Is this boiler behavior normal?

Sethamin

Background: I am a new homeowner with a one-pipe steam heating system powered by a 210k BTU input gas boiler. I've read "We've Got Steam Heat", which taught me some basics in how my heating system works. Last heating season, I saw some seemingly strange behavior from my boiler; I would regularly see the 0-30 pressure gauge get into the 10-15 psi range, which made me suspect either a stuck pigtail or bad pressuretrol. This past summer, I replaced the pigtail and tee'd off a 0-3 PSI low pressure gauge on the top of the pigtail.

So I fired up my boiler for about 30 minutes this morning for the first time this heating season as a test run. It took 6.5 minutes before the needle on low pressure gauge begin to wiggle a little (not sure if this is relevant - if that's longer than normal, perhaps it means my boiler needs to be skimmed?). After that, it got a little weird. My main pressure gauge was at 5 PSI before the low pressure gauge moved from 0. Steam seemed to already be flowing through the system at this point (the headers were hot to the touch). Once the low pressure gauge hit 0.5, the 0-30 pressure gauge was around 6.5 PSI. It then climbed to 1.0, at which point the lower water cut-off kicked in, and the automatic feeder may have added more water. It then fired again, and climbed slowly back to 1.0 (0-30 pressure gauge was around 7.5 now) before just kind of dropping back to 0. The boiler was firing this entire time. It repeated this process 3 times over the next 10 minutes or so (climb to 1.0, drop back to 0), at which point I shut it off. At no point during this process did I see the pressuretrol kick in (I tested it and pushing up on the pressuretrol does shut off the boiler). My pressuretrol is configured to 0.5 cut-in with a 1.0 differential.

Is my boiler working correctly? The differential between the low pressure gauge and the main pressure gauge is worrying to me, and it's a brand new pigtail so it can't be clogged. Maybe one or the other port is clogged? I also don't understand the behavior where it climbs to 1.0 PSI and then drops back to 0; I thought the pressuretrol is what's supposed to regulate the pressure, but that never kicked in. Any help and/or explanations appreciated.

KC_Jones

Just a homeowner, but first thing I would say is that 30 PSI gauge is bad and I wouldn't trust it at all. If that 0-3 is brand new trust it, the behavior sounds sort of normal for amount of time and pressure. The other problem sounds to me like the condensate isn't getting back to the boiler quick enough and when it does get back it's coming in slugs so you get pressure and then a bunch of water comes back to the boiler which can and will drop the pressure. On mine I see this on burner shut down it will go into a vacuum because I am not sending steam and condensate is still returning putting a partial vacuum into the system. This could also be why your LWCO kicked in. Like I said just a homeowner, but I am sure a pro will chime in with more possibilities. Also post some pictures of your near boiler piping and return piping that can usually help with diagnosis. The pressurtrol will only do something if you hit the pressure it is set for. If it is set the way you say it won't stop the burner until you hit 1.5 PSI which you never did.

Jamie Hall

Sounds like KC has a pretty good take on it.

A points. First, as he says, all the pressuretrol will do is turn the boiler off when the pressure rises too much. Yours sounds as though it is working just fine.

Second, the 0 to 30 psi gauge is there to keep the insurance company happy. You can safely ignore it, most of the time -- especially since you have the low pressure gauge on there (what does it read when the system is off, though?)

Skimming won't make a bit of difference to the behaviour you are seeing. As KC says, it sounds more like slow condensate return somewhere. Is there any water hammer?

Sethamin

That all makes sense, and would explain the behavior I'm seeing. I know of at least one section of condensate return that's probably clogged, since it feels cooler to the touch than the sections both before and after it when the boiler is on.

Is there any easy way to find all clogged sections and clean out the returns? Or do you have to replace those sections of pipe altogether? While my risers are all black pipe, the returns all seem to be made of copper.

Also, I posted some pictures of the near boiler piping and controls (as suggested) for reference purposes.

Edit: Also, there's no water hammer in my system. You may notice the split rings on my supply pipes in the picture, but those are just there because I like having well supported pipes that don't move around. I did just it to be thorough, not because there was any particular problem.

