testing a standing pilot soleniod valve with a AA battery?

[clothe]

how can you test a standing pilot soleniod valve in a honeywell combination gas valve if you don't use a thermocouple? normally, you would use a thermocoulple to send 30 millivolt to the standing pilot soleniod valve to allow gas to flow to the standing pilot. My question is: can you use a AA battery to test a standing pilot soleniod valve without causing damage to the gas valve or yourself? is there a better way? please help. new at this.

frank

[Profiler]

AA seems like it would be too powerfull when the pilot uses millivolts to hold it open.

[clothe]

you're absolutely right. i wonder if there is another way.

[amickracing]

AA battery and some resistors?

[clothe]

how many and what size?

[Profiler]

AA batteries + some resistors = too much work. Maybe if you've got some free time you could invent a new tool for testing the pilot solenoid.

[clothe]

im surprise. you would think that there would be something out there are ready.

[amickracing]

AA batteries + some resistors = too much work. Maybe if you've got some free time you could invent a new tool for testing the pilot solenoid.

Oh come on now?! How long have you been around here? You know sometimes we make stuff that has no real purpose, and if you pay yourself for your time would be too expensive to be practical, but where's the fun in that.

And... I have no idea how many and what size...

[hvaclover]

Does size really matter?:rolleyes:


Now I have a case of PILOT ENVY. Thanks a bunch:mad:

[clothe]

it would be a nice thing to have, i think. if you ran out of thermocouples and don't have the time to run to a supply house because it's late. you can't decide if it's the thermocouple or the gas valve. sure you can test the voltage coming out of the thermocouple, but you want to be 100% sure it's the gas valve. maybe i'm reading to much into it. like i said i'm new at this.

[ch4man]

http://cgproducts.johnsoncontrols.com/MET_PDF/121310.PDF

[WhoIsThat?]

how can you test a standing pilot soleniod valve in a honeywell combination gas valve if you don't use a thermocouple? normally, you would use a thermocoulple to send 30 millivolt to the standing pilot soleniod valve to allow gas to flow to the standing pilot. My question is: can you use a AA battery to test a standing pilot soleniod valve without causing damage to the gas valve or yourself? is there a better way? please help. new at this.

frank

The short circuit current of an AA cell could be 1.5/0.1 = 15A. It depends on the cell internal resistance. A 9v battery might deliver 0.1A. Nicads can deliver enormous short circuit current.

How much current does the solenoid take, or what is its resistance? If it's
1 Ω
10 Ω
100 Ω
@30mV
then you need a resistor in series with the 1.5v battery of value
51 Ω
510 Ω
5.1k Ω
available from Radio Crap or www.hosfelt.com.

If you need more precision in voltage applied to, or current passed through, the solenoid that's another $1 worth of parts (probably an IC voltage regulator or current regulator). You may also want to add a battery test light so you know you're working with a good battery, but if you temporarily borrow the battery from another piece of test equipment, then it can check if the battery is good.

You have a link to the specs for one of these solenoids for current and/or resistance? Pass/fail specs would be good, too.

Ohm's law!

[rich pickering]

Just to confuse he issue, ever had a tcouple read good, but the valve won't open? Changed the valve and it still won't work?

I've got a couple of tcouples on my desk that will put out 28 mv, but the tips are burnt off. I'm assuming there is not enough current being produced.

[ch4man]

open reading ( measurement taken with pilot on, t/c not connected) will tell you how good the pilot flame is.

closed reading (mesured with a t/c test adaptor) will tell you how strong the t/c is.

drop out test tells how strong the safty magent is.

do the closed reading both with the main flame on and off to check for the cold junction getting too hot

[clothe]

thanks. i'm actually thinking of buying it.

[WhoIsThat?]

that will put out 28 mv, but the tips are burnt off. I'm assuming there is not enough current being produced.
This kind of says that TCs can fail by getting a high internal resistance, while still having a satisfactory open circuit voltage.

What is the voltage when this TC is connected to a valve?
What is the valve solenoid resistance in that case?

Finding electrical specs on these components is very difficult.

[clothe]

thank you for info. i quess i will going to radio shack today.

[corny]

If you cant determine which piece of equipment in a standing pilot system is bad without a battery and resistor then you dont need to be working on the system.

If you show up at someones house or business and you need to parts change the thermocouple to find out of the existing one is bad....then you need to politely excuse yourself while you go to the supply house and get a part that you really should already have on your truck....

Dont encourage people to use a battery to test a safety magnet because the next thing you know....someone with no common sense is going to leave that battery on overnight...or just for an hour or so and they are going to eliminate the most important part of the pilot safety system.

[WhoIsThat?]

If you cant determine which piece of equipment in a standing pilot system is bad without a battery and resistor then you dont need to be working on the system.

