Taco Switching Relay POWER

helpmeheat

Hi all,

I recently purchased a Taco SR502-4 Switching Relay in an attempt to clean-up/simplify a natural gas hydronic setup at my house. I *thought* I had things wired up correctly to at least check some initial functions, but I can't even get the power LED to light up on the Taco!

Here's what I've checked so far...
--Coming from the break panel I have 120VAC terminated into the 'INPUT' of the Taco (N - WHT, H - BLK, ground - Copper)
--I checked continuity across all the fuses and they're all buzzing. (Plus, they visually look fine.)

Is there something else needed to power the PC board of a Taco? I have had zero luck with the documentation from them, honestly.

Happy to post more pictures if needed. Thanks!




A few things to note here -- I replaced the stock transformer with a beefier one because I plan to power two separate thermostats and I *hoped* the boiler 24VAC circuit, but I haven't been able to get that far due to this issue.

EdTheHeaterMan

If you removed the transformer from the Taco Control, you will not get a power indicator light. The transformer that comes with the control is to power up the control and should not be used for other purposes.

EdTheHeaterMan

My guess is that the printed circuits on the back of the bard are fried somewhere. Somewhere that is not fuse protected.

This is an illustration of one of the printed circuits on the back that might be compromised. the white and black on the 2 pin plug are not intended to be wired up to something outside the control box.

Good luck with getting Warranty on a control you altered.

Alan (California Radiant) Forbes

All the boilers I've ever seen have their own transformers.

helpmeheat

OK well that's very useful information! I guess I misinterpretted the intended use of one of these switching boards. I replaced the transformer because previously there were two transformers mounted to the outside of the boiler and I thought I was "replacing them" with this controller.

I then saw how weak the included transformer was (thinking this was intended for the external devices) and thought I was "upgrading" it by splicing in a much beefier one.

Turns out that the transformer was not intended for any of that...

I hesitate to ask for further advice on this because I'm sensing a level of sarcasm already (although... to be fair I see the National Sarcasm Soicety avatar haha) but truly I appreciate the feedback thus far! I'm not looking to modify the plumbing by adding zone valves at the moment so perhaps the Taco should just be removed from the equation.

helpmeheat

Written a slightly different way... I wish I had drafted up the design and posted it here BEFORE purchasing (and voiding) the Taco. haha

Zman

You should be able to troubleshoot this with a multimeter. Do you have 120 volt to the transformer? Do you have 24 volt from the transformer to the board? Polarity? Neutrals, commons, grounds all prove? If you smoked the board, you should be able to see the bad spot if you flip it over and look at the back.

GroundUp

I have seen this quite a few times, and every time has been a bad transformer. Is it possible the one you swapped in is bad? As Zman mentioned, a multimeter should get you an answer pretty quickly