Crown Aruba air blockage

Discussion in 'Boiler Forum' started by Not Handy Mike, Jan 23, 2012.

  1. Not Handy Mike

    Not Handy Mike New Member

    Messages:
    5
    Location:
    New York
    I have a crown aruba boiler and after experiencing gurgling for a few days, the hot water is not making its way to the second floor baseboards. I feel hot water on both sides of the solenoid valve for this zone, but a few inches further up the pip it gets cold. I am thinking I may have a air pocket or simply not enough water in the system. Is draining and re-filling the system pretty simple? How do I know when the system is full. I do not see any level gauges anywhere? Do i need to turn the boiler entirely off to do this or just turn the thermostats down? Thanks!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Except for maintenance, you probably should never drain the system! If you hear gurgling, and it is a hot water system (i.e., not steam), then you have air. To get the air out, the last thing you want to do is drain it. Somewhere, there needs to be a fill valve. Also, you need to know what the system pressure is so you need a pressure gauge. Depending on how many stories the water has to be pumped, would somewhat depend on the normal working pressure, but many are around 15psi. When properly set up, there is NO air in the system, and it is pressurized to the system design. A pump often cannot self-prime and push water through an air pocket, so you need to go to the highest point, find a place where you can purge air while filling it. WIthout seeing your system, it's hard to tell how it was designed to be done, but somewhere there is likely a connection to the cold water supply, connected through a backfill preventer, into the boiler water system. Sometimes, there's an autofill valve, but it may be shut off and unable to maintain pressure in the system. Also, you will have some sort of expansion tank in the system, and it may be waterlogged. Depending on the type, it may need to be drained, or if it is a bladder type, replaced. This is required since when you heat water and the system is full, the water expands...it needs to go somewhere, and that is the expansion tank. WIthout it, the pressure will rise, the safety overpressure valve will (or at least should) open, to drain off enough water to maintain the max pressure. But, when it cools off, the water shrinks, and might suck air into the system, leaving you deficient.
  3. Dana

    Dana In the trades

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    What Jim said- you want to purge the air, not drain the system. Hopefully there is a convenient purging valve already installed somewhere at a high point on that zone.

    Air in the system is murder on pumps, and creates air lock/flow conditions as described. Most systems have air-scoops and air-bleeder valves to help rid the system of the entrained bubbles that persist even with the most diligent of manual purging efforts. (Every 2-3 heating seasons I clean the screen-filter on my system, and end up having to do some minor air purging, and can usually hear the occasional surging hiss as the primary pump chews on another bubble if I put my ear to the pipes, but the air-scoop usually takes care of it after a week or two of heating system use.)

    Auto-fill valves are commonly installed, but are something of a solution-problem. If the system ever develops a leak it keeps the heating system going, but can also increase the size of the flood. Anytime there IS a leak in the system it needs to be dealt with quickly though. If the fill valve is closed it still has to be quite a large leak over a large amount of time to ever become a safety/steam hazard, as long as the boiler is at a lower elevation than most of the system (as in a basement, or something.) The boiler will hiss sizzle & bang a bit at low pressure resulting from a leak, but that would also be an indicator that somethings amiss- the system should stay pretty much the same pressure all the time. With an auto-fill it can be leaking for quite some time undetected, but with a manual fill (or a ball-valve in series with the auto-fill, and turned off) it lets you know.
  4. Not Handy Mike

    Not Handy Mike New Member

    Messages:
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    Location:
    New York
    Thanks and status

