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  1. #1
    Join Date
    Feb 2012
    Posts
    3

    Question Air in Heating System

    I have a 30-year-old forced hot water heating system that runs on gas (via a conversion burner, it was originally oil). I have it tuned up in the fall but it always seems to get air in it fairly soon. In late December one zone got air-bound. I had both zones thoroughly purged of air, but within 2-3 days I could hear a little gurgling, and now, 6 weeks later, both zones are noisy when the heat comes on. The noise doesn't bother me that much, but I'm concerned about the inefficiency of the system and also worried about it getting air-bound again. Is there a more permanent way to fix the problem?

  2. #2
    Join Date
    Aug 2008
    Posts
    69

    Default Re: Air in Heating System

    MLC:

    If you had the system serviced by a service tech person (usually at the start of the heating season), and you pay for a service contract with them, they should be able to get the air out on a permanent basis; if you are dissatisfied with the service, consult the Yellow Pages under "Heating Contractors" & try another tech; if you want to try to solve this on a DIY basis check the info & sites below & report back with your results, good or bad.

    Air in the heating pipes is no big disaster----but it DOES cause an aggravation in having to listen to the noise whenever the system comes on, and it DOES result in an inefficiently-run heating system that cost more $$$ to run----the problem should be addressed ASAP.

    The sites below provide info as to the various causes of air in the heating pipes; read thru the sites, & try some of the things suggested; these are essentially DIY procedures that could take several hours if you do a good job, & could well solve the air problem.

    First check the boiler gauge (on the front of the boiler) to see that you have at least a 10-12 psi reading on the "water pressure" needle (there are 2 needles on this gauge; one measures water pressure, the other measures water temperature); If the WP is less than 10 psi, you will have to add more water to the boiler to avoid excess air in the system.

    You will notice on the various photos that there are air bleed valves NEAR the boiler, and usually on each radiator/baseboard convector throughout the house, as well---it's important to bleed ALL the valves noted by opening them & listening to see if you hear any air escaping, and then see some water coming out of the particular valve you are bleeding before you close it.

    Some valves may be so caked with mineral deposits (as seen in the photos) that they can't be made to bleed any air/water out of them-----these will have to be replaced, or at least completely cleaned until they expel air/water.

    Please post back to report on your progress and to advise if the bleed valves are badly caked with minerals & need replacing, and to report if you open any air valves & NOTHING comes out; the last site below may not apply to your system; it is designed to be used by those who DO NOT have any bleed valves on the radiators/baseboards, & thus their system needs a forced air purge.


    http://www.inspectapedia.com/heat/AirBleedValves.htm
    http://www.inspectapedia.com/heat/Air_Removal_1.htm
    http://www.inspectapedia.com/heat/Air_Removal_2.htm
    Last edited by brewster; 02-08-2012 at 02:47 PM.

  3. #3
    Join Date
    Feb 2012
    Posts
    3

    Default Re: Air in Heating System

    Thanks for the detailed reply, Brewster. I think I'm going to get a service tech to work on the problem. I notice the guy who bled the system in December left a note to the effect that the pressure gauge on the boiler reads 12 psi above actual, based on the readings he was getting on his own gauge. Without accurate pressure readings it doesn't seem like a good idea to DIY the job, especially as I have no previous experience with this.

    Another question: the burner on the boiler comes on periodically all summer, even though there's no call for heat. (I think the boiler originally supplied the house with hot water, but now there's a separate on-demand hot water heater.) Last summer I shut the boiler off, and as soon as it cooled down it started to leak water out the bottom. The service tech in this case told me the boiler wasn't designed to cool off, and said I had 3 options: 1) turn the burner back on and leave it on all summer; 2) invest in a new boiler; or 3) inject the boiler with a sealant which was unlikely to work very long, if at all. I went with option 1, but would appreciate a second opinion. Thanks.

  4. #4
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Default Re: Air in Heating System

    I would suggest a new gas boiler,if the boiler is leaking water when it cools down it is probably leaking when it gets hot also, you just don't notice it because the vapor goes up the chimney, if a lot of make up water is added into the system that is where the air is coming from after the oxygen gets boiled out of the water. A new boiler will cost you more initially, but the gas savings if you go with a higher efficiency boiler should pay itself off soon, the bad thing about a leaking boiler is you never know how long it will last, and yes the boiler liquid, or sealer is a temporary fix! Good luck!

