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  1. #1
    Join Date
    Jul 2010
    Location
    Scarborough/Toronto, Ontario
    Posts
    8

    Why isn't water from boiler reaching last circuits on manifold?

    Hello,
    Water from our boiler is less and less often reaching the last four loops on the 17-circuit manifold, and I was wondering whether the problem is the pump or the water supply or something else (for example, two of the rads in the house are leaking near the bleeder valve, and tightening things accomplishes nothing; replacement of parts has had to wait until the new year).

    Background: We have just moved into a ~2200 sq-ft, 75-year-old house with a very recently updated hydronic system: 2-year-old boiler (RBI Spectrum), pex tubing, supply and return manifolds, each with 17 inlets/outlets: the inlet and outlet nearest the boiler are capped; there are 14 rads (2 years old), and I presume each has its own loop; there is a loop for a subsystem of three radiant-heated floors (4 sub-loops) with its own 2-speed pump; I'm darned if I know what the unaccounted-for loop does. The previous owner did not, however, replace the auto-feed, the circulator pump, the pressure relief valve or expansion tank when he replaced the boiler. We replaced the pressure relief valve and expansion tank before we moved in because they were not working.

    The radiant-floor loop is meant to be fed from both a solar thermal system in the garage and the boiler, but the primary solar loop is not working properly, so we've closed the secondary solar valves on both the return and supply lines for the radiant floor subsystem, and now that subsystem is being supplied by, and returning water to, the boiler alone. The inlet & outlet for the radiant-floor subsystem are third from the end on the supply and return manifolds.

    When we first started the rad/boiler system up for testing and maintenance, there were three rads that did not get warm: 1 of the 2 in the basement, the wild rad on the main floor, and one small rad on the 2nd floor. Eventually, as we let the boiler run longer, all but the small rad on the second floor got hot (That one heated up _once_ recently. After we'd had some trouble with the system and called in a repair person on Dec. 20, the rad got hot when the system was turned back on, but the little rad stayed hot only a few hours).

    Two days after that, Dec. 22, the pilot light went out and could not be relit, and we had a wait of several hours before someone else from the same HVAC company could come to replace the thermocouple. In the meantime, water began to drip out of the pressure relief valve, and from around the valve at the top of the expansion tank, so we turned off the water supply to the boiler. When the tech came, he said that the leaks happened because the auto-feed mechanism is old and unreliable and needs changing very soon. I could not tell you now whether/how much the tech turned the water supply to the boiler back on; I know it is not fully on, because there is room to move the valve to the left. Because of his worries about the unreliability of the autofeed, I'm chary of fully opening up the valve lest there be a catastrophic failure.

    In any case, now, both of the basement rads (the originally 'cold' one _and_ the leaking one) as well as the wild rad frequently go/stay cold when the boiler comes on and the other rads heat up. In fact, fairly frequently -- I'd say 'more often than not' lately -- the last four inlets/outlets on the manifolds do not get warm, so the radiant-floor loop is gettin no hot water either. Aside from the perplexing question of how four loops at the end of the manifold correlate with four rads _and_ the radiant-floor loop, I would like to know why hot water does not regularly reach the four circuits at the end of the manifold. If I open the bleeder valve on all the rads, water comes out immediately.

    The repair person we had in on Dec. 20 to service the rads said that the little rad on the 2nd floor doesn't get hot because the pump is not big enough for the job (it's a Taco 007). He also said we ought to get a 24-hour circulating pump so that the basement would not get so cold when the boiler was not running. The Husband (a pretty savvy DIYer who, nonetheless, admits he doesn't know anything about boiler systems) fears the HVAC guy is trying to sell us something we don't need (The Husband is also something of a penny-pincher).

    So, why is the little rad on the 2nd floor consistently cold, _and_ why are the last four circuits on the manifold increasingly frequently cold? A weakling of a pump? Not enough water? Leaking rads? A combination?

    Also, if I open up the water valve to the boiler very slowly, will I avoid hastening the auto-feed's failure?

    Thank you for your patience in reading this.
    MMI

  2. #2
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159
    With the leaks comes air, or without proper balancing the last 4 are the "design legs" which are the most difficult to make work SO you have a balancing/ pump problem.
    All this needs a good contractor who really understands hot water.
    Have you called the original/ installing contractor who proudly left their sticker/ name on the installed unit? It would be helpful since they are the ones who know what was installed. Make sure they clearly leave behind a schematic of the install
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  3. #3
    Join Date
    Jul 2010
    Location
    Scarborough/Toronto, Ontario
    Posts
    8
    Thank you, genduct.
    We don't know who put the boiler in (there was no sticker on the boiler, oddly enough), but we're pretty sure it was the previous owner who did everything else. And it's one cockamamie 'design,' I can assure you. He's another penny-pinching DIY-er, but with little know-how. He seems to have balanced his ignorance with a lot of self-confidence. The cockamamie-ness was hidden behind gyprock panels on the basement walls and ceilings, and we've taken a great many down, both to do other work and to investigate the heating system. We're just never going to seal it up again.
    The previous owner has gone to great lengths to stay incommunicado, I'm afraid. He left no schematics, explanations, instructions, sketches... Oh, he left the manual for the solar and radiant-floor loop pumps.
    We're trying to learn things on our own and call in tradespeople who can tell us what's what (ah, the looks on their faces as they survey the 'system'!).

