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Propane solenoid equivalents that won't draw so much power when open

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I use two propane bulkhead cabin heaters.  They are light, simple and draw only an amp when in use.  Except, having two propane tanks (I have a catamaran, so two hulls to heat) means using two solenoids that each draw nearly an amp on their own.  This doubles my electrical draw for heat on a limited house bank.  I'm hesitant to eliminate the solenoid for obvious reasons but looking for another way around the problem.

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Yes, they are very power hungry. It is common in solenoid circuits to open actuate them with a pulse of full voltage and then hold them open with about half voltage. It is a characteristic of the beast. Something like an automobile start switch could accomplish this. A resistor in series with the "Run" position would lower the current. Some kind of geeky R-C circuit might work as well. Maybe somebody makes a little box that does this? Prevents the solenoids from cooking themselves to death, too.

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I don't much care for those power hungry valves either. There used to be a bistable gas solenoid valve marketed for this out of Britain, but I can't find it anymore. Here is a DYI approach from the RV business:

Quote

Peter, 
I do know what you are up to, but it would seem as though you are trying to take a very expensive and work intensive approach to a very simple problem.
Let me expound on my solution. (before everyone asks for pictures, I will need to completely disassemble my solution to take pictures so it may be a while).
What I did was to remove the solenoid coil from the LP valve exposing the stem of the valve. Inside this stem is a plunger which is activated by the electromagnet coil. I replaced the coil with a piece of 1/2" PEX tubing with two rare earth magnets glued to the outside of the PEX and an old choke cable (which I suspect most of us are old enough to remember) as the actuator which moves the PEX with magnets attached back and forth along the valve stem. I routed the choke cable to the equipment bay and put the push/pull knob near the existing LP electric switch. When I want LP off or on, I need only to push or pull the choke cable knob and it slides the PEX/magnet assembly towards or away from the LP valve stem thereby actuating or deactivating the plunger and the valve. 
The net result is that I can now leave the amp sucking LP switch in the off position and still have a convenient way to turn the LP on or off as necessary.
I will try to take the time for pictures soon if anyone wants them.

Bob

If you search for bistable gas solenoid you come up with a number of hits (it is not an uncommon configuration), for example or here. The safety issue would be that most control circuits and sniffers do not contemplate this sort of valve and would not shut off in the event of a sniffed leak. You would need to modify the controller. 

 

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The red warning lamp is a feature I would not want to eliminate.

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39 minutes ago, Rule69 said:

~~I~~ would be hesitant to hack a device intended to reduce the probability of a horrific immolation event for myself and my neighbors. However, the Google links to this interesting discussion with interesting comments and interesting example files with 12v values: http://www.electronicdesign.com/analog/what-s-all-solenoid-driver-stuff-anyhow

I suspect that for a manually switched circuit you could remove everything except the resistor and capacitor and add a high value discharge resistor to the cap. But, I could very well be mistaken and there's that whole immolation thing. How many amps is worth a point of fiery death probability?

In my usage, no sniffer, it is the red lamp that reduces the risk of immolation. So the type of circuit that energizes the immolator while also lighting the lamp does not matter much. Here is a "starting" type switch that would work (kinda pricey?). A 6 Ohm 5 Watt resistor in the ON leg might do the trick. Reduce the power by about half. YRMV.

https://www.amazon.com/Momentary-Ignition-Toggle-Switch-Terminals/dp/B00JWZ8NYO

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In that case the best solution consists of deleting the solenoid entirely and putting a toggle switch for the big red light right next to the tank valve. Turn on the valve, turn on the switch and vice-versa.

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2 hours ago, IStream said:

In that case the best solution consists of deleting the solenoid entirely and putting a toggle switch for the big red light right next to the tank valve. Turn on the valve, turn on the switch and vice-versa.

Just put the light there and never turn it on. No light, no danger, right?

More to the point, if you found a suitable bistable solenoid, you just need to build a simple little circuit for the output of the control. There are so called programmable relays that would do what is necessary with a few jumper wires. It would apply a momentary pulse to the solenoid coils when the output line changed state. There is a slightly greater chance of a failure in the open state, but not much. 

