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Gemstone
Premium
join:2000-12-20
Long Island

Honeywell Round Thermostat

I have an old Honeywell round thermostat on the wall... It has only 2 wires going to it... Is this a low voltage or line (high) voltage thermostat?
--
Go Mark Martin!



bbrcat
Help Fight Cancer
Premium,MVM
join:2000-12-09
NH
kudos:3

It is low voltage



Gemstone
Premium
join:2000-12-20
Long Island

said by bbrcat:

It is low voltage

I am reading about 32VAC across the terminals... I had thought low voltage was about 24VAC?? Here are some pics (sorry for the "blurry"):












--
Go Mark Martin!


bbrcat
Help Fight Cancer
Premium,MVM
join:2000-12-09
NH
kudos:3
reply to Gemstone

You can get a bit of a 'zap' either way, but I consider both low voltage. Then again, I am no expert on this, so maybe someone will reply with more accurate info
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Team
Discovery



alphapointe
Don't Touch Me
Premium,MVM
join:2002-02-10
Columbia, MO
kudos:2

1 recommendation

reply to Gemstone

24VAC nominal voltage. Since you're reading a transformer with no load, it's normal to read a bit higher like that.
--
"When the hammer drops, the bullshit stops"



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
reply to Gemstone

LV 48 (or is it 50?)



SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:3

1 recommendation

reply to Gemstone

The answer is, it's low voltage thermostat.



Gemstone
Premium
join:2000-12-20
Long Island

Thanks for all the responses...

The reason I ask is because the Honeywell Model RTHL3550D thermostat I want to buy says it runs on 24VAC (actually it says 24V)... I want to be sure my 32VAC will not cause damage...
--
Go Mark Martin!



ArgMeMatey

join:2001-08-09
Milwaukee, WI
kudos:2
Reviews:
·voip.ms
·AT&T Midwest
·Time Warner Cable

said by Gemstone:

The reason I ask is because the Honeywell Model RTHL3550D thermostat I want to buy says it runs on 24VAC (actually it says 24V)... I want to be sure my 32VAC will not cause damage...

Contact Honeywell pre-sales support and ask them what the acceptable range is. I've done this using online chat so I had a record of what I was told.

You can also find your control transformer and see if it has multiple outputs. It would be unusual to have a 32 VAC transformer, but it's not out of the question that a nominal 24VAC xfmr would put out 32 VAC, especially if it's older and manufactured to looser tolerances. Or there's a slim chance it has more than one tap.

For my doorbell I have a 3-tap that does 8/16/24, but my HVAC transformer is fixed. I just measured it with an analog meter at 24.5 VAC, although it is currently loaded by the zone controller.

If in doubt, you can probably swap out the transformer cheaply as long as it's not part of the furnace or some other controller.
--
USNG:
16TDN2870
Find your USNG coordinates:
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Gemstone
Premium
join:2000-12-20
Long Island

said by ArgMeMatey:

said by Gemstone:

The reason I ask is because the Honeywell Model RTHL3550D thermostat I want to buy says it runs on 24VAC (actually it says 24V)... I want to be sure my 32VAC will not cause damage...

Contact Honeywell pre-sales support and ask them what the acceptable range is. I've done this using online chat so I had a record of what I was told.

You can also find your control transformer and see if it has multiple outputs. It would be unusual to have a 32 VAC transformer, but it's not out of the question that a nominal 24VAC xfmr would put out 32 VAC, especially if it's older and manufactured to looser tolerances. Or there's a slim chance it has more than one tap.

For my doorbell I have a 3-tap that does 8/16/24, but my HVAC transformer is fixed. I just measured it with an analog meter at 24.5 VAC, although it is currently loaded by the zone controller.

If in doubt, you can probably swap out the transformer cheaply as long as it's not part of the furnace or some other controller.

I contacted Honeywell via their online form... Waiting for a response...

The control transformer is part of the oil burner (Riello)... It is marked as 24VAC output... Only has 2 terminals... I measure 32VAC across the terminals...
--
Go Mark Martin!


ArgMeMatey

join:2001-08-09
Milwaukee, WI
kudos:2
Reviews:
·voip.ms
·AT&T Midwest
·Time Warner Cable

said by Gemstone:

The control transformer is part of the oil burner (Riello)... It is marked as 24VAC output... Only has 2 terminals... I measure 32VAC across the terminals...

