zone valves and Circulator

h12721aa

     

I have a question, on my old set up the Circulator



is on the return side of the boiler, on the print of the new boiler they show



the circulator on the supply side after the Air scoop. Old and new are both Burnham Boilers the new one is a MPO IQ84.  Does it



matter? I am thinking to go  with three circulators 2 for 2 zone baseboards and 1 for indirect domestic hot water.

Or should I use zone valves.



Also they show a cut off and supply valve as a screw (turning ) type and

then also ball valves in a other lines. What is the reason for this? Could I use ball valves for

everything?











Thanks    Hilmar

Ironman

Circ Placement

The proper place for the circ is on the supply line, after the air separator IF the expansion tank connects to the air separator. The place where the expansion tank connects to the system (Point of No Pressure Change) is what determines where the circ should be placed. The circ should be place immediately down stream of the PONPC pumping away from it, not towards it.



For many years, the circ came attached to the return of boilers because it could be crated and shipped easier like that. The shipping department made that decision, not the engineering department - they knew better. That lead to a whole generation of "techs" thinking it belonged on the return. The misconception is still very prevalent.



The reason for this is that if the circ is pumping away its pressure differential is ADDED to the static fill pressure of the system. If it is pumping towards the PONPC, the circ's pressure differential is DEDUCTED from the static fill pressure of the system.



What this means in practical terms is that if the circ is pumping away as it should, there will always be positive pressure at the highest point of the system if all else is right. If it's pumping towards the PONPC, then then highest point of the system may have low or negative pressure when the circ is running. The can cause air problems, cavitation and other issues.



Get Dan's book "Pumping Away" for a thorough explanation.

Jason_13

If I could Add

In the late 50's the first wet rotor one piece circulator was introduce. This is when it all changed due to a big change in the circulator. Residential they move much less water than the three piece circulators like the B&G 100 or Taco 110.Therefore air elimination is done with adding pressure to the system. This will make the air bubbles smaller trying to add them back into solution. Smaller bubbles are less buoyant and will not float back up the vertical pipes as easily. As of the late 50's all wet rotor circulators should be mounted after the expansion tank connections be it on the supply or return. Yes you can still put the circulator on the return if the expansion tank is on the return common piping. If done that way the only disadvantage is air elimination is not quite as good.

Air elimination is best on the hot side of the boiler. When the water is heated it starts to separate the air from the water. When the water passes through an air separators there is an agitation that will complete the separation and vent it out. Hotter water is easier to get rid of the air.

With that said I do believe that with the use of more radiant and ODR becoming more popular the use of more upscale air elimination like micro-bubblers should be mandatory.

h12721aa

zone valves and Circulator

     OK on placing the Circulator.

   Now should I use 2 Zone Valves or 2 Circulator for the heat and 1 Ciculator for the DHW ?

      Also they show a cut off and supply valve as a screw (turning ) type and

then also ball valves in a other lines. What is the reason for this? Could I use ball valves for everything?

Hilmar

Ironman

Circa or ZVs

It really depends on the flow requirements of each zone. I generally prefer circ's over ZVs and the price is about the same if a panel is used with each (recommended for ZVs, required with circ's).



If a ECM circ is used, then ZVs would be used with it. The indirect is almost always better served by having its own circ properly sized for it.



It doesn't matter if it's gate valves or ball valves, unless the "screw" valve you're referring to is a globe valve being used to throttle the flow.

h12721aa

Zone Valve and Circulator

(if a panel is used with each)



Could You explain this?

thank you Hilmar

Ironman

Control Panels

Look up Taco SR504 pump panel or ZVC 404 zone valve panel.



The SR504 controls circulators; the ZVC controls zone valves.