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Multiple valves per zone question

Discussion in 'Irrigation' started by Critical Care, Sep 30, 2005.

  1. Critical Care

    Critical Care LawnSite Bronze Member
    Messages: 1,654

    What are the limits for running more than one valve off of a controllers single zone output?

    I know that some controllers can safely run two .3 amp (inrush current) 40 ohm valves simultaneously per station. With a 1.5 amp station output current, it would appear that current wise some controllers should actually handle more than two valves. But understanding that two valves in parallel would create 20 ohms, and three would be down at 12 ohms – would that cause the controller to recognize this as a short circuit?

    Or… what about three valves in series at 120 ohms? Will the solenoids fail to activate?

    Here’s a third option. One valve is in series with two valves connected together in parallel. Got the picture? This would be 40 ohms in series with 20 ohms (2 in parallel) for a total of 60 ohms. This isn't too far out of line is it?

    Or a fourth option… One valve is in parallel with two valves connected together in series, and this would give 40 ohms in parallel with 80 ohms (2 in series) for a total of about 27 ohms. That's fairly close to par, eh?
  2. Luke in Nebraska

    Luke in Nebraska LawnSite Member
    Messages: 35

    3 valves on residentials, 4 valves on commercials.
  3. jerryrwm

    jerryrwm LawnSite Bronze Member
    Messages: 1,274

    Check with the manufacturer's specs for each controller. They will usually specify the number of valves that they can operate.

    Many commercial controllers can handle 2 or 3 valves and a few of the higher end models can handle 4 valves. Most residential controllers will handle 2 and occasionally one will handle 3 at a time.
  4. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    Spot on! Gawd did NOT create all controllers equally. :cool2:
  5. Critical Care

    Critical Care LawnSite Bronze Member
    Messages: 1,654

    Looking at the manufacturers specs on the Rainbird el cheapo Ec controller it lists "one valve per station", and shows its output as .65 amps. That's somewhat less than lets say the ESP LX controller with 1.5 amps output, which indicates that it can handle two. However, the ESP Modular at 1.0 amps output also states that it will handle two valves per station. With that reasoning I would assume that the LX could actually handle more... though it doesn't say it. Rainbirds big IM controller has a hefty 3 amp station output.

    Still, if you connected four valves in parallel, the resistance would be down below 10 ohms. I'd think that some controllers even if they could handle the current demand would fail because the 10 ohms would look too much like a short circuit. Maybe?

    Reason I'm wondering about this is because I'm going to go from a 15 gpm service line to 105 gpm. Without digging up the existing 1" lines and reconfiguring the system for more water availability, I'll just opt to irrigate similar areas at the same time. Controller is an ESP LX. I keep thinking that it could handle running three zones at the same time.
  6. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    All controllers are not created equal as Hayes states, also, all valves are not the same either. The controller recomendations assume minimum liablility for the consumers stupidity. I mean after all in todays market, "one a day" vitamins need dosage instructions and disclaimers and warnings to only take them once daily. I have grouped 3 2400's on one station using an indoor Kwik dial. By manufacturer recomendations, this doesn't work. I use two valves instead of boring a drive or something similar to group areas quite often. Your ohm calculations don't matter if you wire in parallel. Your total amperage will. Electricity is a least resistance rule, therefore in parallel, you don't add or multiply. Just make sure your worst loop is within tollerance. I never recomend running valves in series. I always bring individual leads back to the controller and then group. Not because it can't be done, but in my mind it shouldn't. I also never set a master valve without using a seperate common dedicated to it. It's just a personal practice, but a lot of the older controllers wanted it that way and I'm to stubborn to change.
  7. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    We strictly use Irritrol MC+ (103 at last count; aids with remote control capability) controllers on our sites except in nine places where running electricity for a controller was deemed too costly. These areas use TBOS controllers (going to be replaced with Hunter WVS this winter) that are single valve actuation at a time. We require all valve wires to come back all the way to the controllers which gives us various options. I know we've wired as many as three valves (Irritrol Century Plus) and a MV (usually a booster pump) to come on simultaneously without any problem. I actually looked at the specs on these controllers and they'll take 1.8 amps maximum of simultaneous activation. I'm not an electrical/low voltage wizard though I do know what works. :blush:

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