In that case, you might also check a site like heatinghelp.com.

There are probably a million Riello oil burners with identical transformers and all kinds of Honeywell stats, so chances are somebody there has already scratched this itch on their own head.

Best to you.
--
USNG:
16TDN2870
Find your USNG coordinates:
USNGWeb


Gemstone
Premium
join:2000-12-20
Long Island

said by ArgMeMatey:

said by Gemstone:

The control transformer is part of the oil burner (Riello)... It is marked as 24VAC output... Only has 2 terminals... I measure 32VAC across the terminals...

In that case, you might also check a site like heatinghelp.com.

There are probably a million Riello oil burners with identical transformers and all kinds of Honeywell stats, so chances are somebody there has already scratched this itch on their own head.

Best to you.

Thanks!!
--
Go Mark Martin!


DKS
Damn Kidney Stones
Premium,ExMod 2002
join:2001-03-22
Owen Sound, ON
kudos:2
reply to Gemstone

said by Gemstone:

I have an old Honeywell round thermostat on the wall... It has only 2 wires going to it... Is this a low voltage or line (high) voltage thermostat?

I remember one of those with a little vial of mercury to help tip the spring over. Probably a toxic hazard, now.
--
Need-based health care not greed-based health care.


SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:3
Reviews:
·Verizon FiOS

said by DKS:

I remember one of those with a little vial of mercury to help tip the spring over. Probably a toxic hazard, now.

Yes, they did away with those a while back. I have the mercury switch out of one. I use it sometimes when I want to get a no bounce switch closure.


SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:3
Reviews:
·Verizon FiOS
reply to Gemstone

said by Gemstone:

The control transformer is part of the oil burner (Riello)... It is marked as 24VAC output... Only has 2 terminals... I measure 32VAC across the terminals...

I think it's what alphapointe See Profile said; it's unloaded, your meter may be off. Peak voltage on 24VAC (RMS) is 34 volts.

FWIW, I did what you are doing. I replaced the round one with a new HW stat similar to what you are doing. In my case it operates a relay but the voltages are the same.
--
--
--
"Facts do not cease to exist because they are ignored." - Aldous Huxley

HarryH3
Premium
join:2005-02-21
kudos:3
Reviews:
·Suddenlink

1 recommendation

reply to DKS

said by DKS:

I remember one of those with a little vial of mercury to help tip the spring over. Probably a toxic hazard, now.

The little vial of mercury wasn't there to help tip anything over. Look closely at one and you'll see that there are also two wires inside the vial. The thermostat calls for HVAC "On" when the spring tilts the vial enough to move the mercury to the end of the vial where the two wires are located. Mercury is a metal and is conductive. The mercury completes the circuit by shorting the two wires to each other when it rolls to the "wired" end of the vial.


Gemstone
Premium
join:2000-12-20
Long Island
reply to SparkChaser

said by SparkChaser:

said by Gemstone:

The control transformer is part of the oil burner (Riello)... It is marked as 24VAC output... Only has 2 terminals... I measure 32VAC across the terminals...

I think it's what alphapointe See Profile said; it's unloaded, your meter may be off. Peak voltage on 24VAC (RMS) is 34 volts.

FWIW, I did what you are doing. I replaced the round one with a new HW stat similar to what you are doing. In my case it operates a relay but the voltages are the same.

My meter is a fairly new FLUKE #115 True RMS Multimeter
--
Go Mark Martin!

skut

join:2001-11-09
Ajax, ON
reply to ArgMeMatey

Just a thought... make sure the voltmeter you are using is an RMS meter and set to read peak volts.



jack b
Gone Fishing
Premium,MVM
join:2000-09-08
Cape Cod
kudos:1
reply to Gemstone

said by Gemstone:

...The reason I ask is because the Honeywell Model RTHL3550D thermostat I want to buy says it runs on 24VAC (actually it says 24V)... I want to be sure my 32VAC will not cause damage...

The thermostat "runs" on the two AA batteries, it only switches the 24v (32v in your case) circuit, open/closed. If the batteries die, so does your heat.

Add the thermostat to your annual smoke/CO detector battery replacement list, and you'll be good!
--
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