Steam system-low water cut-off question & pressure question

ttekushan_3

Is there a check valve in the return line near the boiler instead of a Hartford loop? Or in addition to it? I suppose it could hold things up if its sticking or partially clogged with all that goop thats also in the return lines.

-terry

SusanC

Steam- low water cut-off question & pressure question

After the gas burner has been firing for a fair time, e.g. on cold days, my boiler gets to the low water cut-off and will repeatedly cut-off because the condensate does not get back fast enough (or the boiler is chasing water out into the returns)or maybe due to some other factor, which you people know a lot more about than I do. I used to have smaller valves at the ends of the 2 mains and the system used to cut out on pressure which probably gave the condensate a little more time to get back to the boiler; but, of course it stopped too frequently due to pressure. I now have Gorton No.1 air eliminators. Having looked in Holohan books, I have my pressure cut-in at 0.5 psi and differential at 1 to give the additive 1.5 - can't go any lower on dial. Even at this low pressure I don't get to pressure cut-off until repeated low water cut-off. (Incidentally, all radiators heat up.) Could I get a better balance by having smaller end of main valves and, if so, are there smaller than No. 1 Air Eliminators? Alternatively, does it make sense to get some type of pressuretrol type thing that would allow cut-off at lower pressure? Regarding pressure, although mine is set to cut off at 1.5 (differential set to 1), the guage, which admittedly is not an ultra-fine-tuned instrument, reads about 2.4 psi when it cuts pressure off; it does read 0.5 on cut-in. Sorry about length of question; I would greatly appreciate input on this issue, which tends to drive me nuts.

thfurnitureguy_6

clogged return

Susan, could be a plugged up return pipe. The hole in the pipe is filling up with rust, closing up, and restricting the water flow back to the boiler. If the leavel returns to normal after the boiler is off for a while this may be the problem.

SusanC

Thanks. I realize there's every reason to believe I have some clogging in returns (old house, old system)but if this is the major problem, why does the water return quite quickly as soon as the burner shuts off; I would think clogged returns would cause slower return. Also, when I let some water out of the boiler periodically (the recommended purge to assure that the low water cut-off does not get clogged), water returns to the gauge quickly except, of course, for what's been drawn out. It seems that my boiler backs water out the returns when running. I would appreciate input on causes/cures for that or whatever else may be causing the low water problem; also the pressure part of the question.

Dave_4

Susan, I'm sure you'll get replies from real pros, but while waiting, here's a few things to ponder. I used to have a similar problem of a very unsteady water line that frequently got down low enough to trigger the LWCO. Since I repiped my near boiler piping and cut the steam velocity in half, plus went to a 2in equalizer, the water line is much steadier. Not saying you have same problems, just something to look at. In addition, once (before finding the Wall) when I was trying to get steam to some distant radiators, I increased the cutout setting on my Pressuretrol to 2 1/2 lbs. and this also seemed to cause erratic water line and trigger the LWCO. So the actual pressure you are getting might be suspect, from what you said. If you have a 0-30 gauge and it is showing any pressure, that probably means pressure is actually higher than the 1 1/2 lbs. you want as a max., which would make the Pressuretrol suspect. FWIW

SusanC

Thanks, all experience and input happily received. I hope I get some more responses. Re: the points you bring up: it looks like I have a 2" equalizer. My water line is not erratic; it gradually goes down to low water cut-off and, once there, the boiler starts up again as soon as a little bit of water comes back, so then it reaches cut-off right off again, so it gets into repeated on and off firing. When the weather is warm, the thermostat is satisfied before this happens, but as soon as it gets a bit cold I reach this cut-off problem. It really seems that the boiler is chasing water out. If this is occurring, what would be the cause? I do have a 0-30 gauge; I think the pressuretrol works at least to some degree because, back in the past, it was set higher, and the gauge registered higher. I don't know if the pressuretrol is allowing 1 psi too much (when it's supposed to cut off at 1.5 and doesn't until 2.4) or the gauge is 1 psi off in accuracy. I should maybe replace the pressuretrol but I would think the boiler should not get rid (temporarily) of so much water, which quite quickly returns as soon as the system shuts off upon reaching set (2 degrees above) temperature. As it is, I often look forward to Spring even after having developed seasonal allergies.

