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[ElectroBOOM] Valve motors inefficient design or fail-safe construction?
Cubdriver:
--- Quote from: golden_labels on May 06, 2022, 08:47:49 pm ---Usually he cares about providing true and valuable information, but I have a feeling this time something is wrong. Instead of a motor constantly pressing against a spring-loaded mechanism, he proposes a controlled motor that opens the valve, stops, closes the valve, stops. While that would indeed would waste less power(1), isn’t the mechanism designed intentionally like that to be fail-safe and close the valve if power fails?
(1) Let’s now ignore whether the waste is important or not. I know we’re talking about fractions of a watt in a hunreds watts to kilowatt range heating system.
--- End quote ---
I suspect that the mechanism is designed like that for simplicity's sake (you apply power to the valve it opens and signals the boiler/circulator that it's calling for heat; remove power and it closes and indicates this as well), and also to be compatible with other types of heating zone valves - a company called Taco makes valves that perform a similar function, but rather than having motors and gear trains, they are even simpler - they use wax motors that rely on the expansion of a wax pellet that's heated when the valve is turned on.
https://www.tacocomfort.com/product/570-gold-series-heat-motor-valves/
Clive explaining the operation of a European version that operates at line voltage (those used in the US run on 24 VAC):
What Mehdi is suggesting would be needlessly complex for what is to be accomplished - while it would save a bit of energy, it would require much more complicated controls (relatively) to work - limit switches for both open and closed positions, a valve actuator mechanism that wouldn't be able to back-drive the actuator motor, and control electronics that send DC of the appropriate polarity to the motor to drive it open and closed. The existing valves (both the motor driven ones he has and the wax pellet type like the Tacos) need nothing more than a simple switch closure to apply 24 VAC to actuate, and removal of the 24 VAC to close. Dead simple.
-Pat
Cubdriver:
--- Quote from: NiHaoMike on May 08, 2022, 12:33:15 am ---
--- Quote from: tom66 on May 07, 2022, 09:52:27 am ---Complaining about 9W of power dissipated in the motor for a heating system that's probably supplying 2-3kW per room - and only supplying that when the zone itself is on - seems like Medhi cannot see the forest for the trees.
--- End quote ---
Those few watts per zone add up if it's desired to run the heating system on battery power. I guess it's safe to assume that such elaborate heating systems are installed in areas where they'll actually be used for a good part of the year, and by extension, winter storms are not uncommon in those areas.
--- End quote ---
They're normally used in multi-zone hydronic heating systems. In the northeastern US where I am, the heat source is often an oil-fired boiler with a burner assembly that consists of an AC motor driving a blower and oil pump (~100 W), and a circulator motor (or more than one if the system is like his with primary/secondary loops using closely spaced tees; another 30 W or so each) to pump the water through the system; other areas may use gas-fired boilers which will have a forced draft blower fan that pulls probably close to what the oil burner draws power-wise, all running on 120 VAC, or a tankless heater like Mehdi has - either gas fired and relatively low current draw or electric, in which case it's likely several kW at 240 VAC. The few watts of power that the zone valves draw is pretty low in relation to everything else, and these systems are not something that you'd typically operate on batteries. If power fails you need an AC generator to run them (though I suppose photovoltaic arrays with inverters would do it too, during the day at least, but I'm not sure how those work power-use wise when the main lines are down).
-Pat
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