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Nairb
Nairb Member Posts: 4
in THE MAIN WALL
I have an old White Rodgers 842A-16 control with a bad circulator relay and want to replace the entire box. Will the Taco SR501 work?

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  • Nairb
    Nairb Member Posts: 4
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    Only wires I can't figure out where to connect on the Taco SR501, would be the gas valve wires (shown in blue)
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,035
    edited November 2023
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    no. Wrong control.  
    The WR control is replaced by Honeywell L7124U or L 7224U. But that Honeywell control is for a line Voltage 120VAC burner.  What gas valve does that boiler have?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Mad Dog_2
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,035
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    the the White Rodgers is a high limit, a low limit, and a circulator relay. The Taco is a circulator relay only.   For safe operation of any boiler, there MUST Be a limit control.  The Taco SR 501 is no a Limit control.   Do not use that control to power the gas burner or gas valve. 

    That would be VERY DANGEROUS!!!

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Mad Dog_2
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,035
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    W hat does it say in this gas valve    24 VAC?   110VAC?  120VAC?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Mad Dog_2MikeL_2
  • Steamhead
    Steamhead Member Posts: 16,886
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    I'd use a Beckett AquaSmart or a Hydrolevel HydroStat to replace both those controls. The new control would mount on the tankless coil where the "hot water control" now is. This would add some energy-saving features to the boiler, and would probably not cost as much to buy.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    Mad Dog_2
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,035
    edited November 2023
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    After some research, the White Rodgers 842A-16 may have a 120 VAC circulator output and a 24 VAC burner output. The L8124E or J aquastat also has a 24 Volt burner circuit. All the other L8124A,C,L, and M controls have the 120 Volt burner circuit. This presents a problem with using this control with your boiler, the wires may not be an exact match an will require some understanding of how to safely connect a 24 volt burner valve to this control.

    Are you still using the tankless DHW coil for you Domestic Hot Water? (meaning that you have no heat AND no hot water).

    My best advise is to use the L7224U as the only limit control. Remove the Aquastat from the tankless coil and install the L7224U in that Well location. You may need to replace the Well Adaptor, since the White Rogers Well Adaptors may not accept the Honeywell sensor probe. Once you have the control mounted, place a 24VAC thermostat on the B1 and B2 terminals of the control and connect the R and C from the secondary side of the transformer on the gas valve. This is the best practice for your situation.

    I am not a fan of the Beckett or the Hydrolevel, Aquastat Relays, but that is a personal choice. If you elect to use those other brands, you will still need to use a 120 VAC to 24 VAC transformer for the burner circuit.


    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Mad Dog_2
  • Steamhead
    Steamhead Member Posts: 16,886
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    EdTheHeaterMan said:

    ..... If you elect to use those other brands, you will still need to use a 120 VAC to 24 VAC transformer for the burner circuit.

    Both Hydrolevel and Beckett make "gas versions" of their units with 24-volt burner outputs. The AquaSmart model is 7610B, the HydroStat model is 3200.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    Mad Dog_2
  • Nairb
    Nairb Member Posts: 4
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    EdTheHeaterMan said:

    W hat does it say in this gas valve    24 VAC?   110VAC?  120VAC?

    Gas valve is marked as 120 VAC
  • Nairb
    Nairb Member Posts: 4
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    Yes, still use the tankless DHW coil as the only source for hot water and heat.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,035
    edited November 2023
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    Good that you replied. I personally prefer Honeywell (Now Resideo) L7224U control for your application. Since your burner (Gas Valve) is 120 VAC then you can use the control as is. Connect the B1 and B2 to the gas valve.

    This will provide the High Limit and also the low limit for DHW.

    https://www.supplyhouse.com/Resideo-L7224U1002-120-Vac-Oil-Electronic-Aquastat?_br_psugg_q=l7224u1002
    and just in case you need it https://www.supplyhouse.com/Resideo-121371M-3-4-Long-Aquastat-Well?_br_psugg_q=aquastat+well

    and use this diagram

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HVACNUT
    HVACNUT Member Posts: 5,858
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    @Nairb, Can you post a pic showing the gas valve ratings?

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