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Robert Shaw gas valve

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Stokehold
Stokehold Member Posts: 43
Came across something a little unusual.
I replaced the gas valve on my brother in law's Miller Nordyne furnace with the direct replacement, a Robert Shaw 7200 DERC. He was having an intermittent leakage problem.
A couple seconds after firing, the unit shut down. It was similar to a bad flame sensor. I believe the flame sensor is part of the igniter on these models (part no. 902661). Several attempts, several fails
I figured it was possible for another part to fail coincidentally, but decided to reinstall the old gas valve and the furnace operated just fine.
What happened here? Maybe the solenoid (24v) is bad or too high resistance causing the burner control to shut down?
In any case, I am waiting for a replacement.
By the way, gas pressure in and out was OK.

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  • HVACNUT
    HVACNUT Member Posts: 5,865
    edited March 2017
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    Did you have to remove the gas train to replace the valve? All grounds are connected? Do all burners ignite?
    Is it Natural gas or LP? Conversion kit?
    What are your lockup and manifold pressures?
    What's intermittent leakage? From the old gas valve? That doesn't make sense.
  • Stokehold
    Stokehold Member Posts: 43
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    His LP gas company discovered the leak and said it was the valve. Apparently, this has been known to happen as valves age.
    Anyway, they did not red tag the unit because after running a cycle, the leak stopped. Obviously, they advised immediate replacement of the valve. The gas, although a small amount, was accumulating in the manifold/combustion chamber and clearing when the air induction came on.
    The in pressure is 11.0" and the out is 10.0" on both the old and new valves.
    They are both convertible and accomplished simply by flipping a stem on the regulator.
    The solenoid is 24.0 Volt at .35 Amp on the new valve. I neglected to check the amp rating on the old valve, but it shouldn't make any difference because this is a Nordyne replacement.
    Again, it behaves exactly like a bad flame sensor. However, the old valve works.
    I was thinking that if the new valve solenoid was defective and the resistance too high, the Honeywell control would lock out.
    I have returned the valve and am waiting for a replacement and am curious what I should consider if the problem should reoccur.