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Air keeps returning - ideas?

I bought a 1954 home in May. Moving into winter, I doubt the woman who lived here was EVER warm enough. The first days below freezing the house wouldn't get over 67F. I work on the industrial side of the business but I am not experienced with the commercial products used in this house but am learning quickly. First thing I started was bleeding the air out the system. The water was so black that turned into shut down and flush. Before starting, I noticed she had a plastic pan under the pressure relief and there was a small amount of water in it. So while I had the system down and cold, I relieved the pressure and checked the pressure on the surge tank bladder. It was at 30 psi. Since this is a single story home - boiler in the basement - I dropped it to 15 psi. I set the make up regulator to give about 18 psi cold and 25 hot (there is some some creep which I think is normal). Bled the system of air both at the boiler then at the baseboard radiators. The pressure relief stopped it's intermittent spitting...for a while. The pressure crept back up which tells me the make up valve is sticking or leaking. It had warmed up outside for a while so I stopped working on it. When it got cold outside again, the system still couldn't keep up. I went and checked the temperature setting on the boiler and it was set for 160 F! It wasn't that cold outside yet and all I could think of was the poor woman freezing her but off last winter. Set the temp up to about 185F (Per weil mclain manual) and that problem went away.

Air came back again - sounding like a drain pipe when a toilet flushes in a couple of rooms. Replaced the two TACO vent valves with Watts vent valves and bled the system again at the radiators - twice now. I’ve kept an eye on the pressure and shut off the make up after bleeding so the pressure would stay the same. Check it every couple of days to be sure it doesn’t drop until I replace the make up valve. Lasts about a week and the air comes back. No leaks anywhere that I can find. I've purchase a new regulator make up valve with a vacuum breaker because a county inspector noticed there wasn't a vacuum breaker(don’t get me started about dynamic water pressure being too low here – ok for boiler but not for water powered sump pump). Also bought a spirovent jr. to install though it will will only fit in the main supply leg to the original radiators and not a small loop added later when a breezeway was closed in and more radiators added.

I beginning to think my issue is that the water boils in the heat exchanger because the flow isn't high enough. I can hear it very slightly just before the burner shuts off. Of course I may be hearing air or just expansion from heating up, it’s not continuous. Before I cut in to replace the make up valve and install the spirovent, any suggestions? I am used to having supply and return gauges with estimated pressure drop so I can tell if the differential pressure and flow are correct on the big industrial jobs I work with. Being an older house with no info on the design, I have no way of telling what the correct differential should be. How can I check flow? It looks like a Grunfos pump. Will amperage on the motor be accurate enough to tell me if the flow is in range? One big circuit - no zone valves or zone circulators.

So suggestions welcome before I replace the make up valve and add a spirovent.

Comments

  • Snowmelt
    Snowmelt Member Posts: 1,334
    To figure out flow, let's go back to basic. Gpm = btu divided by delta tee x
    That's the btu that you need for the job.
    Send a pic of the boiler near piping.
    I would think because you don't have a air Seperater in your system that the water evaporates new air is introduced to the system then the air in the fresh water comes together and makes one big air pocket.
  • wmtandson
    wmtandson Member Posts: 62
    shut off feeder if pressure drops over time =leak
    unless air is still trapped and still needs to be removed
  • Snowmelt
    Snowmelt Member Posts: 1,334
    Not necessarily, if you shut the feeder off and the water evaperates, no water will be introduced to the system. It he best way to do this is on a system that has a digital pressure guage. I personal did it with a Navien system were when it was nice out it took month to lose water presure. When December came along (boiler ran everyday) it only took 4 days to drop pressure and go on a lock out.
  • hot_rod
    hot_rod Member Posts: 16,286
    Once you determine the system is tight and leak free, either you did not get a good thorough purge, or air is entering the system.

    Piping, pressures, component location are all part of air ingress.

    Take a look at this journal dealing with air in closed loop systems.

    http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_2.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    RobG
  • wmtandson
    wmtandson Member Posts: 62
    hot rod! good read!
  • dedobias
    dedobias Member Posts: 6
    Thanks everyone. Tough to get an overall picture because the boiler is in a corner. So here are a couple of different angles. Obviously the vents are not in a good location and there is not an air scoop. I doubt they do much of anything. I was planning on installing the Spirovent in the middle of the straight pipe to the left of the vent on the top side which is the bigger side of the system 1 1/4". It is also the only location with a reasonably long section of straight pipe. The lower smaller pipe is the added loop to the breezeway.

    No one commented on my settings for pressures and temp so I guess I'm OK there.

