Operating pressure question on single pipe steam

Christian Garibaldi

Hello everyone! I was hoping to get some advice regarding if what I have learned recently with my heating system should be considered normal or not. I have a Weil McClain EGH -95 natural gas boiler running to 18 radiators in this old building. There are two main loops that basically split off of the main riser from the basement and travel around the footprint of the building at the ceiling of the first level (Building is 25x100) with the risers feeding off to either the upper floor rads or dropping down to the ground floor rads respectively. The mains are not insulated (and I keep toying with if its worth the expense to insulate them or not since they are in what can be considered living space anyway)

Anyway, the system runs fine, the building heats, albeit not dead on perfectly in terms of evenness but it is an old firehouse with 13 ft ceilings and masonry construction and no insulation (yet) built in the late 1800s. This year when I was getting ready to do my startup maintenance and flush the boiler and check over the system, I decided to purchase and add a vaporstat and a 0-5 psi gauge and wire it in series with the pressuretrol. I have the vaporstat set at 8 oz and when the system runs, I really dont build any notable pressure at all. The first fire up I set the thermostat
to max and figured let it just crank for a couple of hours. It did, the building got sweltering hot, during that time I checked all my venting and joints etc. The boiler gauge never really lifted above a fluttering 3 or 4 oz. I could unscrew any rad vent and steam would come roaring out and the all rads were hot all the way across. I did find a few rad vents that werent closing fully and I replaced them and also I had a packing nut on a gate valve for one of the ground floor radiators condensate bypass that was cracked so I replaced that as well, and I also had a bullhead tee at the end of the front main near my main vents that had a pin hole in the casting so I replaced that fitting as well. I began to fear that perhaps I might have a hole in the boiler somewhere so after shut down and fully cooling it, I removed the pressure relief at the top of the boiler and flooded the boiler up to the top of the nipple and let it sit for a couple of days to see if I had anything leaking from the sections. I was all bone dry. I replaced the safety relief valve with a new one while it was off, and when I added the vaporstat, I built the tapping with all new nipples and fittings and pigtails for both the gauges, pressuretrol and vaporstat. So basically, I really couldnt find any obvious leaks that could bleed pressure when the system was under a long firing. Yet the gauge barely lifts above 4 oz when its really flying. To verify, I closed down half of the raditors and just to verify the vaporstat operation, I lowered its setting to 5 OZ and ran the boiler. I understand that I essentially undersized the connected load, or oversized the boiler depending on how you look at it, but when I halved the load, the boiler pressure eventually came up enough to trip the vaporstat set at 5 oz (I had lowered it just to test its operation since I was never nearing anything above that anyway) and it kicked back on when it dropped to the differential. So, ok the vaporstat works, the system is solid, and minor leaks I found have been addressed for now. I have plenty of main venting (4 B&J big mouths and 3 gorton #2s at the end of the mains, plus 4 gorton air eliminators on the returns down in the basement boiler room). When I reintroduce the full rad load to the system, the pressure again barely moves. And when it does, it is doing it in cycles about a minute apart.....it will read 0, then start fluttering a little then go back to zero and so on.

So I suppose, aside from my realizing I essentially wasted a couple of bucks on adding a vaporstat, which itself isnt even getting tripped because the system really never climbs in pressure, as well as getting even more of an understanding of my system (Ill chalk the price of the vaporstat up to the cost of learning hahaha) my question is, should I care that the system never builds any real pressure? I mean even after a continuous firing for literally 2 hours with no shut down, its not really up there, so its almost like why did I even bother installing it, but its there now so whatever. Now enter real world heating scenario where I have the thermostat set at 62 lets say and it kicks on and off as needed just to do its thing. Or is my boiler sized so perfectly well to the connected load that this is perfectly acceptable and I should just not be concerned with what it is actually doing in terms of pressure. Unless my logic is wrong, that my boiler will never cut off on pressure, regardless if its the coldest day of the year and lets say it literally ran continuously for hours on end, but what is determining my cycles is essentially just my thermostat?

Oh...and I do apologize for writing this novel....If youve made it this far....I do thank you :-)

haventseenenough

I think you need one or the other, not both controls.

KC_Jones

haventseenenough said:

I think you need one or the other, not both controls.

Having multiple is not a problem, and many areas actually require 2. Having redundant back-up is never a bad thing IMHO.

I wouldn't worry about not building pressure as is said many times on here you don't want to.

I too did the same as you when I installed my new boiler, paid for a vaporstat and really didn't need it. It is what it is at this point.

Well matched system, be happy!

Christian Garibaldi

OK, cool, I appreciate the insight. I just wanted to verify I wasnt missing something.

EBEBRATT-Ed

@Christian Garibaldi
I have been posting about this on this site for a few years.

If the boiler is properly sized vaporstats and low pressure gages are completely unnessary.

If you want to pay the extra $$$ and put them on that's fine they do no harm and it give you the ability to have a gage to watch I guess.

