zone valve placement

cutter

I have heard others and people on this site recommend putting zone valves on the return zone line. In the Caleffi idronics journals they recommend the supply side because it prevents heat migration into the zone circuit when the zone valve is closed.
The return water is usually 20 degrees cooler and zone valves have a maximum temperature limit so I am leaning towards the return side. Does it really matter or is the return side the most practical?

newagedawn

i like the supply side best

hot_rod

The valve will shut off in either S or R just fine.

If the zones run up from a header, like this drawing you may get buoyancy induced "ghost" flow if the valves are on the return side, so supply side is suggested.

Temperature should not be an issue, Caleffi valves are rated for low pressure steam applications. The composite case insulates much of the piping heat away from the motor and switch.

A pressure bypass valve or delta P circulator are good design practice with multi zoned systems.

NY_Rob

Don't think it makes much difference supply vs. return.

I went for a location that would provide easy access for install, manual activation, replacement, etc... that just happened to be the supply side.

There is a rambling "banging zone valves" thread currently running where "inertia" of the water in 200 ft of pipe before the zone valve was brought up as a possible cause of the banging. I'm not suggesting it's the cause of the banging... but you won't have inertia if the ZV is on the supply vs. return side.

Mark Eatherton

hot rod said:

The valve will shut off in either S or R just fine.

If the zones run up from a header, like this drawing you may get buoyancy induced "ghost" flow if the valves are on the return side, so supply side is suggested.

Temperature should not be an issue, Caleffi valves are rated for low pressure steam applications. The composite case insulates much of the piping heat away from the motor and switch.

A pressure bypass valve or delta P circulator are good design practice with multi zoned systems.

A.K.A. one pipe thermosiphon... The only real potential advantage to having them on the return is longer life expectancy due to moderately cooler water temperature exposure to motor windings.

ME

Ironman

A note of caution: zone valves and check valves don't play well together. Regardless of where you place the zone valves, remove any flow checks from the zone circulator and lines.

Parachute

@Ironman. What would be the potential detrimental effect of having a check valve at the end of a zone before it enters a return header to prevent ghost migration into the other zones?

Ironman

Think about it: when the zone and the check valve are both closed, that loop is isolated from the expansion tank. There's no means to compensate for thermal expansion or contraction. When the valve opens - BAM!

NY_Rob

If your t-stats control the zone valves directly- you may still need a flo-check in the spaceheating loop because the ZV's will still be open on DHW priority call.
IFC and pump flange flo-check work well if the ZV's are close to the CH pump on the supply side.

cutter

A.K.A. one pipe thermosiphon... The only real potential advantage to having them on the return is longer life expectancy due to moderately cooler water temperature exposure to motor windings.

ME


Mark, my current zone valves have not worked for 10 years or longer. They are placed on the supply side and are about 1 foot or so from my wood burning flue pipe that used to get up way above 400 degrees. I kind of thought the combination of supply side and close to the very hot flue may have caused a short life span of the now junk zone valves. My new location for these zone valves will be in a lot cooler place. Maybe I should just take into the consideration of access for service. Thanks for the comment.

cutter

Ironman said:

A note of caution: zone valves and check valves don't play well together. Regardless of where you place the zone valves, remove any flow checks from the zone circulator and lines.

Bob, I have a variable speed pump that came with the flow check not installed, I will use that pump for the zone valve circuit. Thanks for the suggestion

cutter

hot rod said:

The valve will shut off in either S or R just fine.

If the zones run up from a header, like this drawing you may get buoyancy induced "ghost" flow if the valves are on the return side, so supply side is suggested.

Temperature should not be an issue, Caleffi valves are rated for low pressure steam applications. The composite case insulates much of the piping heat away from the motor and switch.

A pressure bypass valve or delta P circulator are good design practice with multi zoned systems.

Hot Rod, two of the zones are above the boiler but the piping runs down hill before it goes up to the above boiler zones. I am using a Wilo variable speed pump like you suggested, on a long ago post. I have have been thinking about this for the last 3 years or more and I need to get it in this summer. I have all the big parts, just need to do the install and piping.

hot_rod

Thermal drops can also help prevent ghost flow. You need to drop 18” or more, then back up. We learned this on the early P/S Piping arrangements .

Also when the valves are powered and full open, the motor stalls and basically becomes a 5 watt heater. So the motors do run very hot. If you touch one you might think the motor is stuck or defective due to that temperature

Normally open, power to close motors don’t tend to last as long as they spend so many hours in that stall position. So temperature is a factor for the life of any electric motor.

cutter

Hot Rod, I will be going down around 4 feet and under the concrete floor to a wall then back up to the zones above the boiler.
I have seen In idronics where they recommend a foot or so from manifold to a pump but did not know the reason.
I did not know that about the zone valve. Thanks

On the post about the caleffi pressure/temperature gauge, That is a 16 mm square for wrench size and the heat probe is not long enough to reach the boiler with a nipple and coupling added to the gauge so a standard wrench can be used to tighten the gauge. To tighten the gauge a thin wrench would have to be fabricated , or else use an oil filter wrench to tighten up the gauge. I used an oil filter wrench to remove the gauge from the boiler. I wrapped a couple wraps of cereal box around the gauge first.

hot_rod

hard to predict thermal drop performance. that whole concept is a buoyancy driven movement. If you have a large temperature difference the potential is much greater. that is how old gravity systems worked and thermosiphon solar thermal.

The gauge we sell is just a basic replacement sty;le, we don't offer the extended shank or extended sensor versions. we see it used in the hydrosep ports from time to time.

I have some old tappet wrenches, sometimes called lock nut wrenches that were my dads, very thin open ends.

HomerJSmith

Ironman, I'm not so sure I'm buying your reasoning about the check valve, zone valves, and expansion tank thing.

Dennis

Most important; read the installation instructions, most valves have specific requirements concerning in what plan the motor is installed. Had a manager of a local supply house as me if I ever heard of 8 Honeywell zone valves going bad in less then a month. Sure I have they are most likely installed with the motor facing down. Opps! The contractor had to eat 8 zone valves, no warranty.