Wiring TACO SR502-4

JackW

In the process of redoing my 2 zone radiant heating system I've added a secondary circulator along with the 2 primaries. As I understand it the secondary will come on along with either or both primary circulators as needed. I'm using a Taco SR502-4 switching relay and would like to know if there is a way to wire it to control all three circulators. I've included it's wiring diagram below.
Thank you,

Jolly Bodger

That board only has two relays. It can be done but you will need two more relays and the knowledge to wire them in. Or you could just get a zone controller with a primary pump relay.

STEVEusaPA

Why do you have 2 primary circulators, and one secondary? I think you mean the opposite.
You run both your zone circs off of the taco, and your primary (boiler loop circ) off of the aquastat. Not quite sure what @Jolly Rodger is trying to have you do.

Jolly Bodger

@STEVEusaPA, good call. I missed the pump relay in the aquastat.

Dave H_2

Or use the SR502-EXP, it has an extra terminal for the primary circulator, ends up being less expensive and easier to install.

You may not want to leave a circ connected to the boiler aquastat, it could only run if the boiler is firing. Depends upon what the OP is looking for in each Circ.
I think we need to know what are your intended results before we can give rock solid info.



Dave H.

Jolly Bodger

The pump relay on a aquastat come on when call for heat is on the T terminals. The burner firing is a separate switch controlled by temperature of the water. the pump will run as long as something is calling for heat. The burner will cycle to maintain water temp as long as the call for heat is active.

@jackw please post a schematic of your piping so we can make sure we understand how your pumps need to be controlled.

JackW

@STEVEusaPA because I have a two zone system and that's what the diagram at the back of my boiler instructions call them.

JackW

@Jolly Bodger Here is a picture of my system so far. Please note I don't have the expansion tank and fill valve plumbed yet.

Jolly Bodger

This clears up a lot. You don't have an aquastat on that micro boiler. It also does not need a thermostat signal as it will activate heating on flow. All you need to do is turn on the pump and it will heat. Since that is the case you can use the "isolated end switch" to close a relay to your primary (boiler) pump.

STEVEusaPA

First time I ever saw an installation manual with no wiring diagram at all.
Is there a wiring diagram inside the cover or could you take the cover off and show a picture?
In a normal situation, the X-X from the Taco (in your first pic) would go to X-X or T-T on the boilers aquastat.
Your primary circulator would be wired to C1 & C2 on the aquastat.
So any call for heat (1, 2 or both zones-circs on the left) triggers the primary circ to run (the one next to the boiler), which is what you always want.
Super clean soldering, overall very nice work.

HVACNUT

@Jolly Bodger Never let your kids draw on important diagrams.😁

Jolly Bodger

@STEVEusaPA from what i saw it is a thankless water heater and triggers on flow. no wiring or external controls. Unless you saw something different.

@HVACNUT , I usually use a drafting table. And you can see why! My kids actually draw much better.

JackW

@Jolly Bodger No offence but I don't understand what you drew. Zone One and Zone Two will go out to my primary circs. I don't know what to wire the single secondary circ to. I don't understand what to do with the relay.
Thanks,

JackW

@STEVEusaPA usa I don't know if there is a diagram on the inside of the cover or not I'll take the cover off and look, thanks. Thanks for the complement, appreciate it. It's been an adventure that's for sure.

HomerJSmith

Nice clean install, congradulations. I like 10 pipe dia of straight pipe before a pump inlet and 5 pipe dia of straight on the outlet.

I would just slap an Xtank under the Webstone vent.

Jolly Bodger

@JackW , might want to get the SR502-EXP Mentioned above then. It would be a cleaner install.

Yes the Zone 1 and Zone 2 terminals will get wired to your pumps. H to the black wire in the pump and N to the White wire. These Primary pumps as your schematic all them are actually "Zone" pumps. Because each one serves a Zone of your heating.

The pump that serves the Bridal Loop with your boiler is your Primary Pump. This will need to run anytime a Zone calls for heat. This can be done many ways.

