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Can I use the screws of an end switch on a ZVC or SR board to check continuity?

Yes, however you might not get a good reading if the screw is not clamping a wire. Instead, use the test points on the front of the board, or look on the back of the block for the exposed test points.

Can the outdoor reset control PC700 be used with a SR board when used in a primary/secondary piping system?

You certainly can, however, the PC700-2 cannot operate the system pump when any of your heat zones call for heat. You will have to run the system pump continuously. An Alternative is the PC702 2 boiler staging control which works as a reset control, and boiler staging control. You will need to turn the boiler rotation off, put the mode switch on the control board to normal, and Wire the primary pump to ZR with the jumper left in the place.

Can use the priority feature on a SR502/503 when used with an SR503/4/6 EXP?

Yes, remove jumper on ZC &ZR of EXP board. Run a wire from P on SR502 or 3 to ZC and Prioity Switch OFF

How do I run a system pump on my SR504/506?

Leave the jumper in between ZC ZR and tie the hot leg of pump to the ZR terminal. Tie the neutral leg of the pump to the neutral coming from your power supply. ZR (with jumper in) will put out 120V when any zone calls for heat.

How do I wire a Honeywell V8043F Zone Valve to a Taco ZVC control board?

Wiring from a Taco ZVC valve terminal block at the bottom of the board to the Honeywell V8043F valve is as follows: Screw term. #1 goes to TR term. on the V8043F Screw term. #2 goes to TH term. on the V8043F Screw term. #3 goes to the lefthand end switch term. on the V8043F Screw term. #4 goes to the righthand end switch term on the V8043F Nothing gets connected to the TH/TR terminal on hte V8043F. See diagram attached.

Attachment: Wiring Guide

How do I wire a White Rodgers 1361 Zone Valve to a Taco ZVC control board?

From the Taco ZVC valve terminal block going to the White Rodgers valve as follows: screw term. #1 to screw term. #1 on the WR valve screw term. #2 to screw term. #4 on the WR valve screw term. #3 to screw term. #3 on the WR valve screw term. #4 has no wire connected to it on the ZVC control. From screw term. #2 from the WR zone valve goes to the right-hand thermostat screw term. at the TOP of the ZVC thermostat connections.

Attachment: Wiring Guide

How do I wire a ZVC404 or ZVC406 so the system pump does NOT run on a DHW priority call?

The wiring diagram on the instruction sheet for optional system or DHW circulator causes both the system & DHW pump to run when there is a DHW call. If you only want the DWH circulator to run then the wiring is as follows; Instead of bringing 120v into the right side of the extra end switch, you only have to put it into the common screw terminal of the dry contacts. Then connect a wire from the N/C terminal on the dry contact to the right side of the extra end switch. Now when there is a DHW call the power will be removed from the extra end switch.

How do you wire a 3 wire thermostat to a SR control board?

On the old -2 revision boards (SR503-2) you can connect the R & W wires from the thermostat to the {TT terminals} at the top of the SR board. The common wire (C) from the thermostat can be wired to the common screw terminal of the 24v terminal block on the left side of the board. On the new revision 4 models (SR503-4)there is R,W,C at the TT connections.

Attachment: 3 Wire Thermostat Connected to a SR Board

I have a gas boiler with Taco controls that is short cycling. The problem seems to relate only to the 2nd floor zone. What can be causing this?

Check the heat anticipator on the thermostat for the zone or zones you think are short cycling. The thermostat should be on an inside wall, with no radiation under it, and away from outside drafts. Also check that there are no bad connections and that 20-gage wire is used, not telephone wire. The current draw should be about 1 AMP. When the boiler cycles, watch the water temperature to see if the boiler aquastat is cycling the boiler. The upstairs zone might be small and not much of a load on the boiler. You might want to lower the boiler water temperature until the outdoor temp drops. Our PC700 is an outdoor reset control used in conjunction with our -EXP controls.

I have a Honeywell L8148E limit control which came with my gas boiler. It has one 24vac zone for a thermostat. I want to implement the SR503 into the circuit, as I have two zone 120vac thermostats. I need to know what the output of the thermostat zones are, along with a n/o contact set I can use for the 24vac zone on the Honeywell. It will be used for a cold start boiler operation with continuous ignition.
  1. Put all of your circulators on the SR503.
  2. Remove the circulator that is attached to the L8148E and transfer it to the SR503.
  3. Run thermostat wire from the X-X terminals of the SR503 to the T-T terminals of the L8148E. If you don’t do it this way, you will have to power one of the X terminals with 110V and run a black 110v (hot when X-X close) back to the \”B\” terminal of the aquastat to fire the boiler.
  4. Use the same power supply coming from the boiler safety switch to power the SR503.
I have installed a sr503-1 with priority in a primary secondary loop and an in direct water heater (priority). In total I have four pumps, one for my primary loop and one for each of three zones. I want my primary pump to come on for 2 zones but not to come on when my indirect water heater calls for heat. Can this be done?