Dave_4

Pressuretrols aren't cheap, so maybe before you do that you need to verify what pressure your boiler is running. If you are interested, I previously bought (at a Wallie's suggestion) a Wika 0-5 psi gauge and replaced the 0-30 psi. I know Code requires a gauge that reads high enough to verify the check valve, but this will tell you what the actual pressure is, and later you can pipe it in parallel with the 0-30 gauge. If interested,here's a link to buy the Wika gauge. http://www.gaugestore.com/products.asp?dept=1123 The part no. is 33021. If you find later that you need to replace the Pressuretrol, you might want to consider using a Vaporstat instead. There are some worthwhile advantages, and I am in the process of doing that very thing, since my 18 year old Pressuretrol is dying.

SusanC

Thanks again & additional experts,please some help. I am most interested in the low water problem, which appears to be as follows: during burner firing water appears to be backing out of boiler and/or, once water level gets low during the cycle, maybe steam is getting to the wet return through the equalizer and preventing condensate from entering the boiler - I suggest that because my Hartford Loop is a bit high. (I'm a bit worried about having it lowered because I don't know if the people will know the height of the crown sheet - no specs for this old Homart boiler seem available.) As soon as the boiler stops firing and thus is not producing steam pressure, the condensate re-enters the boiler as indicated by gauge glass. Experts, what is the most likely cause of my temporary, but important, low water?

chuckNJ

slow return

Hi Susan, another HO here - I had a similar issue with low water in the heat up cycle - it was clogged wet return. The most water is out in the system during "pickup" - while a cool/cold system is heating up and filling with steam. If water is backing up from the return into the far end of the main, this water will tend to condense more steam there, essentially adding more water that can't get back quick enough. (I was able to hear the water in the far end of the main).

You say the condensate returns "quite quickly" - in my case, the water line would come back to normal within a minute of shutdown. (If you are talking only a few seconds, then there may well be a different issue). If you haven't done so already, shut the boiler down once it goes out on low water to measure the time to get all the condensate back.

Per the discussions on Hartford loops and near boiler piping in LAOSH (sorry I don't have my copy handy to give a reference), the preasure in the boiler is equalized to the return by the pipe of the same name to eliminate back preasure on the return.

In my case, a good power flushing of the return cured the problem (I will have to continue to flush it periodically as there is still plenty of hard scale in there that didn't come out which is restricting the old pipe's capacity.)

In order to be able to flush the return with street water preasure I had to invest in some additional pipe work at the end of the returns. Valves are needed to close off the returns from the mains at the far end (away from the boiler) and also at the rise into the hartford loop so one does not flood the above the water line portion of the system when flushing. Of course drain cocks at both near and far ends of the return for hose attachment to inject water and drain it are also required.

This pipe work, while not trivial, was considerably less expensive than replacing the entire return (and if one did have to also replace the return piping, you would want to add these maintenance valves anyway).

You also mentioned a concern with your Hartford loop - I'm sure a picture may help someone from among the Pro's to comment.

Hope this is helpful.

SusanC

thanks chuckNJ. I'm betting on clogged returns. Water doesn't return in seconds; begins to return as soon as boiler stops firing but takes possibly 10 mins. Also, the last 1/2 inch or so does not return for quite awhile; I'm betting again on clogged returns and probably a few minor sags that slow things down. I'm wanting to flush the returns in approx. the way you mentioned. As for cleaning the boiler itself, I am reluctant to use chemicals because people in the field say this often leads to problems; unfortunately people behind desks seem to like chemicals so one is caught in between. How do you feel about this issue?

Re: the Hartford Loop, mine is higher than the boilers low water line, which I understand should mean it's too high. I'm wondering if a too high Hartford Loop might impede flow of condensate through returns to boiler. I'm not good in hydrodynamics so I don't know the answer to this question.

SusanC

No check valve; just a Hartford Loop but one that is higher than the boiler low water line

ttekushan_3

hmmm.

could be a problem. If the return line leading into the Hartford gets steam hot, then its the steam in that close fitting there thats holding back the water. I must admit, however, that this is usually accompanied by a disturbing water hammer when the boiler shuts down.

