You are not logged in.


Dear visitor, welcome to SPRINKLER TALK FORUM - You Got Questions, We've Got Answers. If this is your first visit here, please read the Help. It explains how this page works. You must be registered before you can use all the page's features. Please use the registration form, to register here or read more information about the registration process. If you are already registered, please login here.

Attention: The last reply to this post was 2014 days ago. The thread may already be out of date. Please consider creating a new thread.

Message information
Automatically converts internet addresses into links by adding [url] and [/url] around them.
Smiley code in your message such as :) is automatically displayed as image.
You can use BBCode to format your message, if this option is enabled.
Security measure

Please enter the letters that are shown in the picture below (without spaces, and upper or lower case can be used).

The last 10 posts

Sunday, May 12th 2013, 9:21am

by Scott76

The old timer was a Rain Bird Rain Clox RC-8A. I replaced it with a digital timer, Rain Bird ESP-RZX6 Outdoor. After talking with the engineers at Rain Bird about this particular issue, they advised me that no current timer manufactured by Rain Bird will power the valves due to the internal logic of the new timers. They stated that the amp out put is limited to 0.5 to 0.75 amps and the Thermo-Hydrolic valves require 1.5 amps. Their solution was mentioned by Wet earlier, put a second power supply, isolated from the timer and a bunch of relays.


I had the power supply from the old manual timer that was in the house. The power supply was still functioning, so it became the second power supply. It got wired with to the 120V AC feed with the new timer. I wired the field common to one of the power supply wires. The power supply wire went to all 6 relays on the input point of the relay. The always hot side of the relay got covered to prevent shorts. The always off of the relay got wired to a single zone per relay. The timer got wired to the isolated trigger on the relay. Wired the common from the timer to each relay and each zone to a single relay.

How it worked:

When the timer is run the zones activate the relays which allows the old power supply to power the system up. Everything work with no errors.

How to identify the valves:

Thermo-Hydrolic valves are very old and should only be found in old systems (30+ years old) on the residential side. They can only be powered by the old style manual timers. There is no digital timer on the market (that anyone I talked with knows of). The single biggest clue is the valves take almost a minute to open and close. You will start the zone and about a minute into the run the zone will finally start. The nice part about the valves is they are basically bullet proof. The valves I encountered had been in he ground for 37 years with no replacements.

Sunday, May 5th 2013, 2:14pm

by Wet_Boots

I believe you are overstating the current requirement of those valves. One thing that is helpful, is that the valve 'operator' is a simple resistance heater, as opposed to a solenoid, which draws more current than its wattage indicates (which is why both solenoids and supply transformers are given 'VA' ratings, rather than simple watts and amps)

Just for grins, I run the 800-foot maximum of run for number 14 zone wire through a calculator, and it returns as 2 ohms, which calculates to just about 2 amps maximum of valve draw. That raises the possibility that a controller capable of powering at least 3 modern solenoids per zone might be capable of operating those Thermal Hydraulic valves. I would be looking for any controller with a large (50 VA minimum) power supply transformer, and that rules out even the good entry-level models.

What was the original controller? What did you install to replace it?

Sunday, May 5th 2013, 11:26am

by Scott76

I would think it would. Based on the information I've gathered, the Thermo Hydrolic valves require 2 or 3 amps of power vs the 0.75 amps the current timers put out. That "overdraw" is what is causing the timer to error out currently.

Saturday, May 4th 2013, 5:38pm

by Wet_Boots

I meant disconnect the master valve at the controller - the idea is to see if a single zone being powered triggers an error message

Saturday, May 4th 2013, 4:51pm

by Scott76

After talking with a local expert that has run into this exact problem, the plan sounds like wiring an ice maker relay in with the second power supply and the common and master valve zones. This should allow the system to power up on the old power supply and not the timer supply (which can't handle the valves). Just waiting on him to provide the wiring diagram on how to do it and then I will complete the job (hopefully).

Wet, I would disconnect the MV, but these valves are buried with no valve boxes, as was the standard in the area in 1976.

Friday, May 3rd 2013, 7:09pm

by Wet_Boots

Having a master valve is tough, when it is also a high-draw valve. You might disconnect the master valve, and see what happens with the controller when you just power the zone valves.

Friday, May 3rd 2013, 10:45am

by Scott76

I'm attempting to work through the problem. When I find a good solution, I will post it here.

Friday, May 3rd 2013, 8:22am

by Wet_Boots

Maybe you can work out the electrical requirements of your valves from this page

Thursday, May 2nd 2013, 2:18pm

by Wet_Boots

There's plenty of headroom to operate in, money-wise, as an old-style electromechanical controller has a current-day value of about one thousand dollars. Relays aren't too expensive.

Thursday, May 2nd 2013, 1:53pm

by Scott76

I still have the controller and it still functions. The client wanted the newer digital timer because they are easier to operate. So I have basically 3 options; replace all of the valves, get 6 relays (5 zones and a master), or find the needed wiring harnesses to make the old timer function again. This problem is getting worse by the minute.