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Taco SR405 relay box fuses

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metropical
metropical Member Posts: 9
in Gas Heating
It appears the SR405 on my heating system has blown it's Fuse(s).
No power light, no circulation, no heat, fkn cold at 26ºF.
Are there spare fuses within the box .... in theory?
If not, what kind of fuses are they other than 5A? Are they minis or regulars or ...?
If the fuse(s) blow again upon replacement, does that point to the Taco pcb itself or possibly a dead wall stat? Is there any way to check which it might be.
I have a DVM and and reasonably confident around 120v and LV DC circuits.

Comments

  • HVACNUT
    HVACNUT Member Posts: 5,846
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    SR504.
    Remove the fuse and test it.
    There should be a spare fuse on the board or the inside  the cover if it's a newer revision. 

    metropical
  • Jamie Hall
    Jamie Hall Member Posts: 23,395
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    At the risk of being a pest -- fuses don't blow, unless they are very very old or have been provoked. It might be worth finding out why it blew...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    metropicalSTEVEusaPA
  • Derheatmeister
    Derheatmeister Member Posts: 1,548
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    Generally... If it blows again something is over amping it..
    Our Company policy is to check the Amp draw of anything that is hooked up to it before closing the ticket... If you have a Circulating Pump For example a 15/58 Grundfoss Circ which draws approx .7 amps and it is drawing double that it would be time to change it. Check the Name plate of the Circ for a proper amp draw.
  • metropical
    metropical Member Posts: 9
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    thanks for the spare fuse info. I'll go look.
    As I said and all have suggested, what might have caused the fuse to blow (I assume just one) besides age?
    Bad stat, locked circ pump .....?
  • metropical
    metropical Member Posts: 9
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    spoke with tech at Taco. He says because it's 12 yo-ish best to replace box.
    I may go with whichever relay is bad if I can figure it out, as a temp fix, just to get heat up.
    There 1 spare 1A fuse, I assume 24 vt relays. And one spare 5vt, I assume 120 vt relay.
  • metropical
    metropical Member Posts: 9
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    all fuses checked good. so I figured perhaps, if I'm lucky, a relay pin may have oxidation or other funk on it. Re-seated all the relays and powered up. So far so good.
    Time will tell.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,799
    edited February 2021
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    If fuses look good and no lights the 27 V transformer went bad in control ... Try pushing on transformer see if the lights come back on until you replace control .. Sometime the connection of the transformer to the board breaks down . Temporary fix for heat

    There was an error rendering this rich post.

  • metropical
    metropical Member Posts: 9
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    eh .... like I said, re-seated everyone and all is well. I'd say oxidized pins on fuse, relay or their respective holder/sockets.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,799
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    Board could be breaking down , Buy a new one to have on hand to replace ...

    There was an error rendering this rich post.

    metropical
  • metropical
    metropical Member Posts: 9
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    yea, thinking just that.

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