Looking for a used Rainbird RC7A or RC7C

Discussion in 'Irrigation' started by CMKC, Apr 22, 2005.

  1. CMKC

    CMKC LawnSite Member
    from KC
    Posts: 18

    I have a customer that wants to sell her house just as we were starting to replace her old valves. The Thermo-Hydralic valves that she has still work but take too long to close and need the voltage that the RC7A(now named RC7C) puts out to operate.
    I can fix the controller if any of the gearing is broken I just need the transformer and the basic components to work.
    Help me out if you can!

    Thanks,
    CMKC
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,880

    and just replace all the old valves at one time. Then, if the controller has problems, you can use something simple, like a Hunter SRC. Considering the cost of a high-output controller, like a Rainbird RC-7C, updating the valves makes more economic sense.
     
  3. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    Not sure I understand your corelation between the valves closing slowly andf the voltage output of a controller.

    The RC puts out 24 VAC as does the SRC, the TC, the RM, and any other controller out there. Now granted they all put out as much as 26 - 27 VAC but that does not effect the closing or opening speed of a valve.

    Electricity unlike water does not take seconds to travel from the controller to the solenoid. There is a slight delay, but we can't field measure that time. When electricity goes in the voltage comes out the other end of the wire immediately.

    Now as to the valves closing slowly - that is not a function of electricity. When the power goes off to a valve, then the hydraulic actions take over. Water coming into the valve on the topside of the diaphragm through the metering orifice at a faster rate than is ported out through the exhaust port, thereby causing the valve to close. The diaphragm spring pushes the diaphragm down, but it does not hold it down. That is a function of the water and pressure.

    It sounds like you have diaphragm problems. Try changing a couple of the diaphragms and see if the performance increases. Older Toro 250 series valves are notoriously slow after a number of years due to metering pin wear on the plastic. Richdel 205 series also wear at that point. Weathermatic valves get slow because the metering holes in the diaphragm stretch over time and slow the closing time.

    I would venture a guess that even if you changed the controller you would find that the valves are still closing slow. Controllers have a minor function in the operation of a valve - they either supply the electricity to turn the valve on or they shut off the supply of electricity to the valve. Everything else is then a function of the valve itself. While the controller is the easiest component to change, it is not usually the culprit in valve failure.

    Jerry R
     
  4. CMKC

    CMKC LawnSite Member
    from KC
    Posts: 18

    Here is a little more info on the situation. The valves are very old...the customer does not want to dig up her yard to replace adn does not want to take the time or pay the expense of replacing the valve(I suggested that already) Since she is moving she just wants to make the valves work again(they did work when a RC-7A was in the house it has since been replaced and the valves now do not work) This means finding a RC-7A. I know that the valves will work once a get that controller back.

    The slow closing valves are not a problem and will eventually close. I have had Thermohydralic valves take 5-10 mins to close in the past so I am not suprised by this.

    Thanks for you help and let me know if you have a used RC-7A.

    Thanks
    CMKC
     
  5. Luke in Nebraska

    Luke in Nebraska LawnSite Member
    Posts: 35

    The valves he is talking about have wax solenoids. They take alot of time to shut off, because the wax has to harden for the vales to shut off. The vales still use 24 volts, but draw more amps than regular valves. The RC 7A will put out enough amps to run these vales where other controllers will not. Your locol sprinkler supply house should carry a new transformer so you can fix your problem.
     
  6. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Most mechanical clocks, including the RB RC series allow up to 2A, Most of our newer valves don't run anywhere near this draw and most new controllers have a bus fuse that is less than 1A. .75A and .5A are very common. Is the controller inside? The RC7bi is still in production. Tell your local dealer you need a 2A output clock or.........

    Everyone ready, cuz here comes mickey. You could put a electrical box below the controller and install relays to take direct power from the transformer to the valves. I would think this would be the more expensive route with controllers getting so much cheaper, but maybe not.
     
  7. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,880

    and an entry-level controller won't provide it. You may find that the dollar cost of a Rainbird RC-7C (a RC-7bi won't cut it) exceeds that of the replacement valves. If replacing all the valves means digging up multiple locations, the homeowner will probably want the expensive timer. Of course, it is just possible that the valves are all fine, and only want sufficient power.

    For those that are wondering what sort of valve is involved here, the Rainbird Thermal-Hydraulic valves used the controller power to internally heat a sealed chamber of fluid, which would expand, and push open the valve directly, with no diaphragm or solenoid needed. They operated slowly, which was good for fighting pressure surges, and were entirely indifferent to dirty water.
     
  9. ACC

    ACC LawnSite Member
    Posts: 64

    My friend's Rainbird RC-7A just failed. It was originally installed about 1982. What are the chances the two control valves (two stations) to which it sent signals are thermal hydraulic and so high amp demanding? I do hear buzzing from one of the two valves, just like modern solenoid valves that may be close to failing.

    No luck finding replacement parts for the RC-7A. We hope to install a Hunter controller tomorrow.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,880

    Not likely a problem. The only brand name in valves that is pure poison is Imperial. There may not be a solid state controller in existence that doesn't see them as short circuits.
     

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