If you show up at someones house or business and you need to parts change the thermocouple to find out of the existing one is bad....then you need to politely excuse yourself while you go to the supply house and get a part that you really should already have on your truck....

Dont encourage people to use a battery to test a safety magnet because the next thing you know....someone with no common sense is going to leave that battery on overnight...or just for an hour or so and they are going to eliminate the most important part of the pilot safety system.

Troubleshooting by parts changout vs. troubleshooting by independent test.
:confused:

[clothe]

just trying to learn more. i don 't think i would actually test a gas valve with resistors and a battey. or would I. no i wouldn't.

[WhoIsThat?]

Anyone got e-mail addresses for OEMs for technical questions on tcs and gas valves?
Their websites fall a bit short for this type thing, I don't like being put on hold for 0.7 hr.
:confused:

[corny]

Troubleshooting by parts changout vs. troubleshooting by independent test.
:confused:

You are doing an independent test.....you are checking the magnet and valve...to save a trip...but you are using a battery and not the right component for the sytem.

There is a reason why manufacturers dont recommened this one....and why they dont sell a rig to get the battery into the circuit..... And this isnt the first time this has been discussed....and there is a reason why you dont have old timers out there with homemade test rigs...

Its just something you shouldnt be doing to a customers piece of equipment....

If you have to make two trips to the supply house...first to get a thermocouple that is bad and then later to get a valve or magnet that is also bad then you can professionally explain to the customer why they are paying for two trips....

But the simple fact is that it is going to usually be the t couple OR the magnet OR the valve itself... and a combination of problems... so if you have a bad t couple....that is most likely going to be the only problem at the valve...

Customer sees you hooking that battery up to their valve to test it and some of them will be blaming every problem down the road on that......

You start telling folks about your new test idea and some dumbass is going to try and leave one in circuit for an extended amount of time......and this is one stupid idea as you have basically bypassed the primary safety on the equipment...... yes the battery will eventually wear down.... but if that furnace is running with a bypassed safety even long enough for you to run to the truck for a part...you have entered into a dangerous situation....

If you want a test rig ....buy yourself a couple of thermocouples and throw them in with your test adapter.... buy two long ones that can be used on a variety of equipment.... at least you are testing the valve and safety magnet with the proper "tool" instead of something that nobody in an official capacity has ever recommened.

[rich pickering]

This kind of says that TCs can fail by getting a high internal resistance, while still having a satisfactory open circuit voltage.

What is the voltage when this TC is connected to a valve?
What is the valve solenoid resistance in that case?

Finding electrical specs on these components is very difficult.

Don't remember readings. Bottom line is, pilot won't stay lit, check voltages, change the t-couple. Still won't stay lit, double check readings, make sure you have a good flame. Got a good reading, good flame and a new t-couple and it still won't stay lit, change the valve. You can usually change the t-couple quicker than you can take all the readings. And if you need to change the valve, might as well change the t-couple at the same time.

Probably 90% of the time, you can overthink problems with a 24v valve. mV valve problems are a whole different beast.

[WhoIsThat?]

A Robertshaw reference on thermopile operated valves (750mv) indicates the resistance of the valve coil at about 11 ohms.
I take this to mean it takes 750/11 ~ 75 mA to move a valve armature. The force is proportional to amps through the coil x number of coil turns.

Using the same 75 mA with 30 mV comes in at 1/2 Ω resistance. An alkaline AA cell has 0.2 Ω internal impedance, so an AA cell puts 1.5/(0.2 + 0.5) = 2A into a 75 mA coil. This is 700x the normal coil power dissipation.

If you want 4 mV into a 0.5Ω coil you'd need a 180Ω, 2w resistor in series with the 1.5v battery. The resistor will get warm.

As mentioned upstream in this thread, I'd also use, as a first choice, known-good thermocouples to test valves [providing there is no way for a bad solenoid to ruin a good thermocouple].

Supposedly "Baso"
http://www.baso.com/
make testers where you can dial up the mV you want.

You could also use a milliohmmeter or microohmmeter, with Kelvin clips, to measure these coils.

A millivoltmeter would also come in handy, or some device that converts commonly available DVMs into millivolt or microvolt meters. This would be a battery operated DC amplifier with a 10x or 100x voltage gain. Parts cost, $10. I design, you build and test.

If your situation makes no sense, it means you are assuming something that isn't true. Figuring out what the faulty assumption is can be really hard work. All of us make hundreds of assumptions every day without even knowing it, and usually the assumptions that adults make are true, usually.

[condenseddave]

I have an ancient tester made by Honeywell that tests thermocouples and thermopiles. I think I posted a pic of it here about 110 years ago.
I don't carry it anymore, as I RARELY see anything with a thermocouple or thermopile, but I'd recommend anyone that does work on standing pilot systems get a tester for them, with the necessary adapters. It really makes life simpler.