Gas shut off valve

[programmergeek]

I called Asco they don't make anything (but close) all there valves require about 5 psi or power to stay open etc. One other application is for the outside gas grills to shut down the natural gas. Here we have a bunch of people with grills piped off there houses natural gas. Perodically they get left on and will just burn out there for days till someone notices they are on.

 

[apostolakisl]

I called Asco they don't make anything (but close) all there valves require about 5 psi or power to stay open etc. One other application is for the outside gas grills to shut down the natural gas. Here we have a bunch of people with grills piped off there houses natural gas. Perodically they get left on and will just burn out there for days till someone notices they are on.

been there, done that.

Of course, every natural gas appliance has a built in automatic on/off valve. Many of these don't even use power at all. Most gas hot water tanks don't even have an electrical hookup. Anyone know how those valves work?

 

[WayneW]

Of course, every natural gas appliance has a built in automatic on/off valve. Many of these don't even use power at all. Most gas hot water tanks don't even have an electrical hookup. Anyone know how those valves work?

In the old days, they used millivolt valves & thermocouples. http://en.wikipedia.org/wiki/Thermostat#Mi...olt_thermostats
I don't know what a modern device would do without a pilot light and no power source.

 

[apostolakisl]

So I wonder how such micro current is able to open/close a valve? Even if you were only powering a tiny solonoid, it would be hard to open/close a valve utilizing the gas pressure as the power source since it is also so small. However it happens, it does work well and reliable. I have never had a hot water tank fail at the valve.

Interesting that the article you site says most on demand tankless heaters use pilots. Mine don't, I believe it is spark ignitied, but definitely no pilot in there.

 

[hult]

I called Asco they don't make anything (but close) all there valves require about 5 psi or power to stay open etc. One other application is for the outside gas grills to shut down the natural gas. Here we have a bunch of people with grills piped off there houses natural gas. Perodically they get left on and will just burn out there for days till someone notices they are on.

Are you saying that you require a normally open valve? If so, count me out. Too many handy-dandy ways to create disaster ;-) including the grill application you mention.

If on the other hand, you need/want to be be conventional (and safe) and so use a normally closed valve, see (eg) http://www.ascovalve.com/Common/PDFFiles/P...t/8040_NCR1.pdf

ASCO 8040G023 is a direct-acting (not "pilot") 3/4" combustion valve valve for natural gas that operates between 0 and 5 psi differential pressure

Choose 8040G23-120/60 for 120VAC or 8040G23-24/60 for 24VAC.

In stock here: http://www.regulatorstore.com/searchprods.asp

Or eBay Buy-It-Now for $65 here: http://cgi.ebay.com/ASCO-JKF8040G23-120-US...=item33616a769e as I suggested previously.

HTH ... Marc

 

[hult]

So I wonder how such micro current is able to open/close a valve? \

Legacy valves powered by thermopiles are low voltage ("millivolt") not "micro current" as you suggest.

For example, http://customer.honeywell.com/techlit/pdf/...00s/70-2216.pdf works with a standard 750 millivolt thermopile but, as I understand it, can require as much as 250 mA of current (1/4 amp) to stay open. It uses a servo valve and regulator to minimize power ( V * A) required to keep the valve open. The diagram of the electro-mechanical workings of the valve is very detailed.

Still -- 0.75V * .25A is < only 0.2 watts!

The gas-fired boiler in our family home in Minnesota still runs entirely on a millivolt system. Water circulation to radiators is density-driven convection -- so no VAC is required for circulating pump either. If there is natural gas, it runs, making its own electricity for the control circuits using a thermopile in the pilot-light flame.

If the requirement is dead-quiet dependability, this 110-year-old system, converted from coal to natural gas early in the last century, beats every "modern" heating system hands down. It has required no significant maintenance of any sort in at least 30 years.

... Marc