This is a project to limit the infloor heat to a garage.
The object is to interface with the existing pumps and control system to apply heat to the floor only if the return water is < a set value.
The interface is implimented by breaking the normal direct connection between the thermostat and circulating pump control, with an interface that operates the circulating pump periodically while monitoring the return water temperature. If the return temperature remains below a set temperature during the interval, the relay for the boiler is activated and the pump stays on until the return water exceeds the set value by a number of degrees. The interface will operate only if the thermostat is calling for heat, ie, <50F.
This appears to be doable with a 08M, 2 inputs and 2 outputs and some long time intervals. It would be nice to have some advice about interfacing the temperature sensor, 28VAC I/O, and pump relays.
- What is the best temperature sensor to use with the 08M in the 32 to 130F range? This sensor would be clamped or otherwise thermally connected to the return pipe.
- Would optical isolation be needed on a 28 VAC 08M input, or a simple diode, capacitor, resistive divider, and Zener diode circuit?
- Any recomendations for driving low current 28VAC thermostat relay? Would optical isolation be recommended here also? The low current 28V signal, that replaces the thermostat signal, maybe doable with a 5VDC coil relay driven directly from the 08M or with a simple transistor coil driver.
- it maybe best to drive the 110AC 90 watt circulating pump motor with a solid state relay to minimize the interface to the 08M. Or possibly a relay circuit like the 28V circuit above.
I could scratch this out myself, the object is to see how the system works with a minimum of gotchas. Any comments or suggestions appreciated. I don't have a way to, or know how to get a schematic on this page other than manually drawing it.
The object is to interface with the existing pumps and control system to apply heat to the floor only if the return water is < a set value.
The interface is implimented by breaking the normal direct connection between the thermostat and circulating pump control, with an interface that operates the circulating pump periodically while monitoring the return water temperature. If the return temperature remains below a set temperature during the interval, the relay for the boiler is activated and the pump stays on until the return water exceeds the set value by a number of degrees. The interface will operate only if the thermostat is calling for heat, ie, <50F.
This appears to be doable with a 08M, 2 inputs and 2 outputs and some long time intervals. It would be nice to have some advice about interfacing the temperature sensor, 28VAC I/O, and pump relays.
- What is the best temperature sensor to use with the 08M in the 32 to 130F range? This sensor would be clamped or otherwise thermally connected to the return pipe.
- Would optical isolation be needed on a 28 VAC 08M input, or a simple diode, capacitor, resistive divider, and Zener diode circuit?
- Any recomendations for driving low current 28VAC thermostat relay? Would optical isolation be recommended here also? The low current 28V signal, that replaces the thermostat signal, maybe doable with a 5VDC coil relay driven directly from the 08M or with a simple transistor coil driver.
- it maybe best to drive the 110AC 90 watt circulating pump motor with a solid state relay to minimize the interface to the 08M. Or possibly a relay circuit like the 28V circuit above.
I could scratch this out myself, the object is to see how the system works with a minimum of gotchas. Any comments or suggestions appreciated. I don't have a way to, or know how to get a schematic on this page other than manually drawing it.