Wiring time delay relay for steam boiler with smart Stat

dabrakeman

This thread is in reference to a couple recent ones discussing usage of a time delay relay to limit boiler burn time and set delay before refire. Specifically my question is concerning the wiring where it may or may not be as straightforward as "in series with the stat". I am no electrician but would like to be able to wire this myself if at all possible so seeking some advise from others that may better comprehend the situation.

I have a smart thermostat that needs continuous power thus it has a 3 wire system with a common wire. When it was originally put in I had issues because the way it was originally wired the power to the stat was really still in series with the ptrol and LWCO so if the LWCO for instance activated it cut the thermostat off from power causing the stat to have to reboot. The reboot would only occur after the LWCO allowed power to be restored to the boiler and this reboot usually ended with the stat causing control issues wildly off target. This issue was completely resolved by wiring a relay in that isolated the thermostat power supply from the control/safety devices. The devices of course still function and shut off the boiler when needed but the stat is allowed to continue to do what it was doing without loss of power. This of course would not be an issue with a simple battery powered thermostat.



So, now I am not sure where exactly something like the Macromatic TR-6512U gets spliced in? Attached is a photo of the wiring/spaghetti at my boiler. The bundle from the thermostat is wrapped in the brown jacket from which the red, white and black wires are active. The relay installed to take care of the above described issue is hanging from the wire. Would it be the white wire (marked with the arrow) that is delivering the thermostat command and thus would it be in that length of wire before the relay that the new time delay relay would be spliced in?

On another note I have been in discussion with the thermostat manufacturer about adding this function into their software options. They already have a min run time option. Just need a max run time with selectable delay to refire...

acwagner

What are the make/models for the boiler, thermostat, and the time relay?

dabrakeman

The boiler is a Weil-McLain EG/PEG-65. Thermostat is Ecobee 4. Intended time relay is Macromatic TR-6512U.

PMJ

@dabrakeman , attached is the wiring diagram that has worked for a couple of people with an Ecobee.

If you can, verify that your current setup looks like the first page. If so, the diagram on page 2 should work. I have written in the terminal numbers on the Octal base of the Macromatic.

Take the extra time to verify things before doing anything. Perhaps the guys who did it recently can help.

dabrakeman

@PMJ Thank you. Per the stat wiring photo attached I have a red wire in Rc (hot), white wire in W1(control) and black wire in C (common). At the boiler it appears both the red and black wire go straight to the transformer (to R terminal and what appears to be the center terminal G respectively). The white goes to the relay that was put in to remedy the previously described issue. Am I understanding correctly that the Macromatic would actually REPLACE this relay that I currently have installed and shown in the picture above?

So if I understand the new diagram correctly now my white wire would go directly from the stat into terminal 7 of the Macromatic. Red Rc and black C unchanged from stat to transformer as they currently are. If that step is correct then what I need to decipher next is which of my wires go to terminals 1, 2 and 3 in your diagram. Currently I have three black wires attached to the current relay. The small guage wire (bottom right in above picture) goes from the relay to the C terminal on the transformer. So it seems logical this same wire would now go to the Macromatic terminal 2? The other two wires are bundled together and labeled "To Thermostat" and the one opposite the white wire on the relay goes to terminal Y of the transformer (lower right in picture) and the other black wire goes to the center terminal G on the transformer (the wires are so tightly packed at the transformer it is difficult to be 100% sure it terminates in the center G terminal, other slight possibility it terminates in the C terminal at top right). Is this enough information to know which of the larger guage black wires would go to terminal 1 vs terminal 3 on the Macromatic?

Appreciate the hand holding here...

SteamCoffee

So, what happened?

dabrakeman

Still not 100% sure on the wiring. 99% sure. My question is still with terminal 1 and 3 on the Macromatic. The two heavier guage wires in my current relay would go into those (one currently goes back to terminal R on the transformer and the other to center terminal G) but I just don't know if it matters or not which goes in 1 vs 3 on the Macromatic.
@PMJ has been a help but his setup is a simpler 2 wire stat configuration. I am not concerned that I could not put it all back the way it currently is if it didn't work out (i.e. boiler wouldn't fire) but am concerned whether or not I could fry something else in the process if done wrong. If things seemed functional I certainly could then test to make sure both my LWCO and Ptrol were still functioning correctly. I have not ordered the MM yet since this is not an urgent matter but a nice to have matter

Mark N

Dabrakeman. if you're not sure what to do leave it alone. Terminals 2 and 7 are the coil of the relay. When the thermostat calls for heat 24vac is applied to terminals 2 and 7 energizing the coil and causing the normally open terminals 1 and 3 to close. Terminals 1 and 3 closing completes the circuit to energize the gas valve.

dabrakeman

Since I never build pressure except when doing 2+ degree recoveries from setbacks (I have 654sqft boiler and 531sqft in radiators usually with two closed thus 459sqft typical) I will experiment first for a while just incrementing the recoveries with programmed thermostat settings. Can do pretty much unlimited scheduling with the Ecobee. Since I know it takes about 50 minutes to start building pressure over 0.25psi on a cold recovery and about 40 minutes on a warm recovery and that I can easily recover 2 degrees within those time periods I can stage a 5 degree recovery doing say +1deg at 5AM, +2 deg at 6AM and +2 deg at 7AM. In most cases this should allow at least 20 minutes of off time heating throughout the recovery and avoid any pressure build. I could probably recover a little faster and still avoid pressure but thjis should cover the coldest days without having to keep reprogramming. If did the Macromatic purely on time it would need similar amount of adjustment unless truly activated off of a low pressure.

acwagner

If you're not cycling on pressure during a typical call for heat then using the thermostat to step recovery like you mentioned is the best way to go.