Why do I have 2 pressuretrol setups on my steam heat boiler?

JJ_4

I'm a homeowner. My house was a commercial building to start with and has two "regular" pressuretrols. A boiler tech once told me that the city required two in commercial buildigs for redundancy. Maybe that is the case here?

The Jeff Next Door

Why do I have 2 pressuretrol setups on my steam heat boiler?

I've read the book "We Got Steam Heat" and it has been a great help - my wife is the president of our building association, a 12-unit renovated in the 80's with gas-powered steam heat. I've learned to identify a lot of what is going on with the system based on my reading, but can't figure out why the boiler has 2 pressuretrol setups. Any ideas? One is on the front, connected to the gas cutoff, and the other is on the back, near the emergency release valve.

I'm including links to photos to make it clearer. Any help would be appreciated!

http://www.flickr.com/photos/jrwelch_nh/2433150664/
http://www.flickr.com/photos/jrwelch_nh/2432336757/
http://www.flickr.com/photos/jrwelch_nh/2433151092/

Steamhead (in transit)

The one on the right

has a manual reset, so if it trips someone has to go down there and push the button on top. This way, you know something went wrong and can call for service.

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The Jeff Next Door

The one on the right

I understand that's why there are 2 pressuretrols on the front, but I have 4 total - 2 on the front and 2 on top in the back (as per the photos).

nicholas bonham-carter

why 2 pressuretrols??

thats looks like a peerless 211a like mine,maybe about 1 mil btu?
does it have the "mod-u-pack" 2,or 3 stage burner?
if so it may have been added later and came as a kit with 2 more pressuretrols.i don't know why the extra pair would not have been mounted where the original was,except for one thing.i have suspected that the standard peerless mounting point has a large mass of water between the steam chest and the pressuretrol which may make it difficult for the control to "feel" the few ounces of pressure i am trying to maintain.
if you are lucky enough to have the staged burner installed you may get better control by putting those pressuretrols on one pigtail and a tee so they are each "on the same page".better yet replace the pressuretrols with 0---16 ounce vaporstats and
cut the full burner out at 2 oz.,then the low stage continues until 12 oz.this imitates the old coal fire which starts out hot and then drops to a simmer while every body sleeps , with just enough steam to fill the radiators.
i also suggest you buy the lost art of steam heating by the esteamed host of this site,and also a sensitive pressure gauge reading in ounces from gaugestore.com so you know what your real pressure is.
once you get eveything working right in a steam system you can feel sorry for lesser mortals who do not enjoy such a primally satisfying method of heat.
good luck--nbc

Boiling Point

Pressure Controls

Looking at the pictures, the two on top appear to be the operating and manual reset pressure controls. As for the two on the front, perhaps one is for modulation(the right one) and the left for a outside weather head (i.e. Heat Timer or Fuel Watchman)