    Thank you, again, for the reply.
    MMI

  4. #4
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159
    You Canadians are so polite!
    I don't know if I could have said something as nice as:"He seems to have balanced his ignorance with a lot of self-confidence" to describe the situation, If I were in your shoes.
    Sounds like you are going to need someone to try to "reverse engineer" your system.
    If you are new owners you may have some recourse to offset the cost to do this, especially if this DIYer didn't do the work with the "benefit' of a permit that should have had the design schematic attached. Better find out the implications before you call the local Bldg Inspector to inquire. You may wind up "in the soup" moreso than the original owner.
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  5. #5
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Could be just an air lock. Did you vent (bleed) the radiation?
    Remember, Air Conditioning begins with AIR.

  6. #6
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,934
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  7. #7
    Join Date
    Jul 2010
    Location
    Scarborough/Toronto, Ontario
    Posts
    8
    Hello, Kevin O'Neill,
    When I loosen the screw on the bleeder valves, water comes out immediately. The small rad on the 2nd floor just dribbles a little, but water comes out. If there's an air lock, where is the air locked and how do I force it out? Except for that one ornery rad, the top floor rads heat up promptly.
    Oh, uh, does air go to the physical top of the system (the 2nd floor) or to the end of the system (the last circuits on the manifold)?
    And here I will add another dumb question or two: is there a difference between an air lock and "air in the rads"? How long should I let a rad bleed for?
    All morning the water circulating in the radiant-floor loop was cool. This afternoon, hot water crept its way into the circuit. Golly, I hope I can rustle up a couple more heating contractors to come in soon to quote on working on the system.

    A question to genduct:
    What are "design legs"? Googling gets me a list of sites about furniture design. :-)

    MMI

  8. #8
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    911
    Although i don't claim myself to be an expert in hydronic heating, I can atleast try to help you locate the original installer.

    Look on the gas pipe that feeds the boiler, we are required to put a pressure test tag on it.. This should have the contractors name and installation date on it, however some contractors don't affix them to the piping

  9. #9
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Quote Originally Posted by MotherMayI View Post
    Hello, Kevin O'Neill,
    When I loosen the screw on the bleeder valves, water comes out immediately. The small rad on the 2nd floor just dribbles a little, but water comes out. If there's an air lock, where is the air locked and how do I force it out? Except for that one ornery rad, the top floor rads heat up promptly.
    Oh, uh, does air go to the physical top of the system (the 2nd floor) or to the end of the system (the last circuits on the manifold)?
    And here I will add another dumb question or two: is there a difference between an air lock and "air in the rads"? How long should I let a rad bleed for?
    All morning the water circulating in the radiant-floor loop was cool. This afternoon, hot water crept its way into the circuit. Golly, I hope I can rustle up a couple more heating contractors to come in soon to quote on working on the system.

    A question to genduct:
    What are "design legs"? Googling gets me a list of sites about furniture design. :-)

    MMI

    You are doing it right. There may be an air lock in the concealed piping. You will need a contractor to purge that.
    Remember, Air Conditioning begins with AIR.

  10. #10
    Join Date
    Jul 2010
    Location
    Scarborough/Toronto, Ontario
    Posts
    8
    Dear firecontrol,
    Pics? Really? Of what, precisely? I know I could show everyone a regular riot of 90-degree elbows in the pex lines, but I'm not sure how it would enlighten. :-)
    MMI

  11. #11
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,934
    How about pictures that show what you described in your first post. You're asking those here to suggest what might be wrong just like you've asked the technicians that have shown up to "look" at your system. Pictures of what those technicians looked at will greatly help the experts here, well at least this one.

    Over 50% of my work is fixing hydronic systems that others have put together that don't heat as hoped, promised or expected.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  12. #12
    Join Date
    Mar 2003
    Posts
    7,314
    Water is like many humans, in that it will try to take the easiest way home. If you have a single manifold with multiple(17) takeoffs, the little pump that can(the taco 007) is probably doing its job, BUT the water will flow through the path of least resistance. There needs to be a way to balance flow through each circuit, and also a way to get the air out of each circuit. These devices may or may not exist, but without pics its impossible to tell. In addition, there needs to be enough pressure in the system to get the water up to each heat emitter.

    lets look at flow first. in your example of seventeen zones, lets say you require one gallon per minute of flow through each zone. That would equal seventeen gallons per minute right? ok good, now, if your pump is capable of doing that it will, assuming there isnt too much restriction placed upon it( pump head). the problem starts with the road (the tubing). if you take the easy road, the shortest loop, there is less restriction than taking the long way around, the longest loop. So, it will be easier for the pump to push through a loop that is say ten feet, than it is to push through one that is thirty right? since that is true, there needs to be a way to equal those loops out in terms of resistance, which is a balancing valve. If you get all loops to have the same exact resistance, water would flow evenly through the pipes, ASSUMING that you have enough pressure in the system for the level to reach the highest point.

    The pressure goes something like this. for every two feet of vertical rise in the piping, you would expect to see close to one psi at the gage. so, an average home might go up twenty feet from the boiler to the highest point in the heating system. Based upon our "rule of thumb", we would generally expect to see ten to twelve psi at the pressure gage on the boiler. This is accomplished in several ways, the auto fill and the bladder tank being part of it. if you get a leak, you lose system water, and also pressure right? lose that and the water doesnt get to the top.

    There is a lot that goes into a PROPERLY operating system, and usually the good guys out there make it look too easy. may I suggest that you find one of the good guyds around here to come help you. I am sure there is someone local enough here to come help. I make that suggestion for two reasons, first, you came here for help. Second, most guys hanging around here are pretty good, and come here to get even better, a sign of a good mechanic. good luck.

  13. #13
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159

    What are "design legs"? Googling gets me a list of sites about furniture design. :-)

    The design leg is the most difficult path that the fluid needs to take. Same term if fluid is water or air. Once this has been determined you then can figure the pump or fan pressure needed to move the fluid.
    Let me know if you need further explanation.
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

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