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Posted by Mark P. LeGassey on August 11, 2008 at 19:10:50:
In Reply to: Re: Pressuretrol pigtail clogging posted by HeatPro on August 11, 2008 at 11:20:18:
can you explain the 1 to 1.5 subtractive differential. i see on thr pressuretrol the psi scale and how to adjust this value with the screw setting. i don't understand the subtractive differential. As far as a blowdown is concerned i am not sure what this is. i keep a supply of hercules boiler additive in the boiler at all times this has helped alot. can explain a blowdown and how to do it. thanks for your help.
: The elbow shouldn't impede the reading.
: However, you seem to be getting a lot of floating crud up into the pigtail, you might need a thorough blowdown more often.
: Residential one-pipe systems are designed about 1 psig, so ordinary settings are 2 to 2-1/2 psig with a 1 to 1.5 subtractive differential. There are additive-differential controls, so become familiar with what you have, read the instructions for it on the web before fooling with it. The lowest you can get it without causing problems is the best.
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