To get email notification when someone adds to a thread you're following, click on the star in the thread's header and it will turn yellow; click again to turn it off. To edit your profile, click on the gear.
The Wall has a powerful search engine that will go all the way back to 2002. Use "quotation marks" around multiple-word searches. RIGHT-CLICK on the results and choose Open Link In New Window so you'll be able to get back to your results. Happy searching!
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.

Three port thermostatic mixiing valves

SantilalSantilal Posts: 30Member
Hi



When you look up the Cv of a three port TMV, is the pressure drop and flow based on flow from one inlet to the outlet or both inlets to the outlet, or does it not really matter. I am thinking about the circuit where a TMV is used for boiler protection - the biggest pressure drop is likely to be across the TMV, but I can't get my head around if it makes a difference if one or both ports are open?



Also, we use metrics in NZ but most Cv's I have seen are based on imperial measures - are there conversion factors to convert Cv's or do you just have to develop your own?



Thanks.



Regards,



Santilal
· ·

Comments

  • hot rodhot rod Posts: 3,692Member ✭✭✭
    The metric flow factor unit is Kv

    Kv would be cubic meters per hour (m3/hr.) of a 16• c water with a 1 bar pressure drop.



    Cv is GPM of 60•F water with a 1 psi pressure drop



    Kv = 0.862 x Cv



    The thermostatic valves built for boiler protection have larger flow rates and are usually a fixed temperature cartridge.



    The pressure drop either Cv or Kv is the flow thru the valve to the outlet.



    Keep in mind a valve with a Cv of 3 can flow more then 3 gpm, but you will have additional pressure drop.



    Here is a little spreadsheet we use to calculate flow, pressure drop, and gpm. I'll see if we have one in metric units if you would like.
    png
    png
    Screen shot 2013-06-30 at 9.55.46 PM.png
    0B
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    · ·
  • SantilalSantilal Posts: 30Member
    Thanks

    Hi



    Thanks for that. From your answer it appears that the Cv is not dependent on either or both hot and cold ports being open or closed.



    Cheers.



    Santilal
    · ·
  • hot rodhot rod Posts: 3,692Member ✭✭✭
    correct

    what comes out of the mixed port is the blend of the H &C port. If it needs more hot, that port opens as the cold closes down. The wax cartridge inside move the spool up and down to vary then opening into the valve from the H & C
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    · ·
This discussion has been closed.

Welcome

It looks like you're new here. If you want to get involved, click one of these buttons!