Can Changing A Thermostat Fry A Furnace Board

Supplant thermostat without turning off furnace electricity?

• Thread starter Sukhoi
• Starting time date Dec 2, 2014

• #1

I desire to install a basic Honeywell programmable thermostat: http://yourhome.honeywell.com/abode/Products/Thermostats/seven-Twenty-four hours-Programmable/RTHL2510C.htm

The furnace is an ancient in-wall gas unit, no blower, with just R and W wires to a very old barely operation thermostat. It's a very simple millivolt setup. My problem is the wiring in this (rental) house is a mess and none of the normal fuses in the box cut power to the furnace. It appears to be hardwired to the firm primary, which I don't want to deal with.

It'south only a 24 V system so I'g non too worried almost getting shocked, but I've read it tin can hurt. If I clothing gloves is it safe to do this work with the wires energized? What society to remove and install them? I'yard guessing remove W then R. On new thermostat wall plate install R then W? The wall plate is divide from the control unit so I don't retrieve I need to worry nigh frying the command unit since it's made to pull off with the power yet turned on. Is at that place much chance of pain the furnace transformer if I do the wires in the correct society?

Mar 1, 2014

2,010

888

136

• #2

I installed a honeywell thermostat here at piece of work, very similar to yours. I plugged and unplugged it in at least a dozen times, probably closer to ii dozen. I did it blank handed and had no problems. Pretty sure I fifty-fifty touched the wires, merely non real certain. Yous will exist fine. I will caution yous though if y'all touch the wires while they are live they will arc and cause the beautiful blue light that causes your heart to beat fast. However information technology was a instance of no harm no foul for me.

Of course my case is different than yours because our transformers are different, simply just use mutual sense and you will be fine. If you article of clothing gloves make sure they are tight fitting. That mode you can get a meliorate grip on the wire and be able to move the wire around better (that is the condom guy in me talking).

One thing is to put the wire in the terminal, tighten the screw and then pull on the wire. You want to brand sure information technology is seated right.

• #3

User safety handled needle nose pliers to to handle the wires maybe? At least I presume rubber handles won't carry.

• #4

I will caution y'all though if yous affect the wires while they are live they will arc and crusade the beautiful blueish light that causes your heart to shell fast.

Wait, what?

I have nothing to contribute to the thread...other than to state that there'due south no way in hell I'd change out a live wired *anything*.

Let us know how it goes!

Jun 19, 2000

18,890

640

126

• #v

If you know where the transformer is located, why non disconnect 1 wire at the transformer prior to doing the swap? What'south going to occur is that in line-fishing the wires out of the backing plate they are going to touch. Yous'll effort to not have that happen just you know Murphy'southward Law, right? It will be the same state of affairs when feeding them through the new backing plate.

Disconnect 1 wire at the transformer or cocoon the start wire you remove in electrical record so if they touch the circuit tin't be completed.

The order in which you remove and connect them doesn't thing.

Edit: Getting shocked is not pleasant. Just recall kids, information technology'southward not the voltage that'southward going to harm you it's the amperage. Is that relevant in this state of affairs, no, but why create sparks when you lot can very easily not create sparks? That's why I gave the advice I gave.

May 22, 2012

6,430

291

121

• #half dozen

lol the thermostat is just a switch that'due south information technology.

all it does is connect them together when you need heat/air-conditioning and disconeect them when you lot don't.

non smoke and mirrors folks.

if yous have ac yous should accept 3 wires iirc

oh and some AA batteries.

• #7

How electrical shocks happen
http://lee65.hubpages.com/hub/How-do-you-get-electric-shocks

(a) When two wires are at two different voltages and they come into contact with each other, a current volition laissez passer through them.

If they are not in contact, but your body connects the ii wires by touching both of them at the aforementioned fourth dimension, so an electric current will pass through your body and yous will become the shock.

(b) If you accidentally touch the energized Live wire or other, alive parts of an energized electrical appliance, while some other part of your body is likewise in contact with the NEUTRAL wire, a electric current will pass through your body. Then you will go an electric shock.

(c) If your body is in contact with the Alive wire, while another part is touching a grounded object, you volition also become an electrical shock.

(Notes: A grounded object is:

ane. Anything that in good contact with earth mass, like water pipes. Nearly regime require that water pipes be grounded. Notwithstanding, even if some pipes are not grounded, the pipes that are laid partly or wholely underground (i.e. the mater mains coming to the business firm) are actually in good contact with world mass.