  5. #5
    Join Date
    Aug 2008
    Posts
    69

    Default Re: Air in Heating System

    MLC:

    Yes, it sounds like a new boiler is the way to go: if the present unit is 30 years old, that means if you buy a new boiler the engineering design improvements built into the new units will save you lots of $$$ & you can get rid of the problems associated with the old unit; another problem with the old boiler is that (like you suggest) it was used also as a source of the hot tap water for the house (domestic hot water, DHW); that means that you have what's known as a "triple aquastat" inside the boiler that fires the burner regularly to keep the boiler water hot so hot tap water will always be available; thus you'll be wasting gas most times of the year with the old unit; it's unfortunate that you bought an on-demand HWH, which are often expensive to buy & install; the standard setup for a new boiler is to buy a gas-fired 3-pass boiler by perhaps Crown, Dunkirk, Peerless, Utica, Biasi, etc, and also a companion unit known as an indirect hot water heater, IHWH); the IHWH is simply a 30 gal or 40 gal heat exchanger that uses the hot boiler water to heat the DHW & is known as a very efficient way to maintain your heating & DHW needs; a new 3-pass boiler would provide approx 85% to 90% efficiency in comparison to perhaps 50% or 60% efficiency with the older unit you have now; the IHWH (Triangle Tube, HTP Super Stor, Weil-McLaine, TFI Everhot) have a track record of lasting decades without any problems, & there is no burner on them to burn extra fuel, or no need for an additional flue.

    The standard procedure is to consult the YP under "Heating Contractors" and get at least 3 separate estimates from different contractors for a new unit & perhaps an indirect HWH------the estimates can very considerably in price range as well as equipment installed by the particular heating tech---also ask family, friends, co-workers, etc. if they have had a recent boiler install & if it was a good experience, or not.
    Last edited by brewster; 02-09-2012 at 09:57 PM.

  6. #6
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,100

    Default Re: Air in Heating System

    Your heater is 30 year old? consider yourself lucky, but it's time to replace it. You won't find a better solution than this.

  7. #7
    Join Date
    Feb 2012
    Posts
    3

    Default Re: Air in Heating System

    Thanks so much for the advice, everyone. Not happy about replacing the boiler but after 30 years I guess it's time. I wish the previous owner of my house, who installed the separate on-demand HWH, had gotten a little more advice first!

  8. #8
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Wink Re: Air in Heating System

    People tend to do as little as possible if they plan on selling there house soon,we call it the fluff and buff! The price they paid for the on demand hot water heater and it's installation cost could have paid for 1/2 the price of a new installed boiler. I am amazed at how much stuff people try to cover up, I have seen door and window sills, foundation sills, and support posts partially made out of wood putty, then painted over and said to be new, I think people tend to think they are going to be taken for a ride with there expenses,but it is probably cheaper to replace it than cover it up, and have some peace of mind, get a few quotes on a new boiler and take it from there, some gas companies are offering interest free loans and rebates if you upgrade your gas equipment! Good Luck!

  9. #9
    Join Date
    Feb 2012
    Posts
    2

    Default Re: Air in Heating System

    This system gets its name from the way it uses the difference between the outdoor air temperature and the indoor air temperature to heat or cool a home. During the summer, the air source heat pump functions as an air conditioner; during the winter, it runs in reverse to provide heat. Properly installed and connected to a well-designed (and tight) duct system, an air source heat pump can deliver up to three units of heating (or cooling) energy for every unit of electric energy it consumes except in very cold weather, when a backup resistance heating system must supplement the heat pumpís output.
    Because it heats and cools, an air source heat pump is a good choice for replacing an existing heating and cooling system or when you need a new furnace and want to add central air-conditioning. Look for a heat pump with a high HSPF and SEER rating. The best units have a two-stage compressor that runs in a low-power, energy-saving mode most of the time, along with a variable speed blower motor that minimizes noise and energy consumption.

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