Running wire for a thermostat

branimal

I'm renovating a three family home in Brooklyn, NY which is heated by a 1-pipe Gas Steam boiler/ radiator system. New boiler installation.

The contractor hooked up the boiler to a Honeywell thermostat using the old thermostat wiring. The wire runs from the thermostat along the wall, out the side of the building, down the facade, to the backyard and then back into the building. Terrible, I know.

I have a shaft-way open for some electrical work and I'd like to run a thermostat wire down that pathway.

I might use a Nest thermostat so I can control the system using Wifi.

A/C will be windows units that tenants control themselves.

1. Should I use 18/5 wire? Extra wire's in case some go bad.
2. Is there a special casing / jacket to protect the wires in the run? I realize they are low voltage and don't need to be inside EMT / Conduit, but I don't want them getting damaged.

Thanks.

STEVEusaPA

You can run it in conduit. Good luck with the Nest. Post the make/model number of your boiler so we can see if they're may be a conflict.

ScottSecor

@branimal I suggest at least five conductors, labor is about the same to run the wire regardless of how many conductors. If there are a bunch of line voltage wires in the same chase you might have problems in the future with electrical interference. I would suggest at least five conductor shielded wire, 18 gauge would be your best bet. The shield will help prevent issues in the future while providing at least one extra conductor.

Solid_Fuel_Man

For what it's worth, I run 18/7 to all thermostat locations in new construction. The shielded wire may not be needed, but isn't a bad idea either as it also gives a degree of added abrasion resistance.

branimal

Boiler is Burnham Independence KIN-7.

I'm not going to put it in the same EMT pipe as the electrical wiring.

@ScottSecor : Is this Southwire 18/5 wire considered "shielded"? The insulation is made of 6 mils of polypropylene and a brown PVC jacket.

https://www.homedepot.com/p/Southwire-250-ft-18-5-Brown-Solid-CU-CL2-Thermostat-Wire-64169644/202316418

HVACNUT

You dont need shielded wiring, but NYC code might require you run the wiring through rigid conduit. The only way you can have a low volt circuit in the same conduit with a line (120) volt circuit is if the wires are of the same gauge.

ScottSecor

@branimal the wire in your link does not appear to be shielded. Like other more qualified than me mentioned above (I'm not an electrician), the shielded wire is not required. I thought it might me a good idea to run shielded as an extra layer of protection, especially since it appears to be difficult to run wires in your house.

Jamie Hall

Thermostat wire doesn't have to be shielded. It's just on/off -- no high frequencies or digital signals.

Please do yourself a favour: don't use a Nest. There are a number of other thermostats out there -- Honeywell makes a whole line of them -- which offer wi-fi monitoring if you need it without the fancy intelligence (and unverifiable data harvesting) of the Nest.

Nests work well for forced hot air systems where there are no privacy concerns. They don't work well with other systems --and aren't intended to.

branimal

Just realized this is a long run. 35-40 feet to get from the shaft-way to an ideal thermostat location. 35-40 feet just to get to the basement. Another 60 feet in the basement to get to the boiler from the shaft-way. Add in turns. Might as well get the 250 ft roll.

branimal

Jamie Hall said:

Thermostat wire doesn't have to be shielded. It's just on/off -- no high frequencies or digital signals.

Please do yourself a favour: don't use a Nest. There are a number of other thermostats out there -- Honeywell makes a whole line of them -- which offer wi-fi monitoring if you need it without the fancy intelligence (and unverifiable data harvesting) of the Nest.

Nests work well for forced hot air systems where there are no privacy concerns. They don't work well with other systems --and aren't intended to.

Interesting point about the Nest. What exactly are the issues? Not sure I'm following.

ChrisJ

branimal said:

Jamie Hall said:

Thermostat wire doesn't have to be shielded. It's just on/off -- no high frequencies or digital signals.

Please do yourself a favour: don't use a Nest. There are a number of other thermostats out there -- Honeywell makes a whole line of them -- which offer wi-fi monitoring if you need it without the fancy intelligence (and unverifiable data harvesting) of the Nest.

Nests work well for forced hot air systems where there are no privacy concerns. They don't work well with other systems --and aren't intended to.

Interesting point about the Nest. What exactly are the issues? Not sure I'm following.

They're a toy.

If the run is very long you might want to see if you can go up a size to 16 gauge. I ran 18\8 for my last run and then ended up using a Honeywell Prestrige which only needs two wires.

The Prestige is what most would consider a real thermostat.

ScottSecor

I agree with others, avoid the Nest stat with steam (or hot water) systems.

Jamie Hall

The Nest obtains its advantages by being "intelligent". That is its shtick, if you will. It senses when there is occupancy, and tries to "learn" when that will happen. Then it will adjust the heating (or cooling) schedule so that when no one is present it turns down the heat -- or turns up the air conditioning -- to save energy.

Taken at face value, great idea.

The biggest problem is that that sort of up/down scheduling works well enough for forced air systems, which can respond quickly to relatively large set point swings -- that is, they can heat or cool the air in a space relatively quickly. It does not work well for hot water systems or steam, which respond much more slowly, and works exceedingly poorly for radiant systems, which are even slower.

It is possible to turn off that feature -- but if one does, why bother to spend the money for it?

To me and to some other people, a more significant hazard is that even if that feature is turned off, it remains connected to the internet, and is sending data on whether the space is occupied or not. If your internet security is really good (strong firewalls, strong passwords, encrypted wi-fi, the works) this is, perhaps, not really a problem. If not, you have no way of knowing who is looking at when your space is occupied -- or not. If it's the nosy neighbor, OK. If it's the local burglar, maybe not so OK...

pecmsg

branimal

Nest is getting returned to home depot. Thanks Jamie and others!

