struggling to install a new Taco SR503-5 relay

donl1150

I am struggling mightily. I am sure the problem lies in the microswitch terminations but I am not familiar at all of how the Taco relay device works. Here is what I have: It's has 3 - Ecobee Smart Thermostats Enhanced, 3 - Honeywell 40003916-026 control valves on a 3 zone radiant in-floor boiler heating system. Each zone has its own circ pump and there is also a master circ pump. 

I am installing a  new Taco model  SR503-5 - 3 Zone Switching Relay. 

The propane boiler is a model  Burnham model 204PS-BEI2

The Honeywell valves each have 2 yellow wires for the valve motor and 2 red wires for the valve micro switch.  

In summary, here are the wires: 

Ecobee

R, C, W1

Honeywell valves

Y1, Y2

R1, R2

I have a  24v 40mva external transformer available if it is needed and can be utilized somehow. 

R, W

Tell me which wires should connect to each other and which should be wired into which Taco terminals.

Ecobee

R to ?

C to ?

W1 to ?

Trans (if needed)

R to ?

W to ?

Honeywell motors

Y1 to ?

Y2 to ?

Honeywell MicroSwitches

R1 to ?

R2 to ?

The key Taco terminals are Zones 1,2,3. Each have R,W,C And also X-X

Could somebody tell me how the wiring scheme goes? I'm not concerned about the 120v circ valves, they are already in positions 1,2 & 3 on the 120 side.

mattmia2

why do you have both per zone circulators and zone valves? how are they plumbed?

That panel is made for zoning by circulator so it doesn't have terminals for zone valves although you might be able to parallel them with the thermostats with some creativity.

EBEBRATT-Ed

@donl1150

I will take a stab at this. Look for a diagram later tonight.

Alan (California Radiant) Forbes

I just had to do this on a job in the City with pumps and zone valves on each loop. This way, the pump only comes on after the zone valve has opened.

hot_rod

what size transformer is in the relay box? The Va of the zone valves?

EdTheHeaterMan

This sounds like someone is doing a little overkill. Can you post a photo of the piping to include the zone valve, water mixing device (if any) that lowers the water temperature to the radiant floor tubing, and the circulator pump for one zone (or all three zones if they are close enough together). If that is not possible can you draw a diagram of how the parts are all piped to the boiler and the floor tubing manifold(s)

EDIT: Do you know what version of the Taco SR503 you have? Older version(s) with the metal cover, or the plastic cover SR 503-4 and the latest SR 503-5? They are all a little different.

109A_5

I would do it like this, using your external transformer since you have the added loads of the zone valves. Thermostats control the zone valves, the zone valves control the Taco SR503-5.

SR503 XX goes to TT on the boiler.

Looks like the boiler TT is P5-7 and P5-9

EBEBRATT-Ed

Here is my version down and dirty and quick. I may have missed something.

Don't know if the main pump is powered from the boiler.

You may need some sensors wired

I did not show ground wires that are required

ZONES.pdf

EdTheHeaterMan

Here is My version. I think it is eactly like @109A_5 and @EBEBRATT-Ed diagrams but sometimes it is easier to see it in the complete form and not just the part you are asking about.

This is using the SR503-5 control. If you are using the SR503-4 I can re-do it with that control's diagram.

EDIT:

I would also recommend using a Lil Popper or a 3 Amp Auto fuse on the R side of the 40 VA transformer before connecting to the thermostats.

And … NO I don't really sell them…. It was a joke from a while ago. These things will keep the factory installed smoke inside the transformer.

109A_5

If your Taco SR503-5 has the optional additional transformer for the additional loads of the zone valves and powered thermostats. You could do it this way.

EdTheHeaterMan

@109A_5 said: "If your Taco SR503-5 has the optional additional transformer for the additional loads of the zone valves and powered thermostats. You could do it this way."

(Ecobee load + Zone valve Load) x 3 + Taco 503-5 load =

(3.5 + 7.7) x 3 + 1.8 = 11.2 x 3 + 1.8 = 33.9 + 1.8 = 35.7 VA

That might be getting a little too much for the Taco 503-5's onboard transformer. (which is only 20 VA without the optional second 20 VA transformer for a total or 40 VA).  I would stick with using the auxiliary transformer if you already have it. 

hot_rod

The Caleffi pump relay box has a replaceable 40VA transformer onboard, that would eliminate the extra transformer and wiring

If you haven’t purchased parts yet.

