This is the situation - I have three heat sources, called CHP, burner 1 and burner 2 on the same circuit. All three feed to the same heating manifold, with various heat demands.
Preferably I want to heat with the CHP; if that is not sufficient, additionally with burner 1; and only use burner 2 if that is still insufficient. The CHP is always running and not controlled for temperature.
The reason for this scheme is that the CHP burns (free) sewage gas and earns money (electricity), burner 1 burns sewage gas and burner 2 uses (expensive) natural gas. Burner 2 is installed in case all other heat providers fail or the sewage gas runs out.
Here's my idea for a control scheme, where the actual temperatures are more examples than set in stone:
- In normal operation, the return flow is 75 °C or higher
- If return temp. < 73 °C, burner 1 is activated and heat controlled to 73 °C return
- If return temp. < 71 °C, burner 2 is activated and heat controlled to 71 °C return
In the last case, burner 1 should run at nominal power and burner 2 at enough power to raise return temp. to 71 °C.
Will I run into problems with two burners on the same circuit controlling for different temperatures?