Vaporstat Wiring

Nick_37

I am about to replace my defunct Pressuretrol with a Honeywell

Vaporstat L408J1009. I checked the wiring diagram in the manual and it

says that I need three wires (R W B) for this model and I currently

only have two wires connecting the old PA404A. Will this be an issue

for the installation?







I'm just a homeowner following the advice on the site - hence the new vaporstat - so any help is appreciated.

4Barrel

make/break

the three connections on your new vaporstat allow for make/break switching. your only interested in the connection being completed on pressure rise to set point, so connect your old pressuretrol leads to the R & B terminals and you'll be fine. the diagram on page 6 of your L408J instructions is helpful to study...

Nick_37

Circuit

Thanks 4Barrel. I was studying pages 5 and 6 in the manual which seemed confusing because of the W connection. I will connect only the R and B as instructed. When would the W connection come into play?

4Barrel

R-W connection

i was confused about that as well. the r-w connection "makes" when you above the set point, so there could be some purpose to it, but that is past my level of expertise. for the purposes of simple pressure limit, the b-r (or r-b, doesn't matter) is all you need. most posts on this wall say to set vaporstat upper limit to 12 oz, and differential to 8 oz. you might want to search older posts for more advice on this point. if you don;t have one, a low pressure gauge is handy as well. lots of posts here on how to pipe one in to your set up.

Nick_37

Gauge

I have the 0-3 psi already successfully installed. I was pretty sure the Pressuretrol wasn't working properly but couldn't be sure until I had the gauge installed (the other gauge was completely fried). Now I know the boiler is overshooting and not cutting out hence the install of the Vaporstat.

Alan (California Radiant) Forbes

R-W

Many manufacturers will make their controls a little more sophisticated by providing single pole, double throw (SPDT) switching.  In this case, the R-W connection could turn on an alarm or turn on a light on a remote control board to tell an operator that the boiler was steaming.

4Barrel

double throw

alan - totally off topic here, but since you mention double throw - i'm having a doozy of time with an iso relay that was recommended to use for my LWCO icw my electronic t-stat. it called for a "single throw, normally open" relay (as simple as you can get, right?). PEX sent me a DPDT. now i'm only using one pole, but the DP switching is causing my t-stat to lose power when the t-stat calls for heat. any thoughts on how to wire a DT so it works more like a ST, and i maintain power at all times to the t-stat?

Alan (California Radiant) Forbes

Post

it as a new topic in "The Main Wall" forum (the other forums don't get as much traffic).I don't have time to wrap my head around it right now; I'm just between jobs.

4Barrel

will do, thanks!

will do, thanks!