Taco SR506 Zone controller failure

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Old 02-19-10, 05:28 PM
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Taco SR506 Zone controller failure

What is the life expectancy of the relays inside the controller?

Two days ago the temperature in one of the zones kept rising and it was getting hot in the living area...... After making sure that the thermostat was not calling for heat I checked the LED's on the SR506. Only the green (power) LED was on none of red LED's (zones) was on but the circulator was running. Took the cover off the zone controller and tapped on the relays and the circulator stopped. Swapped the suspect relay (zone 3) with a relay from another zone (zone 5). Today zone 5 was getting too hot.

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Old 02-19-10, 06:55 PM
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Good question... I would expect a minimum of 5 years, and personally I think 10 years shouldn't be out of the question.

I feel that the design should include 'arc supressor' circuits on the board across the contacts. A series resistor/capacitor. Economics drives the design though, so you won't see that anytime soon. If a manufacturer can save a buck by removing 'un-necessary' components, they will.

At one time I pulled manufacturer info off one of those relays and was able to find them in Mouser, or Digi-Key, but I can't find that info now. Give it a shot, you can easily save at least 50%... buy a spare.
 
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Old 02-19-10, 07:09 PM
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It is 3 years old, I would expect a relay to last for a good 10 years. Worked on systems and equipment over 15 years old and never had to change a relay.
The cheapest I found was $5.83, I'll be ordering a couple....

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Old 02-19-10, 07:14 PM
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Can you post up a link to the $5.83 supplier/part? I'm running a couple of these relays, only 2 years old but would prefer to have a spare on hand.
 
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Old 02-19-10, 07:19 PM
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Old 02-19-10, 07:43 PM
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Thanks Emil, I'll try to remember where I save that info this time!

I think Taco charges about $20 for the replacements...
 
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Old 02-20-10, 09:58 AM
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You are welcome, I ended up ordering from digikey Digi-Key - Z788-ND (Manufacturer - LY2-AC24)

They have them for $8.40 but unlike allied Electronic they did not charge me a processing fee and the shipping is a bit cheaper.
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Old 02-20-10, 06:14 PM
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I installed a new system last year with a Taco SR506..... I'm at 1.5 yrs so far.... maybe I should order a spare relay just incase..... lol
I would hope that mine would last at least 10 years....
 
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Old 02-22-10, 03:33 PM
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Originally Posted by NJ Trooper View Post
Good question... I would expect a minimum of 5 years, and personally I think 10 years shouldn't be out of the question.

I feel that the design should include 'arc supressor' circuits on the board across the contacts. A series resistor/capacitor. Economics drives the design though, so you won't see that anytime soon. If a manufacturer can save a buck by removing 'un-necessary' components, they will.

At one time I pulled manufacturer info off one of those relays and was able to find them in Mouser, or Digi-Key, but I can't find that info now. Give it a shot, you can easily save at least 50%... buy a spare.
Taco have revised the PC boards quite a bit on these and the ZVC boxes, for the better and for the worse.

Hard to give a life expectancy on a relay, what is the load and how many cycles per day does it see.

Contacts will get pitted and erode fast with high current loads of course.

I have seen some pretty old SR boxes out there, but like anything quality drops as price does. Price drops as competition grows. You know the story
 
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Old 02-22-10, 06:02 PM
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I found an LY2 socket in my pile of junk , so my project for the weekend was to build a test fixture and try to duplicate the failure (make the relay get stuck) and perform a root cause analysis (just like being at work only i'm not getting paid for it and the wife looking at me funny).
I used a inductive load to simulate the current drawn by the circulator and switched the relay on and of at the same rate (cycle) the zone was cycling at. (I spent most of Sunday in the boiler room and of course the wife was not happy) but could not duplicate the failure.

So, the plan for this week is to use a junk circulator as a load and an to cycle the relay's test fixture automatically every time the zone cycles using a current probe and a function generator triggered by a current probe.

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Old 02-22-10, 07:35 PM
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Originally Posted by esalman View Post
I found an LY2 socket in my pile of junk , so my project for the weekend was to build a test fixture and try to duplicate the failure (make the relay get stuck) and perform a root cause analysis (just like being at work only i'm not getting paid for it and the wife looking at me funny).
I used a inductive load to simulate the current drawn by the circulator and switched the relay on and of at the same rate (cycle) the zone was cycling at. (I spent most of Sunday in the boiler room and of course the wife was not happy) but could not duplicate the failure.

So, the plan for this week is to use a junk circulator as a load and an to cycle the relay's test fixture automatically every time the zone cycles using a current probe and a function generator triggered by a current probe.

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Have you done any load tests on the circs to see if it was drawing more current?

Maybe you just had a bad relay...... it happens.... its electronics....
 
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Old 02-23-10, 10:03 AM
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Shoman,
I did measured the current and it was within the nominal current listed on the pump. I'm suspecting the spring is weak. Just did not have much to do for the weekend and it was something to do.

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