[CountChocula]

Hi Everyone. Cool site so far....great info.

So I replaced a WIFI Honeywell Thermostat in my sisters house and was done in five minutes.

Thought I could do same at Mom's house for her birthday present bought her a new one. She has bad arthritis and two artificial knees so wanted her to control the temp from bed in the morning.
Thought it would be five minutes.

I was wrong

Have a Honeywell RTH9580WF (Touchscreen color wifi thermostat)

I've Googled and searched til my brain hurts and I'm out of beer.

Please help my Mom know her only Son is not a complete idiot!!!



Ok so the problem is what everyone seems to have which is no C wire.

Read where you can replace the G with the C at the thermostat and replace the G with the C at the Furnace Control Panel.....PROBLEM IS THERE IS NO C AT THE CONTROL PANEL!

I've attached pictures below.

No extra or unused wires in thermostat wire.
Lennox Gas Furnace with Air conditioning.
Single family home built 1989....HVAC original same year.

At Furnace Control Panel: There is R W Y G T
R= Red to Thermostat
W= White to Thermostat and a jumper with a RESISTOR? to T
Y= Blue to Thermostat and RED to 2- wire cord (I THINK AC UNIT)
G = Greeen to Thermostat
T = Jumped with RESISTOR? to W and WHITE to 2-wire cord (AC?)

There are two leads tapped into W and T that go to the humidifier also.


At Thermostat:
W= White
G= Green
R, Rc = Jumped to Red
Y= Blue

Please please please advise!!
I'm trying to install as a surprise because she hates new technology haha and if she knew I couldn't install properly she'd already be throwing things at me. She's really sweet though and goes to church 3x a week haha.

Thanks a million for any advice!!!!!!!!!!

Cheers,
The Count

 

[beenthere]

T is the common/C.

 

[yuri]

It is a old G14 Pulse furnace. You may want to budget for a new furnace or replace it as there are some obsolete parts in it. I replaced Mom's 5 yrs ago and I am a Lennox tech.

Hard to find old school techs who know how to fix it also.

 

[user_12345a]

Haven't read the original post, but tell your mom to get that pulse furnace pressure tested.

The heat exchangers fail and can leak exhaust.

Most heat exchangers run on under negative pressure so air leaks in rather than exhaust out when there's a crack.

The pulse doesn't run under negative pressure; not something i;m well versed on, but it runs more like an engine with small explosions rather than a simple gas burner.

It was the first and only pulse force air furnace; after two models, lennox abandoned the concept and went for the less troublesome conventional design.

Otherwise, I've experienced old 1980s lennox stuff and it's really solid, well built equipment especially the furnaces. As long as this unit still works and is safe, it should be kept; any replacement even from lennox won't be nearly as well built.

This was a top top of the line unit in it's day - high efficiency. The new high efficiency stuff may have nicer controls, but you won't be nearly as well built. Spend $4000 and after the warranty the third world parts will start failing, heat exchanger will crack in 10-15 years instead of 20-30+.

 

[supers05]

As beenthere said, t is your common. You have to jumper y to g at the furnace for the a/c to work right.

Cheers!

 

[user_12345a]

Don't new stats still energize G with a call for cool, or has something changed?

Or is the advice to use the G wire as a common, sacrifice continuous fan.

 

[CountChocula]

It is a old G14 Pulse furnace. You may want to budget for a new furnace or replace it as there are some obsolete parts in it. I replaced Mom's 5 yrs ago and I am a Lennox tech.

Hard to find old school techs who know how to fix it also.

Thanks for the reply! You're spot on....Couple of years ago was having some problems and one tech did turn it away saying he can't fix....found another old school guy who rebuilt I'm guessing the heat exchangers and is chugging away with no problems.

 

[CountChocula]

Haven't read the original post, but tell your mom to get that pulse furnace pressure tested.

The heat exchangers fail and can leak exhaust.

Most heat exchangers run on under negative pressure so air leaks in rather than exhaust out when there's a crack.

The pulse doesn't run under negative pressure; not something i;m well versed on, but it runs more like an engine with small explosions rather than a simple gas burner.

It was the first and only pulse force air furnace; after two models, lennox abandoned the concept and went for the less troublesome conventional design.

Otherwise, I've experienced old 1980s lennox stuff and it's really solid, well built equipment especially the furnaces. As long as this unit still works and is safe, it should be kept; any replacement even from lennox won't be nearly as well built.