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4 hours ago, IStream said:

In that case the best solution consists of deleting the solenoid entirely and putting a toggle switch for the big red light right next to the tank valve. Turn on the valve, turn on the switch and vice-versa.

Not a bad idea. She's a big boat though. That's a long walk back there in the morning when I'm groggy and anxious for coffee. Wifey could make the trip but she is getting more and more unreliable.

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Well it's good to know that I'm not the only one who would prefer a better solution.  Thanks for the ideas.

Despite a reference by DDW regarding sniffer's that would shut down the system, my current understanding of the 'value' of the solenoid is to provide essentially a 2 valve integrity to the propane system.  Tank valve open, solenoid closed, heater valve closed.  (2 out of 3).  This permits the desired remote operation.   I do not (will not) have an integrated sniffer.  Having the solenoid adjacent to the tank, also means shutting off gas flow in the event of a leak somewhere in the line before the appliance.

Most of the valves linked are either too big or not rated for combustible gas.

I've considered a manual valve in the cabin somewhere in the supply line yet readily accessible.  Two problems are needing to cut into the hose and add new fittings or at least add a length of hose between the new valve and the appliance that keeps the valve somewhat away from the appliance.   However, I cannot find a valve that is a turning valve that can clamp down like a propane tank valve  (i.e. positively seal).  I have a 90 degree T-valve to the BBQ but it seems to leak as I must keep the BBQ regulator connected to keep from draining the tank.  Basic 90 degree valves can be inadvertently over rotated just a bit and I think this is my issue.  Anyway, I no likey.

I did try to find and price a valve with a remote actuator but it looked like I was getting up to a $500 ea  price tag, what with an indicator light/control panel etc. 

Finally, because I'm a piss poor DIY guy.  I'd like to know what the 'standard'  (hah) size and thread types are simply on the solenoid valve.  They seem to be different on each side, not simply a male/female version of the same thing. If I have to cobble something together what type threads am I looking for? Also what are the pressures, supply at the tank is around 110psi and after the reducer it's 6 or 3psi??? What is the normal flow rate capacity?  ( I sometimes run the heater, the BBQ and a stove burner or two simultaneously.

 

 

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On the high side you need something for about 200 psi or more. I think propane can get up to 160 or so if the tank gets nice and warm. After the regulator the spec is around 10" of water, that's around 0.5 psi. Flow rate on the high side almost any flow will feed a huge fire 'cause the gas is high pressure and dense. It expands many times through the regulator and now flow rate is an issue. Keep in mind that pressure drop due to flow in pipes is the fourth power of diameter so a very small difference in diameter matters. 

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Might sound crazy, but if you have a 120 Volt PSW inverter you can get a 120 x 24 VAC transformer (door bell transformer would work, but a small $50 control power transformer would be better, there are some plug in ones for $15 to $20).  Then, get a 24VAC Solenoid valves.  Actually I bet you can just replace the coils on your existing valves.  Using AC gives you the advantage of inductive reactance.  When the valves close the air gap decreases which increases X_L and dramatically decreases current.  With DC there is no such thing and the resistance of the wire rules the day.  24VAC coils are extremely common in HVAC and industrial applications for this reason.

I have some little solenoids and inverters laying around, maybe I'll do an experiment today.   With a small inverter this might actually be less than 2 amps.  Do NOT try this with a MSW inverter.   

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I take it you have a tank for each hull and each tank has it's own solenoid valve? Some more options:

1. pull/push cable attached to a manual ball valve in the propane tank compartment. Not sure that the actual sleeve for the cable is gas tight. But no power requirement at all.

2. Eliminate one solenoid by teeing into 1 tank connection downstream of the solenoid valve (we had a cat and that is how we fed a heater in one hull and stove in other hull. Just need a longer hose from hull #1 to hull #2.

3. Inlets/outlets can be 1/4" and 3/8" NPT. Some valves have 1 size in and 1 size out that are different. No real standard.

