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Thread: burner pressure 5" vs 3.5"

  1. #1
    DIY Junior Member
    Join Date
    Jan 2010

    Default burner pressure 5" vs 3.5"

    Hello all,

    I am trying to find a replacement for a Robert Shaw R110RTSP that has failed. Lowes carries the updated version of that thermostat but it has a main burner pressure of 5". My old failed unit is 3.5". The exact replacement is via the net and over $200. The one at Lowes is $60
    My question is can I use this new t-stat safely on my water heater? ...or am I totaly out of the ballpark? anyone, anyone.....Bueller?
    Thanks much!
    stinking and greasy in MI
    Last edited by cajar; 01-26-2010 at 12:04 PM.

  2. #2
    DIY Junior Member stas4j's Avatar
    Join Date
    Jan 2010
    Houston, TX


    I had exactly same question on this forum (with no answer). You can still see my thread on the main page of the tanks heater forum. Supposedly you can change main burner pressure from 5" to 3.5" but you need to connect a manometer to the pressure tap near the main burner tube. I would guess the valve will work even without adjustment but I don't know how efficient it will be in turms of burning the gas at the right rate. I myself ended up purchasing exact same replacement for $80 from online retailer (I am not sure if I am allowed to post the link here, but I can send a PM to you if you want). It turns out that these valves are of very poor quality, they all leak gas from under the gas control dial. Also with the new valve that I replaced the water temperature depends on the ambient air temperature - if it is cold in the garage, the water is hot. If it is warm in the garage, the water temperature drops. I do not know why.

    I think White Rogers thermostat may be the better alternative to Robert Shaw / Unitrol.


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