Thermostat Conundrum

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Hiya Folks, I'm in the process of installing a unit heater in the garage. I've got a Totaline 474-0100 TStat that I'm trying to get wired up. This is a simple 2 wire system. I'm getting no display on the TStat. I've got one of the wires going to R and the other to W1 and have confirmed I'm getting 24V. Now I would suspect a bad display at this point but I took it in the house and wired it into our furnace the exact same way and get a display just fine. Any ideas? Thanks much, jlc
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Does the heater come on when the two thermostat wires are touched together?

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comes on as well.
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Sounds like a temperamental thermostat. I'd get a new one

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James,
You said you had one wire going to R and one going to W1 but no ground. Find a ground on the furnace controller and attach it to the ground connection on the thermostat. I think ground is C on furnaces. You do need three wires.
Dave M.
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Interesting. I don't have a ground pin on the TStat. The closest thing would be C on the Stat. What confuses me though is that I took the stat inside and touched the wires to R and W1 only and the display worked fine (no third wire). I'm going to have to keep working on this! Cheers, cc
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Obviously, the tstat is electronic, i.e. "display." Does it run on batteries or on the 24 VAC? If it runs on the 24 VAC, you need a return path (common) to make the tstat work.
James "Cubby" Culbertson wrote:

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the heater to the TStat. I've tried landing on both W1 and C with no luck. The crazy thing is when I touch the wires to it in my house (different furnace), the display works just fine. I'm at a loss. Cheers, cc
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Since you mention a "c" terminal, I'm thinking this thermostat may need a power supply of 24 volts. Some series 80 thermostats use batteries and a current robber circuit to charge them, but some digitals need a power supply. If that's the case, you'll need at least three wires. 24 volts would go on RH and C and the return to the heating relay would go one W1. Check the wiring instructions and see if it doesn't explain or at least show how many wires go to the stat

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If connecting the thermostat inside your house "the exact same way" to your furnace produced correct display / results, I assume you made a 2 wire connection to "R" and "W1" as well. You should try reversing the two leads when reconnecting your garage unit heater. I know this is an A.C. 24 volt loop, and polarity should make no difference, but perhaps one of the 2 leads from the unit heater sits directly at the 24 volt source and needs to be connected to the opposite thermostat terminal from the one you originally tried.
Smarty

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If he made the connection at a time when his furnace wasn't calling for heat, he would get 24 volts

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I found your stat on the net and it does require a common wire to operate

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Ok. So are you saying I definitely need 3 wires here? The heater only provides for two. I tried jumpering (is that even a word?) W1 and C and that didn't work. I have 24VAC from the furnace going to R and tried to connect to both W1 and C (even jumpered the W1 and C together with no results). What baffles me is that when I tried it on the other system, connecting to R and W1 produced a display yet in the garage I don't get the display when attached to those terminals. It's very odd. Cheers and thanks for the help! cc
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In or on the wiring chamber of the unit heater is a transformer. You would have to run the "third" wire, for "C" to the that transformer. I'm sure you can find digital thermostats that operate on a two wire system without the C

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In looking at the wiring diagrams for the heater, one of the TStat points is already directly connected to the transformer so not sure there's another connection for me to make there. Thanks for all the help! Very helpful. Cheers, cc
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Exactly, one wire is already connected to the transformer and goes to the thermostat. There is another terminal on the transformer which will have other wires on it presently, but a wire from the "C" terminal of the tstat goes to this transformer terminal as well

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I gave up. I went and bought another tstat and all is well now. I really wanted to use that one as it has a low setpoint. Maybe I'll troubleshoot it this next summer! Cheers, cc
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James "Cubby" Culbertson wrote:

Just an idea/suggestion based on experience of son in law some years back. He bought a programmable timer-thermostat and had trouble hooking it up. IIRC it was a type that required to have a heater of at least 500 watts connected all the time. The current flowing through the thermostat to the heater was required to operate the thermostats internal circuits. Again remembering; In some ways the thermostat could be considered to be 'in series' with the heater across the 230 volt input. Our 35 year old thermostats were of the 'plain old' variety and all our electrics having given very little trouble since 1970 I was unfamiliar, until then, with various other 'programmable' and 'smart' thermostats now available! You may be able to download the spec. sheet for the th.stat on the web?
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