Pressuretrol pigtail issue and upgrading Pressuretrols to Vaporstats

sreja

Ok guys, got a tricky one for you here -- it involves pigtails or the lack thereof.



We have a stream boiler for a condo that I'm trying to get to run a lower psi.



It's a Peerless boiler is about 4 years old and runs well, it has a multi-stage (mod-u-pak) controller system that uses 4 separate pressuretrols (see image), to regulate gas burner anywhere from 50% to 100% burn rate.



So I have two basic questions:



One, I'm thinking we might try to move to vaporstats; i was thinking i might leave the high cutoff pressuretrol alone, and maybe the main operating range pressuretrol alone, since those can be set to pretty high end of the range (high cuttoff at like 5 psi, and main operating range between 1 and 4 psi for example).



And then use vaportstats to adjust firing between 50-100% when it is in the 1-psi range to try to keep the pressure stable. I suppose replacing the main operating range pressuretrol with a vaporstat that goes up to 5psi wouldnt be a terrible idea either.



Not sure if the pressure gauge should be replaced too - current one goes -30 to 30psi?



So my FIRST question is, any suggestions about the above that i might be overlooking?



--



Now my SECOND question is trickier, it involves the need for a pigtail.



I *believe* that the top two pressuretrols have stopped working (or working well); i used to be able to adjust the ranges so that they kicked in, and now they seem to either not work at all or work very sporadically -- most of the time acting like they see no pressure at all -- and seeming to kick on only randomly and when tapped hard.



So here is my theory:



I understand the need for pigtails to protect the pressuretrols.. and i think i understand the fact that the Peerless boiler installation manual for general pressuretrol doesn't use a pigtail because the pressuretrol piping has T that dips down and then back up and ACTS LIKE A PIGTAIL. This took me a while to understand but there are posts on the Wall about this.



SO.. my theory is that when all 4 pressuretrols were hooked up in this configuration, what we have is the BOTTOM TWO pressuretrols protected by a water bubble like a pigtail, BUT THE TOP TWO pressuretrols unprotected -- thus explaining the fact that i believe they are failing.



So my question is -- do you think i'm right? are the upper two pressuretrols not protected and so need to be piped differently (either with a pigtail or piped like lower two). What about the pressure gauge? does it need to be on a pigtail or looping Tee?



Apologize for the long post -- hoping some of you experts will be able to make some sense of my questions..

nicholas bonham-carter

you're right!

look at my setup, also on a peerless 211a [sadly no mod-u-pak yet].

you definitely need to mount those devices from the lower location, but piped up high. as you can see, i have dual pigtails in addition to the main "dropped instrumentation header", but they are not absolutely necessary, and could be straight pipes. notice that i have a shelf bracket to provide some extra support, and your setup will be longer, so definitely needed.

i think that you may be able to get by with only a single vaporstat to control the switching to low fire.--nbc

BobC

Add pigtails and a low pressure gauge

The safety pressuretrol can be left as is because a vaporatat in that position would be a waste of money.



The staging pressure controls should be below 2psi, well below that for the lower two stages, there shouldn't be any reason to go above that pressure. For that you will need vaporstats for these two controllers.



If you keep that piping setup I would put the upper two on pigtails and add a spot for o low pressure gauge (2 or 3 PSI on a pigtail also). I think your right about the upper two controllers not being protected as they are now.



Bob

sreja

pigtail variations

You have a very sweet setup nicholas.



The mod-u-pak seems to me WAY overkill for a steam boiler running at very low psi; being able to switch from 0->50->75->100 just doesnt make sense when one is talking about a range from 1-3psi.



BUT, having at least one intermediate rate (50 or 75) could definitely be useful in terms of being able to keep the boiler pressure steady.



Now on your setup you really have pigtail mania -- you have the pigtails AND the low-dip Tee mount which should both be providing the same protection as a pigtail, right?  Theoretically you don't need both right? I see you also have one of your pressure gauges mounted after the pigtail -- is that just to give you extra security to know the pigtail isn't clogged? or is it to protect the low pressure gauge?



And just to make sure we are in agreement -- you agree that the two upper pressuretrols in my setup are at a high risk for damage (wheras the lower ones are in effect "pigtail" protected) is that right?

sreja

pigtail variations

Thanks Bob -- I'm feeling quite proud that i may have sussed out the fact that the upper two pressurerols are not protected.  i really wonder why peerless does not provide an installation diagram (not that i can find) of the 4 pressuretrol setup for their mod-u-pak system. [they have a 2 pressuretrol setup diagram where they are protected]

sreja

pigtail variations

nicholas,



what's the upper pipe you have on the far left side that is just capped off at top for? just in case you want to add something later? or to help clean?