TSTAT C wire connection to Burnam series 2 boiler/R8285D

woobagooba

Folks. I need to replace battery powered TSTAT (W/R) with a wifi connected TSTAT also needing a C wire. I have an extra wire available to get C from the boiler to the TSTAT.

TSTAT W is connected to R8285D G. TSTAT R is connected to R8285D R.

Where should I be connecting the TSTAT C wire on the R8285D?

BTW I am not understanding why TSTAT W goes to R8285D G terminal.

Thank you







https://customer.resideo.com/resources/Techlit/TechLitDocuments/68-0000s/68-0088.pdf

Jamie Hall

We need to know what, if anything, is connected to the auxiliary circuit (marked with the triangle 3) on the circuit diagram and how, if at all, that is connected to the boiler. There's more to this wiring than you have described so far.

EdTheHeaterMan

The Series 2 boiler has gone thru many different control systems and I can not find the wiring diagram that uses the R8285D type control. This is a similar boiler wiring diagram that uses the control you have. Here is my best guess to where you should wire the R and the W and the C from the thermostat to the boiler
if your boiler has a different diagram then please post a photo of the actual boiler wiring as it exists now. zone valves and zone relays will make this wiring suggestion VOID

EdTheHeaterMan

BTW I am not understanding why TSTAT W goes to R8285D G terminal.

Thank you

The R8285D is designed to add central air conditioning to existing furnaces back in the 1950s through the 1980s. The G terminal on a heating and cooling thermostat is designed to bring the furnace fan when the compressor would operate by the Y terminal on the thermostat. That way the AC coil got cold and the fan would operate by way of the relay section of the R8285D.

Now there is a ready made control for air conditioning add on that is very popular in the HVAC industry. Just about the time that boiler manufacturers started to do something called "Package Boilers". Before 1950 every boiler that was installed was put together in the basement or boiler room. The asbestos insulation was slapped on, the shiny cover was added, the pipes were then added then the controls were added then the wires were added and in about 3 days you had a new heating boiler in your basement.

Package boilers became all the rage when it was discovered that the boiler did not need to be so big. the Package boiler was introduced with all the controls and the circulator pump and the relief valve and the pressure gauge and the shiny insulated cover already assembled in the crate. Just put the boiler in the basement and connect the radiator pipes, the vent connector to the chimney and the thermostat and house current wires to the control junction box. That could happen in just one day. WOW!

So why do you need to know all this? You asked about the G connected to the W. When the boiler manufacturers needed an inexpensive control to turn on the circulator and the gas valve at the same time, the selected the R8285D because it was able to do what they needed. Who cares if the relay was connected to the G (because it was designed to turn on the fan on the AC system) Just connect the W to the G and the relay can turn on the circulator pump. Plumbers who usually install these boilers don’t need to know that the boiler control was supposed to be an air conditioning control. Just tell them “That’s the way it is” forget about the W on that control, it don't do nothin’ anyway! Look at the back of the W terminal on your R8582D, it is just like the Y, there is nothing connected to it.

109A_5

Hello @woobagooba,
Anything connected to the relay contacts of the R8285D ? Maybe they just connected up the available wires to the available terminals on the thermostat, the C was missing.

EdTheHeaterMan

109A_5 said:

Hello @woobagooba,
Anything connected to the relay contacts of the R8285D ? Maybe they just connected up the available wires to the available terminals on the thermostat, the C was missing.

He is talking about a boiler that is using the R8285D as a circulator relay. There are usually 2 black wires attached to R and G on the boiler that say T T on a little tag tapped to the wires. That is why W on the thermostat is connected to G on the boiler. It makes the relay pull in to operate the circulator. It depends on what year the Series 2 boiler was built, it must be pretty old if it has that old style control. Look up Series 2 boilers today and you get the integrated boiler control with the Molex plugs to everything.

That's why I asked for the wiring diagram from the boiler he is working on. I can't find the Burnham version that uses that R8285D control, so I took a random boiler diagram that uses that control to illustrate where the C wire goes

109A_5

Hello @EdTheHeaterMan,

woobagooba said:

BTW I am not understanding why TSTAT W goes to R8285D G terminal.

I overlooked the "TSTAT W" in this sentence above, which is why I asked "Anything connected to the relay contacts of the R8285D ?" Also I did not see two Red wires and two Black wires as specified by the R8285D documentation, rather Red, Yellow, Black, Blue.

What you stated makes sense for circulator control.

woobagooba

Thanks all. I'll put a multi-meter on it to confirm.