Taco Switching Relay Not Responding to Thermostats

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Old 10-17-15, 03:52 PM
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Taco Switching Relay Not Responding to Thermostats

Hello, I have a Lars EDP 110 boiler with 4 zone baseboard and 2 radiant zones. There is a Taco 6 zone switching relay with priority controlling the 4 baseboard zones and a second Taco 2/3 zone switching relay for the radiant zones.

None of the baseboard thermostats when turned on result in the Taco 6 zone relay to call for heat. Jumping any zone T to T does not work. All fuses look good. Wiring has not been changed and it worked in the past. The radiant zones in the 2/3 zone relay both work fine.

How can I troubleshoot this?
 
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Old 10-17-15, 04:28 PM
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All fuses look good.
Fuses? What kind of fuses & what makes them look good?
 
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Old 10-17-15, 06:31 PM
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When you say a "6 zone switching relay" what exactly do you mean?

ZONE VALVES? or PUMPS?

Model number ZVC___ or SR___ ?
 
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Old 10-18-15, 11:01 AM
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It has circulators. 6 zone switching relay is SR506. Inside the SR506 there are some small glass fuses which all look fine.
 
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Old 10-18-15, 11:07 AM
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On the Taco panel, is the top "POWER" LED lit?

When you operate the thermostats, do the associated ZONE n LEDs light?
 
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Old 10-18-15, 11:25 AM
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Yes the uppermost LEDs are on on both the SR502 and SR506. When the t-stat is turned on, the SR502 associated zone LED lights, a relay clicks but no circulator turns on. On the SR506, relay clicks but no LED or circulators. Both have 120v and the T-stat TT connections show 24v.

I said before the radiant zones were working (since the LEDs lit) but realized they are not turning circulators on.
 

Last edited by boulderz; 10-18-15 at 11:28 AM. Reason: Error
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Old 10-18-15, 03:00 PM
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How many pumps?

Are they all wired to the 506?

And the 502 is wired to one of the 506 thermostat inputs?

Try to describe the wiring... i.e. ENDSWITCH on 502 goes to _____ , ENDSWITCH on 506 goes to ____ ... that sorta thing.
 
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