Gas Pressure Manometer Installation

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bananaboy22

#1: Post by bananaboy22 »

Hey there, Im looking for some direction on installing a gas pressure manometer/gauge on my old San Franciscan 25lb roaster.

Ive had a plumber install a gauge (reading 0-10 Inches Water Column, the smallest range of gauge I could find) by tapping the burner manifold and connecting the gauge with a small section of pipe.

However, when the gas valve is opened and the burners light and are taken to the maximum setting, the needle on the gauge moves to not even .5 IWC. My plumber explained that this makes sense, because as the burners open the pressure will drop, because gas is coming out. This is not enough range to make tracking gas adjustments useful.

So I'm wondering how anyone else has installed a gas manometer in a roaster that didn't come with one, and how they achieved a sufficient range of readings. Thanks

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Chert

#2: Post by Chert »

Do you know what pressure is delivered to your control valve? in a small home unit, a gas regulator, preferably two stage, brings gas pressure to 11 inches water column. But your much higher BTU device, must need more than 11 inches gas pressure to work. My 500 g roaster sees 5 inches at my highest setting.

I will ponder your question out of interest. And learn along with you or maybe offer an answer.
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Brewzologist
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#3: Post by Brewzologist »

I use propane on a small roaster with gauges on either side of the valve. I typically run 6kPa (~25" wc) pressure into the valve and a max of 5kPa (~20" wc) after the valve. I don't know natural gas or the SF-25 but would think it would use a lot more than 10" wc ?! FYI; once I over-pressured my gauges, damaging them irreparably and they didn't ready correctly. Hopefully that's not the case with your new gauge.

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Chert

#4: Post by Chert »

bananaboy22 wrote:
Ive had a plumber install a gauge (reading 0-10 Inches Water Column, the smallest range of gauge I could find) by tapping the burner manifold and connecting the gauge with a small section of pipe.s
Can you show an image of this?

In my little roaster, a nozzle of a submilimeter orifice sprays gas into the burner. I can measure gas pressure at a point beyond my 11 inch pressure regulator and after my control valve but before the little orifice. If your manifold is just a tube with no flow limiting orifice, you would need a very sensitive low pressure gauge. Perhaps you could install an orifice to target the highest flow you need at the intake pressure of your gas regulator and place that in-line before the manifold, a pressure gauge of an appropriate range between that orifice and your control valve.

It might be simpler to change your control valve to one that turns one full turn between max and closed. You could graduate that to track your gas settings without use of a pressure gauge.
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