New Taco 501 zone added to 2 zone 2 Aquastat system - Malfunction

Give me about 30 minutes and I will figure this out for you.

Just double checking. the Resideo control should be L8148E. Is that correct?

Here are the obvious wires. All the Neutral wires are in White and they are probably already connected that way. The pump motors have a neutral connected to C2 on the L8148E and the pump motors are inside the respective relays are connected to the Neutral with wire nuts or screw terminals and the neutral from the source panel is connected to the N or #2 terminal on all three controls.

once you verify above, then we move on to the L1 or Power or Hot 120VAC wire. That will be the black wire from the main boiler switch

• Black from the switch gets connected to L1 on the L8184E
• and H on the Taco SR501
• and #1 on the R845A

First control is the R8148E

• Black hot to L1 and white neutral to L2
• This control stays connected as the factory designed it.
• T and TV get low voltage wires from the thermostat for only 1 zone. The thermostat that matches the pump that is connected to the L8148E.
• Remove the other thermostat wires from T and TV, they are in the wrong place
• There may be a factory jumper from Z to W or not. If it is there, leave it there.
• B1 and B2 get connected to the low voltage gas valve circuit including any safety switches connect the like the spill switch or the roll out switch or the electronic ignition control. Leave that alone also.
• Finally the circulator pump gets connected to C1 and C2

Next Control is the R845A

• Black hot to 1 and white neutral to 2
• Place a 14 Gauge jumper wire from #1 to #3
• Connect #4 to the Circulator hot lead and #2 to the circulator neutral lead
• Connect the thermostat for that zone to T T
• #5 and #6 will complete the low voltage circuit for the gas control. with low voltage wire.

Next Control is the SR501

• Black hot to H and white neutral to N
• Place a 14 Gauge jumper wire from #1 to #3
• Connect #4NO to the Circulator hot lead and N to the circulator neutral lead
• Connect the thermostat to R and W
• #5 and #6NO will complete the low voltage circuit for the gas control. with low voltage wire.

Burner connection. You must do this properly so all the limit and safety devices are connected properly. There is a Z terminal on the L8148E control that is low voltage and that terminal gets connected to the #5 terminal on the SR501 and the R845A controls with a low voltage wire. To make that easy, use the white wire to connect Z with #5 and #5 from the three controls.

There is a B terminal on the L8148E that has a Torx screw with a Blue wire under it. That needs to have the #6 and the #6NO connected to it. So use the Red wire from the low voltage wire to connect B to 6 and 6NO and leave the Blue wire connected also

This will insure that all the safety devices on the boiler are connected for all the zones.

But you need to double check this by:

• Turn the switch off on the boiler 
• Set the Taco SR501 zone circulator thermostat to call for heat.  
• Make sure the automatic vent damper is closed.
• Disconnecting the hot wire to the circulator pump so the boiler will reach the limit temperature quickly
• Turn on the electric switch and observe the call for heat from the Taco relay.  It will click
• The vent damper should open before the gas valve opens to make the main burner flame.
• Once the boiler reaches the limit temperature the burner should stop.  
• Now you can shut the switch off, put the circulator wire back on and turn the switch back on. The pump will lower the boiler temperature and the burners will relight

This test should be repeated on the R8148E control

Then you are good to go.