Primary/Secondary

Steve_45

1)Can the Crossover pipes be 3/4 or must they be 1 1/4 also?
2)Which is the correct location for my Bell and Gossett thermoflow Balancers Location A or B? Last loop is 1 1/4 should I add on to the primary’s length so that last loop can also be 3/4(If 3/4 is OK) i.e I already have the Balancers and they are all 3/4

3)The last question is electrical in nature. I have a Taco SR506-EXP switching relay. I don’t want the primary circulator to go on when the DHW heater circulator is on.. I understand that when any thermostat calls for heat, the appropriate circulator will go on and the end switch
(X and X terminals) will turn on the primary circulator AND boiler (Aquastat L8148A). I also understand that if zone 6 is switched to priority setting all other zones will stop until zone 6 (DHW) is satisfied. Is it correct to think:
a) When zone 6 calls (X and X terminals will be off)
b) If so, so is control power to Aquastat L8148A therefore Boiler will not start
c) Boiler will come on anyway because temperature
will drop to the 20 degree differential of the Aquastat
so there is no need to start the boiler it will go on when water temp. drops anyway

Waylon Lowery

I'll take a stab at this one.

1) Yes the bridges can be 3/4". Since the boiler has an input of 175,000 btu/hr and assuming that it is 84% efficienct would yield an output of 147,000 btu/hr. For a 20 degree delta T your primary loop should be flowing approximately 15 gpm. Since you have 4 bridges you will want 3.75 gpm to cross each bridge. A 3/4" pipe will carry 3.75 gpm without any noise or exteme head.

2) You will probably want circuit setters at both locations. At location A you would want a circuit setter to help the control and operation of the injection pumps (I guess they are injection). At location B you would want a circuit setter to make sure that each bridge is seeing 3.75 gpm.

3) To answer your question, when operating in priority the SR506 will still close the X and X relay when the domestic zone is calling for heat. Also, if you aren't going to operate the primary pump when the domestic pump is on....then you had better change your piping. Right now if the primary pump is off the domestic pump will just pump in a circle around its closely spaced tees. You need to move the return pipe for your domestic over to the return side of the boiler. Nonetheless, since your zone controller will shut off all of your zone pumps when the domestic is calling; I don't see why you would need to turn off your primary circulator. I would just let your primary circulator run off of your boiler, and keep your piping the way you have it.

Hope this helps.

Steve_45

Thanks Waylon, I missed that in my drawing. I revised the
drawing to refect your correction. Three questions:
1) can the circuit setters just be gate valves to restrict
the flow to get the approx. 4 gpm accross the bridges?
2) If X and X terminals are on won't that make the primary
pump ran and the boiler as well? It just sames like a waste
to have the water running around the primary loop when the
DHW circulator is right at the beginning of the primary.
3) Am I correct in assumming that if the DHW heater calls
for heat and its circulator goes on, shortly thereafter the
boiler will come on because of the Boiler temperature drop?
thus having no need to get power to Aquastat control circuit?

Steve_45

revised Drawing

Waylon Lowery

I would...

1) Use globe valves or circuit setters. If you don't have the capability to check the flows across the circuit setters you could preset them off of their curves, and check/balance them only if absolutely necessary.

2) The x and x on the SR506 will go to T and T on the Aquastat. If you wire the primary circulator to C1 and C2 on the aquastat the circulator will run even when the domestic zone circulator is running. To get around this you will need to use a 120 V ice cube relay with the coil being energized by the domestic circulator. When the coil pulls in it should break the normally closed contacts going to the Primary circulator. Problem Solved.

3) No you are not correct. You must close T and T on the aquastat to enable the boiler to fire/operate based on the aquastat settings.

Good Luck!

Steve_45

Thanks Waylon.
Globe valve over gate valve?

Waylon Lowery

Globe valves...

for balancing. Gate or Ball valves for positive shut off.

Steve_45

Thanks alot Waylon. Your help is greatly appreciated.

Weezbo

here is a way....

do as suggested,connect the return from the water maker to the return of the boiler ,on a "T" just ahead of your return temp gauge "T"at the boiler.dont even worry about domestic priority setting,treat it like any regular zone,it will work fine. I often use zones and not 007's and do the take offs to and from the water maker as suggested....with 4 bedrooms 3 1/2 baths wirllpools...works fine without the recirc... i use a recirc on the hot potable for immediate hot at the fixtures though...