Unfortunately, not with the control you have. Alternatively, you can use the SR503 as it is currently wired, but install a SR501 to energize a system pump whenever any of the three zones call for heat, and bring the aquastat from the indirect to a separate SR501 for the DHW pump, and bring the isolated end switch directly to the boiler TT terminals circumventing the system pump.

I need technical details on how the ZR and ZC terminals interface with the aquastat on a boiler. I wire many boilers and all directions specify cold start or hot start, black box type instructions. I do not fully understand the inner workings, or what happens electrically with either application.

In our Control Instructions, we give two examples: a cold start boiler or a tankless coil boiler. For the cold start, the X, X goes to the TT terminals in the boiler control. For the tankless, the ZC and ZR go to the ZC, ZR terminals of the boiler. Boiler controls that don\’t have ZC and ZR terminals can be hooked like the cold start. These hook ups are conditional, in that you move the circulator that was originally wired to C1 and C2 over to the Taco Control.

If you plan to leave the circulator on the boiler aquastat, and a thermostat connected to the TT terminals of the aquastat, you will need to get into the firing circuit of the aquastat. This would be the ZR connection. Run a wire from the ZR of the aquastat to the ZR of the Taco control. If there is no ZR, run a black wire from the ZR of the Taco control to the B terminal of the aquastat.

When an aquastat has the ZC and ZR terminals, the ZC is connected to the low temperature switch of the aquastat and to the ZC terminal of the Taco control. The ZR is connected to the ZR. These will be 120 Volt wiring. When the boiler water temp is too low, the low limit switch connected to ZC opens and drops the voltage to the ZC of the Taco board, killing all the pumps until the boiler catches up. The ZR is a 120 Volt supply to the burner circuit to fire the boiler, but this goes through the high limit switch to control the boiler water temperature.

I need to power my thermostat as there is C,R,W terminals on the Thermostat. How do I get a C connection? I have a SR board.

On all of the SR multi zone boards, except the SR502 &503, the TT terminals at the top of the board are: Right Hand T is R, Left Hand T is W. You can pick up the C terminal from the Common -24 Volts terminal block next to the transformer. Note: The SR502 and 503 boards the Right Hand T is W and the Left Hand T is R

If a ZC wire from the aquastat is wired to the SR board and the temperature of the boiler is low, will the indicator lights be on, and the circulator be on if there is a call for heat?

The indicator light will be lit but the circulator will not come on until the boiler aquastate is above the low temperature setting and the ZC terminal puts out 120Volts

Is the SR EXP switching relay control and the ZVC EXP control for zonevalves compatible; or used together?

No, on like controls can be used together.

My thermostat needs power, and are C, R, and W terminals on the thermostat. Where do I connect the C wire on my ZVC board?

On a ZVC board your T terminals at the top of the board are where your thermostat is connected. The Right Hand T is R, Left Hand T is W. Go to the bottom terminal strip, where you connect your zone valves, with terminals 1,2,3,4 and connect your C wire to terminal #1. This is your C terminal on all of the zone valve blocks.

What are the ZC and ZR terminals on the Switching Relay boards and how are they used?

ZC/ZR terminals on the SR board go to ZC/ZR terminals on the triple aquastat with ZC/ZR terminals, using minimum 14 gauge wires. These terminals will prioritize domestic water coil. When there is a demand for heat from the thermostat, ZR becomes hot, sending 120 volts to the triple aquastat. When the boiler temperature rises above the minimum temperature setting (typically 140°), ZC becomes hot, sending 120 volts to the SR board and powering the relay for the circulators. To recap, the circulators cannot run until the boiler is keeping up with demand.

Why do the relays chatter when a zone calls for heat on a SR502-2 or SR503-2?

A common mistake that is made when wiring the incoming power to the board is to put the 120v hot lead (black) to the P terminal instead of the H terminal. The P terminal stands for priority.

Why is it that in the Taco controller module the terminal 3 & 4 have to be jumped for 2 wire zone valves?

The 3 and 4 terminals are looking for a zone valve end-switch closure to close the main end-switch which is typically interfaced with the boiler thermostat terminals. If you use a two wire zone valve without an end-switch we need to simulate an end switch closure by placing the shunt across the 3, and 4 end-switch terminals.

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