Grallert

Wouldn't a ZVC be a better option? Or am I missing something?

Alan (California Radiant) Forbes

@109A_5 and @EBEBRATT-Ed got it right. My method works, but it's way more complicated than it needs to be.

EBEBRATT-Ed

@Alan (California Radiant) Forbes

Your way works as well. Everybody's brain works different. Sometime mine doesn't work at all!!

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1881176#Comment_1881176

I believe the ZCV control won't operate 3 circulator zones. That is why I made the wiring diagram that is in my previous post. You could add a ZVC to the system if you don't like to have all that extra wiring hanging around the zone valves with no electric box to put them in. Then you can have the end switch operate the individual pumps. I believe the micro switch is rated for 120 VAC but then you will need to add electrical junction boxes each zone valve that has 120 VAC connected to the end switch.

What is missing here is the fact that the piping has zone valves where all they needed was Flow Control Valves or IFC pumps. Since the piping is already done, and the system just needs to be wired up, I think the simplest thing is to make the thermostat operate the zone valve, the end switch operate the corresponding pump thru the SR503, and the SR503 operate the burner. Thermostat calls > valve opens > pump operates > Burner operates.

109A_5

https://forum.heatinghelp.com/discussion/comment/1881189#Comment_1881189

@Alan (California Radiant) Forbes Why do you think your way is more complicated ? It looks the same to me, just draw with the thermostat and the zone valve placed differently on the drawing.

I included the external transformer since @donl1150 stated he had an external transformer and it is a good idea the have the thermostats and zone valve loads on the external transformer if there is any doubt of the SR503-5's transformers' ability the power the extra loads.

@Grallert not sure the ZVC would give you the same circulator control on a per zone basis. And I understood it as @donl1150 already had a SR503-5. It would be nice if there was a box that would support zoned circulators and zone valves. Although it is usually one or the other, unless there is some odd issue.

Grallert

You guys are right. I did miss something. Rereading I see the circs which I had missed 🙄

donl1150

Thanks everyone.  I woke up in the middle of the night yesterday with what I thought would work.   I gave it a try on one zone and sure enough it did!  So I spent yesterday getting all components down to their individual wires and started over fresh.

I hadn’t seen your comments until just now.  But what EdTheHeaterMan shows in his post is exactly what I did with the exact unit I had already purchased.  The challenge was to keep all the wiring to a minimum and as neat as possible.  I used WAGO’s instead of wire nuts and that helped a lot.  I kept the stat connections inside the Taco and put all the others in a separate adjacent box.

The single level on-slab house was built in ’99 and at the time this system was primary heat source.  As for being an overkill design, I would have no idea but it does provide nice heat.  We bought it in ’23 and when the AC died in ’24 I replaced it with a heat pump.   Thus I qualified for interruptible electric rates and made floor system the backup.  I replaced all the old stats with Ecobees at that point.

My current problem started a month ago when during the middle of the night, all Ecobees went black.  After some digging, I discovered one of the 3 original mechanical relays had failed. So I limped along with only 2 zones but decided to replace the other 2 relays since they would probably give out soon too.  Not knowing anything about how these things work, I chose Taco only because the circ pumps are Taco.

Instructions for this stuff are not homeowner friendly so I was pretty much trial and error with some help from ChatGPT.  I learned that I needed to keep use of the existing external xfmr sine the Taco on-board unit was insufficient for the 3 ecobees + the 3 zone valve motors.   Once I reached that aha moment and drew it out on paper, it was clear what needed to be done.  So everything is up and running perfectly now.  

BTW, the heat pump is on a separate Ecobee and xfmr.  I have a lot of remote sensors on the system as well.  4 are connected to the heat pump stat sensing room temp at eye level in 4 different areas.  Each of the 3 zone valve ecobees have a single remote connected to its particular stat located near floor level in each of the 3 areas.  I have the comfort settings on the heat pump unit set at 70 and the settings on the radiant system set at 68.  This way the heat pump provides the majority of the heating while the floor stays ‘idle’ ready to take over when the heat pump can’t keep up.  It worked great until the relay died and of course it was when the temps went below 0.  It was chilly in here a few mornings - 59.  Our gas fireplace worked overtime for a few days!

Again thanks everyone.