[ElectroBOOM] Valve motors inefficient design or fail-safe construction? - Page 1
Forum section: electronics / general

author: golden_labels
author_rank: Super Contributor
timestamp: May 06, 2022, 08:47:49 pm
content: In his most recent ElectroBOOM video, Mehdi makes a comment on a “inefficient” valve design: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.

author: nctnico
author_rank: Super Contributor
timestamp: May 06, 2022, 09:06:56 pm
content: A simpler fail safe system is to use a valve that shuts down when the water temperature gets too high. In my (zoned) floor heating system I have a valve that stops the motor when it is opened of closed and another (passive) valve that shuts down the water flow in case the water gets too hot.More generally speaking: chances are high that in case of a power failure, the water stops circulating anyway.

author: HuronKing
author_rank: Frequent Contributor
timestamp: May 06, 2022, 09:54:40 pm
content: Electroboom giving bad advice? Say it ain't so.

author: tom66
author_rank: Super Contributor
timestamp: May 07, 2022, 09:52:27 am
content: 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.

author: elekorsi
author_rank: Regular Contributor
timestamp: May 07, 2022, 11:23:37 am
content: What on earth is that?He should blur that out on the video, as this is some seriously disturbing content

author: Towger
author_rank: Super Contributor
timestamp: May 07, 2022, 11:35:22 am
content: Wirenuts, you never see those abominations in this part of the world.The problem with closings valves on the event of a failure is it can stop the water flowing in the system and in turn cause the boiler to over pressure/vent very hot water/explode, if there is an issue with the thermostat (s).

author: elekorsi
author_rank: Regular Contributor
timestamp: May 07, 2022, 12:25:48 pm
content: Well i know that they are wire-nuts, but at least some sort of junction box could be used, not just leaving them flapping around...That boiler will not over pressure if all the valves closes, it has enough of safety elements integrated. It will just normally shut down when there will be no heat consumption...And i agree, much better solution is an actuator with two simple integrated end switches that turns the motor off in its end positions...

author: golden_labels
author_rank: Super Contributor
timestamp: May 07, 2022, 04:07:02 pm
content: Did anyone actually read what I asked about?

author: floobydust
author_rank: Super Contributor
timestamp: May 07, 2022, 05:06:51 pm
content: There is no decent "fail safe" system for hydronic heating. It's just people following some old convention.Zone valves can be normally open or normally closed. The normally open valves require constant power to stay closed, the normally closed valves require constant power to stay open. They have a spring return. Really old zone valves were motorized both ways, with a limit switch at each end. They wouldn't help because a closed valve will just stay closed.Modern buildings and hydronic heating designs use normally open valves because they "fail safe" in theory. If there is an open circuit or loss of power, the valve springs opens for full heat and there is no danger of pipes freezing.One example is apartment buildings, condos where the suite is unoccupied and has power shut off- the 24VAC zone valve transformer is not energized and you don't want the suite cold, so it defaults to full heat.No matter what it's a crappy design. Running glycol gets rid of the zone freezing (aside from other plumbing) but there is a big hit in efficiency as glycol is not as good as water.With hydronic heating, you really need a low temp alarm. Nobody has rolled out a smart zone valve yet.Note modern googlegarbage thermostat like the Nest does offer"HVAC monitoring"offered in some regions but it looks like children wrote the software for it.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: May 07, 2022, 11:07:37 pm
content: Even at $30-something each Mehdi overpaid for the replacement motors. They should be more like $10.I had exactly the same failure of one of those kind of Honeywell zone valves. Looked up the price of entire valve... "how much?!". Looked at just a replacement 'head'... "how much?!". Fortunately found just the motors on eBay for just £7! It may be a made in China knockoff, but so far it's lasted just as long as the Honeywell original.Here in the UK those valves typically run 240V AC. I wonder why they use 24V in Canada? Guessing some kind of regulatory thing so plumbers can wire them up without having to be a certified electrician.

author: floobydust
author_rank: Super Contributor
timestamp: May 08, 2022, 12:19:54 am
content: 24VAC the circuit, thermostat and wiring is low voltage Class 2 energy-limited and no fire or electrocution hazard. Same for doorbell circuits. i.e. transformerhttps://www.hammfg.com/electronics/transformers/class-2/ba-c-d-eWhy would you need two tradesmen, plumber and electrician to replace one. Is that how it is in the UK? Sounds expensive.Common here is HoneywellV4043which have been around since 1965. They can last 20 years no prob. You can buy a replacement motor/gearbox or ball/o-ring if you're into repairing them but tradesmen just replace the whole thing for max profit on the callout. The valve's claim to fame is long life because the ball rotates with every open/close cycle and wears evenly. If you have a lot of trapped air in the system the oxygen apparently deteriorates the ball.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 08, 2022, 12:33:15 am
content: Quote from: tom66 on May 07, 2022, 09:52:27 amThose 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.Quote from: floobydust on May 07, 2022, 05:06:51 pmNormally closed but with a set screw to keep it open a little when "off" would be a good compromise. Or perhaps have a valve that's normally half open, with one polarity to close it and the other polarity to open it?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: May 08, 2022, 04:57:16 am
content: Quote from: floobydust on May 08, 2022, 12:19:54 amNo, only a single tradesman. Such work is typically done by a 'heating engineer', who is certified to work with gas as well as does the plumbing and electrical.I'm not totally sure whether they're actually required to be certified in the same way that electricians are, possibly because a heating system may be treated like any other electrical domestic appliance as far as regulations goes.Everything on your typical UK central heating system runs at 240V - valves, thermostats, etc. - I think because before the arrival of sophisticated digital control systems, control would be achieved by connecting things in series. Look up "s-plan wiring diagram" for an idea.

author: elekorsi
author_rank: Regular Contributor
timestamp: May 08, 2022, 06:57:27 am
content: I still don't understand why should there be any failsafe state on such simple thing. If the power fails the boiler will shut down and the pumps will not run, so why would there be a need for the failsafe state of the valves? If freezing is such a problem, the system would also need redundant pumps, so if one fails, the other one kicks in...but we are talking here about house central heating and not some multi MW steam boiler...

author: Siwastaja
author_rank: Super Contributor
timestamp: May 08, 2022, 06:59:53 am
content: Besides, these motors are engineered to save every cent in manufacturing. They could easily just spend $0.20 in thicker copper wire, which could halve the consumption without having to make any major changes. This would also stop the motors from failing early as the windings would run cooler. But there is no incentive to do that.

author: Cubdriver
author_rank: Unknown
timestamp: May 08, 2022, 08:20:04 am
content: Quote from: golden_labels on May 06, 2022, 08:47:49 pmI 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

author: Cubdriver
author_rank: Unknown
timestamp: May 08, 2022, 08:48:33 am
content: Quote from: NiHaoMike on May 08, 2022, 12:33:15 amThey'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