TACO sr504-4 to Honeywell Aquastat Wiring


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Old 10-03-20, 10:19 AM
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TACO sr504-4 to Honeywell Aquastat Wiring

I am upgrading my hydronic heating system by replacing the old Honeywell relays with a Taco sr504-4 Switching Relay.

EQUIPMENT: I have a Becket Burner with a GeniSys Advanced Burner Control; a Honeywell Triple Aquastat MDL# L8124A, C L8151A; a Taco sr504-4 Switching Relay; and 3 Taco Circulating Pumps. I opted to use the “Alternative Wiring” option on the Switching Relay’s instruction sheet as opposed to the “Cold Start Boiler Wiring” to take advantage of the Hi/Lo limits on the aquastat.

COMPLETED WORK: The 2 “slave” Honeywell relay boxes are disconnected from the aquastat and circulators. All 3 120v circulators are now wired to the switching relay. All 3 24v thermostats are now wired to the relay. The factory installed jumper on the switching relay’s ZC-ZR terminals was removed and the ZC-ZR terminals on the switching relay have been connected to the ZC-ZR terminals on the aquastat. Since the aquastat is now powered (120v) via the switching relay I disconnected the 120v line from the L1-L2 terminals on the aquastat. The burner is still connected to the B1-B2 terminals on the aquastat.

QUESTIONS: 1) Currently, there is a jumper across the T-T terminals on the aquastat – Do I remove the jumper? 2) What, if anything gets connected to the T-T terminals on the aquastat? 3) What gets connected to the T-T terminals on the GeniSys Control to trigger the burner to fire?
 
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Old 10-03-20, 10:40 AM
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Welcome to the forums.

There are many ways to wire boilers. Many are convoluted and don't follow any particular method.
I like pictures. I can see the wiring in the pictures and I know how it's been done.

You said the TT terminals were jumpered on the aquastat. That would mean that the 120v circuit was switched to the aquastat. Now you want the aquastat to be powered all the time and the TT terminals get shorted to start the burner. The XX terminals on the 504-4 get connected to the TT terminals.

The burner is still connected to the B1-B2 terminals on the aquastat.
That would mean the aquastat would supply the 120v to the burner controller.

 
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Old 10-04-20, 07:01 AM
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Hi, what is the exact model # of the GeniSys control? As suggested pics would be helpful.
Geo🇺🇸
 
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Old 10-04-20, 07:25 AM
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Is that it? I don't know what to make of this warning:

Warning:When using Alternative Wiring diagram, wiring instructions must be followed so power originates from the boiler aquastat. Failure to follow these wiring instructions may result in a secondary source of power being connected to the boiler that may activate it under certain circumstances, causing injury or death.
 

Last edited by PJmax; 10-04-20 at 10:09 AM. Reason: labeled picture
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Old 10-04-20, 10:13 AM
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I haven't used that Taco controller to switch line voltage but it looks like Zc and Zr are line voltage outputs. They don't want you to use two different sources of power. That is so if the boiler is shut down.... the aquastat won't get 120v from the Taco.

The Taco controller gets connected to the same source of power that supplies the boiler so that when the safety switch is off..... everything is dead.
 
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Old 10-07-20, 02:43 AM
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Thumbs up Taco sr504-4 to Aquastat Wiring

Thank you for the suggestions and detailed schematic provided by zoesdad. I just want to verify one item of concern. The schematic provided by Taco shows the Isolated End Switch at the 24v bank of terminals. The schematic provided by zoesdad has this end switch at the 120v bank of terminals. See highlighted areas on attached schematics. Any thoughts on this would be appreciated. Thank you, Jerry
 
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SR504 to Aquastat Wiring.pdf (1.30 MB, 28 views)
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Old 10-07-20, 08:21 AM
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Hi, in you pic the supplies for the Aquastat and the Taco tie together and should be controlled by the same boiler service switch, as for ZC, ZR connect as shown in the Dia.

Geo🇺🇸
 

Last edited by Shadeladie; 10-07-20 at 11:04 AM.
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Old 10-07-20, 01:02 PM
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JV,
If you go to the sight below and scroll down to wiring guide and go to page 90. This is a simplistic schematic of the wiring to your aquastat minus the circulators which you already know how to wire.

The thing to remember is to leave the wiring on your aquastat as is EXCEPT for the C1 & C2 which will go to the SR504 and the TT will be removed because you are setting up alternate wiring as for a tankless which means the ZC & ZR will be used to keep the boiler at a constant setting and will not let the pump run until the boiler temp is above the low limit setting.

On your SR504 you want to remove the jumper for ZC & ZR and wire to the proper terminals on the aquastat and you DO NOT connect your end switch to TT on the boiler. Both the aquastat and the SR504 need 120V to the proper terminals.

Hope I haven't confused the issue.

https://www.supplyhouse.com/Taco-SR5...witching-Relay go to wiring guide on page 90.
 
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Old 10-07-20, 02:03 PM
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spott –

I found the diagram and it is in fact the 90th page – but at the page bottom of the page it is actually labeled 88. Just wanted to mention that in case others are as dense as me and read the wrong diagram - lol.
 
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Old 10-10-20, 04:17 AM
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Thank you all for your help!! The wiring of the new Taco switching relay is finally done and the burner now cycles as it should in conjunction with the hi - lo settings on the aquastat.
Now I just have to get the air out of two of the three zones and I'm all set for the winter.
Thank you again.
Jerry
 
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Old 10-10-20, 09:52 AM
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Good job. Thanks for letting us know how you made out.
 
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Old 10-12-20, 01:22 PM
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Jerry Verbair “Now I just have to get the air out of two of the three zones and I'm all set for the winter.”

JB might consider an easy, cheap way to vent by installing Watts auto vents at high point of each zone and forget about manual venting.

Watts at $8.29 are very reliable and can be opened for servicing. The first generation auto vents leaked and got bat rap.

Manual venting at basement level boiler is wishful thinking. Gave up on that years ago. Would not know where to start on my 8 zone, 12 element system. Yesterday switched on boiler for season and

https://www.supplyhouse.com/Watts-05...Vent-3679000-p
 
 

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