4. This sort of thing for a magnetically actuated latching valve. This one is only for water, not gas however

https://www.amazon.com/dp/B00WAIO34E?psc=1

5. Motorized ball valve. Didn't know you could get them for so cheap!

https://www.amazon.com/Motorized-Valve-Stainless-U-S-Solid/dp/B06WWPZWGZ/ref=pd_day0_328_8?_encoding=UTF8&pd_rd_i=B06WWPZWGZ&pd_rd_r=PTK8Y4SCFVK926NJ3T94&pd_rd_w=eXzBu&pd_rd_wg=Mk2Ei&psc=1&refRID=PTK8Y4SCFVK926NJ3T94

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14 hours ago, jason128 said:

Bep marine make a valve and controller with built in gas sensor  that uses .2 a

 

My BEP gas detector / controller is a poorly constructed PIA. YMMV.  Also, you still get the solenoid current draw when the gas is on. I've never run the LP long enough for that to be an issue but the OP is looking at two times lots of hours. 

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Quote

 

No you are wrong on the current draw.

The bep one one uses a cleaver trick of doing a 1a pulse, then 0.2a to hold the solenoid.

i only know this as I made the mistake of replacing the rusted solenoid with another brand, and had issues.

the controller with built in detector is 12 years old  and runs fine. I’m surprised yours is poor quality, I always saw them as expensive but good quality

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1 hour ago, jason128 said:

No you are wrong on the current draw.

The bep one one uses a cleaver trick of doing a 1a pulse, then 0.2a to hold the solenoid.

i only know this as I made the mistake of replacing the rusted solenoid with another brand, and had issues.

the controller with built in detector is 12 years old  and runs fine. I’m surprised yours is poor quality, I always saw them as expensive but good quality

I could be wrong on the current draw, I haven't measured it. I've got a BEP Contour GD-L. It doesn't say anything about pulsing the solenoid in the manual. It claims that total current is 350mA max and it's on a 2 amp fuse. I have replaced the solenoid without any problems. My particular BEP controller is poorly constructed and gives lots of nuisance alarms. Sample size of one and all.

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There is a device that lowers the power of the propane Solenoid valve using a DC to DC converter to provide a regulated voltage to the solenoid. Search for Propane Solenoid Valve power reduction device on eBay.

John

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On 10/13/2017 at 6:34 PM, jason128 said:

No you are wrong on the current draw.

The bep one one uses a cleaver trick of doing a 1a pulse, then 0.2a to hold the solenoid.

i only know this as I made the mistake of replacing the rusted solenoid with another brand, and had issues.

the controller with built in detector is 12 years old  and runs fine. I’m surprised yours is poor quality, I always saw them as expensive but good quality

The current drawn on activation will be higher than the current when the solenoid is in its energized position.

That's just in the nature of the initial load, which will be about 5+ times the normal load.

The same thing happens when a motor starts, the current will be 5+ times the running load.

That's why motors cook if they can't spin.  Similarly, solenoids that are prevented from fully engaging (opening in this case), also cook.

Replacing a coil in a cooked solenoid without freeing the mechanism will cook another coil.

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A latching relay is a solution to your problem but it will take some fiddling to make it compatible with an automatic cut-off system.

Latching relays have a mechanical latch which will hold the solenoid in its activated (in this case, open) position, so that it just takes a momentary pulse to activate it, then it pulls no current until another pulse is sent to deactivate it.  That may require an extra wire, a two-way centre-off switch or diodes to function, or you may find a latching relay that will activate with a momentary pulse and deactivate with a second pulse.

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Harry,

You're mistaken on both counts.

Latching relays are great, but this isn't a relay application, it's a solenoid operated valve.

While there is inrush current in a solenoid, that's not what's Jason was discussing. Jason was talking about a controller that applies a full voltage in order to actuate the valve and then pulse width modulates that voltage in order to hold the valve open. This works because once the valve plunger moves, it takes substantially less magnetic force to keep the plunger in the open position.

These things are generally marketed as Solenoid  or Coil Economizers. There's a good app note on the last two pages of this pdf.

 

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8 hours ago, harrygee said:

A latching relay is a solution to your problem but it will take some fiddling to make it compatible with an automatic cut-off system.

