Need a simple diagram for Weil-Mclain EG boiler to Resideo switching relay panel.

egnuol

I could use some help with connecting the boiler (TT) contacts on the Switching Relay Panel to the boiler operating controls to power the boiler. I have mounted a separate relay for this purpose but confused on connecting to the boiler controls. Would appreciate any help. Thanks, Darrel

Jamie Hall

Eh? The principle is simple enough. The boiler will fire and run any time there is a closed circuit between the T and T terminals — provided of course that that safeties are closed as well. So what is needed is a connection — or connections — to provide that closed circuit when wanted.

Note that there is no voltage or power source of any kind in that closed circuit!

Now the normally open contacts of your relay can provide that closed circuit (so, of course, would a plain vanilla two wire thermostat's (such as a T87) R and W connections…). So the next question is — what is the circuit (including a power source) to power the relay?

Alan (California Radiant) Forbes

This is for a Taco SR-501 switching relay. When the thermostat calls for heat, it closes the dry contacts X2 and X2 to turn the boiler on.

You can also power the pump via contacts X1 and X1. These terminals are powered (not dry) because of the jumper between H and X1.

I don't know which switching relay you have, but the dry contacts are often called "End Switch".

You shouldn't need the separate relay you spoke of.

egnuol

I will be back. The boilers (2) in question are at our church and I will double check this and get back to both of you. Thanks again, Darrel

EdTheHeaterMan

When I Google "Resideo Switching Relay Panel" the first thing that shows up is the R845A switching relay. The second one is the R8845U. Both can do the same thing but are labeled differently.

And there are several things on a Weil Mclain EG boiler that can be connected to or removed from the boiler's wiring system that the switching relay can be used for.

Weil McLain has more than one series of EG boilers. The current production is Series 6 and each has a different wiring configuration.

Finally you mentioned that there are 2 boilers. That will complicate things a little. But more important is: how many thermostats are in the building(s) that these boilers provide heat for. The Switching relay is usually used for only one of the zone thermostats on a boiler system. Knowing that will help in determining how to connect the Resideo control you have.

If you have a standard switching relay, You may find this helpful.

This is a normal way to connect a zone circulator pump to bring on the boiler You may have an R832 relay that is similar but you connect. the X X on the relay to the boiler T T on the boiler control.

Where you connect the 5 and 6 or X and X on the switching relay will depend on how the two EG Boilers are connected.

Pictures of where the Resedio relay is going, how the boiler controls are connected and how many zones will make it easier to make YOUR wiring connections more accurate.

EdTheHeaterMan

OOPS. I forgot to put the zone thermostat on the T T terminals of the Resedio relay. the top T T are where you connect the room thermostat wires.

I JUST THOUGHT OF SOMETHING.

You may be using the switching relay to turn on both boilers with one thermostat like this.

In this case you have only one thermostat for the whole building. The thermostat gets connected to the Resideo relay at T T and then 3 and 4 get connected to the T T on boiler #1, and 5 and 6 get connected to T T on boiler #2.

We definitely need more information about your heating system.

egnuol

There are 3 heating zones in the church. The 6 circulator zone Resideo Switching Relay (HPSR106) will control each zone separately and have 3 relays for spares as needed. There are 3 thermostats one each for the zones. I wanted to have one boiler (sorry, these are WM EG-50 series 1, installed in 1985) on at a time by shutting off the other boilers circuit. I have run wire from the Resideo switching relay(TT) to one boiler then to the other boiler (parallel). But I thought I needed a relay here for each boiler but maybe not. Hope this clears thing up a bit. Thanks for your time, Darrel

EdTheHeaterMan

Darrel, it appears that you want to stage the boilers on a Lead/Lag control and have each boiler swap which boiler is the primary boiler so that one boiler is not always the primary boiler. To be sure that this is what you want. Is just one boiler sufficient for the entire church property, (all 3 zones operating simultaneously) under the design conditions (coldest day of the year)?

OR

Do you need both boilers to operate at the same time on very cold occasions?