    Thanks for the replies. They are very helpful! Pressure was low -- around 10psi, so I added water until it raised to about 16 psi. Flow has begun to the upper level and we have some heat. it does not feel as hot as normal, but does seem to be increasing over time. I can not locate a vent on any of my baseboards. They seem to simply be a pipe that runs up and back down with fins. I checked both ends of the baseboards. Any chance the vent is somewhere in between the ends. I still hear some occasional gurgling, but much less than before. I also did open the bottom drain of the expander and it was dry. I purge out a little water until it ran clear (after a couple of seconds, but did NOT drain the system. Again, thanks for all the help.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    A good system design has an air extraction device. You may have one, but it may be gummed up (well, rusted up or full of crud). You should locate yours, and if all rusty, replace it. Some places don't put a purge valve up high, but it definately does make it easier to get the air out. Keep in mind that the fresh water you add has a bit of air disolved in it, so each time you add some, it either provides oxygen to rust something, or accumulates and creates blockages...ideally, your system is filled once, all of the impurities react with whatever they can react with, and then it essentially becomes inert. Adding water on a regular basis hurts the longevity of the system. No oxygen, no rust or corrosion. Chlorine doesn't help either, nor do the added minerals often disolved in tap water.

    Sometimes, the only reliable way to get all the air out of the system is to first, isolate the boiler, then run full supply pressure through the pipes until you've flushed out all of the air (similar to what happens when you shut the water off to the house, then refill them)...the act of running pressurized water through the system will flush out the air. This should be your last choice, though. If the water is now flowing, if your air extraction device is working, it will purge the final little bit as it gets disolved then stripped out.

    Some air extraction devices work better than others. My limited experience has a Spirovent that seems to work well. Lifetime warranty, but it may need some maintenance occasionally. Some of the 'tophat' devices tend to rust out and the float plunger gets hung up and they no longer work, but they're cheaper. Come summer, or now if you still have trouble, you might find a place upstairs where you could add a drain valve you could open and let it run until you stop getting air out. Since the air will tend to rise, that's the easiest place to purge it rather then trying to flush it out from below.
  6. Not Handy Mike

    Not Handy Mike New Member

    Messages:
    5
    Location:
    New York
    Yep, there is a vent above the Filtrol tank.It has a plastic cap like you find on a bicycle tire on it. No air is coming out, but I remember when I was having the no flow problem, there was water on top of it and on the ground below it. It seemed like water had burped out of the vent. Maybe I'll give the vent a light tap to see if I can free up any crud that may have gotten stuck. Should the cap be put on tightly or left somewhat loose? I will try to avoid the full replacement until the weather warms up just in case the replacement doesn't go smoothly (speaking from personal experience here). Thanks for all your help.
  7. Not Handy Mike

    Not Handy Mike New Member

    Messages:
    5
    Location:
    New York
    Hey, I'm back again. After several days, the boiler lost some pressure again and flow to the second floor dropped off. Added mote water to get the pressure back up, but also noticed the drain valve is leaking. I briefly flushed it as part of my early diagnostics and wonder if some crud got stuck in the trim and now it isn't sealing. It is a very slow drip.ould that be enough to cause the boiler pressure to drop. If so, rather than replacing the valve, can I just screw on a cap fitting to stop the leak?
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,816
    Location:
    New England
    It doesn't take much of a water leak to drop the pressure over several days, so yes, that could be the problem. And, you can screw on a cap rather than replacing the valve - the only thing that may happen is eventually, it may be hard to take off, but nothing a big pair of pliers shouldn't take care of (and it may not happen).
  9. Dana

    Dana In the trades

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    If it's just a drain/purging valve, go ahead and cap it.

    But to be clear, if you're talking about the dripping of the valve with the small "tire cap" type cap, automatic air venting valves shouldn't be capped in non-venting (gas or water-tight) way or you will have defeated their air-purging function. If that's the only water leak in the system (doubtful, but maybe) there may either be a bit of particulates or crud keeping the seal from working perfectly, or it's just plain had it an needs replacing. The valving on them is operated by a small float, and as bubbles accumulate above the float the float drops, opening the valve to let the air out. But with a gas-tight cap it will cease to function. They're cheap to replace, but should last at least a decade or more in most systems.
  10. Not Handy Mike

    Not Handy Mike New Member

    Messages:
    5
    Location:
    New York
    Thanks for the replies. No it is not the vent cap (bike tire cap). It is the 1" drain for vacating the system. I think the plastic cap on the vent was just left resting loosely on the vent to prevent dirt from dropping in. I will buy a cap for the drain and see what happens. Again, I really appreciate your insights. They have been very helpful.
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