My new wall heater has a gas valve that is thermostatically compatible. The most common thermostat for this heater is called a "microvolt" thermostat. It apparently get its microvolts from something heated by the pilot light.
What I can't seem to get my head around, is how can such a small amount of power manage to horse-open the rather high flow gas valve?
Him No manual to read? My guess is the micro current triggers power to the valve coil. Definitely it can't directly control the valve.
The something is a thermocouple. It is actually millivolts not microvolts. The common name for that system is "powerpile" which might be a Honeywell trademark. We used to have that system on an old steam boiler. It worked well and as long as the natural gas flowed there were no worries about power outages.
The valve is designed so that only a small amount of energy is required to open it.
It uses a pilot generator to make electricity which powers the coil on the valve. The down side is that it generally takes a while to operate, unlike a 24 or 120 volt coil valve
hat is thermostatically
Sounds like it's the same type of system used on most water heaters that also don't have any external power source to open the gas valve.
Wrong - it most definitely DOES directly control the valve as microvolr controlled gas appliances are the only ones that will work with the power out and no batteries required.
is thermostatically
It is. I don't see them on conventional heating systems anymore. They were great when the power went out. Once the thermostat called for heat, it took a minute or so for the valve to open
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