Taco SR 501 wont turn on boiler

parkingnotice

This is a radiant floor system. Have new Thermolec TMB boiler replacing Hydro Shark boiler. The HS was switched from a Taco SR501 which started the pumps, which ran the water through a flow meter, which kicked on the boiler. There were no TT connections inside the boiler itself. The Thermolec works differently and has its own pump relay and control board with C and W1 contacts inside the boiler. C and W1 on the boiler are wired to 6NO and 5 on the Taco as per the Taco and the Thermolec diagrams. I have 120v into the Taco. I have 24v at the TT terminals in the Taco. The Taco is on (green light), I call for heat (red light) and then nothing. I thought the Taco, when TT calls for heat, is supposed to switch 6NO and 5 and send signal to boiler. I am getting 0 volts between 6NO and 5 all the time, Taco on or Taco off.
What am I missing? Am I supposed to be getting any reading between 6NO and 5? Or do I need to jump 24v to 5?

STEVEusaPA

Don't jump 24v to 5.
What do you have on H and 3?
Why can't you just wire the thermostat to C & W1? Why do you need the relay?

parkingnotice

My Thermostat is a Tekmar smart thermostat. It needs its own 24v supply. As per the Thermolec instructions I have to provide my TStat with its own power and use an isolation relay to switch the boiler.

unclejohn

It should work if wired as you described. Double check wiring and try jumping 6no and 5 boiler should start if not check boiler.

parkingnotice

Ok. Thanks. I did try to jump 6NO and 5 and nothing happened. I will check the boiler when I get home.

unclejohn

So your tstat is wired to the isolation relay coil and the TT contacts of the Taco control go through the relay contacts.

unclejohn

Make sure boiler is in the Electric only position.

parkingnotice

Yes. My Tstat is wired to the TT terminals of the Taco plus the Com. It is a Tekmar smart Tstat. Smarter than me.
The 6NO and 5 then go out to boiler C and W1.
I'm not sure what you mean by "electric only position" except I think you are referring to the Thermolec boilers that are dual-fuel. This one is only electric. Is there still a switch? I'll look for that when I get home. There wasn't anything about that in the manual.

Zman

If Jumping the electric boiler does not start it, I would start looking at the safety's. A flow switch or high limit....

parkingnotice

I just found a note in the troubleshooting section. This wasn't in the manual at all. I found the troubleshooting pages in the brochure, but not the installation manual. Go figure. I do not have a load management control. I'm going to try and jumper the S1 and S2 when I get home.

parkingnotice

Ok guys....S1 and S2 jumpered. Nothing. Ran through the testing sequence. I have no power on the 24v side of the transformer. So that's that. Brand new boiler. Contacted the manufacturer.

unclejohn

Don't be mad at me but you do have 240v to boiler correct.

Alan (California Radiant) Forbes

That's a good question......

parkingnotice

Hilarious. Yes, of course. 240v on 60amp double pole breaker.
It was in fact the transformer. Dead on arrival. You’d think it got tested before it left the factory. Cest la vie.