2. Or anything that is purposely connected to the globe mass, similar the street lamp posts in front end of the house. Practise non be fooled by the innocent-looking lamp posts, the compound lighting posts or the brusque bollard lighting posts at the park or by the street in front end of the house. Many grown adults accept actually been electrocuted and died simply by leaning to the metal posts.

3. Or anything that is electrically connected to the house world wires, like the metal conduit, the metal casing of the washing machines, etc.)

• #viii

If you know where the transformer is located, why not disconnect one wire at the transformer prior to doing the swap? What'due south going to occur is that in fishing the wires out of the backing plate they are going to touch. You'll attempt to not take that happen but yous know White potato's Constabulary, right? It will be the same state of affairs when feeding them through the new backing plate.

Disconnect one wire at the transformer or cocoon the showtime wire you lot remove in electrical record so if they affect the circuit can't be completed.

The order in which you remove and connect them doesn't matter.

Edit: Getting shocked is not pleasant. Only remember kids, it's not the voltage that's going to harm you it's the amperage. Is that relevant in this situation, no, but why create sparks when y'all can very hands non create sparks? That's why I gave the communication I gave.

No inkling where the transformer is. Wires come out of the crawlspace, so I assume information technology's down in that location or backside an odd painted-over switchplate embrace near the furnace.

I had already been planning on taping the wires every bit I remove them, so I'one thousand just going to go alee and do it. They are quite separated on the old thermostat, and removal should exist easy to do without shorting anything.

Mar i, 2014

ii,010

888

136

• #9

This is quondam but notwithstanding applies today.

How many mail list subscribers does it take to alter a light bulb?
Answer: ane,331

i to modify the light bulb and to postal service to the mail listing that the light seedling has been changed

14 to share similar experiences of changing light bulbs and how the light seedling could have been inverse differently

vii to caution about the dangers of changing light bulbs

27 to bespeak out spelling/grammer errors in posts about irresolute light bulbs

53 to flame the spell checkers

41 to correct spelling in the spelling/grammar flames

156 to write to the listing administrator complaining about the light bulb discussion and its inappropriateness to this mail list

109 to post that this list is not about calorie-free bulbs and to please take this email exchange to another list

203 to demand that cross posting to other lists about irresolute light bulbs be stopped

111 to defend the posting to this list saying that nosotros all apply light bulbs and therefore the posts *are* relevant to this mail list

three to post nearly links they found from the URLs that are relevant to this list which makes light bulbs relevant to this list

306 to argue which method of changing light bulbs is superior, where to buy the best light bulbs, what brand of light bulbs work best for this technique, and what brands are faulty

27 to mail service URLs where ane tin run across examples of different light bulbs

14 to post that the URLs were posted incorrectly, and to post corrected URLs

33 to concatenate all posts to date, then quote them including all headers and footers, and then add "Me Too."

12 to post to the list that they are unsubscribing because they cannot handle the lite bulb controversey

xix to quote the "Me Too's" to say, "Me Three."

four to suggest that posters request the lite bulb FAQ

48 to propose new change.lite.seedling newsgroup

47 to say there is already an alt.low-cal.bulb newsgroup

143 to ask if anyone e'er did change the lightbulb

Mar 3, 2000

49,918

622

126

• #10

I've never, ever turned the ability off to bandy out a thermostat. But I haven't done one for about 6 years. I dubiousness annihilation has changed though, probably still all low voltage.

• #11

lol the thermostat is but a switch that's it.

all information technology does is connect them together when you need oestrus/air-conditioning and disconeect them when you don't.

not fume and mirrors folks.

if you have ac you should have iii wires iirc

oh and some AA batteries.

It is more like three - 24 with 5-seven being the most common for annihilation in that last xl years.

Air conditioning unit would be typically common - fan - Air-conditioning - heat
Information technology also could be: common - fan ane - fan 2 - AC stage 1 - Air-conditioning stage 2 - heat stage 1 - heat stage 2 - 24Vac
Or even more than convoluted if heat pumps and aux heat and cooling with stages and emergency rut become added in to the mix.

• #12

Yay, did information technology hot with no bug. I'thousand still alive, and more importantly the furnace seems to work.

Mar 1, 2014

2,010

888

136

• #xiii

Yay, did it hot with no problems. I'1000 yet alive, and more importantly the furnace seems to work.

Cool. Glad to hear it and thank you for the update.