Latching relays have a mechanical latch which will hold the solenoid in its activated (in this case, open) position, so that it just takes a momentary pulse to activate it, then it pulls no current until another pulse is sent to deactivate it.  That may require an extra wire, a two-way centre-off switch or diodes to function, or you may find a latching relay that will activate with a momentary pulse and deactivate with a second pulse.

A latching solenoid defeats much of the purpose of having a solenoid at all, which is to have the propane system safed unless actively powered.

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Thanks, that's new to me.

I haven't come across a system that reduces the current when the solenoid is in the open position but I can see the benefit.

This place is an education.

Cheers

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This might be what you are looking for-if it can support your inrush current for your particular valve-hit and hold circuit, unlike latching the NC function should not be impaired.  I imagine other people make similar circuits or you could build your own also.

https://chromspec.com/pdf/e/bf04.pdf

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On 6/5/2018 at 6:00 PM, harrygee said:

The current drawn on activation will be higher than the current when the solenoid is in its energized position.

That's just in the nature of the initial load, which will be about 5+ times the normal load.

The same thing happens when a motor starts, the current will be 5+ times the running load.

That's why motors cook if they can't spin.  Similarly, solenoids that are prevented from fully engaging (opening in this case), also cook.

Replacing a coil in a cooked solenoid without freeing the mechanism will cook another coil.

 Yep completely agree with all you are saying.

i found out the hard way the bep system does a lower hold current- I was too cheap to buy the bep replacement solenoid - and the replacement needed more current hold than the bep unit would supply.  The gas would flow for just long enough to convince myself everything was all running- then stop as soon as I tried to have a coffee.

so some other sucker does not fall into the same tramp- this is from bep 

The 600-GDL has a "pulse and hold" feature which allows the solinoid valve to to be opened, using full power, and then reducing power to hold the valve in the open position. This reduces power consumption and heat generated whilst the valve is in the on position.

 

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I just read my earlier post, something I should have done before posting it.

I meant 'latching solenoid".  A relay would be no good to you, as a couple of posts have pointed out.

I don't know if latching solenoids are available to suit propane.  They're used in applications subject to violent shocks and, probably, many other applications.

The issue of being incompatible with an automatic, fail-safe cutoff system remains.  You'd have to have an audible / visual gas alarm  and switch off manually.

There's a lot to be said for keep-it-simple so the recommendations to try a mechanical cable / linkage system might be the go.

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Solenoids use electromagnets.  Electromagnets use coils which are low resistance and draw a lot of current.  What is needed is a solenoid that stays open by electrostatic rather than magnetic force.  There aren't any that I can find. 

A good second best would be a circuit that uses an electromagnet to open the valve, then cuts off the current to the electromagnet.  The valve is held open using a permanent magnet.  If the user selects close, or If power is lost, a second circuit with stored charge (eg. in a capacitor) is triggered to drive the current in the electromagnet the opposite way,  closing the valve.  The valve is held closed by a second permanent magnet.  Not 100% fool proof but better than nothing.  

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21 minutes ago, dash34 said:

Solenoids use electromagnets.  Electromagnets use coils which are low resistance and draw a lot of current.  What is needed is a solenoid that stays open by electrostatic rather than magnetic force.  There aren't any that I can find. 

A good second best would be a circuit that uses an electromagnet to open the valve, then cuts off the current to the electromagnet.  The valve is held open using a permanent magnet.  If the user selects close, or If power is lost, a second circuit with stored charge (eg. in a capacitor) is triggered to drive the current in the electromagnet the opposite way,  closing the valve.  The valve is held closed by a second permanent magnet.  Not 100% fool proof but better than nothing.  

You're describing a latching solenoid.

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I think it would be neat, if someone made a Morse control cable operated valve.  Something with a control arm on it, and a guide for the cable all mounted together.  May have to do some studying. 

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4 hours ago, Zach said:

I think it would be neat, if someone made a Morse control cable operated valve.  Something with a control arm on it, and a guide for the cable all mounted together.  May have to do some studying. 

Seems to me that you get all the complexity with fewer benefits but whatever. You could glue a magnet on to your cable, remove the coil from your solinoid, and fasten the lot together so that the magnet actuates the valve. Or you could walk over to the bottle and use the attached valve. 

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