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?
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
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!
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
James "Cubby" Culbertson wrote:
Yeah, it's digital. I've got the "hot" and the "common" wires running from
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.
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
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
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!
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
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.
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
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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