• #14

Yay, did it hot with no issues. I'g still alive, and more importantly the furnace seems to piece of work.

I've done it without turning off the furnace/primal Ac in the past twice, one time in my house, once for my in-law. My Air conditioning transformer blew within a yr or so subsequently. Some affair happened to my in-law unit also, don't know the exact details, simply she got talked into getting a new AC and furnace...Coincident? not sure, simply I will make sure I turn them off side by side fourth dimension I change the thermostat.

• #15

I've washed it without turning off the furnace/primal Ac in the past twice, once in my house, in one case for my in-police force. My AC transformer blew within a yr or so subsequently. Some matter happened to my in-law unit of measurement too, don't know the exact details, but she got talked into getting a new AC and furnace...Coincident? not certain, merely I will make sure I plough them off side by side time I modify the thermostat.

I think mine should be fine. The style this new thermostat is you lot pull a connector apart when you have the main unit of measurement off the mounting plate to replace the batteries. I never touched the wires to anything during the whole operation, and then I was dealing with an open circuit the whole time. I'm sure it's designed to replace the batteries with the furnace powered, as near ane% of homeowners would plough off the ability to do that even though the manual says to.

Jun 13, 2000

26,185

ane,600

126

• #16

The real key here is to make certain you lot wire it up correctly, keep the wires from touching each other, and don't have the batteries in the thermostat when you wire it. Other than that, it'll be fine. Thermostat wire is like 16-18 gauge wire normally....it's not exactly a usher of more than than a few milliamps.

• #17

Batteries? Mine doesn't have batteries.

• #xviii

Batteries? Mine doesn't have batteries.

Well aren't you special?

• #19

Master milk shake is correct, information technology's simply a low voltage switch.
R, Chiliad, Westward, Y, and C are just near the virtually you will see these days, nearly 2 phase units that would require w2 and y2 have been replaced with automobile staging units. They automatically go into 2nd stage if the new target temp isn't reached withing a set time.
Close action
RG = fan only
RW = heat
RY = A/C
C = common (used to power smart stats bombardment free)
You volition but get shocked if you stick your tongue on information technology, in which case you more than likely deserve it.

• #20

Apparently so going past this thread. I stand on a mountain overlooking the peasants purchasing batteries for their thermostat.

• #21

Chief shake is correct, information technology's simply a low voltage switch.
R, Thousand, W, Y, and C are just about the most you will see these days, most 2 stage units that would require w2 and y2 accept been replaced with motorcar staging units. They automatically go into 2d stage if the new target temp isn't reached withing a set time.
Shut activeness
RG = fan only
RW = heat
RY = A/C
C = common (used to power smart stats battery free)
Y'all will only get shocked if you stick your natural language on it, in which instance you more than likely deserve it.

None of the HE ones recently [that I take had to piece of work with] are "motorcar staging." Even the ane just put in 2 weeks ago however uses a controller. Almost that I have dealt with use the 5 wire cablevision as a "Remote command panel" that connects to a 12-24 wire + control box attached on the furnace itself. Stages are controlled via indoor / outdoor delta and "temp delta requested" blazon determination on the on the furnace controller.

On the modern HE 95% or 97% efficient furnaces there are to many controls to hit that number with a basic 5 or 7 wire 24V stat. Something quite a few people are learning in the Google / Nest earth where tstats like the Nest simply can't control furnaces with variable burners / variable blowers / humidity management amidst others.

-edit-

FYI I know that some of the 70-80% efficiency units allow you lot to bridge the W1+W2 and then set a switch to for "ten amount of minutes on -> enable stage 2" for the people that can't or deceit be bothered to install a proper multistage tstat. These are slowly existence phased out because they tend to lower the efficiency ratings and burn the unit longer with a outburst of heat at the end of the run which makes the furance feel "drafty" until the second stage kicks in and finally warms the business firm. Well-nigh people with these units mutter of wide temp swings in the winter / summer. This is less "auto" and more than of a "last ditch effort" way.

• #22

Before we had a thermostat, I turned the oestrus on and off by connecting wires and never got shocked.

October 22, 1999

11,601

vi,052

136

• #23

I used to ever modify thermostats hot, just once when moving out of a rental I had my wife swap the thermostats (we had installed a programmable touchscreen and they had a $x POS). I am not sure which wires she touched together, but she somehow fried the transformer. Now I e'er plough off the power to the furnace before I bandy ane.

