Steam Boiler Pressure & Some Of My Adventures

cobyschaef · October 7

*Long post ahead*

Alright, long time reader, first time poster, but I'm looking for some help with my steam heating system. I've read up almost as much as I can on this, but nothing specific to my situation. Wisdom comes from a multitute of counselors, so I'd like to hear what the multitude thinks.

Unfortunately I don't have pictures right now, but can get some later tonight when I get home.

Bear with me as I fill you in on some of the context. I have a Burnham MST396, single pipe steam system. I've been trying to do some much needed maintenance on it, as it's never really had any maintenance done, and the system had several leaks in it when we purchased the home a few years ago. When I purchased the house it had 3 radiators that were leaking horribly. Here is what I have done to the system so far over the past 2 years.

- leaking radiator #1 removed and line in basement capped off
- leaking radiator #2 replaced and works great
- leaking radiator #3, I just found a replacement and will have it swapped out in the next few weeks
- replaced leaking gauge glass and valves
- leaking radiator valve replaced (I still have one that leaks out of the top and needs replacement)
- skim tappings installed and boiler skimmed. Probably needs it again. Poor thing probably has never been skimmed
- sludge drained and hercules boiler cleaner added and system run. I just finished the 2nd round of cleaner and will drain it again and refill using 8 way treatment
- basement piping partially insulated, will be finished before the heating season
- someone wired in an aquastat which kept the boiler at 180 degrees when not calling for heat. I have a separate hot water heater, so I only just disconnected this. Before this past year, I had little to no knowledge of my steam system, so this didn't seem out of place to me.

Here's a little more context. I have hard water, 14 gpg. The amount of makeup water that has been put in is excessive. Unless the auto water feeder isn't correct, close to 140 gallons over the past few years have been added. The saving grace may be that the system almost always ran right after, getting rid of any oxygen. Hopefully not a lot of damage done. And there must have been a ton of scale building, hence the cleaning. Though there is lots of water loss, I do not believe this is a cracked boiler situation. No steam coming from the chimney. With the exception of the faulty gauge glass that was replaced, the boiler holds water when not in use. I believe the water loss was simply from the excessive leaking of the radiators. (I'm talking full on sauna in my bathroom from one of them. It was about the same as a 15 minute hot shower).Now that I've cleared up most of the leaks, I've run the system a few times for cleaning and have not experienced much if any water loss. I've meticulously checked all the piping and believe that I have identified all the areas that I lose steam/water. Also to note, I have no main vents. I'm looking for a good solution to that currently. There are no plugs at all that used to be main vents, so I'd be drilling and tapping some tees, though one of my mains doesn't have any tees, only elbows. This may be related to my currently dilema, but I truthfully don't know. So let's get to that.

In the process of doing my boiler cleaning, I determined that it did a great deal for the efficiency of the boiler. The reason I determined this is because the pressure gauge on my boiler climbs much more quickly now than it did before. Now I know what you're thinking, how high is your gauge climbing? You need hardly any pressure at all to run steam. Exactly where my question lies. Until these past few weeks of diving deeply into steam, I never realized that my pressure gauge should not be climbing up to 10 psi. My pressuretrol was maxed out at 8 or 9. I've never touched it. I just set it to 1.5 with the subtractive diff at 1. That was today. I turned the system on to see how long it would take to heat up and start bringing the steam to the radiators. Only about 10 minutes in and the pressure gauge was up to about 5 psi. Near boiler piping was still stone cold except for the pipe coming directly out of the boiler. It ran for a few more minutes and got up to about 12psi. Only after this point did I start getting steam to all of the radiators. This is normally where the boiler had been operating. Again I had no knowledge that it shouldn't be this high. So, armed with this knowledge, I've come to several possibilities.

1. The pressure gauge is faulty
2. The pressuretrol pigtail is clogged
3. The pressuretrol itself is faulty (I don't think I've ever had the pressuretrol turn the boiler off, so my guess is that it's not detecting the actual pressure)

I don't know if lack of main vents contributes to this. It makes sense to me that if the air cannot get out quickly enough, that should build some pressure, but I don't know about 12psi. As a side note, all my radiator vents work. I do hear the air coming out of them, and from what I've read they should be pretty silent, but they all close properly.

