Question on Zone Valves

[Countryboy1966]

I am about to begin re-plumbing my OWB and my house which I will cover under another thread for entertainment purposes, plus to show what happens if you don't properly research and plan things.

I've been studying boiler system plans and I have a few questions.

-As far as a zone valve is concerned, I only need to get one with the same size inlet as the pipe on the line it is feeding correct?

-I believe I am understanding that zone valves can be purchased normally open or closed. I know what that means, but I would want to have normally closed correct so it only opens when the zone is calling for heat?

-I see a lot of plans with individual circ pumps on each zone line. Is this for better control within each zone so head pressures remain more constant?

Thank you in advance.

 

[Nofossil]

My thoughts - keep in mind that I am not a plumber and may not actually have any idea what I'm talking about. Don't believe everything you read on the Internet.....

Zone valve are designed to present a pretty large flow restriction so that the total flow through the system will increase in proportion to the number of active zones, and so the total flow restriction of each loop will be very close to the same regardless of differences in plumbing (since the zone valve provides so much flow restriction). In most cases, the internals are the same and the pipe size is only to make your life easier.

Normally closed is most common.

You can go with either a zone valve for each zone or a circulator for each zone. Circulators will provide a much higher flow rate, but also use much more power. If you have REALLY long zones with a lot of baseboard on each, then circulator per zone might give you better performance. I prefer zone valves myself for the lower power consumption and since they prevent 'ghost flow' in configurations where that might happen otherwise.

 

[in hot water]

zone valve, any valve really should be sized by the flow rate you intend to move thru it. Referred to as the Cv rating. A zone valve with a cv of 7.5 would flow 7.5 GPM with a one pound pressure drop thru it. You can flow more than the Cv but you get more pressure drop.

Zoning with valves was very common early on 60- 80's. Radiant Floor heating brought zone pumps ,mainly due to the pressure drop thru long, small diameter loops, requiring high head circs.

There is a big movement back to zone valves due mainly to the introduction of delta P pumps. A delta P pump changes it's speed and output automatically based on the number of valves that are open or closed. The also use permanent magnet motors ECM and are 40- 60% more efficient also.

One of the challenges with a high flow zone valve is the ability of the mechanism to stop the flow. If you need a high flow valve a motorized ball valve allows for a full port and higher GPM.

Some manufacturers offer zone valves in several Cv ratings even in the same pipe size. We offer 3.5, 5 and 7.5Cv valves. The lower Cv have smaller ports and can close off against higher pressures, typically high rise commercial buildings applications.

You may find 1/2" zone valves with the same Cv as a 1-1/4". Same orifice is used regardless of the pipe size. So buying a larger pipe size zone valve doesn't always get you a higher flow vale, just a piping convience.

There is a place for both methods pumps or valves for zoning, it really has to do with you required flow rates. etc.

hr

 

[Countryboy1966]

Thank you for your responses!