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Hydronic loop on Steam Boiler

hvacL1fe
hvacL1fe Member Posts: 1
The hydronic loop I've been having issues with is off of the water base of the steam boiler. The customer has had issues with this loop not heating off and on. I isolate the loop, pressurize it and nothing comes out of the bleeder on the baseboards and 1 radiator on the second floor even when they are heating. They also have a baseboard in the steam system that only heats half way through it. There is no heat exchanger in the hydronic loop which I thought was the correct way to pipe it. Just a circulator off the bottom of the boiler. I really need some help here
jascosupply

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 20,440
    No heat exchanger? And you're trying to get up to the second floor? No can do. Even if you could persuade it to hold suction up there cold, you'd never get it to do it hot and you lose circulation.

    Sometimes you can cheat a little with that kind of arrangement -- a first floor baseboard, for instance -- but second floor? Nope.

    Steam baseboards -- your other question -- are always problematic. Is it piped with a return? Or an inlet and a vent? Either way it needs a lot of pitch so the condensate can drain, and if it's vented you'll need to experiment with vents to find a size that works.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • TonKa
    TonKa Member Posts: 65
    edited December 2022
    Jamie, I don't think your viewpoint that you can't run the zone to the 2nd floor without a heat exchanger is correct. This article by Dan Holohan explains how to do it:


    Done right, you should be able to get the loop up over the boiler's waterline to around 30 feet.

    mattmia2Long Beach Edethicalpaul
  • pedmec
    pedmec Member Posts: 713
    You absolutely can do i. Done about a dozen this way. Up to 30' above the boiler. You need to make sure you have no air vents on the loop or your going to allow air in and then lose the loop. Check valves on both side of the loop at the boiler. 2 purge valves in the loop to bleed the loop with a hose. Make sure the purge is before the circulator so it bleeds thru circulator.
    mattmia2TonKa
  • mattmia2
    mattmia2 Member Posts: 7,165
    You also need a bypass that brings some of the return water back in to the circulator to keep the water cooler so it doesn't flash to steam under the vacuum from the column of water up to the second floor. if you don't have the bypass it will work when the boiler is cooler but when the boiler is up to steaming temp it will flash to steam in the piping so you will see intermittent issues with it not heating.
  • pedmec
    pedmec Member Posts: 713
    Installation of an aquastat on the supply line should prevent the flashing of the heating loop. i've done it both ways and never had a problem without the bypass so i stopped installing it. what you really need is to install a wye strainer before the circulator. sediment will get stuck in the impeller and kill the circulator.
  • mattmia2
    mattmia2 Member Posts: 7,165
    Wouldn't controlling it on an aquastat mean it could only heat when there isn't a steam heat call?
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,057
    edited December 2022
    It sounds like you are saying the loop is empty; it's losing its water? You have to fill it with a hose from a sink or somewhere with pressure. There should be a service valve on the loop for this. The pump is a 𝘀π˜ͺ𝘳𝘀𝘢𝘭𝘒𝘡𝘰𝘳. It won't pump water up from the boiler to fill the loop. It only circulates water that is in there.

    If the loop is losing its prime, or the water's falling out of it, you have an air leak in the loop above the water line. There shouldn't even be a bleeder valve on those radiators for that reason. Even a little air leaking into the loop will drop the water out of it which can air-bind the circulator and cause it all to stop.