So here's where I'm at. I'd like to just remove the pigtail and see if it's clogged. But I can't remove it without taking off at least the LWCO. I can do that but I'd probably rather just cut and replace the pigtail. I plan to extend it out with a brass nipple so I don't have this problem in the future. I also plan to put an additional pressure gauge on a tee with the pressuretrol so I can see if there is a discrepancy between the two gauges. My concern is that when I do that, if the pigtail is indeed clogged leading to the pressuretrol not detecting the pressure, what will happen when it actually does? It seems like my system would short cycle really early and doesn't seem like I'd actually get steam to my radiators based on my experience with it today. Additionally, I'm not sure what this should look like, but after having the boiler on the gague keeps its pressure for quite a while. I turned it off at 1pm and it probably will still be around 2 or 3psi when I get home in an hour or two. There's more I'm forgetting for sure, and I don't have pictures as of yet, but any thoughts on the situation are appreciated. And thanks for making it to the end of my sort of long post 😀

Edit: this post here seemed to be something similar, but as this is not my specific scenario, it didn't give me answers that I needed. https://forum.heatinghelp.com/discussion/201488/some-help-advice-pressure-shut-off-pigtail#latest

ethicalpaul · October 7

Your post is too long 😅

The saving grace may be that the system almost always ran right after, getting rid of any oxygen.

This is always the case with fresh water added to a boiler. I don't think it helps that it boils immediately after adding it. The oxygen gets released into the boiler steam chamber and attacks the metal. But that doesn't mean your boiler is in trouble. We don't know its current condition. Just fix the leaks and move forward.

Get vents on your main(s) but you already know this.

Don't worry about short cycling. The burner shuts off for a minute then starts back up, no big deal. The steam pressure won't drop below zero so it isn't going to stop steam going to the radiators. (It's the lack of main venting that is your problem here)

Jamie Hall · October 7

I'm going to bet that a) that pigtail is clogged and b) there is a way to get it apart without major trauma. Can you send us some pictures of the setup?

Oh and c) there's a good chance that the pressure gauge is lying, but you have to have a 0 to 30 psig gauge to keep the insurance boys happy — so keep it and, as you suggest, put a nice new low pressure gauge on the poor thing somewhere.

Do the radiator vents open properly? Do they close?!

109A_5 · October 8

As stated above verify / repair the pressuretrol functionality.

I'd do an EDR (Equivalent Direct Radiation) survey and compare that number to the Sq. Ft. on the boiler's rating plate. Your boiler may be oversized, it may be more oversized since you removed a radiator.

As an example my system (slightly undersized boiler) with the main vent in use or valved off the boiler pressure NEVER goes over 2 inches of Water Column (0.07 PSIG). With the main vent in use the main just fills much more quickly, so less fuel burned to purge the air out of the main.

As a second opinion a low pressure gauge could be added to another boiler tapping or a Tee added to the skimming port pipe. Some folks like a 3 PSI Gauge (kind of almost useless in my case). If your system truly goes over 3 PSIG a valve to protect the low pressure gauge should be added to that gauge only.

mattmia2 · October 8

I'm assuming this is one pipe, only one pipe connects to each radiator?

It may have done ok without main vents on coal, with an automatic boiler with gas or oil it needs main vents.

you can see if the pigtail is clear by just unscrewing the pressuretrol from it.

you can probably either tighten the packing or add some string packing to stop the leaking valve stem.

Steamhead · October 8

https://forum.heatinghelp.com/discussion/comment/1867103#Comment_1867103

Remove the pressuretrol and blow into the pigtail. If it's clear you should be able to blow right through it.If you can't, then remove it. If it's brass you can usually flush it out by just sticking it into a hose outlet and turning on the water- you might get splashed though. If it's steel, it's probably rusted, so replace it.

We like to put a 1/4" tee with a plug in the bull under the pressuretrol. This way we can check it without removing the control- just remove the plug and blow into it.

EBEBRATT-Ed · October 8

Agree with @ethicalpaul main venting and venting in general is you issue. If you pressure gauge is reading correctly and you have pressure, and the piping is cold you are air bound.

cobyschaef · October 8

https://forum.heatinghelp.com/discussion/comment/1867096#Comment_1867096

I'll have to get a few pictures in the morning. But I believe the LWCO will prevent me from turning the pigtail fully.

Yes the radiator vents all open and close properly!

109A_5 · October 8

Depending on the LWCO you have, you may be able to remove the unit from the sensor to give you more room to deal with the pigtail. One example:

cobyschaef · October 8

Here are some pictures, including some of the near boiler piping. I managed to get the pressuretrol off. Also I think I know why it wasn't working. When I went to turn the pigtail to remove the whole thing, the pressuretrol snapped right off. There was definitely some corrosion on it. So I'll be replacing that now 😅

mattmia2 · October 8

Get a vaporstat and a low pressure gauge now that you have to replace it. that pigtail is brass.