My biggest problem is that all the talk of vapor stats and low pressure gages lead people to believe that there boilers should be building pressure when the opposite is true. If you can heat the building without gage pressure so much the better.

The only reason this came about is because most boilers are grossly oversized.

Sound like you have a good handle on this and that your boiler is running well.

Christian Garibaldi

Thank you, I understand and I certainly learned something. No harm in that. And yep...now I essentially have a vaporstat for **** and giggles and a gauge to watch that barely moves hahaha. And here I was secretly hoping that in the back of my mind that my boiler was way oversized at @400k btu input and that it was done just because when the city owned and operated this building as a firehouse, that they just erred wayyyy on the big side anticipating that the garage door would be open more than it was closed and such with the trucks coming and going and now that its just little old me residing here trying not to get clobbered on gas bills, that when the day ever came to replace the boiler, that I could drop down to something that wasnt so powerful and energy hungry and capable of heating the entire neighborhood if needed ;-). Sort of like backing out a big block hemi with a blower on it jsut to drive up the block to get some groceries

On the topic, I really have gone back and forth with if it would truly be of any benefit in terms of cost and ROI to insulate all of the mains on the first floor. I know that it wouldnt hurt and I fully understand the reason to keep the latent energy inside the pipes and help it to reach the radiators, but if they themselves are acting as a source of radiant heat is that necesserily a bad thing? When I roughly price out the costs for all of the sizes and lengths and elbows and tees etc ranging anything from 1" to 6 inches, it will be in thousands of dollars, plus its not the prettiest thing to look at with big fat wraps on so many pipes, so I am on the fence. I certainly think that if I insulated the header and risers, and returns in the basement that wouldnt be bad, esp since the returns are run around most of the perimeter of the basement contacting the masonry walls directly butted up to them (Which also could be an issue with trying to squeeze insulation effectively around them fully) but they are all done in copper, not iron (I didnt do it, that was done when the city owned the building and probably back in 2004 when the current boiler was installed if I had to venture to guess. all of the returns are iton on the ground floor and just as they poke into the basement, they were turned to iron. theres even some short remnants of asbestos insulation around a couple of drops, so I imagine that whatever they had boiler wise prior, has insulated cast iron runs down there, but then it was all replaced when the weil mc clain was put in...which DOES have a proper iron riser and drop header and near boiler piping in case you thought it had copper there too) Again, in a perfect world, all iron fittings throughout, fully insulated, and I could heat the entire place with a bic lighter for $1 a month....but here I am instead.....contemplating if I should move a couch down to the basement right next to the boiler so my guests and I can get our moneys worth out of the new boiler parts I added. Instead of "netflix and chill", its "Lets watch the gauge barely move and gaze at how shiny that vaporstat is and chill" hahahhahahaha

EBEBRATT-Ed

Maybe you could insulate the boiler room piping. If the remainder of the basement isn't that cold you could insulate a little at a time. You could request gift cards for pipe insulation for Christmass

gfrbrookline

In my system we had a few radiators that were hung on the unfinished ceiling of what used to be the supers apartment in the basement. The mains were wrapped in asbestos. I am assuming they heated the space since a super would likely take care of himself first.

The unit has since been refurbished and the radiators are now enclosed in a finished ceiling, can we say a crude approach to radiant floor heating in the unit above. The unit is now heated by a HW loop off the boiler.

If you insulate the mains and add ceiling radiators the offset of your edr might balance out but the cost of the project probably wouldn't justify the expense.

mikeg2015

I agree with the above. Properly piped and sized system should not build any pressure. For there it's jut a matter of balancing how evenly things heat up by increasing main vents if possible and reducing size of radiator vents the heat too fast. "tame the steam".

System was likely designed a a vapor vacuum system running on coal. SO piping is oversized and creates no backpressure. SO as long as all the steam is "Consumed" it will never build any pressure.

Christian Garibaldi

I am 100% certain that at some point in the past there was coal fired boiler in this place. There still is the old coal delivery chute in the apparatus floor in the truck bays that lead into the basement along with evidence of the old spent coal pit in the floor. Theres a mound that is poured over with concrete in the basement slab which I sledgehammered a hole in when I first moved here, wondering why was underneath it and beneath is all clinkers and theres still the old shovel they probably used that is still stuck up in the ceiling rafter above it. Also when I began assessing the system years ago, the "Main vents" were two measly, non functioning painted closed Kelly air vents with a tiny orifice in them, one for each main loop. Since then I have replaced them with plenty of main vents. Then at some point prior to the current boiler and setup, there was oil fired boiler since there was an above ground oil tank as well in the basement which we removed.

And yes, pipe insulation from Santa may be the way to go! hahaha

JUGHNE

I would guess the heating system was oversized even beyond the standard overkill of the day.

We just built a new fire hall. I called out for 4 separately fired infrared hanging heaters. This is double of what was needed to maintain the building. However we have 9 overhead doors that could be opened. Frozen and ice covered equipment returning.
For us this gives redundancy in the event of a heater failure.
I would imagine that was the case then.