Elevated pressure in steam system after asking for a 5 degree temp rise at thermostat

RossL

This is my first post, but I've been reading the forum for some time and think it's great!



<strong>Background:</strong>



I have a single pipe, gas-fired steam boiler system. Recently I replaced all my radiator vents with Varivalve heat-timers. The ones I had were all cheaply made and many were whistling &/or gurgling. I didn't know when the previous owners put them in, so I just got good new vents. I also replaced the packing material in 3 of the radiator's shutoff valves because the shutoff valves were gurgling around the stems. After doing this, I adjusted all the radiator valves to try to get even heat.



I ended up closing down most of the upstairs vents because the upstairs gets warmer in general and also the heat seemed to arrive at the rads upstairs & down at the same time that way. The vents on the largest radiators downstairs are full open. The upstairs is still warmer, but I think that's simply due to the rising heat in my small house. I can feel it going past when standing on the stairs.



Replacing the vents quieted the system down a lot. I never had hammering, and I don't now. I had some water rushing sounds, but that was because previous owners had shut-off valves half open. I opened all valves and one rad still needs a little pitch added yet to be completely free of water noise.



<strong>The issue</strong>:



I recently I was woken in the morning by the return of a shutoff valve gurgling at the stem. I went to check the boiler pressure and my 0 - 30 psi gauge read just over 3 psi. I'd never seen it that high before. I've never seen that 0 - 30 psi gauge even move when observing the boiler during a cycle.



I checked the pressuretrol and it's at 0.5 cut-in & a differential of 1. Seems to me I should never reach 3 psi... only 1.5 max? <em>could I have a bad pressuretrol?</em> I have my thermostat set to go down at night, so the programmed morning rise is 5 or 6 degrees.



I recently took some water out and replaced it as I was told to do to keep sediment down (a <strong>side question</strong>: should I take a gallon out & replace once a month?), so at first I thought maybe I'd put too much water back in or something, but my sight-glass shows me I'm good.



<strong> No main vents...?!</strong>



One thing that has stumped me is I cannot find any main vents in the basement... I can see 3 mains, all pitched toward the boiler... but no main vents in sight. could they somehow be removed? I don't see any logical place they would have been before the pipes turn to go up into the floor/walls. <em>Could the lack of main vents lead to higher pressure?</em>



One of the mains may have one at the end under a finished ceiling in the basement, but the other two I can see where they turn to go up into the floor/wall (see pics).



Also, there is a 4th "main" that has been capped on the other side of a wall in the basement when a small rad was removed from the kitchen during a renovation (before my time). That 4th "main" seems to be where a return comes back (smaller non-insulated back pipe coming from left in one of the pics?). Could that capped "main" actually be a great place to vent the return...?... assuming that is the return, which is something I don't understand about a one pipe system: why is there a return if the system uses the same pipes to send steam & get condensate back?



Any help would be great!

RossL

Pics

Seems the pics won't open up, at least not on my computer.



I can right click & select "open in new window" or "open in new tab" to get them to come up larger.



Thanks again,

Ross

steamedchicago

pressure

Pressure rises when the boiler makes steam faster than the system condenses it. That can happen because you don't have enough (or any) main venting. That should be fixed. It's quite possible you never had any main vents; some coal systems didn't, because the boiler came on and stayed on for long periods (all day, if not longer), so the air removal happened much less often than it does on a gas or oil fired boiler with a thermostat, where the boiler can come on and off dozens of times a day. You can cycle on pressure coming back from a set back, because once you get the pipes hot, the boiler will be producing steam faster than the radiators condense it. If the boiler is oversized, it will also cause cycling on pressure. As for your gauge/pressuretrol, neither the 0-30 psi gauges supplied with the boiler, nor pressuretrols are noted for being precision instruments, and gauges are generally inaccurate at the low end of their range.

McSwiggin

Pressure

My 0-30psi gauge on my boiler goes up to about 7psi when the system is running. Naturally I freaked out and thought there was something wrong with my boiler, as my pressuretrol is also set to 0.5psi with a 1psi delta. Rather than replacing my pressuretrol, I added a gauge on the same pigtail as the pressuretrol,a 0-15psi gauge that I got for free from work. That gauge never goes above 1.75psi because my pressuretrol cuts out at about that pressure, yet the gauge on the boiler still goes to 7psi. Long story short, the gauge on my boiler isn't accurate. If you are really concerned, add a lower pressure gauge to your system near the pressuretrol.

RossL_v2

Thanks! & Where to add main vent?

Thanks to both! I suspected as much, but am by no means an expert.



Would the capped part of what appears to be the return be a good place to add venting...? Take a look at the attached an annotated picture and pic of the capped part.



As for the gauge, that also makes sense! What makes no sense to me is to use a 0 - 30 psi gauge for a 0 - 2 psi system... but if it's code, I guess it made sense to someone...



If the pressure is truly not even 3 psi, I guess I could tighten some packing nuts and see if that is all that is needed for the gurgling.



Thanks again,

Ross

McSwiggin

Vents

I am a homeowner, not a pro, so keep that in mind when you read my posts. The point of the main vents is to get rid of all the air in the mains, so that the radiator vents only have to remove the air from the take offs from the mains and the radiators themselves (though I am considering adding larger vents before my radiators on my 2nd floor, I need more research though). Anyway, I believe the location of the vents depends on what type of system you have, counter flow or parallel flow. So research that a bit. But keep in mind the point is to remove the air and fill the mains with steam. So adding a vent to that capped plug will only fill that small section with steam, which will do you no good because there are no risers there.



Have you bought any of Dan's books? They are really helpful.