Wiring - TACO SR501

JaymeHart

I have a buzzing Honeywell RA-89A that I am going to replace with a TACO SR501. Currently, the boiler has 2 zones with separate thermostats: (1) a single-pipe steam heat main zone for the majority of the house, and (2) a hot water loop for a single radiator in an addition. The RA-89A controls the hot water loop. Power to the RA-89 comes in from the boiler, and then activates the circulator for the hot water loop.

I don't need the hot water loop thermostat to trigger the boiler for heat, just to trigger the circulator to run. The water should always be hot enough from the normal steam operation.

Do I wire the TACO for "Typical Wiring (Cold Start)" for the circulator, and just not connect the "To: TT to Boiler" part?

dko

Yes, to simply replicate existing scenario:

EdTheHeaterMan

Tha buzzing or humming is not an indication that the control is going to fail. You can most likley leave it there for years. (I tell my customers that the control just forgot the words, if you put the sheet music in plain view the humming may stop) Since you have been operating this way for ages, you probably do not need to operate the boiler for the circulator zone to heat. However if you have the rare occasion where the boiler does not have sufficient hot water to heat the circulator zone, you can use the additional relay contacts 5 N/O and 6 COM to operate the boiler with the addition of an Aquastat to keep the burner from operating long enough to make steam. Here is the diagram you might use for that. Place the Aquastat in a tapping below the water line set at 160°. When the water in the boiler reaches 160° the burner stops but the circulator keeps operating.

Just an option if you find that you need it some day.

JaymeHart

Thanks, DKO and Ed. Yes, the RA89A has been buzzing for years, and I left it not worried about the buzz. But now my mother-in-law is staying with us in the basement, and I need to get rid of the buzz. (And I am quite fond of my MiL, so this is a priority).

Thanks all for the help, and verifying the wiring for me.

Joe Mattiello

Yes, cold start which means boiler will go to Ambient temperature when there’s no load 

Alan (California Radiant) Forbes

But now my mother-in-law is staying with us in the basement, and I need to get rid of the buzz. (And I am quite fond of my MiL, so this is a priority).

Why don't you sleep in the basement, then? : )

EdTheHeaterMan

Alan (California Radiant) Forbes said:

But now my mother-in-law is staying with us in the basement, and I need to get rid of the buzz. (And I am quite fond of my MiL, so this is a priority).

Why don't you sleep in the basement, then? : )

Seriously Alan. No matter how much you love a MiL... They are still just a mother-in-law. Get Real! Next thing, you will be quoting Henny Youngman!

"Just got back from a pleasure trip... I Took my Mother-in-law to the airport!"

Alan (California Radiant) Forbes

My mother in law suffers from acute diabetes and hay fever... I always try to cheer her up with chocolate and flowers.

JaymeHart

One additional question: If I switch instead to the TACO SR502, I could wire both thermostats in to this single switching relay. Power wires in via the 120V connection, the hot water loop hooks up as a circulator.

In that scenario, I cut the wire from the original steam thermostat and feed it to zone 1 . I still have the other end of that transformer wire connected to the boiler (just 2 wires, no common), used to trigger the boiler steam production (Assuming a 24V tap on the boiler transformer).

https://www.yumpu.com/en/document/read/11323360/sr502-102-168-insh-w-fuses-taco-hvac

I think I wire it as the first diagram on that sheet. The boiler transformer wire gets wired to the TT connection (24V).

(I like this option better if it works this way, since I could finally get a common wire wired up for the steam thermostat).