There is a Lead/Lag control that is under $200.00 wholesale cost that can operate one boiler or the other but not both at the same time. It will automatically swap from boiler A to be on to boiler B to be on with every other call for heat.

To get both boilers to operate at the same time based on the outdoor demand, you will need a control the may have a wholesale cost over $500.00

With the Existing controls you have there will be no way to automatically stage one boiler for milder months and have both operate at the colder months. You must do that manually with your present set up.

EdTheHeaterMan

This Diagram may be what you are looking for. The manual switch can be placed on thermostat wire that connects the HPSR106 terminals marked T T Boiler that will connect to both boilers. However you must place a manual switch on each of the Red wires in order to turn off the boiler you do not want to operate as shown in the manual example

Manual switching is the lowest cost but someone must be in charge of swapping the boiler switches each week (or month) of the heating season. Without the person reversing the switches regularly the same boiler will be the heating boiler

The middle price options is the Lead Lag control that will automatically swap the boiler on every call for heat. https://www.supplyhouse.com/iO-HVAC-Controls-IO-LL-24V-Lead-Lag-Controller-in-Metal-Enclosure?_br_psugg_q=io-ll It can be used for either heating of cooling and here is the heating setup. but it will not operate both boilers at the same time.

And the more eloberate control would be a true boiler controller with Lead/Lag and outdoor reset capabilitiesI have installed and worked on this control and it has several energy saving features if the church can afford it. https://www.supplyhouse.com/Tekmar-261-Boiler-Control-Two-Stage-Boiler-Setpoint-4153000-p

You can clearly see that this control is built fot exactly what you are doing. You should have someone that is familiar with controls like this to install it. I can provide the wiring diagram if you plan to go this way. The Left side input #1 & #2 will get the signal from the Resideo Switching Relay, with a little help from a transformer in the Boiler Control Relay. The left side input #3 & #4 may also need to have input. It has been a while since I worked on that model

Let me know if this answers your questions!

egnuol

Thanks Ed. I think the manual set-up will work. These old boilers are living on borrowed time, so to speak, and we are expecting that. One boiler has been OK with handling the load except for extremely cold conditions maybe a week at a time. We are OK with monitoring that cold spell if needed. I do like the idea of Lead/ Lag Control though. I am still confused on where to tie into the boilers from TT on the HPSR106 switching relay. I have wire running from the HPSR106 relay TT to the boilers but not sure where to terminate at the boilers end. I have the wire from one boiler to the other boiler in parallel and relying on shutting off the power to the boiler when I switch boiler demand. Hope this isn't too confusing. Thanks again Ed.

EdTheHeaterMan

i am going to take a wild guess and use this wiring diagram for your WM EG-50

It may not be exact but the important part is there. For a series 1 you may not have the vent damper, so your diagram will be a little different. the important part of the diagram is this part. It controls burner and the circulator when there is a call for heat from a thermostat or BCP (or Boiler Control Panel). That part looks like this

I show it here on this diagram you already have above, but I removed one of the boiler pictures and substituted the diagram, so you can see where the wires from T T on the HPSR106 get connected to the boiler wiring. R & G

On the diagram, you can see where the "Thermostat or BCP" is located in a Red oval. That red oval Thermostat or BCP is connected to the R and the G on the transformer relay control inside the front cover of the boiler. I have placed the Red wire on the R terminal (on both boilers), then that wire goes to a switch, then the other end of the switch gets connected to the T on the HPSR106. The other T on the HPSR106 gets connected to the G on both boilers.

I Hope this clears up the question of where the T T from the HPSR106 gets connected to the boiler.

egnuol

Thanks Ed. I will check this out maybe later today. I appreciate your late night response!! Also, the wiring diagram for the vent damper will be useful as I had to change one boiler over to a standing pilot from the Relite Spark. Thanks again, Darrel

PS- I'm glad we retirees haven't retired for the second time.

egnuol

Just a follow up on my inquiry. Ed, this worked great connecting the switching relays to the boiler controls the way you showed on the diagram. I was delayed on hooking this up but finally finished. Thanks again, Darrel

egnuol

I forgot and also wanted to thank everyone who responded. I appreciate all the responses. Thanks, Darrel