109A_5 · October 8

Looks like it has been leaking for a while. The old version PA404A was brazed at the point it broke at.

Steamhead · October 9

That MegaSteam is an excellent boiler, but whoever installed it completely disregarded the piping instructions. Your system will run much better when it's repiped. What model is it- should be MST-something.

cobyschaef · October 9

https://forum.heatinghelp.com/discussion/comment/1867225#Comment_1867225

mst396

Happy to hear any repiping suggestions!

109A_5 · October 9

The manual shows how it should be done.

https://s3-us-west-2.amazonaws.com/catsy.782/MegaSteam+IO+Manual.pdf

patrykrebisz · October 9

Your boiler should take in only around 5 gallons of fresh water per heating season. Your 10 year old boiler should take in just about 40-50 gallons. Since it has taken up around 150, you can be sure that the life of the boiler was cut down by around 3x times. Typical boiler lasts around 30 years, so at 10 years, you are at the end of the boiler's life. I know you don't want to hear it as boiler replacement is ridiculously expensive. (~$5k for a new boiler and ~5-10k for labor).

That said, because the steam can work on miniscule amount of pressure, even badly corroded boiler can produce heat.

In a perfect world you would replace your dying boiler and get someone knowledgeable to install it correctly BUT the world isn't perfect, thus you need to come up with temporary solutions:

Replace the pressuretrol and set it so it cuts out power to the boiler at 2psi
Right now your radiator vents act as "main vents". Add main vents to the ends of the pipe so the radiators heat up much quicker and your boiler doesn't have to work "overtime." And yes, without real main vents, your boiler pressure will raise quickly.

Your boiler is "dead" so further fresh water take up shouldn't be your main concern. That said, if you do the above, with everything you have done, you might get a few seasons out of this boiler.

ethicalpaul · October 9

I don't think there's enough information to say how long this boiler will last.

Steamhead · October 9

https://forum.heatinghelp.com/discussion/comment/1867236#Comment_1867236

MegaSteam boilers should last for decades.

mattmia2 · October 9

https://forum.heatinghelp.com/discussion/comment/1867225#Comment_1867225

I would note that it is piped very wrong but it might still work ok, if it works ok I wouldn't worry about it.

I'd fix the venting and see what happens. It could just be lack of venting but it also could be water that isn't being separated because of the improper/nonexistent header keeping the steam from progressing out to the radiators where it can be consumed instead of building pressure.

If the water line is unstable or there is banging then the near boiler piping definitely needs to be fixed.

cobyschaef · 2:26AM

https://forum.heatinghelp.com/discussion/comment/1867304#Comment_1867304

I do believe I have some surging going on, but I think that's because there's still some oil on the top of the water. I have it a good skim the other week, but I likely need to do it again. As for banging, I usually have a little bit when I first fire up the system for the year, but it generally goes away quickly. Part of it I know is from The one radiator I have that has a leak in it. They reduced the size of the pipe before going into the valve so there's always excess water in the radiator. But I'm replacing this radiator anyway and we'll bring the piping back to its original size. So I'm definitely going to fix my known issues first, but if other things like my piping need fixing, I'll get to those, too.

109A_5 · 3:39AM

Does the riser from the boiler split into two mains at the Red box ? Is the other ends of the mains at the Red arrows ? If so, if the two mains and radiator venting are not symmetrically equal as far as air venting and steam flow, air may be trapped in the actual functional farthest part of the system until it is hopefully vented by the farthest radiator(s) venting the asymmetrical part of the system. Not an optimum configuration.

I believe to avoid this issue the 'steam main extensions' should each have its own main vent (sized to balance the mains) and each (individually) should drop down to about the level of the bottom of the boiler then combined together (as a wet return) to go to the Hartford loop. Presently it is combined way above the water line where steam can flow from one 'steam main extension' into the other.

mattmia2 · 4:15AM

didn't notice that but that is probably what happened to the vents, whoever didn't know what they were doing with replacing the boiler removed the vents in the dry returns at the boiler and connected them together above the water line.

cobyschaef · 12:33PM

https://forum.heatinghelp.com/discussion/comment/1867384#Comment_1867384

The red box actually splits into 3. One feeds the radiator that is right above the boiler, only a few feet of pipe. The pipe to the right splits at the end and feeds 1 radiator on the 1st floor and 2 on the 2nd. The pipe to the left is the longest run and feeds 3 radiators, one splitting off and going to the other side of the house. And yes the red arrows are the wet returns.

mattmia2 · 4:48PM

those are dry returns. wet returns are below the water line.

Steam Boiler Pressure & Some Of My Adventures

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