    It's a bit of an oddball arrangement; we see lots of them in Brooklyn. They work well once you fill the loop and then keep the air from leaking into it. ... Until the circulator fails, but that's another story.
    TonKa
  • Jamie Hall
    Jamie Hall Member Posts: 20,440
    I was thinking more in terms of reliability. If the temperature in the circulating loop is kept below the boiling point of the water at that elevation AND if there are no air leaks at all yes, it will work without a heat exchanger. For example, water in a closed loop will boil at a height above the boiler of 15 feet if the temperature of the water is 180 F. At 160 it will boil at 23 feet. At 120, you're good to 30 feet. More or less. And so on. Keep the circulating temperature low enough and you will be fine...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 7,165
    Isn't there something about keeping the circulator below the water line and sizing it so that it can push water up to the top of the circuit if needed too?
  • TonKa
    TonKa Member Posts: 65
    edited December 2022
    I was thinking more in terms of reliability. If the temperature in the circulating loop is kept below the boiling point of the water at that elevation AND if there are no air leaks at all yes, it will work without a heat exchanger. For example, water in a closed loop will boil at a height above the boiler of 15 feet if the temperature of the water is 180 F. At 160 it will boil at 23 feet. At 120, you're good to 30 feet. More or less. And so on. Keep the circulating temperature low enough and you will be fine...

    I don't think your boiling points for the water at various distances measured in feet is remotely correct. The water at the top of the loop without a heat exchanger is at zero PSI. Water at zero PSI will boil at about 212 degrees Fahrenheit. Even if that system was in Denver (where you could only get the water up about 25 feet), water at zero PSI will boil at about 202 degrees Fahrenheit.

    And, while it is true that if there are air leaks in the loop it won't work, I will point out that if there are air leaks with a pressurized loop and a heat exchanger, you have a water leak with pressure behind it.
  • TonKa
    TonKa Member Posts: 65
    edited December 2022
    mattmia2 said:
    Wouldn't controlling it on an aquastat mean it could only heat when there isn't a steam heat call?

    Wired correctly, It'll heat when the boiler is making steam, too.
    Long Beach Ed
  • TonKa
    TonKa Member Posts: 65
    I was thin0king more in terms of reliability. If the temperature in the circulating loop is kept below the boiling point of the water at that elevation AND if there are no air leaks at all yes, it will work without a heat exchanger. For example, water in a closed loop will boil at a height above the boiler of 15 feet if the temperature of the water is 180 F. At 160 it will boil at 23 feet. At 120, you're good to 30 feet. More or less. And so on. Keep the circulating temperature low enough and you will be fine...

    Where did you get those numbers for the boiling point? Water at the top of the loop is at zero PSI, no?

  • mattmia2
    mattmia2 Member Posts: 7,165
    TonKa said:



    I was thin0king more in terms of reliability. If the temperature in the circulating loop is kept below the boiling point of the water at that elevation AND if there are no air leaks at all yes, it will work without a heat exchanger. For example, water in a closed loop will boil at a height above the boiler of 15 feet if the temperature of the water is 180 F. At 160 it will boil at 23 feet. At 120, you're good to 30 feet. More or less. And so on. Keep the circulating temperature low enough and you will be fine...


    Where did you get those numbers for the boiling point? Water at the top of the loop is at zero PSI, no?




    No. You need to start talking psig or psia here. It will be negative psig equal to the height in water column of pressure minus a little for the pressure the circulator adds unless it is higher than the atmospheric pressure in water column at the top of the column.
  • mattmia2
    mattmia2 Member Posts: 7,165
    TonKa said:


    mattmia2 said:

    Wouldn't controlling it on an aquastat mean it could only heat when there isn't a steam heat call?

    Wired correctly, It'll heat when the boiler is making steam, too.


    It can't. If the boiler is steaming it is very close to boiling and will be too hot to not flash to steam under the partial vacuum in the loop, the aquastat should be shutting it down until it is cooler.
  • TonKa
    TonKa Member Posts: 65
    edited December 2022
    mattmia2 said:
    It can't. If the boiler is steaming it is very close to boiling and will be too hot to not flash to steam under the partial vacuum in the loop, the aquastat should be shutting it down until it is cooler.




    The loop water temperature is tempered by the bypass. It doesn't approach the water temperature in the boiler unless you adjusted the bypass incorrectly.

