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# A & B Dimension

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Member Posts: 1
Having a discussion with a co-worker, need a definitive statement about the location and application for the A & B dimension on 2 pipe LP steam. I have Dan's books - but they are buried in the basement. Thanks, Glen (Stay safe)

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Assuming gravity return. "B" dimension is 30" for 1# steam pressure.

"A" dimension is 28" for 1 psi steam.

The difference is on one pipe you have steam pressure to help put condensate back in the boiler. On two pipe after the traps you do not have steam pressure to help push the condensate you only have gravity.

if you run higher pressure you have to increase these dimensions
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>>On two pipe after the traps you do not have steam pressure to help push the condensate you only have gravity.<<
Folks who should know better often talk about higher pressure "blowing through trap". Cannot convince to lower pressure.
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Thanks - appreciate the response.
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See attachment

Jake

P.S.

The dimension B is not often seen or understood by many service techs. We know tat you need pressure from some source to put the water back into the boiler. Example, if the boiler is is set to run at 5 psi we know that you need at least 6 psi in the return line to put the water back into boiler so in this case dimension B will be 5 times 2.3 equals 11.5 feet.

in many building there is not enough height for an 11.5 foot dimension B therefore a condensate pump will be needed to return the condensate to the boiler.

• Member Posts: 2,257
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See attachment

Jake

P.S.

The dimension B is not often seen or understood by many service techs. We know tat you need pressure from some source to put the water back into the boiler. Example, if the boiler is is set to run at 5 psi we know that you need at least 6 psi in the return line to put the water back into boiler so in this case dimension B will be 5 times 2.3 equals 11.5 feet.

in many building there is not enough height for an 11.5 foot dimension B therefore a condensate pump will be needed to return the condensate to the boiler.

Has anyone ever seen an injector used to overcome too little B? If boiler is over sized then why not?