This was a top top of the line unit in it's day - high efficiency. The new high efficiency stuff may have nicer controls, but you won't be nearly as well built. Spend $4000 and after the warranty the third world parts will start failing, heat exchanger will crack in 10-15 years instead of 20-30+.

Thanks for taking the time to write that. I believe it was all rebuilt a couple of years ago...good to know. Really irritating that nothing lasts as long as it used to. Damn cheap parts.

 

[CountChocula]

Ok so thanks for all the replies...this site's awesome.

If I'm understanding correctly....I may lose fan alone control, but...

1 )I'm changing the GREEN wire to C on the new Tstat instead of G.
2) I'm connecting that GREEN C wire to T on the Furnace.
3) I'm jumpering Y to G on the Furnace

I haven't actually connected anything yet because I didn't want to screw it up.

Looking to attempt this on Sunday afternoon.

Cheers everyone!

 

[beenthere]

Yes, that is the way to do it.

 

[user_12345a]

You're sacrificing the option for continuous fan - better to pull a new wire.

 

[supers05]

Yes

Cheers!

 

[yuri]

I have worked on and sold the Pulse since the first one came out around 1980.

There is NO way to rebuild the heat exchanger and they went obsolete 15 or more years ago.

The gas flapper assembly is obsolete and same with the air flapper unit. Those were specially made by someone who went out of business. Once the gas flapper goes then game over.

The heat exchanger should be pressure tested by a Lennox pro.

You can keep running it but I would replace it unless you live in a warm climate where you can get by with a few space heaters for a few days until a new one gets installed. Not something you want to try where I am.

 

[123pugsy]

A little hijack, but on topic.

How many conductors should there be in today's thermostat wire?

 

[user_12345a]

A little hijack, but on topic.

How many conductors should there be in today's thermostat wire?

4 is the minimum for 1 heat/1 cool - it's been like that forever.

That's what most contractors will pull; unless you get a intelligent, independently minded contractor who really cares, they'll do the minimum to get the equipment running in accordance with code and install instructions.

I would suggest at least a 6 conductor wire and 2-stage stat for your two-stage furnace; it can work with single stage stat but on a fixed timer. On your setup with the oversized 80k it would probably do just fine satisfying the stat with high heat totally disabled. If I remember correctly, your heat loss is well under even what a 60k furnace puts out.

 

[beenthere]

A little hijack, but on topic.

How many conductors should there be in today's thermostat wire?

Varies with the thermostat. Some only need 2 wires at the stat. And can control a 2 stage A/C, 2 stage furnace, humidifier, dehumidifier, and a ventilation system. Along with slow the bower down to dehumidify.

 

[CountChocula]

Update: Success!!!!!!!!!!!!!!

Thanks to all for your input and advice. :biggrin2:

Thermostat is up and running!
The RTH9580WF is pretty slick too. Once installed...2 minutes of configuring and adding wifi and its all sync'ed up.

Very simple to use.


Someone suggested running a wire to retain fan functionality. I should be able to pull a wire no problem.

If I get around to doing this...then how am I wiring it assuming I did what I posted at the end of page 1:


1 )I have changed the GREEN wire to C on the new Tstat instead of G.
2) Changed that GREEN C wire to T on the Furnace.
3) Jumped Y to G on the Furnace

Cheers x a million!!
Thanks for helping out!!

The Count

 

[supers05]

You one of the wires in the new cable for g. (preferably green, but it's not critical)

Sent from my SM-G870W using Tapatalk

 

[CountChocula]

Hi I'm ressurecting this thread.
The furnace made it through another winter last year!!

I just pulled a brand new wire (PAIN IN THE BUTT!!)
Has 8 or 9 wires so no problem there.

So I had it working before but the FAN would not come on when JUST FAN was selected on the Thermostat.

I'm rewiring this to fix.

Can anyone double check my wiring please!?!?!

On the furnace I only have R W Y G T.
I still have the Honeywell RTH9580WS.
(**NO C WIRE on furnace!**)

FURNACE--------COLOR---------THERMOSTAT
____________________________________
R Red R (Jumper to RH and RC)

W White W

Y Yellow Y

G Green G
(**Y&G should no longer beJUMPED at Furnace)

T Blue C


That look about right?? :vs_worry:

Thanks in advance!!
The Count

 

[user_12345a]

jump R and G at the furnace, see if the fan comes on.