    Thanks for the article Hot Rod. I think the spriovent will definitely help. So will just getting the makeup regulator functioning correctly.

    The pressure gauge does stick a little. It is a combination temp/pressure gauge. Gauges always seemed to me to have short life expectancy. Any suggestions on the best combo gauges out there? Plan on re-aiming the gauge face so I can see it from above when replacing it.

    Thanks again everyone.
  • dedobias
    dedobias Member Posts: 6
    If you notice in the picture looking down on the circulator, there is a 3/8" pipe plug right behind the vertical discharge pipe from the boiler. The manual calls for float vent here. Don't think it will help though. Could I use this port to install a gauge so it is easier to read?
  • GW
    GW Member Posts: 4,536
    Any air vents hidden up in the system? You're positive you have correct pressure readings?
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Snowmelt
    Snowmelt Member Posts: 1,334
    The missing vent behind the supply line you might want to put a shut off then a vent. I would with black pipe start at the supply line come up with a nipple add a tee, on the bull of the tee add a temp and pressure guage with a bushing. Then add another nipple on top these air eliminater company's make vertical air seperators. With those other vent caps on top I would replace them with taco top vents. But that's just me. If you think the pressure reducer isn't doing its job right, to replace it you can use the same union and replace the body.
  • Snowmelt
    Snowmelt Member Posts: 1,334
    About the flow, on a cold day like 10 degrees outside. I don't know where your located. You should have a 20 degree difference so if you have 180 going out of boiler your return should be 160 , that's what most applications are based on.
    Part of the math formula is: total btu of zone divided by ( delta tee "20" x 500 "weight of water x 1 hour.
  • hot_rod
    hot_rod Member Posts: 16,286
    If you are going to add a good air scrubber, and you should, consider a multipurpose device. A handful of manufacturers offer air/ dirt separators, now with magnetic bands to protect ECM circs, should you ever upgrade the pre-war blue one :)

    With a good micro bubble air scrubber you should not need any additional vents in the system, maybe one high point vent near the top as an extra protection.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • dedobias
    dedobias Member Posts: 6
    I'll grab an IR gun from work and shoot the temps supply and return. At this point, working right without air mean more to me than efficiency though I understand that means $ in the bill. The flue damper has been removed. How much does that really save and is it worth the complexity versus the risk if it fails closed? Back to flow rate, i take it amperage on the pump is not accurate enough to mean anything? I'm used to working with large HP motors where you can measure the change. These fractional HP motors have such low amp draw I doubt the change is enough to be accurately measurable. Biggest improvement I can make right now is insulating the attic. About 6" of cellulose is all I have. Lots of work to do putting in soffit chutes and replacing can lights so I can insulate over them.
  • dedobias
    dedobias Member Posts: 6
    In Michigan - 7 F today! System is keeping up!
  • dedobias
    dedobias Member Posts: 6
    By the way, her heat bill was more than mine by about $80 with about 800 ft2 more living space in my house in January last year. My old house had 24" of fiberglass and forced air run at about 72 F. This place with hot water heat probably never got above 65 F in the colder days of January!
  • Snowmelt
    Snowmelt Member Posts: 1,334
    Instead of an ir gun why don't you go to the supply house and get a well thermometer, or a spring thermometer, that's what I use. You should use the flue damper, you don't want a big gust of wind comming down on you. Your better off buying a flue damper and keeping it on the side.
  • icesailor
    icesailor Member Posts: 7,265
    "" Biggest improvement I can make right now is insulating the attic. About 6" of cellulose is all I have. Lots of work to do putting in soffit chutes and replacing can lights so I can insulate over them. ""

    You can't buy the insulation from HD or Lowes cheaper than you can have the same or better product installed by them over your existing insulation. Or by professional insulation contractors. Who HD and Lowes contracts out and keeps a piece of the action.

    They make, use and install special insulated covers that fit over the can lights. Switch out the bulbs to LED's. No heat given off.

    In the snow belt, most all traffic signal lights have been switched out to LED's to save money on energy usage and changing bulb/maintenance. The biggest problem with LED traffic lights is that there isn't enough heat generated by the LED lights to melt the snow like the incandescent's did.

    Been there, done that.
  • Gordy
    Gordy Member Posts: 9,514
    icesailor said:

    .

    In the snow belt, most all traffic signal lights have been switched out to LED's to save money on energy usage and changing bulb/maintenance. The biggest problem with LED traffic lights is that there isn't enough heat generated by the LED lights to melt the snow like the incandescent's did.

    Been there, done that.


    Yup so the pay maintenance to go out, and clean them off usually on OT.........unintended consequences.