What I drew is a way to use the Dry Contact Switch that would normally be used to tell a Boiler that heat is needed. The "XX" terminals on the board a just a switch that closes any time Zone 1 or Zone 2 call for heat. This switch will not handle much load and is not designed for 120 volt power. So to use this switch we need to install a 24volt coil Relay that is capable of handing the load and voltage of the pump.

The Relay in a Box model RIBU1C would work well here. Since the "XX" terminals are a Dry Contact or Isolated Contact 24 volt Power needs to be supplied to one contact. When the switch closes the 24 volt power will be supplied out of the other contact. this power get wired to the 24V coil wire on the relay and the Coil Common wire goes back to the common of the 24 volt supply.

The RIBU1C also has a 120 volt coil wire. This would not be used. just put a wire nut on it.

There will be three wires left. Common which will get wired to a 120 volt Hot (L1). The N.O. wire (Normally Open) will get wired to the black wire in your pump. The N.C. (Normally Closed) wire will not be used and must be capped with a wire nut. The white wire from the pump goes back the neutral of your 120 volt circuit.

I can draw it out in more detail if needed. Just give me time to sit down a the drafting table or have one of my kids do it for me smile:

I'm just now realizing that you probably do not have all the controls you need for this install looking at the picture. This looks like two in-floor heat manifolds. Is it PEX Pipe in Concrete? Or one of the other methods. Is there flooring on top and if so what kind?

JackW

@HomerJSmith thank you very much, I'm flattered. I plan on dropping down about 4" for my fill valve then teeing off to the left for the expansion tank and straight down for a drain.

JackW

@Jolly Bodger Yes, it's 1/2" pex in concrete. So the best install is to get the SR502-EXP and not use my SR502-4?
I looked for the SR502-EXP at Supplyhouse.com but nothing come up, is it under a different name?

JackW

@Dave H_2 I think that's the route I will go but like I told Jolly Bodger when I type in that model at Supplyhouse.com nothing comes up.

JackW

@Jolly Bodger did you mean SR503-EXP?

Jolly Bodger

@JackW , the SR503-EXP will work. just gives you an extra zone you wont use. The important part is to have the Primary Pump terminals. This pump will come on when any zone calls. The SR502-4 can be used but it is going to require more field wiring and not be as clean an installation. Your piping is so clean and straight it would be a shame to clutter it up with junction boxes and wires.

Have you concidered temperature control on the water side? I'm building infloor myself with 1/2" PEX in Gypcrete on my wood subfloor. I've been warned about shocking the slab with to high a water temp when the slab is cold. The talk was about Concrete at the time and cracking it. And if you are putting a floor covering on it there will be a MAX surface temp to consider.

I ask these questions because you may need a temperature controller that could also control your pumps.

JackW

@Jolly Bodger this is a redo of my previous system that I had running for 14 years. I used a 30 gallon water heater but it blew this fall when I was filling it so I decided to redo the whole system. It never did work right when I tried to run both pumps because I didn't have it set up correctly, hopefully this new setup will cure that. I don't know if I need a temperature controller or not, how do I determine that? I believe I can control the temperature of the water with my boiler, I think the default is 120 degrees. The slab is well insulated with 2" of pink styrofoam underneath and along the outside walls. I ordered a Taco SR503-EXP-4 last night, want to do it right and have it look nice.
Thanks for all your help.

Jolly Bodger

I would start another thread about the water temp. I've done a lot of boiler work and serviced some infloor but have not had a chance to install much. The project I'm doing now is my own house. I'm using geothermal heat pump to heat the water. I's going to involve a lot of controls.

What you have there looks like it will do a good job for you. I'm guessing the old water heater was not 120k BTUH. So you have more power. It might heat the slab too quickly.

JackW

@Jolly Bodger Good point, I'm sure it wasn't rated very high, never gave that a thought. I will start a new thread and ask about that, thanks. Good luck with your project.