purge, what is it? post and pre

ted_2

what is it ? postpurge and preurge

Gary Fereday

purge ?

pre purge generally relates to letting the air out of a fuel line. and post purge usually relates to allowing the air out of a existing water line, could be pre purge if it were the first time the water was introduced.

Paul Cooke

The way I see it

What you are describing is what happens when a bunch of guys get together and wind up having too much to drink. This kind of human behavior usually ends during late adolescence, but in some breeds it persists well into middle age.

Feel free to ask this question again when Timmie and the others return from the Gathering.

-Fluffy

Doug Lee

purge

pre-purge is the cycle the burner goes through before the burner lights to prove system safties and purge out the combustion chamber. post-purge comes at the end of the burner cycle to purge out the combustion chamber before the fan shuts off. hope this helps.
Doug.

J.C.A.

Give Doug a cigar !

Prior to these phases in burning oil , it was the main reason for a unit producing almost all of the "soot" that GAVE (notice the word, GAVE) it the reputation for being a "dirty fuel " . With the advent of pre/post purge controls and valves, the cleaniness factors are getting closer to any fuel to fire heating appliances .

By the way , I tried to talk my old company into doing a delayed oil valve on any install of any kind , but was always shut down due to it adding a few more dollars to the overall cost . Hindsight being 20/20 , I should have been WAY MORE insistant on this .I believe it would have saved many oil co's, many customers from switching to an alternative fuel . Good explanation Doug . Chris

newlove

post purge question

JCA--What would be a rule of thumb for duration of
post purge?

J.C.A.

Newlove...

Some are controlled by a push of the button , (like some of the newer Honeywell controls ) and some are factory set (like the CCT controll , which can be ordered with any time for either pre or post timing you desire . I had one made with a 30 second prepurge and a 2 minute postpurge for a special situation .) I believe that the CCT 60200-02 comes standard as a 15 second pre and a 15 second postpurge set up . I haven't spent a whole lot of time with the Honeywell 7184 , but understand it is field programmable . Set it up the way and times that you want or need ,by the manual. I think the times will be different for different situations . How far is the appliance from the chimney ? Does the natural draft work when the burner isn't firing ? Is there a power venter with its own post purge timing relay ?

It sounded like an easy question to answer didn't it ? The variables change for every different heater .I find that having serviced the account for a while and knowing the charictaristics of the use of the appliance seem to determine the timing for me . Hope this helped . Chris .

newlove

Post purge question # 2

JCA thank you.
I HAVE 2 AFG with co & smoke on shutdown.Useing 30sec post
purge the co & smoke is greatly reduced.Is this caused by
lower nozzle tem or what? Thanks again newlove.

J.C.A.

Positive...

Positive electrical shut off for the fuel pump and enough air to get the remaining "stuff " burnt or vented out .
The pre purge acomplishes its magic by getting the pump up to speed BEFORE letting the fuel fly , thereby establishing and stabilizing a draft , and believe it or not , the time the fuel spends in the fuel unit getting "beat up" also helps to get it just a little bit warmer and again making it a little easier to ingnite and /or burn as clean as the oil that was in the assembly . A little electric valve, with the proper circutry to hold the motor going for just a little longer did all that ! (Most of the controls set up for post purge will require a second "Live wire" , after the service swicth independant from the high limit, and to the wire marked motor. The motor wire FROM the control will be dedicated to JUST the motor , not the motor/transformer and ignighter) Hope I helped more than confused. Chris