    I just read the article again. I still don't see where there's a vacuum. I'm not sure what you're talking about. I'm not saying Dan Holohan can't be wrong, but you seem to be contradicting him. I am also not sure what you are implying about Long Beach Ed mentioning in this thread all the setups he's seen in Brooklyn with this exact configuration.

    Long Beach Ed
  • mattmia2
    mattmia2 Member Posts: 7,165
    Oh, ok, i read it as you were suggesting you could use an aquastat instead of a bypass.

    The bypass is necessary because there is a partial vacuum anywhere above the water level of the boiler that increases as you increase height above the water line of the boiler.

    I think this is Dan's example(worded much less eloquently than he would say it). Think of a straw in a glass of water. If you put your finger over the end of the straw and lift it up without lifting the end above the surface of the water there will be a column of water in the straw. If you release your finger that column of water will drop down in to the glass. The weight of the water is creating a partial vacuum above the water and holding it in the straw. When you release your finger you are letting air in and letting the pressure return to atmospheric pressure. It is the same thing holding the water in the pipes above the water line. If you open a vent or have a leak at the top of the loop, it will return to atmospheric pressure and the water will fall down in to the boiler.
  • mattmia2
    mattmia2 Member Posts: 7,165
    This part is wrong:
    Q: Where does this pressure come from?
    A: This is the static pressure we talked about before. It comes from the weight of the water. The higher the column of water, the greater the static pressure at the bottom will be.

    heating p163 300x178

    Want another example of static pressure? Think of the water in the ocean. There's no pressure at sea level, but as you dive deeper and deeper, the pressure increases because there's more water sitting on top of you. In our zone, "sea level" is the high point.

    This is true of the ocean because the top of the ocean is open to the atmosphere. When it is sealed at the top, the pressure is 0 psig at the bottom and the pressure decreases from there.

    This is why there is a 30 ft limit, 30 ft of water is approximately atmospheric pressure.
  • Jamie Hall
    Jamie Hall Member Posts: 20,440
    Or to look at it another way. We are very accustomed to just saying "psi" (or ounces!) -- but when we do that, we are talking about psig -- that is, pounds per square inch gauge pressure. Which is the pressure measured in relation to atmospheric pressure -- whatever that may be where we are at the moment, and the weather we are having. However, all calculations involving thermodynamics -- including such things as boiling point, "npsh" (net positive suction head -- pumps) and the like need to use absolute pressure -- psia. That is the pressure not referenced to sea level, but to an admittedly abstract perfect vacuum. (the same thing is true of temperature -- all thermodynamic computations use absolute temperature -- Kelvins or Rankine -- instead of our quite arbitrary Fahrenheit or Celsius scales -- which is referenced to absolute zero, where all thermal motion of atoms ceases).

    Once one gets into the habit of mentally translating everything into absolute measurements, a lot of things get much simpler -- and make more sense.

    Like the pressure of water at the top of a sealed pipe extending up 33 feet or so. Which would be 0 -- psi absolute. Or would be, if the darned water didn't "boil"...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    mattmia2
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,057
    edited December 2022
    The loops work. I'm in an attic room now 23-feet above the steam boiler. It's heated with a loop of 1/2" baseboard piped off the base of the boiler. It has a Taco 007 stainless pump that's 10 years old.

    It's piped with a bypass that I've never had to open. I suppose the loop loses enough heat before it's pumped. Never heard it cavitate. I use a two stage Tekmar thermostat. Stage 1 operates the pump. If the boiler's cold and the room temperature doesn't rise, Stage 2 fires the boiler to a high limit that varied by outside temperature.

    About 13 miles from Brooklyn, where lots of basements and attics are heated like this.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,121
    once the loop is filled with water it essentially becomes a closed loop even though it is in contact with atmospheric pressure,

    As such the circulator does not have to lift the water to the top of the loop. It just circulates it. The weight of the water falling down the return line equalizes the weight of the water going up
    ethicalpaulLong Beach Ed