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RAWAL devices....opinions?

JUGHNE
JUGHNE Member Posts: 9,770
I haven't seen any recent posts concerning these.
Are they still or were they ever a favorable item?
Hoping for better humidity control in my own home.

Do they have sticker shock?
Usually when you Google an item someone will pop up with a price, didn't happen.
I have only about 2 months of cooling needs here, above 90 and company from the city are the determining factors.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,024
    I have used them. Basically hot gas bypass to the suction line. I mean you can builds your own with an extra txv which is used as a desuperheating txv.

    I haven't bought one in a while, think there located in MA. Hate to mention a price because I will probably be wrong but $1000 rings a bell
    JUGHNE
  • JUGHNE
    JUGHNE Member Posts: 9,770
    In 2003 I added 2-- 2ton 12 seer AC's to my house of 2300sq ft.
    Thinking I could pull down quick with the 4 ton capacity and then coast on one 2 ton system. I should of went with 2--1.5 tons.

    Have 2 zones, zone A gets its return air from zone B and B gets RA from A.....crazy idea at the time and works fairly well with one 2 ton AC. It does pull down quick when needed but even with one AC on we have fairly high humidity.....comfi but feels a bit sticky. And to get drier we have to go below 74 on Tstat.....I start to feel chilly then.
    Wife is happy so of course so am I ;)

    That is a lot of outlay for 2 months of cooling. Looking at filter change history, with the General AC-1, Merv 11 for each unit, I average 4-5 seasons per filter...cooling only BTY.

    If R-22 units were still available I could change out the cond units to 1.5 tons for less money than the RAWAL system for each.

    By the time I really get concerned about it the AC season is nearly over and I think about heating. I have only done this for 14 years.
  • hvacfreak2
    hvacfreak2 Member Posts: 500
    I usually get involved with these to solve oversized system problems ( it happens a lot in commercial plan and spec ). These really save the day when an engineer specs a 5 ton where a 2.5 would have been plenty.

    But yeah , I can see these being a solution for dehumidification. On a call for dehumid start the cooling system with fan on lowest speed , need to get the suction pressure to drop so the RAWAL valve opens. I'm not sure how aggressive you can be with the dehumid setpoint with no reheat. Lennox has a neat setup that uses a reheat coil and a desuperheating kind of arrangement with a stepper valve , and no hot gas line required.
    hvacfreak

    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

    JUGHNE
  • ratio
    ratio Member Posts: 3,187
    If you're really looking for humidity control, as opposed to capacity control, perhaps one of these will work. I do believe it will be cheaper than a RAWAL valve.

    NB: I have never installed one, but I have considered one for a building that I'm responsible for.

    JUGHNE
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,024
    They also (Trane) I think makes a unit with hot gas bypass and uses discharge gas for the reheat coil $$$$$$$ though
    JUGHNE
  • JUGHNE
    JUGHNE Member Posts: 9,770
    I see that would be less money and less labor.
    I have 1/4 HP motors running on low speed already.
    So this control would slow them down even more than that?

    I have always envisioned some motor control using delta T.
    This seems like the answer.

    Question: if this is available for PSC motors why do we have ECM variable speed motors being the currant rage?? I suppose low amp draw is the answer as I think about it. Also sensing CFM as static changes?
  • ratio
    ratio Member Posts: 3,187
    I'm not sure what the turndown would be. As I understand things, those (PCM) motors aren't multi speed, they're multi power. The lower speed taps just reduce the power, & the motor slips more. Contrast that to a three phase VFD, which actually changes the line frequency to the motor to change it's speed. The ECM motors are actually three phase motors with the VFD electronics tucked into the bell end. I haven't made a great study of them, but if their claims of efficiency gains have any truth to them, PCM motors are horribly inefficient. Which is quite possibly true.

    The sensing CFMs is interesting. Apparently, the controller in the motor spins the wheel up to a certain RPM, then cuts the power & sees how long it takes to decelerate to a stop, which is dependant on external static. Once you guess that, you can cypher up how much air you're moving at different RPMs. I'd be interested in a study of the accuracy of that.