I'll pick a Honeywell Prestige.

Ok so I just got a pull line from the 3rd floor to the basement.

I looked at the boiler's thermostat receiver hookup . It looks like electrical and thermostat wires are spliced in the same box. See pic.

And another pic of how the exisiting honeywell thermostat is wired.

Wellness

Seconding @branimal, I'm puzzled by the recommendation to use shielded wire for thermostat connections. Shielded wire does not provide any electro-magnetic interference or radio frequency interference protection unless it is carefully grounded. In addition I would think pvc conduit would provide far greater and (probably cheaper, per linear foot) physical protection from damage.

branimal

Can I use a staple gun to secure thermostat wire to joists and studs?

Jamie Hall

branimal said:

Can I use a staple gun to secure thermostat wire to joists and studs?

Yes... carefully. Best to use the special ones made for securing cable, though.

ChrisJ

branimal said:

Nest is getting returned to home depot. Thanks Jamie and others!

I'll pick a Honeywell Prestige.

Ok so I just got a pull line from the 3rd floor to the basement.

I looked at the boiler's thermostat receiver hookup . It looks like electrical and thermostat wires are spliced in the same box. See pic.

And another pic of how the exisiting honeywell thermostat is wired.

I don't know that Home Depot carries something like a Prestige.

HVACNUT

A Honeywell RedLink wireless Interface is what you need. With a Honeywell thermostat of course. Not sure if the Prestige offers wireless but other models do. @ChrisJ ?

ChrisJ

HVACNUT said:

A Honeywell RedLink wireless Interface is what you need. With a Honeywell thermostat of course. Not sure if the Prestige offers wireless but other models do. @ChrisJ ?

The newer Prestige are all Redlink.

This "kit" comes with everything but the internet gateway
https://www.supplyhouse.com/Honeywell-YTHX9421R5101WW-Prestige-IAQ-Kit-with-RedLINK-Includes-White-Thermostat-EIM-Wireless-Outdoor-Sensor-2-Duct-Sensors

Here's the internet gateway. This plugs into a hardwired internet connection and communicates with the system via Redlink
https://www.supplyhouse.com/Honeywell-THM6000R7001-RedLINK-Internet-Gateway

You can also add wireless Redlink sensors as well
https://www.supplyhouse.com/Honeywell-C7189R1004-RedLINK-Enabled-Wireless-Indoor-Air-Sensor

STEVEusaPA

In your pic it looks like low voltage wires going to box that houses a transformer, which is quite common, and correct.

ChrisJ

STEVEusaPA said:

In your pic it looks like low voltage wires going to box that houses a transformer, which is quite common, and correct.

Code allows low voltage to be in the same box as 120\240 outside of an appliance?

Steamhead

ChrisJ said:

STEVEusaPA said:

In your pic it looks like low voltage wires going to box that houses a transformer, which is quite common, and correct.

Code allows low voltage to be in the same box as 120\240 outside of an appliance?

On Burnhams of that vintage, as well as Crown and Force boilers, it's OK. Both the line and low voltage transformer connections are inside the box. As long as everything is insulated for the higher voltage, it's not a problem.

If you're wary, bring the thermostat leads outside the box and splice your thermostat wires onto them there.

HVACNUT

I guess theres no choice with that transformer. Even replacement boiler installs when converting from line to low volt controls, the thermostat wire is typically 14/2 romex. We always routed the 14/2 thermostat wires out of the junction 1900 box at the boiler. Low volt spliced outside the box. Line volt inside the box.
What's the VA rating on that transformer? If you're going to do anything, make sure its 40VA . Age alone, if it were me, I'd replace it while I'm doing the job.

JUGHNE

Devices like that transformer typically have the 24 volt leads sticking out side the box. (think of the old fan relay/transformer). Those leads are insulated for 600 VAC as is the line voltage wiring inside the box.
It is actually a cleaner looking job to take the 24 wire inside and not have the splice showing on the outside.

ChrisJ

Guys, that's not what I asked.

Is it code to have low voltage stuff in the same box as high voltage if it's not on an appliance and part of it's design?

Steamhead

I'm pretty sure it is, as long as all the wires are insulated for the highest voltage in the box.

Solid_Fuel_Man

It is only code to have both low (less than 50 volts to ground) and high voltage in the same box as long as all the wires are rated for the highest voltage present in the box.

General use T-stat wire rated "voltage limited" and is only good for less that 50 volts to ground technically. So it cannot be in the same box as the 120volts, unless a physical and listed divider is used for separation. You can, however, get wire rated for 300 volts, but why bother? Just replace the transformer with a 40va transformer with the connections on the outside. Then make all your splices in a separate box if you dont like the rats nest look.

Appliances do this type of thing by having adaquite space between low and high voltage or by dividers, think of that plastic thing in a Taco switching relay.

JUGHNE

Or in a central AC unit. There is an attempt for barrier with the pressboard around the low voltage junction....apparently enough.

Solid_Fuel_Man

It's the minimum to get the listing. After that they dont much care.

STEVEusaPA

Solid_Fuel_Man said:

...
Appliances do this type of thing by having adaquite space between low and high voltage or by dividers, think of that plastic thing in a Taco switching relay.

Is that what that is for? I though it was to make the space in the control smaller & even harder to wire for anyone but someone with the hands of a 8 year old.

JUGHNE

Some early air handlers for heat pumps had all the low voltage hanging out thru a 1/2" knockout with grommet.
I would remove the grommet and install a handy box with a chase nipple and connect all the lo voltage inside hiding the wirenuts.