zone valve question

Wayco Wayne_2

We are installing a large (for us) boiler system of 1.2 million btu's. We have 6 zones of varying sizes. I usually use Caleffi Zone valves but their largest zone valve is 1-1/4" with a cv of 7.5. My biggest zone is 2." Should I reduce down to the zone valve or find another manufacturer that makes 2" zone valves? What problems could I be facing?

Ironman

CV Rating

You need to size it by the cv rating, not the pipe size. That, of course, means you need to know the flow requirements for each zone.



Belimo makes larger size zv's.

hot_rod

Consider

Pumps instead of valves. If that 2" zone is 35- 40 gpm that may be an expensive zone valve. Probably not a spring return type thus more complicated wiring. See what every zone flow rate is. I agree Belimo is a good source for high flow zoning valves

Wayco Wayne_2

What if

I used two 1-1/4 zone valves and teed them together downstream?

SWEI

What is the capacity

of the zone?  How many GPM at what ∆T will answer the question.



Any reason not to use a pump as Bob suggested?



Is the main circulator fixed speed?  Is it being replaced?

Wayco Wayne_2

I was

Planning on using a Wilo Stratos 2x3 x35 on six zones. the largest needing 35 to 40 gpm.

SWEI

why not

a few smaller Stratos pumps?  How many zone valves are there?  You can run a Stratos ∆T if you need to.

Wayco Wayne_2

6 zone valves

Ranging from 1" to 2 " Why break it up into multiple circs. One oughta work. Or am I missing something? BTW I found Belimo had the 2" zone valve I needed. Thatnks for the suggestions.

SWEI

how many GPM?

really is the question.  Belimo makes good stuff -- I greatly prefer their CCVs over zone valves.



What you are likely missing is the opportunity to tune the flow for each zone independently, which would be trivial using separate ECM pumps.  Adding circuit setters or proportionally-controlled CCVs would probably cost more at those flow rates.

Wayco Wayne_2

?

What are CCV's?  My gpm's are; 40, 15, 8, 8, 5, and 5.

SWEI

CCV = Characterized Control Valve

Basically a ball valve with a special characterization disc which produces linear flow rates based on position.  The first two pages of https://www.belimo.us/belimo/media//Technical_Documents/Characterized_Control_Valve/CCVTechDoc.pdf describe the concept quite well.



Without knowing loop heads, I'd probably spec a single Stratos for the 40 GPM loop and another for the 15 GPM loop.  I'd set those for the most ∆T I could tolerate on those loops at full load.  The 8,8,5, and 5 loops might get individual small pumps (Bumble Bees most likely) or be combined into one or two groups on a ∆P circ with zone valves.

DanHolohan

PDF

Post PDF

Wayco Wayne_2

Still need an answer. why circs instead of zone valves

??????????

SWEI

Circs instead of zone valves

mainly to provide zone by zone flow control.   If I had CCVs and proportional controls I could use a single ∆P ECM circ, but I might still separate out that 40 GPM zone since it represents almost 2/3rds of the total system flow.  While ECM circs can modulate flow, they are still centrifugal pumps, and as such, pay a price in hydraulic efficiency when operated near the bottom of their range.  What does the giant pump do when only one of those 5 GPM zones is calling?



Are there additional downstream control valves?

Wayco Wayne_2

I was thinking

Of using the large Wilo for the 15 and 40 and using a smaller circ for the single digit zones. I'll look at the pump curves tomorrow.

SWEI

That should work

even with bang/bang zone valves!

The Steam Whisperer (Formerly Boilerpro)

Check out White Rodgers ZV's

They are basically a full port design.  The 1 1/4 inch has a lot of flow capacity and are pretty inexpensive.  They are what I used to use whenever I needed a lot of capacity.

Wayco Wayne_2

Thanks

I'll remember that for next time. I've already bought a Belimo with a cv of 57 for a 2" zone valve. Since my gpm is 40 I'm good with that.