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auto-feed on or off for boiler for hydronic baseboard heat ?

ron Member Posts: 143
have a question regarding typical 100k btuh boiler feeding 2 zones and an indirect water heater.  there is a watts auto-feed one-way valve which reduces pressure to ~15 lbs for the boiler, along with a stopper valve.  And there is an expansion tank.  I do not have a low water cutoff device.

What's the preferred practice for this stopper valve?

(a) should the valve be left on so the boiler always has an input of water and stays at the 15 psi of water pressure, especially since i don't have a low water cutoff?

(b) but i would think the system is not suppose to leak therefore once the system is pressurized and working that you could shut this valve off.  this way if there is a leak you don't have a flood.

(c) i don't have a lower water cutoff on the system.  if i did then would it be

preferred to shut the auto feed valve off?  I also see articles about low water cutoff failure so it seems like a catch-22.

(d) thanks.


  • M Lane
    M Lane Member Posts: 123

    Do your bicycle tires stay nice and hard for extended lengths of time? Pumps work via pressure differentials, they don't actually push water. Leaving your make-up water fill valve on provides a push to maintain pressure. If you are afraid of a flood you should call a pro in to do a pressure test/inspection.

    Your boiler may have an integral LWCO, but if not I would add one; I consider them the most important of the safeties.
  • STEVEusaPA
    STEVEusaPA Member Posts: 4,958

    Add the LWCO, close the valve to the water feed.  If there is a leak, especially when you are not home, you will have a mess.

    A boiler is a living, breathing (well maybe not living or breathing) beast (ok NOT a beast), that needs some TLC and more attention then a scorched air system.

    I have the LWCO, and the feed valve closed.  I also walk by my boiler every day, on the way out and when I get home, and glance at the boiler gauge and the display on the Tekmar boiler control.
  • ron
    ron Member Posts: 143
    edited February 2014
    bicycle tires?

    sorry i don't get the bicycle tire analogy.

    and you also said, " Leaving your make-up water fill valve on provides a push to maintain pressure."

    can you further explain that?   how does that do anything to help or hurt the system provided there is no leak.

    to clarify, my setup that came with the house is this:  a taco zone valve on each of 2 returns, into a 1" copper pipe to taco 007-f3 circulator just before going into boiler.  boiler output makes about 3 foot straight run before hitting the big cast iron air scoop with expansion tank, then splits into the 2 zones to go upstairs.  And i have an indirect tank on a separate circulator tee'd off the output of the boiler returning to a T placed between output of the taco 007 and input of boiler.

    what has me confused is a low water cutoff.  how do those work actually, because if it works like it sounds it's completely pointless.  i have 2 floors above the boiler, if i lose water the upstairs bedrooms first get noisy hearing a waterfall in the pipes then i get no heat.  unless a low water cutoff monitors pressure i don't really see the point in one, not with boiler at lowest point in the system.  I would have to lose over 20 gallons of water before there's no water in the boiler, at which point if water didn't flow because the system is half empty the water in boiler would just heat to 180 then shut off right?  or am i missing something?  do people have their boiler installed in the attic where it's a  high point in the system?

    the reason i ask all this is i had the circulator gasket leak a few weeks ago.  replaced it purged the system, everything has been working fine.  i shut the auto feed off maybe 3 days after, and i want to say the boiler gauge has been at 20 psi ever time i glanced at it until 2 days ago when it happened to be at 0.  so i opened the auto feed valve and very little water went in over maybe 3 seconds and brought it back up to 20 psi on gauge.  what would cause that?  there is no evidence of water leakage around anything near the boiler.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    NO leak is a good leak...

    I prefer to install a low water cut off and a low pressure cut off because you will lose pressure before you lose water (belts and suspenders).

    I also don't leave the make up on because I have caused LOT$ of inadvertent damage by leaving one on in a weekend home.

    Some manufacturers (B&G IIRC) suggests turning the make up off after initial fill.

    A great company I use to work for was told by their liability insurance company that they could no longer install automatic water make ups on their heating systems (new ones), so we developed a device call a PIG (Pressure Induced Glycol), which got its start in snowmelt system, and was used to keep the glycol pressurized, but not diluted.

    It is essentially two expansion tanks. One, is the actual expansion tank. The other one is charged with the working fluid, and compensates for the loss of water while the system is going through de-aireation. Once de-aireated, provided you have NO leaks in the system, the pressure should be very stable.

    Someone here has a picture and a drawing of the device. It was the ONLY way our liability insurance company would continue to take our money, and MAYBE cover us for any potential losses we might incur.

    We are trying to propose a change in the code that makes it against the code to have an automatic makeup on any glycol induced systems. Maybe, in the future, we will propose the same feature for truly closed loop hydronic heating systems. If there is a leak in your system, you need to FIND it and FIX it. If you ignore it, your system will go away… And we DON'T want THAT to happen.

    We put out bumper stickers at the AHRI with the RPA logo on them that state "Have you hugged your boiler today?" They were a BIG hit. Going to have to print more for future shows.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
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