Turn on the Heat

% start synopsis % start main

A heating controller for a hybrid system: a Solvis buffer and heating circuit, a heat pump, and a KWB pellet burner. Independent units on MoaT-Link compute the heating curve, pick the heat source, and drive the heat pump, the burner, the heating valve and the water pump.

% end synopsis

The controller consists of these units, each a separate MoaT-Link service:

moat dev heat run runs all units but the watchdog in one process; moat dev heat run UNIT… runs some of them. Each unit waits until no other process runs it, so a second instance is a hot standby. The units read their sensors from, and write their commands to, the Modbus pollers (moat modbus dev poll) of the heat pump and the Solvis controller; moat dev heat pwm drives the water pump's PWM output, and moat dev heat modbus_mon restarts a stuck Solvis poller. The package moat-dev-heat-service has systemd units for all of these.

Other commands:

• moat dev heat stop stops the units in an orderly way: the heat pump is switched off and cooled down before the water pump stops.
• moat dev heat off shuts the heat pump down at once (emergency).
• moat dev heat override sets or clears an operator override, e.g. to keep the heat pump off.
• moat dev heat migrate converts the legacy controller's configuration and state to the units' MoaT-Link items (once).
• moat dev heat record records MoaT-Link data for tests. moat dev heat sim, in the separate moat-dev-heat-sim package, runs a plant simulator on MoaT-Link.
• moat dev heat status reports the controller's health: the units' and the PWM daemon's services, the Modbus pollers, the error records, and the Solvis' and the pellet burner's own error data. It exits non-zero when something is down or in error.
• moat dev heat start starts the heating's systemd units again after an emergency stop, in order, each once the previous one has announced its service; it stops at the first problem.

The units' configuration lives in MoaT-Link (cfg.app.heat.UNIT), overlaid on the package defaults, and takes effect without a restart.

Safety depends on the flow unit: an emergency shutdown, whether by the pump unit, the watchdog or moat dev heat off, asks the flow unit to keep the water running until the heat pump has cooled down. If the flow unit is dead too, the water pump keeps its last PWM. That protects the heat pump from overheating, but nothing stops the water pump afterwards.

% end main