Flow check in injection supply/return?

hydronicsmike

If you have had good luck with the check valves you are using and didn't see any on/off injection to occur as a result of it, can you please share more details ont his check valve with me? I'd be interested to hear who makes the Check Valve that has served you well and keep that in mind if I get asked for it.

I would also love to find out more about the flow setter you are refering to. Thats the absolutely best way to go!

Please advise.

Thanks,

Mike


PS: Sent off a package for the Ted Lowe Fund to our friend Dan Foley. Too bad I can't be present myself for that auction and Radfest. Paul Williamson will be there.

Chris_56

flow control valves in injection supply/return?

In Dan's book titled 'Primary Secondary pumping made easy' on pages 67-68, he indicates that it is very important to have flow control valves in both the supply and return injection lines.

I noticed that Taco offers the 007 with integrated flow check. Any comments/experience using this particular pump as the variable speed injection pump? How important is the flow check on the return injection line if one is on the supply?

hydronicsmike

VSI - you shouldn't require either, if piped correctly (IMO)

When piping Variable Speed Injection Systems (VSI), as long as you have your two primary/secondary tees as close together as physically possible and then a minumum of a 1 foot drop (if more than its better) as your thermal heat trap, you wouldn't need a Check Valve at all. Please review the attached Essay that also explains the piping of Variable Speed Injection Systems.

But to answer your questions, the Pumps with integral check valves have been working fine with Injection. Their built in check valves are fairly easy to open, unlike other spring loaded check valves.

Other than the Pumps with integral check valves, you don't want to have a check valve in the Variable Speed Injection loop at all.

Spring Loaded Check Valves create an on/off Injection system as a pump at very low speed may not provide enough head to open the valve and the controls tend to increases the injection pump output to overcome the problem. But as soon as the check valve then opens up, too much flow is injected and the control will immediately reduce its injection output to compensate for that but then the valve will shut again.

Swing Check Valves have caused some (few that i know of) 'noise' complaints when the check valves flapper chatters of its seat (lack of better terminology) when the pump is operating at very low speeds.

Anyways, I hope this helps. If you have any questions or like to discuss, please dont hesitate to call me at 250-545-7749, Ext. 214.

Regards,

Mike

hr

I feel you do need

a check in the injection line, IF the injection pump does not have an intergral one. Most of the injection specfic circs, like the Grundfos MixiMiser include this check in the volute.

You may choice to add an "off the shelf" spring check, if so, find one with a low "pop" spring. The check valve manufactures have this info in their literature.

I have had limited sucess with thermal traps. Even with ones as deep as four feet from the top of the primary loop to the floor and back up. I'm still of the opinion that a check is needed in at least one side of the injection bridge.

As we know Ma nature hates an imbalance, and if the primary loop is flowing 180° fluid and it sees 70° fluid inches away the hotter fluid likes to go towards the colder side, "ghost flow."

The pressure drop of the check device certainly isn't an issue as that injection bridge pressure drop is near zero and typically a flow setter, or globe valve, (Istec readable flow setters work nice for VS injection systems) is needed to provide some head for "adjustability" and to force that injection pump up onto it's curve.

If not they run at slow rpms and have trouble with said checks. I believe all the new tekmar controls start the injection pump at full speed and ramp down to lower speeds, don't they Mike. This I believe was to handle potentially stuck pumps, as well as assuring the check did pop open and prevent the circ from surging.

The Grundfos Super Brutes have a small electronic device, under the hood, to "tickle" the pump and eliminate stuck rotor conditions. Generally these conditions (stuck rotor)are due to water quality and not pump design, by the way non barrier pex or any non barrier radiant tube is a stuck pump service call waiting to happer, I've found.

I'm a big fan of VS injection mixing, and these are some of my observations from having tried the various methods.

hot rod

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Joe Mattiello

Taco variable speed, with IFC


Taco Variable speed circulators with the integral flow checks are good candidates for injection pump applications. The integral flow check facilitates piping and saves you money, which makes you more competitive. I read pages 67, 68 in Dan’s Primary, secondary pumping made easy, and agree with Dan that flow checks on the supply and return will minimize migration into the secondary loop. Even though the tees for the secondary loop are closely spaced together at the piping interface the pressure drop is still not eliminated. Without some type of flow control valve some hot water will migrate from the primary circuit into the secondary circuit while it’s inactive. The advantage of using an injection pump with an IFC from a performance perspective is the minimal pressure drop through the valve. Additionally, it only takes approximately ¼ psi to open the valve, sufficient to prevent any hot water flowing freely into the secondary circuit when the pump is idle. Adding an external type weighted check on the return side eliminates the call backs, and rework with an unhappy customer.


Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com