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April 12, 2007
Boiler -- Who's right, plumber A or B
Help me figure out which plumber has correctly identified the problem. We have a 4-story, 2-family house on a single zone old fashioned steam radiator system. The boiler is not brand new but not ancient. House was unused for several years before we renovated, and not well maintained in the years before that. The problem is that the bottom floor runs about 8-10 degrees cooler than the rest of the house (thermostat is upstairs). Bottom floor has low ceilings, insulation, and no discernable drafts. This is not a problem of "heat rises." The problem is the room where the thermostat is located reaches temperature before the bottom floor has had a chance to heat up.
Plumber A says -- we need to clean the sludge out of inside the boiler (my guess is nothing like this has been done for years and years, but I don't know how necessary it is). According to plumber A, there must be a lot of sediment settled in the boiler which apparently causes the boiler to think the steam pressure has built up throughout the system before sufficient pressure reaches down to the lower floors. He says that, when the boiler is on, steam goes through the pipes to the top floors first and the pressure is supposed to build up from the top down until it reaches the requisite pressure to shut the boiler but in my case the boiler cycles off due to it thinking the pressure is all there before the steam pressure fully builds up on the lower floors. This seems credible because I have observed the boiler cycling on and off every 2-3 minutes while the thermostat is calling for heat, but I question the diagnosis because the radiators do get hot on the ground floor. Plumber A says I am wasting a lot of energy (and money) having the boiler cycle on and off and that cleaning the sediment out of the boiler will alleviate the problem.
Plumber B says none of what plumber A says matters. We should get new valves on the upstairs radiators to limit how much heat they put out so that the upstairs reaches the thermostat temp more slowly, giving the radiators downstairs time to heat up before the thermostat turns the system off. His solution seems like it may work but I dont' know if he is right that plumber A's diagnosis is irrelevant to the problem. Also, the solution seems wasteful; I don't want to run the heat longer, especially if Plumber A is right that I am wasting energy with the boiler cycling on and off. But if the cycling is, in fact, normal, or unrelated to my uneven heat distribution problem, I want to make sure I fix the problem.
Anyone experienced enough with these old steam systems to have a sense of who's got the better diagnosis here?
Comments
can comment on the problem but i had the "sludge" cleaned out of my boiler when I bought my house and it sprung a leak several days later and had to be replaced... be ready for something like that if you choose route A.
I think you should post your question on heatinghelp.com
Posted by: Anonymous at April 12, 2007 2:38 PM
can comment on the problem but i had the "sludge" cleaned out of my boiler when I bought my house and it sprung a leak several days later and had to be replaced... be ready for something like that if you choose route A.
I think you should post your question on heatinghelp.com
Posted by: Anonymous at April 12, 2007 2:40 PM
I think your main problem is the boiler is cycling too frequently.
found this online:
"Frequent cycling is usually caused by:
Boilers oversized for the load they are serving
Too narrow a temperature or pressure band between on and off operation"
I had a boiler that constantly cycled but it stopped after I had my thermostat and the part of the boiler that the thermostat talks to that controls the cycling replaced. (the later part actually broke so maybe the cycling was signs of its impending demise)
Posted by: Anonymous at April 12, 2007 2:43 PM
can comment on the problem but i had the "sludge" cleaned out of my boiler when I bought my house and it sprung a leak several days later and had to be replaced... be ready for something like that if you choose route A.
I think you should post your question on heatinghelp.com
Posted by: Anonymous at April 12, 2007 2:45 PM
I vote for option B.
Makes sense to me.
Posted by: Anonymous at April 12, 2007 2:55 PM
Typically the pressure builds in the header and rises slowly to the top. The top floor radiators heat up at the end of the heating cycle. Air vents contrtol how quickly certain areas heat up, the larger the hole, the faster the steam will get to that area. Air vents sometimes get painted over or fill up with water and need to be changed. Proper size vents should be installed thorughout. I'm not sure what you mean by lower floor. If the lower floor is on the same floor as the boiler then the only heat would be from pipes on the ceiling and this may not be enough surface area to heat the space. Typically you would run a loop of hot water through baseboard for this floor, if it is the same floor the boiler is on. If this floor is above the boiler and the radiators get hot then you simply don't have enough radiator to heat the space.
Posted by: Anonymous at April 12, 2007 3:03 PM
Thanks for your various coments, and I will try heatinghelp.com, too. Their FAQ page ahs so many options for what might be the problem that i am a bit dizzy.
If it helps, the boiler is in the cellar. The floor I am having trouble getting up to temperature is the basement (garden level apt). It makes sense to me and is my experience that the lower floors heat first, as the lower floors come into contact with the steam first. What plumber A is suggesting is that the pressure starts to build back towards the boiler from the top once the steam reaches the top as the boiler continues to send more steam.
As I read heatinghelp, my problem may be A, or B, or anything that any of the above posters have added. More comments are certainly welcome; I will also try to report back what I learn.
Thanks much.
