep the wood side drawing cleaner.
On a cold start boiler, building calling for heat, the boiler reaches 145F and P3 circulates water through the boiler. This snap stat came on my EKO from the dealer. This is the cold return protection device and much simpler to install and use than a 3 way thermostatic.
P4 moves heat from the boiler loop to the primary loop, when the boiler is 10F warmer than the loop. The sensor is at P2 on the loop.
So on first start up, with a call for heat or DHW the boiler is heating directly to the load, none to the storage.
When the loop temperature rises to 140, which indicates it has, or is keeping up with the radiant floor loads, and DHW via the Phoenix tank capacity, then P1 starts charging the 500 gallon storage. It can run to 180F. I adjust the firein the EKO to the outdoor temperature as best as possible and have not seen any overshooting. The EKO idles if the tank does reach setpoint.
If and when the fire dies out, boiler cools both pumps P3 and P4 shut down.
as long as the 500 gallon storage tank is 150F or more, the thermostat function on the Watts will allow P1 to "unload" the tank. If there is no call for heat or DHW, the loop temperature rises and P1 shuts down.
So far this has been working well. Still moving sensor locations a bit to fine tune but the logic seems correct. Ideally I could get this down to two fairly simple, and readily available controls. One setpiont, and the triple function Watts or equivelent.
The Watts Solar control is a prototype, but I see Steca and a few others offer 3 output solar (differential) controls.
The Watts Solar control reads out all sensor location temperatures and even has a simple data logger and graph display function. It also keeps track of run hours on the outputs and does some simplistic BTU monitoring if you know nd plug in the flow rates.
This is a bit more pump intensive than other wood boiler piping, but pumps can be had cheap on e-bay and it really gives you nice control with every pump sized to its load exactly. With ECM circs, electrical consumption could be cut back to well under 200W for all pumps at design load.
I've played with some Grundfos Alpha ECM circs and P3 and P4 can move their loads with 17- 20W consumption! I'm told those Alphas will be available here in 120V 2nd quarter 2009. They can be purchased online at numerous UK websites, in 230V, however. Mine have inexpensive 120 to 230v inverters to run them. Wilo and Laing have ECM pumps on the market, currently.
I'll try to post a wiring diagram also.
hr