Abracadabra

2-2" risers into a 2" header feeding 2-2" mains?

sounds like a recipe for wet steam to me.

Also, if you know you have a clogged return, you definitely should work on clearing that up first.

Sethamin

Well, it used to be a single 2" riser into a 2" header until a plumber convinced me to have him open up the second port and add a second riser. Would that have been any better or worse?

Also, the blocked condensate line (that I know of) is the return off a smaller riser that feeds two 1" outlets in an extension. Since it wasn't on the main condensate return, I didn't think it was a huge priority to fix.

KC_Jones

The plumber had good intentions, but to make it work it's best the header should have been over sized as well. 2-2" risers work well with a 3" header. I don't think it's the end of the world though...having 2 risers is still a good thing to help stabilize the water line. There are a couple possibilities to clean the return line depending on what you have. Again post some pictures of your suspect return and you may be able to get some suggestions. I know what I do on my system, but every system is a bit different.

Fred

If you could have the header changed out to a 3", you'd be in great shape and it doesn't look like it would be a huge job. Obviously, if you think you have a blocked return, that needs to be investigated and corrected.

Sethamin

Thanks for the advice everyone. I will have my plumber come in and investigate enlarging the header and cleaning and/or replacing my returns as necessary.

While I have everyone's attention, maybe I should also: are my mains vented sufficiently? I have a 25' main and a 45' main, both 2" pipe, and each is being vented by a single Gorton No. 1. Based on my skimming of various threads here, that seems pretty undersized (particularly for the 45' main).

Fred

If you have the head room, you should put a Gorton #2 on the 45' main. The Gorton #1 is probably OK on the 25' Run or you could move the one that's on the 45' main (when you put the #2 on there) and add it to the 25' main on an antler.

KC_Jones

The great venting question! If you don't have it yet I would highly recommend buying the Balancing Steam Systems Using a Vent-Capacity Chart, by Gerry Gill and Steve Pajek sold in the store. It's a pdf download and only costs 10 bucks and it goes to charity. It's very straight forward and quite helpful. You will be able to calculate what you need and at the very least it will get you really close. Some of those vents can be pricey so if the 10 bucks for the book saves you from buying one too many it's worth it to me. Just guessing since I don't have it in front of me, but yeah you sound under vented on the mains. I can't remember who, but there was a rule of thumb mentioned on here of 1 gorton #2 for every 20' of 2" main. One way to find out is to time your mains. From a cold start feel the header once it's hot start timing and then you can follow the heat down the main with your hand once it hits the end stop timing. This gives an idea how slow or fast you are moving steam. You don't want it to take more than a couple minutes to fill the mains. If I may...you might want to think about getting some insulation on that header as well. The insulation can speed the steam up since it won't be giving up so much heat to your basement.

Sethamin

Just bought it, thanks! Looks like this will also help me balance the radiator valves, which is not an acute problem at the moment but could use some improvement.

KC_Jones

Yes it will! I just finished replacing my boiler with a ton of advice off this site. Listen to what the pros say! My system has never run as good as it does right now. This is by far the best "advice" site I have ever been to, filled with great people that really care.

BobC

That really isn't enough venting, a Gorton #2 on the short and 2ea #2's on the long would be much more like it.

Bob

Fred

I have Gerry's venting book and it appears to me that my earlier recommendation is probably all that is needed. The Gorton #2 will vent 1.1 cubic feet of air per minute at 1 oz of pressure and 1.75 cubic feet at 2 oz. According to Gerry's chart, a 2" pipe holds .023 cubic feet of air per linear foot of pipe. .023 X 45ft = 1.035 cubic feet of air so a Gorton #2 should vent that longer run in about 1 minute and the 2 Gorton #1s should vent the shorter run in about the same time.

ChrisJ

I'm currently running five Gorton #1s on a 29 foot 2" main and a single Gorton #1 on a 11 foot 2" main.

My object is to keep pressure as low as possible and I've considered adding more venting. I use multiple Gorton #1s because I don't have the height for #2s. My 0-3PSI Wika gauge doesn't even move when steam starts filling the mains. I am replacing the 0-3PSI gauge with something more useful soon such as a 0-5 oz gauge.