Taco 501 wiring question

TheWeimar

Evening Gents,
Firstly, full disclosure: I am neither a plumber or an electrician. Now that we have that out of the way, I recently installed RHF system in the house and have wired in a Taco 501 to control the circulator pump and signal the boiler to fire. The wiring diagram is quite simple and I fear that my issues may be in the 'original' wiring of my boiler (not done by me). Taco is wired to Nest with resistor installed, when called on it switches on the circ but the 6 and 5 terminals to "TT" on boiler do not send the 24V and the boiler does not fire.
Boiler is a Weil McClain with Becket burner and Honeywell L8148 Aquastat. Not sure this even deserves pictures. Any help greatly appreciated....especially before I lose my mind.

Dave T_2

What is a RHF system?

Terminal 5 and 6n/o close when the relay pulls in. First confirm that the 2 wires connected to TT on the L8148 do start the burner - so jump them together and the burner should fire. If it does not fire than the problem is not the 501 relay. If the burner does start then the 501 relay is bad.

BUT, the L8148 is a burner high limit AND circulator control. So when TT on the the L8148 closes, power is sent to the burner through B1 AND power is also sent out C1. If you have anything connected to C1 (like circulator to another heat zone in the house) it will also run when your 501 pulls in.

The correct way to run the burner with a 501 and 8148 is this;

At the 501, connect a 14ga jumper wire from T1 to T5. Then, connect a 14ga wire from T6n/o and over to the L8148 and connect to the terminal that currently has a blue wire from the factory.



Test to confirm operation and safety. Turn up thermostat to the 501 zone all the way. The circulator should run AND the burner should fire. Let it run till the burner shuts off when the boiler temp reaches high limit while the circulator continues to run.

TheWeimar

Holy crap Dave, that is tremendous!
RHF is rookie talk for Radiant Heat Floor. 

I will give this a try as soon as I can, thank you

STEVEusaPA

Wire aren't you simply controlling the boiler/circulator off of the aquastat?
I'd like to see some pictures.
BTW, how did you set up combustion on the burner.

TheWeimar

Hiya and thanks for the advice. I want to clarify that the 501 is a fully separated zone with its own circulator and I want it to trigger the boiler and other circulator for that system to start. That system consists of the 2nd floor zone, the garage zone and the hot water zone, all controlled by the 8148, taco zone valves and ONE circ pump There is no relay switch controlling these zones, only some wiring in a an enclosure above the boiler (that is the nifty wiring in the pic). Lots of red, white and green wires connected to each other with one red and one white to the TT on the 8148. My question/concern is that if I run voltage from the 501 to the blue in the 8148 and the hot water zone calls at the same time and closes the circuit, won’t there be 240 on the blue and damage the system? So what I'm saying is that I have 1. a boiler with 3 Taco zone valves and one circulator controlled by the 8148 and 2. a separate zone controlled by the Taco 501 and I need the Taco to turn the 8148 on to heat the water and circulate so that #2 can circulate that heat. Taco wiring diagram says wire n/o 6 and com 5 to TT on the boiler, I say BS. Unless my Taco 501 is bad. Should there be 24v at 6 or 5 when the 501 switches on? because there isn't.
#TACO

TheWeimar

STEVEusaPA said:

Wire aren't you simply controlling the boiler/circulator off of the aquastat?
I'd like to see some pictures.
BTW, how did you set up combustion on the burner.

Hi Steve and thank you for commenting. This boiler was installed when the house was built (2006) and has worked fine other than a zone valve failure. The 8148 controls everything through that rats nest of wires (not my handy work!). I guess to answer your question....I'm trying to get away from the wire nut experiment and use a relay switch for my new radiant heat zone.
Here is a question...why wouldn't an installer use a relay to control everything ? To save money and just spend on orange wire nuts?

STEVEusaPA

First of all, nothing goes on the blue, yes you'll smoke it. Follow the 'typical wiring' on the instruction sheet. Wire that zones circulator to the 501 and send 5 N/O & 6 to T-T on the aquastat.
Then when that zone calls it's circulator will come on as well as the common circulator, and fire the boiler.
5 & 6 are a switch. It only has the voltage you send thru it. If the switch is closed you read 0 volts.

The low voltage wiring looks crazy but really isn't. Pretty standard. The simple reason is to save money. Same reason why you bought a 501 instead of simplifying everything with a ZV406.
If I were a betting man I'd say this wire goes back to the aquastat on T-T