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Electronic Ignition / Transformer issue

I am installing an electronic ignition system to light a gas fireplace. I am using the Robertshaw 712-017 kit. For the 24V transformer I am installing a Robertshaw 620-403.

The installation manual says to check the leads from the transformer to see if one of the shows 24V power, in which case the valve wiring must be done a certain way to avoid damaging the transformer. The leads are red and green (black and white on the 120V side).

When I power up the transformer and put my meter between ground and one of the leads, I get around 1.6 on the red and 6 on the green. I was expecting either zero on both or 24 on one and zero on the other, per the installation manual

The transformer is new so it should not at fault. What am I missing or doing wrong?


  • ratio
    ratio Member Posts: 3,653
    The transformer is floating, neither of the secondaries are referenced to ground yet. You should show a nominal 24 VAC between the two secondaries (actual will likely be closer to 27 unloaded). Bond one of the secondary legs to ground, then you'll see (nominal) 24 to ground from the unbonded leg.
    REKBDR Member Posts: 39
    Thanks. Here is what I am dealing with from the installation manual:

    I am guessing that I can hook up the transformer without regard to red vs green because the transformer is dedicated to this circuit and the secondary leads don’t go anywhere except to the fireplace (I.e., no grounding). But I don’t want to damage it because I don’t know what I am doing. Still puzzled by the 1.6 and 6 readings when I test the leads, since the manual suggests that I should be getting zero.
  • mattmia2
    mattmia2 Member Posts: 9,747
    that is a miniscule amount of current flowing between the primary and secondary because of the parasitic capacitance in the transformer.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,102
    Here is something I always put on the R terminal of a transformer. (Red wire if there are no terminals) use a 3 amp fuse (Purple) to protect the gas valve and to keep from letting the smoke out of the transformer.

    I actually use a homemade version of this with crimp spade terminals and some black electricians tape.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    Ed, good advice.