24Vdc isn't going to hurt you though, especially when it is powered by a dinky transformer. My FIL was an electrical contractor for xxx years, he always works on 120Vac and breaker boxes live, he volition shut off 220V, though. I've worked with 120V alive my whole life, likewise, not a large deal, just a little zap every at present and so. You but desire to brand certain yous aren't grabbing the end of the wire or could fall into the breaker panel, since you lot muscles will tense making it to were you couldn't let go.

Disclaimer: Of course you should ever plow off the billow and double check that wires are expressionless before you do any work, don't be dumb.

Commercial aircraft power always worried me, equally it was 120V only 400hz. I heard that the 400hz would tense your muscles and then much they'd hurt for days and information technology could exist very hard to let go/move away.

• #24

None of the HE ones recently [that I have had to piece of work with] are "auto staging." Even the one just put in 2 weeks agone still uses a controller. Almost that I accept dealt with use the five wire cable as a "Remote control panel" that connects to a 12-24 wire + control box attached on the furnace itself. Stages are controlled via indoor / outdoor delta and "temp delta requested" blazon decision on the on the furnace controller.

On the modern HE 95% or 97% efficient furnaces there are to many controls to hit that number with a basic five or 7 wire 24V stat. Something quite a few people are learning in the Google / Nest earth where tstats like the Nest only can't control furnaces with variable burners / variable blowers / humidity management amidst others.

-edit-

FYI I know that some of the lxx-80% efficiency units allow you to bridge the W1+W2 and so set a switch to for "x amount of minutes on -> enable stage two" for the people that tin can't or cant be bothered to install a proper multistage tstat. These are slowly being phased out because they tend to lower the efficiency ratings and burn down the unit longer with a burst of heat at the cease of the run which makes the furance feel "drafty" until the 2d phase kicks in and finally warms the house. Virtually people with these units complain of wide temp swings in the wintertime / summer. This is less "machine" and more of a "last ditch try" style.

Perhaps the difference is canada vs the u.s.a. for models, I haven't lived in 'Murica for ten years, but over the final iii years I've hooked upward 100+ high efficiency furnaces (carrier, train, coleman, napolean, lennox, etc), not a single one has been traditional 2 stage. They don't fifty-fifty have w2 and y2 terminals to bridge. The efficiency is unaffected as they are all certified 96+ with this operation. I agree that the second stage cfm makes the furnace feel drafty, but that'south a characteristic of forced air heat in general and you become that whether you gear up it to phase ii or it sets itself in that location automatically.
Also, might only be my area but I don't think you can fifty-fifty buy a mid efficiency here anymore.

• #25

Possibly the divergence is canada vs the us for models, I haven't lived in 'Murica for 10 years, but over the last 3 years I've hooked up 100+ loftier efficiency furnaces (carrier, train, coleman, napolean, lennox, etc), not a unmarried ane has been traditional two stage. They don't fifty-fifty have w2 and y2 terminals to bridge. The efficiency is unaffected as they are all certified 96+ with this operation. I agree that the second stage cfm makes the furnace feel drafty, but that'southward a characteristic of forced air estrus in general and you lot get that whether you set information technology to phase 2 or it sets itself at that place automatically.
Too, might but be my area but I don't think you can even purchase a mid efficiency here anymore.

Fair point. The ones I deal with allow the unit to beginning in 2 stage if atmospheric condition are correct and provide connections to do that. Example would be say "dark mode" set to 62F then "morning mode" set to 72F would boot on stage two from the offset because of the ten caste F delta. (16.5C to 22C at that place about) Some other case is when outside is below "ten" degrees changes the stage timing as does the delta(temp) / time.

This is generally done with a "controller" bolted to the side of the unit of measurement with the all the wire connections for stage control, humidity etc Then the 5 wire that is in nearly houses gets hooked up to the controller and a control console/display/temp sensor is placed where the old Tstat is.

This makes the furnace basically "uncontrollable" via any of the cheaper systems simply allows installs of new HE furnaces in existing homes with out trying to pull a new 24 wire group up.

• Advertising
• Cookies Policies
• Privacy
• Term & Weather condition
• About us

• This site uses cookies to aid personalise content, tailor your experience and to keep you logged in if you register.
  Past standing to use this site, you are consenting to our use of cookies.

Source: https://forums.anandtech.com/threads/replace-thermostat-without-turning-off-furnace-electricity.2411076/

Posted by: blackburncounce.blogspot.com

Share this post