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Gas Valves

Bob_15
Bob_15 Member Posts: 3
As a beginner in the service end of HVAC I can't begin to tell you how fortunate we are to have this forum.Thank you. Now on to my question-Can the difference in gas valves (redundant-100% shutoff etc.)be easily explained?

Comments

  • tim smith_2
    tim smith_2 Member Posts: 184
    gas valve questions

    Redundant valves have twin built in solenoid valves inside. This way if one solenoid or valve sticks open, the chance of both sticking is very unlikely. Extra safety! Regarding 100% shut off. This usually pertains to the ignition module. Some moduals have continuous retry, which in other words is not 100 % shut off. The ones with 100% usually will retry 3 times or so depending on type and then lock out and won't restart until power is shut off and turned back on. If I remember right, all propane equipment has to have 100% shut off and any boilers with csd 1 requirements.
  • Gas Valves

    The term redundant meaning more than one pertains to gas valves after the early 1980's up to the present being required to have two valves built into the gas valve. Usually the first valve is a solenoid and the second is a diaphragm valve. The deal on this is increased safety, as the chances of two valves sticking open versus just one is much less likely. It is not that single seated valves are unsafe it is that redundant valves are safer. All heating systems since the early 1980's have been required to have redundant valves.

    Concerning the term 100% shut off, this is also related to gas valves. In years past they made gas systems (natural gas only) that had the pilot gas fed directly to the pilot there was no pilot safety. These pilots were called "Wild Pilots" or sometimes "constant pilots". They are called non-100% shut off. If the pilot went out it would stop heating the sensing element (thermocouple, mercury sensor, bi-metal pilot) this in turn would shut of the safety or cause a magnet assembly to be de-energized and shut down. Some have a pilot safety switch built in(mercury and bi-metal pilots)(usually 24 volts) for the main burner only. There would be pilot gas escaping into the chamber. You could do this with natural gas as it is lighter than air and will rise and escape up the flue doing no harm.

    It has always been a requirement for LP gas to be 100% shut off due to LP gas having a specific gravity higher than air. It tends to accumulate and present a danger of ignition and fire.

    If you are interested I have some excellent manuals that explain all of this, e-mail me and I will send you a catalog.
  • paul lessard_2
    paul lessard_2 Member Posts: 192
    Great to have you back Tim!!

    > The term redundant meaning more than one pertains

    > to gas valves after the early 1980's up to the

    > present being required to have two valves built

    > into the gas valve. Usually the first valve is a

    > solenoid and the second is a diaphragm valve. The

    > deal on this is increased safety, as the chances

    > of two valves sticking open versus just one is

    > much less likely. It is not that single seated

    > valves are unsafe it is that redundant valves are

    > safer. All heating systems since the early 1980's

    > have been required to have redundant

    > valves.

    >

    > Concerning the term 100% shut off,

    > this is also related to gas valves. In years past

    > they made gas systems (natural gas only) that had

    > the pilot gas fed directly to the pilot there was

    > no pilot safety. These pilots were called "Wild

    > Pilots" or sometimes "constant pilots". They are

    > called non-100% shut off. If the pilot went out

    > it would stop heating the sensing element

    > (thermocouple, mercury sensor, bi-metal pilot)

    > this in turn would shut of the safety or cause a

    > magnet assembly to be de-energized and shut down.

    > Some have a pilot safety switch built in(mercury

    > and bi-metal pilots)(usually 24 volts) for the

    > main burner only. There would be pilot gas

    > escaping into the chamber. You could do this with

    > natural gas as it is lighter than air and will

    > rise and escape up the flue doing no harm.

    >

    > It

    > has always been a requirement for LP gas to be

    > 100% shut off due to LP gas having a specific

    > gravity higher than air. It tends to accumulate

    > and present a danger of ignition and fire.

    >

    > If

    > you are interested I have some excellent manuals

    > that explain all of this, e-mail me and I will

    > send you a catalog.



  • paul lessard_2
    paul lessard_2 Member Posts: 192
    Great to have you back Tim!!

    I Don't think you could live in florida..they have no conversion burners!
  • Ignition Modules

    When the mandate for shutting off pilots came in the 1970's the first modules that came out using flame rectification to prove flame and spark to light the pilot were two types lockout and non-lockout or continuous try (it would just keep sparking until it ignited), during this time the PV (pilot valve was energized all the time). All warm air furnaces and LP gas systems had to have lockout. Boilers could have it either way, most of them had a continuous try system. With lockout you had timed trial for ignition if the spark did not light the pilot in the alotted time it would go into lockout. The early versions would only try once then lockout.

    In recent years we have gone to continuous "retry" which means we will have spark for 90 seconds, 60 seconds etc depends on manufacturer of the module. If it does not light the pilot in 90 seconds it will shut off for 5 minutes then try for 90 seconds again until it lights it will do this forever. This system can be used on LP and Natural gas systems. Most of the Universal replacement modules have this feature.

    Direct Spark and Hot Surface Ignition use a different set up, they have multiple trys 2, 3, 4, 5 etc. then either "hard lockout" power has to be interrupted before it will try again.

    OR

    On a lot of systems with integrated controls we now have soft lockout. Soft lockout means that after several trys it will shut down for an hour then retry 2, 3, 4 or so trys again.

    Do not confuse Intermittent Pilot Spark Ignited Systems with Direct Burner Ignition Systems (DSI & HSI). They are two different methods of safety.
  • Hi Paul

    They have lots of gas pool heaters. Of course after repairing the technicain has to test the water. I could handle a few years of that.

    I would like to say it is good to be back but after 80 degree days and virgin "pina coladas" it is hard to do.
  • Bob_15
    Bob_15 Member Posts: 3


    Thanks for the clear answers-explained in a way I could understand-I`m sure I will have more questions in the future.
  • Alejo0623
    Alejo0623 Member Posts: 1
    Redundant Gas valves

    can you please send me whatever literature you have on these valves, thank you so much [email protected]