NEST-MCLAIN EG-40 BOILER-HOW TO INSTALL NEST POWER CONNECTOR

ektix23

i cannot figure this out. i have the mclain eg-40 and i bought the nest power connector. i do not know which wires go where please help

Ironman

Don’t use a Nest with a boiler system.

KeithDoell

There is truth that there is no significant savings in energy when a Client has a hot water or steam boiler. The savings of smart thermostats come more into play with HVAC systems. There is a great article that ran recently on the NY times called "When a Smart Thermostat Isn’t the Smart Choice" if you would like to further expand your knowledge on the subject...........

With that said, I have had Clients that wanted the remote operation feature that WiFi thermostats offer. No fancy additional devices are required (like the white device in your photo) but you do need three wires on the thermostat wire. If not, than one needs to be ran and that can be expensive.

Some things are just not DYI as the manufacturer's would like Clients to believe and therefore you would need a licensed Contractor to install properly. But that boiler does have a power lead and a common to give the WiFi thermostat constant 24V power.

Good Luck

EBEBRATT-Ed

Nest's are generally not reliable unless you have 3 wire cable going to the nest for heat R, W, Common.

The best way is to add a relay and a seperate transformer and run a 3 wire cable to the stat.

I have a wiring diagram if you need it

The nest batteries generally can't recharge when hooked up without the C wire

ektix23

yes please provide whatever you can...and please let me know how to use the nest power connector if it could work with my boiler

ektix23

and the crazy thing is i cant find anywhere online someone with similiar situation with my boiler set up

jp44

Probably too late, but may help others.  I have the same setup as you, and also couldn’t find any help online, which is odd.  Have 4 zones, each zone has a relay box near the boiler.  I only have a two wire system.  I simply ran a single wire from the “c” terminal in your boiler picture to the “c” terminal in my first zone relay, about 6’ in length, then leapfrogged from relay to relay until all the c’s were connected.  Now you need a Power Connector for each relay box, which google sent me for free when they emailed me that my nest wasn’t working right.  Just follow the instructions, disconnect your incoming thermostat wires and connect those to the grey wires on power connector.  Then run the R and W from power connector to where you disconnected your incoming thermostat wires.  Then hook up the C on power connector to C on relay box.   Now run a power test at your nest thermostat so it can sense the power connector.  You may have one controller for all your zones, which will simplify.  Just run a short C wire from boiler to zone box.  This took me three weeks to figure out.  Good luck.

pecmsg

Why is it always a N E S T ?

Ironman

pecmsg said:

Why is it always a N E S T ?

Because it’s a fancy piece of junk. But today, everyone wants the latest fancy gadget.

skiereric

Ironman said:

Don’t use a Nest with a boiler system.

Can you elaborate on this?

pecmsg

skiereric said:

Don’t use a Nest with a boiler system.

Can you elaborate on this?

Nest is an over-marketed p o s

every t-stat is better.  

SteamBoiler

ektix23 said:

i cannot figure this out. i have the mclain eg-40 and i bought the nest power connector. i do not know which wires go where please help

I will be honest, you don't sound like you have any idea what you are doing and I would suggest hiring an electrician for what should be an easy job. Here is a wiring diagram for the Nest with a C wire on a Weil McLain. The transformer board photo that you posted, has the R, G, Y, C, W terminals inscribed on it (look closely). If you can figure out how and where to connect R and W for the Nest, you should be able to figure out how to put in a power connector from its instructions. The one caveat with wiring it in the way I did is, R for the Nest is dependent on the low water cut off always detecting water and if LWCO chatters, power to the Nest may be interrupted. I am planning to add an isolation relay and continue using the boiler transformer for Nest power.

SteamBoiler

EBEBRATT-Ed said:

Nest's are generally not reliable unless you have 3 wire cable going to the nest for heat R, W, Common.

The best way is to add a relay and a seperate transformer and run a 3 wire cable to the stat.

I have a wiring diagram if you need it

Not the original poster but here is how I wired mine, the issue is Nest continuous power is now dependent on LWCO always detecting water. I plan to move Nest R to the boiler R (ensuring continuous power) and wire in an isolation relay, normally open switch side between boiler G and Y (thermostat terminals); and the coil side to be connected to Nest W and C; hence continue using boiler transformer power. Eventually maybe add in an external transformer. Please let me know if that makes sense. I would appreciate your posting a wiring diagram.

EBEBRATT-Ed said:

The nest batteries generally can't recharge when hooked up without the C wire

Not sure I agree with this. On a 2 wire connection Nest should charge off R and W when NOT calling for heat. The issue is cold dawn hours when Nest could be calling for heat about 50% of the time over a 6 hour period, that might discharge the batteries but I don't have experience with this.

ektix23

I’m the original poster here. I don’t understand any of this:) I live in 11210. Who can install a nest for me. 

pecmsg

I hate the NEST stat. Just too many issues and problems but great BS marketing! 

Anything is better. 

SteamBoiler

pecmsg said:

I hate the NEST stat. Just too many issues and problems but great BS marketing! 

Anything is better. 

I have installed the Nest and have it functioning robustly, albeit with an external transformer and isolation relay, on my Weil McLain boiler. Comparing Nov 2022 to Nov 2021, we have used 152 therms of gas with the Nest compared to 204 with an old mercury Chronotherm that was short cycling my boiler - I didn't know enough at the time but it was turning off as soon as heat hit the earlier radiators though the anticipator was set correctly. Our home is now much more comfortable and I appreciate the savings since gas is now 2x the cost for "supply charges" for Nov 2022; and the "delivery charges" are now 1.25x. I have a 4 degree setback overnight and recover in 1F steps every hour in the early am so pressure doesn't build up.

On the Nest, I love the ability to look at the heat call durations every day as a proxy for system health. At the beginning of the season I had filled the boiler then removed water since it was surging (initial runs) and I saw a 2 hour heat call on the Nest, sure enough water was low and subsided as soon as I filled water.

I recommend the Ecobee since the temperature differential and minimum heat call duration are programmable but Nest is a perfectly fine alternative as long as one understands its limitations with steam heat. If I owned Nest I would be marketing to the vast majority of the country that is on forced air or heat pump and that could actually use the setback savings (especially in these days of high cost energy), not to the corner case of radiator or baseboard. I have absolutely no affiliation with Nest.

SteamBoiler

ektix23 said:

I’m the original poster here. I don’t understand any of this:) I live in 11210. Who can install a nest for me. 

Since you don't understand any of this you should contact a local electrician or HVAC company that can install the Nest for you. Ask them if they have experience installing Nest with its power connector on a Weil McLain steam boiler. After it is installed, keep monitoring the heat call durations on "History" on the Home app to make sure it is running properly. Make a note of what your boiler run time durations are right now with your old thermostat and the time taken to heat up your earliest and latest radiators. When Nest is installed, make sure you are getting approx the same run times, and that the run times are somewhat similar from run to run. Watch out for overly short calls that may be running the boiler but don't heat up the radiators.

Brian4848

Most of these responses are useless and pompous.  It's surprising this site has lasted as long as it has.  Good luck with your shaming gents! Smh.

pecmsg

Brian4848 said:

Most of these responses are useless and pompous.  It's surprising this site has lasted as long as it has.  Good luck with your shaming gents! Smh.

Took 6 months to come up with that!

JUGHNE

The Nest is just about the only item that gets slammed on this site.

I follow another Heating/AC site and it gets beat up there also.