2 zones, 2 pumps. 2 flow control valves?

delcrossv

Looking at an old school hydronic system- one pump per zone, no zone valves. Am I correct that each leg needs its own flow control valve so one zone won't be pulling from the other? Or am I overthinking this.

At present there's one valve on the send (pumping toward at present) with tees to the two "zones" afterward.

Jamie Hall

They don't need zone valves -- but they may well need balancing valves, to ensure that the each zone gets the water it needs.

dko

I think he's talking about flo-cheks(taco), flow check valve(watts), flow control valve(b&g). not balancing valves.

delcrossv

dko said:

I think he's talking about flo-cheks(taco), flow check valve(watts), flow control valve(b&g). not balancing valves.

Correct.

EdTheHeaterMan

There are two reasons for Flow Control Valves
1. On a tankless coil for DHW boiler you do not want gravity flow from the boiler that is maintaining a minimum temperature. the Flow Control/ FloChek. or IFC check valve in the pump (if it is on the supply) will keep that from happening;
2. To keep a zone circulator from drawing water backwards thru the piping of a zone that is not operational.

Look in this book called Pumping Away starting on page 9. The illustrations and text are really easy to follow.

delcrossv

EdTheHeaterMan said:

2. To keep a zone circulator from drawing water backwards thru the piping of a zone that is not operational. Look in this book called Pumping Away starting on page 9. The illustrations and text are really easy to follow.

This . So, one on each zone?

Wondering why there was only one with the present  "pumping toward" arrangement?

hot_rod

Maybe a sketch of what you have.

Two pumps on the boiler return, one flo-check at the supply from the boiler?

There are different names and devices for preventing flow from a circ when it is not running. Some are brand specific names as @dko noted

delcrossv

@hot_rod Here's what's there. Except to prevent gravity flow, I don't get why only one flow control. Each circulator can get some flow into the "off" zone. 
Is it too little to matter?

delcrossv

As I understand it, pumping  away would have two valves, one per pump.

EdTheHeaterMan

What is the possibility that there was one Flo Check on the original one zone system because it had a tankless coil? Not necessarily the boiler that is there now, but maybe a previous boiler. Then there was a second zone added later in the home's lifetime. But the installer of the second zone didn't get it quite right.

And since the installer got lucky and just by happenstance the two zones were matched close enough that both thermostats would call for heat regularly, so the homeowner never noticed they had a problem. Or if they did, then never did anything about it because “that is just the way it works” Said a unknowing plumber.


I really like to look at old buildings thru the eyes of the heating system and try to see how many heating systems may have been in that old home. Old gravity Cast radiators, with 2" mains that left the boiler room, connected with bushings to 1-1/4" iron pipes that reduce to 1" copper tell me that there were at least 3 different boilers in that home. Then the first one may have been coal that was converted to oil... so that makes 4 different systems if you count the coal to oil conversion as 2 separate heating systems in one boiler.

hot_rod

There are any number of ways to upgrade 
Id bring it into the 2020s with zone valves and an ECM

delcrossv

@EdTheHeaterMan Nope. One owner, all original equipment since 1956. Supposedly the original Series 100 pumps were replaced with the same model in the 90's Never had a tankless coil.
Nicest Crane Sunnyday I've ever seen.

System works, but I don't understand the "why" of it, unless everything gets a little warm even if the associated pump is off.

delcrossv

hot_rod said:

There are any number of ways to upgrade 
Id bring it into the 2020s with zone valves and an ECM

All true, but beside the point (as it ain't broke). Why the one Flo control instead of two? Pumping away using two valves make sense as each circuit is isolated when the associated pump is off. I'm missing something in the logic as to how they got away with a single valve.

EdTheHeaterMan

Agree with @delcrossv. It should have a reverse flow problem.

Since the pump will move the water to the path of least resistance, somehow the resistance thru the boiler and flow control valve, and the path thru the opposite zone that is off, were fairly close. So close that perhaps the amount of flow that would happen by gravity to the non calling zone when the flow valve opened, was equal to the reverse flow of the calling zone’s circulator. If someone replaced one of those B&G 100 pumps with a Taco 007, that balance would be different and who knows what would happen.

By all other scenarios that should not work so well.

delcrossv

So ,based on @EdTheHeaterMan 's comment. any configuration change should include a second flow control valve, yes?
This one was a head scratcher for sure.

EdTheHeaterMan

Yes. You would definitely need 2 flow control valves of some type. You could use this detailed diagram from an earlier comment, or the one next to it. What ever is easier to configure based on existing conditions. Just be sure to pump away from the expansion tank.

Sylvain

have a look at this discussion:
https://forum.heatinghelp.com/discussion/196513/