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wiring help L4081B1013 ctonnected to Taco SR502

Joseph_4 Member Posts: 278
I haven't had a lot of experience with the L4081B. I understand the circulator is controlled by the Low limit side and wont come on till low limit temp is reached (also that Low limit used to maintain temperature when there is no call for heat) . I have a customer with An SR502, The L4081B and a Carlin EZ Gas.( There is also a R122E LWCO)

Im trying to understand the sequence of operation. Does the L4081B always maintain temperature cuz assumes boiler has coil as well? This case boiler coil was cut off.
I want to understand how a call for heat sends power to the Burner and High Limit side when used with the SR502.
When does the B terminal receive power and send back to burner?

here are 2 pictures

The blue wire from the 4081b Low limit side is connecting to main system pump on SR502

From where should the High Limit wire on the 4081B originate from
HHI Services LLC


    HVACNUT Member Posts: 5,876
    That control always maintains the high limit, with a 10° fixed differential. The low side solely controls the circulator. It does not connect to the burner circuit. 
    What do you mean by "main system pump"?
    The blue wire is going directly to a pump? It's not going through a line volt thermostat first? 

  • SteveSan
    SteveSan Member Posts: 235
    @Joseph_4 I reached out to one of our senior techs and it doesn't appear your control would work with the older SR control.
  • Joseph_4
    Joseph_4 Member Posts: 278
    Thanks for the comments. What was done was whoever wired this used TT on a zone on the SR502. On a call for heat sends 120V to power a pump. Instead of going to the pump He has a wire going to both the B terminal on the 4081B and The R on the Right side of control to power circulator. This way only on a call for heat does Burner circuit get power and if hits high limit burner goes off and on Circulator side gets power but power passes to W to actually send power circulator if its above Low limit setting. Creative