Posted by: Anonymous at April 12, 2007 3:27 PM
It's steam, not water, so can't add hot-water loop. Unusual that top floors are warmer, it's often the other way around as steam should fill the lower radiators first. Possibilities:
Lower rads are too snmall, even at full heat. Or upper ones are too big. Hard to correct; you can enclose large rads with a cover and block off some of the venting, but might be better to replace. As a guide, I have 6-section rads on top floor, 8 in middle and 9 or 10 at bottom (seems reversed, but my house is quite uniformly heated.)
Lower rad's air vents are blocked...are they fully hot? You can try balancing the system by putting vents with larger holes on the bottom rads and vice versa on the top ones; you can do this yourself for a small investment to check out. However, balancing it correctly is an art.
B seems more right, tho the sludge may be another issue.
Posted by: cmu at April 12, 2007 3:30 PM
1. Hot water loops from steam boilers are a common installation even one or two stories above the boiler.
2. The problem with this system is in the venting.
If your interpretation of Plumber A’s diagnosis is correct, then he doesn’t understand the system. “Pressure builds up at the top….blah, blah, blah”….It sounds to me like the piping is under vented. That’s what is causing the short-cycling. Changing air vents on radiators is not going to be enough to make the difference.
Plumber B is looking at the small picture and only addressing one problem though his suggestions would probably produce a positive effect.
All that said, Plumber A may have a good reason to believe the boiler needs to be flushed. Is there a lot of dirt/oil in the gauge glass?
Powerless to my sarcastic nature, I offer that it sounds like you’ve got two bad choices for people to work on your steam system.
Posted by: Master Plvmber at April 12, 2007 4:50 PM
Thanks everyone. Master plumber, your points are well taken. Posters on heatinghelp.com suggested balancing, but differently than plumber B. The more comments I get and the more I read, the more confused I become (gr?).
As for flushing, the water in the glass is clear. However, when we first fired up the boiler last fall, we got about three weeks of cloudy, dusty wet steam, particularly on the bottom floor. It has cleared up completely, and the system (knock on wood) is relatively quiet, dry and clean-running. One poster on heatinghelp actually agreed with the "pressure builds down from the top" view, and disagreed with the view that the system heats up from the bottom.
I think I need to look at my system mroe closely in light of everyone's comments and hope for some warm weather soon so I can have the summer to cogitate on the problem. Also, my past dealings with plumber A were decent, so I may run some of these questions by him (as if I now know what I am talking about) and see how he reacts.
thanks again.
Posted by: Anonymous at April 12, 2007 5:09 PM
We have the same problem with our hot water system. My husband thinks it's because we have too small radiators on the garden level. We plan to put larger ones in and put some radiant floor heating under the floor (even though it won't be as good as radiant floor heat set below the tile and wood flooring).
Posted by: Anonymous at April 12, 2007 9:40 PM
plumber B no question.
Posted by: Anonymous at April 13, 2007 8:29 AM
Such a simple and elegant system yet so much confusion!
1. Clean your boiler out yearly! Blow down low water cut-offs weekly during the heating season.
Sludge is probably in there but as far as it being the cause of your problem. No. Definitly not.
2. Venting - Sure you can check the radiator vents. But for steam to rise quickly and evenly heat the entire floor plan you need to do two things.
1. Set your pressuretrol correctly. Low is the word here. Be aware that an L4079 Pressuretrol is notoriously inaccurate.
2. Vent the mains. Check your vents on the steam mains as they go into the risers.
This is most likely the cause. Good luck!
Posted by: BoilerMan at April 13, 2007 1:06 PM
Master Plumber, does that mean you can add a hot water tank to an *existing* boiler also (that doesn't have one?) I wanted to do that 2 years after our W-Mc was installed and the manufacturers told me it could not be done. Hence my comment
Posted by: cmu at April 13, 2007 3:28 PM
cmu - you can add a hot water loop to a steam system by tapping into the boiler below the water level. I've not done it, but we researched it for a house I was renovating.
Posted by: anon at April 13, 2007 4:09 PM
I think what you're saying is you want to add an indirect water heater and have it be energized (or heated) by your steam boiler.
The answer to that is yes. I do it all the time with great results.
Like I said, it is also very do-able to add a hot water radiator zone from a steam boiler.
Posted by: Master Plvmber at April 13, 2007 4:10 PM
I'm far from an expert on this, and have the same problem and a similar system (undermaintained 1 pipe heating system, sludge which I was told to flush once a year, etc.)...
I've heard thermostatic radiator valves are good for this - any expert (or master) plumbers know anything about these doodads?
It seems to be compounded by what appears to be a 1960s era thermostat which is less than accurate. I'm curious if also updating the thermostat with a new digital one will help...
Posted by: Anonymous at April 13, 2007 4:58 PM
definitely upgrade your thermostat to a new digital programable one. a decent one is under $50 and will save you hundreds in heating costs
Posted by: Anonymous at April 13, 2007 5:23 PM
I'd be surprised if a programmable thermostat saved you five cents on your steam heating system.
Posted by: Master Plvmber at April 14, 2007 7:32 AM
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