Taco SR504 relay

hydronicsmike

is a dry contact. No voltage there.

Mike

Brant Beach

Taco SR504 relay

I just installed this Taco relay. I never used one before. I wired it according to instructions for cold start boiler. The t-stats are operating the circs as they are supposed to, but I cant get the 24 volt gas valve to open.
Should I be seeing 24 volts at XX isolated end switch? because I am not. If I run 24 volts to aquastat gas valve operates. Can one of the relays be no good? BB Thanks

Alan(CaliforniaRadiant)Forbes

The SR 504

is a pump controller; the X-X terminals will close on a call for heat and will close the contacts on the transformer in the boiler to open the gas valve.

It sounds as though you have an older boiler without a proprietary transformer on board. What we do is install an external transformer and wire one leg through the Taco X-X terminals and then to the gas valve; the other leg goes through the safety string (high limit, low-water cutoff, etc.) and ends up at the gas valve. When X-X closes, 24 volts turns on the gas valve.

If all this seems strange to you, please get a professional in there to help. If you're not familiar with it, you can do some damage.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

.

There is 24vac (not dc) in the box. You shouldn't need an external transformer; use the internal transformer used to run the relay coils. If you wire it through the relay, as stated above except using the internal and not an external transformer, that should give you a switched 24vac output.

Joe Mattiello

Dry Contacts

No voltage at XX terminals required.

Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com

Billy_5

We wire them throught the aquastat. When the XX terminal makes it closes the TT switch on the aquastat. That will energize the 24 volt burner circuit on your aquastat sending power to the gas valve. What aquastat are you using? Make sure the burner circuit is not 120 volts!!

Empire_2

Switching relay

Picture XX as a open set of contacts. When your t-stat calls, you will see that the pump comes on (as it should) and the XX terminals do nothing more that Close. With no wires going to it, you can take your OHM meter and see this. Michelle is correct and there also alternative ways to Bring the MGV on as long as you have safety controls in place. PLEASE make sure!!! if you are not, get on site help. VERY important...You are on the right track, but need to understand Why, and Why not things are or are not happening. Schematic reading is a MUST and understanding different ways that things are wired is critical... Keep up the good work.... At leawst you asked why.... good job..
Good luck MikeT

Unknown

Billy

It sounds as if he does not have a transformer to provide power for the gas train. He indicated that if he jumped 24v to the gas valve it works. All he has to do is take that 24v source of power and wire it through the x-x contacts of the SR504 and then on through the aquastat to the gas valve. This of course unless he has a motorized vent damper whereby the wiring gets a bit more complicated.

Glenn Stanton

Manager of Training

Burnham Hydronics

www.burnham.com

CharlesInCT

Problem with Taco SR504

I have a Taco SR504 - I installed it about 4 or 5 years ago and it has worked flawless until this week.



It is setup in a Cold Boiler setup with the XX-end Switch going to the TT connection on the boiler - and the 120 Volts output going to various Circulators pumps.



When a Thermostat calls for heat - the Circs are triggered and start up but the XX-end switch is not closing and therefore not firing up the Boiler. If I connect the two wires manually that are connected to the XX-switch it will fire the boiler.



I also checked the OHM settings to make sure the circuit is closing when a zone is triggered but it does not. close the circuit.



Is there a part that can be replaced to correct this behavior ?



Thanks in advanced for any assistance.

CharlesInCT

Likely solved... Problem with Taco sr504

Looking like a Relay OMRON Part LY2 24VAC - I swapped the first one in line with the one in the last slot and it now works - So I need to order a Relay - prob just order a few of them and have some spares..