zone valves

Dave (Canada)

Hello; I have purchased your books Dan on home hydronic systems and I am attempting to install an oil fired boiler and baseboard rads.
I am getting my supplies through my local heating guy.
I am puting in 3 zones using 3/4 inch piping and just recieved my Honeywell zone valves, when checking out the valves I noticed that the inside of the valve
is considerably smaller than a 3/4 inch pipe.
Would this restriction not work against the system of 3/4 inch pipe and cause less heat to flow through the system?
Thanks for your time
Dave Thornton

Unknown

Find of what the CV rating

on the valve is. The amount of water that will flow through a valve is called the flow rate or "CV" Rating.

The CV rating is the gallons per minute (gpm) at a pressure drop of one pound per square inch (psi).

Example:

A flow rate of 3.5 CV would mean that at 1 PSI 3.5 gpm can flow through the zone valve.

As long as the CV rating is matched up to the flow rate in each zone that has been calculated as needed you will not have any problem with heating the zone.

Floyd

Don't worry about it....

those valves are designed that way and will work just fine.
There is a big difference betweena small hole for a very short distance and the restriction of
a pipe over a long distance.
Think of it this way.... if you put your garden nozzle on the spigot ypu will still get a ton of water
through the small hole in it.... but put it on the end of 300' of hose and see what you get..... the
nozzle didn't change, but the restriction of the hose will slow the rate of flow.
My point being that the small hole of the ZV has little effect when considering the overall system.
You've got much more important things to worry about than that!!!!

Mark J Strawcutter

I notice

that Honeywell makes two different Cv rated zone valves in 3/4" and 1"

One is 3.5 Cv with a max close-off pressure of 20psi, the other is 8 Cv but only 8psi close-off.

Mark