Be that as it may, if the return connection is too high and the lines on the return side are hot but cool quite suddenly on boiler shut down, its safe to say that the Hartford connection should be corrected.

The longer run times will lower the water level just below that Hartford return connection and all return water gets stalled in the return lines.

Be aware that pipe fitting work of ANY kind on the steam system will contaminate the water necessitating a skimming of the boiler water to assure high quality steam.

-Terry

chuckNJ

loop

Just a HO, not a Pro, but in both Dan's LAOSH and pretty much all the boiler manuals I have looked at, the Hartford loop connection is suppossed to be 2 inches BELOW the NORMAL waterline. This typically will place it above the low water line.

If the condensate is returning properly, it will be "stacked" in the vertical drops from the mains to the wet return to create the necessary preasure to push back into the boiler. I would think this is probably still happening (and keeping the Hartford loop connection wet) even if your return is so clogged that the boiler is pushing water (as steam) out faster than it can get back.

SusanC

Yes, but on page 81 of "We Got Steam Heat!" it says (no copyright issue with one quoted sentence, I hope): "The "wet" gravity return line, which returns the condensate from the system, rises up from that low point near your basement floor to join with the equalizer at a point that's about two inches below the boiler's lowest safe operating waterline." My close nipple is higher than my low water cut-off level (safe operating waterline). Recently on a warmish day I was checking temperature of the pipes during a cycle (hand as measuring instrument), which seemed (to me) to give me an idea of what was flowing where. In the future I have to do this in colder weather with a longer cycle (could turn heat up now and check, but so far am being patient and also lacking in extra time). Using this method, in warmish weather when I don't get to low water cut-off, condensate apparently is coming down the returns (pipes become warmish) to the T. A pipe (T stem) then goes horizontally near the floor to the bottom of the loop pipe; the horizontal near floor pipe from the T to the bottom of the loop is cold, as is the loop pipe rising to the Hartford close nipple; pipe on the downward loop side to (or from) boiler is also cold (good in that no heated water/steam backing out of boiler, however condensate possibly also not getting beyond T into boiler?); equalizer above close nipple, to or from header, becomes hot, which "looks" like some steam getting down from header to the loop but not beyond. I think last year, when not doing this systematically but when fleetingly checking the pipes, the loop became hot when the system got to repeated low water cut-offs; this makes me wonder if maybe, because of the somewhat high loop, steam from the equalizer gains access to the loop because water has fallen below loop level. If any of this makes sense, does it also make sense that steam gaining access to the loop from the equalizer at low water would prevent condensate from returning to the boiler? Does it also make sense that, even before low water cut-off, the line from the T is clogged to the point that condensate is not returning well to the boiler? In any case, I seem to be answering one of my former questions which had to do with the possibility of water backing out of the boiler: on warmish days at least, with the heating cycle not getting to low water cut-off, nothing seems to be backing out of boiler.

By the way, I think I have a problem with thread methodology in that I sometimes hit the wrong "reply" and my subsequent questions get embedded/indented in the thread where most people don't see them. I'm glad you do. Maybe sometimes I should be choosing "new message on this topic?" It appears I don't know any more about threads than steam heat.

Still wondering about the chemical issue.

Steamhead (in transit)

Chemicals

can be a problem on steam systems, since they can be difficult to flush out when you're done with them.

I also think you have clogged returns. Have them replaced and see how you make out.

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Ron Johnson

Confusion !

Susan, are you living in my basement? I got all that to kid, and no answers. I think I'll take the flash lite down there in that secret corner of the world and look for yo. Good luck,

Ron Johnson

Confusion !

Susan, are you living in my basement? I got all that to kid, and no answers. I think I'll take the flash lite down there in that secret corner of the world and look for yo. Good luck,

SusanC

Thanks; I plan on at least having the returns flushed out and replaced if, upon flushing inspection, this seems the best course. Once returns are disconnected, can one flush with water or air (under pressure, of course).

What do you think re: my "loopy" H. Loop height question? Can this be a significant part of the problem? Also and relatedly, without manual or instructions can an expert determine the height of the crown sheet so he doesn't lower the Hartford Loop too much?

bob young

squick

add a can of Squick to system. good chance it might do the trick. worth a shot . if not replace returns & resolve problem for good.