โNov-28-2017 07:29 AM
โNov-29-2017 05:46 PM
โNov-29-2017 05:21 PM
โNov-29-2017 04:35 PM
pianotuna wrote:
Glad it worked out!
โNov-29-2017 04:33 PM
BFL13 wrote:
Some mentioned about the adjustable swing feature on the better ones. I got the lower cost digital without that. I can see how that could be a useful feature in some scenarios.
I have no clue why those two blue wires have a voltage across them. I started out thinking it was just one of them that was being switched and the other was a ground. Didn't look closely enough at the old one before starting all this. Anyway it turns the voltage on and off between the two wires.
The blue wire shows up in the schematic here and there to the various furnace switches, so it must all have something to do with that instead of just switching one of them. Whatever. "Not my problem!" ๐
โNov-29-2017 04:31 PM
โNov-29-2017 04:12 PM
โNov-29-2017 04:01 PM
BFL13 wrote:
I decided to put the blue wire that was on the old Thermo R Common onto R on the new one, and put the other blue wire from old W to new W.
I still think that must be backwards (isn't "common" negative?)
Anyway, it worked. With it set to "heat" I set target temp at 17C and the display (yes you can see it without any back lighting) showed ambient at 50C so the furnace fired up blower first then heat--all good.
When the ambient got to 17 it kept heating away but then there was a click and the "heat on" went out and the heater stopped and then a bit later the blower. By this time ambient was showing at 18C--confirmed by another thermometer nearby as a cross-check. Good!
So I waited to see if it would stay like that for a while, it did, so I opened the RV doors and a window to cool things down and waited to see if it would come back on and at what temp.
It came back on with the ambient reading 17C but this took a while because it stays warm inside the RV (which is good) So it cycled.
I don't know if that one degree C drop counts as a "short cycle". It would be ok by me if it dropped to 16 or even 15, which is how the old slider temp Duotherm in the 5er acted. But it is ok as is where it would have stayed off longer if I had not opened the doors and a window to cool it down inside. Should be able to live with that action as is.
So another day of adventure completed! Can't say all that was much fun, but it was "interesting" for sure. Thanks again for all the advice, some of which I actually took! ๐
โNov-29-2017 03:57 PM
shastagary wrote:take the two wires going to the furnace. touch them together. If the furnace starts to run, which i suspect it will, connect one wire to the W and one wire to the R on the thermostat.if he connects his 2 thermostat wires tougher the furnace will run that's what a thermostat does. it is a switch controlled by a temperature controlled relay circuit in the thermostat polarity does not matter home furnaces have ac control power to the thermostat. its not that complicated buy the thermostat and hook it up thousands already have.
โNov-29-2017 03:55 PM
โNov-29-2017 03:16 PM
take the two wires going to the furnace. touch them together. If the furnace starts to run, which i suspect it will, connect one wire to the W and one wire to the R on the thermostat.if he connects his 2 thermostat wires tougher the furnace will run that's what a thermostat does. it is a switch controlled by a temperature controlled relay circuit in the thermostat polarity does not matter home furnaces have ac control power to the thermostat. its not that complicated buy the thermostat and hook it up thousands already have.
โNov-29-2017 02:31 PM
BFL13 wrote:
Well this is embarrassing---The two wires into the back of the old thermostat are both blue! I was all wrong about pos and neg.
EDIT--- OR NOT ???
I put the meter across the old one's two blue wires at W and R common and got 13.85 volts. Switched leads and got -13.85 volts. The positive reading was with the pos lead on Terminal R common in the manual's diagram and the neg (common as marked on the meter) on W
Seems backwards? Anyway now I am sort of nervous which wire to put where on the new thermostat.
The wiring diagram on page 5 in that link does show the two blue wires to the thermostat as "Thermo + " and "Thermo" but not where they go in the thermostat.
My manual's diagram says "connect the two wires which run from the furnace to the back of the thermostat base" Doesn't say which terminals for which wire.
โNov-29-2017 12:08 PM
โNov-29-2017 12:03 PM
BFL13 wrote:
https://xtronics.com/wiki/images/Thermostat.gif
Thanks. I don't follow your "going to the furnace" etc. I have the two ( neg and pos) 12v wires coming out the wall and onto the back of the existing Hydro flame mechanical thermostat. The pos wire is switched by the on/off and when on, by the sensor (spring coil thing).
He said it didn't matter which wire I put on W or R in this case. This new thermostat has batteries to run itself.
Ok here is the old one and it does have W and R but I am not sure the neg is really a neg ???? Page 5
http://www.atwoodmobile.com/manuals/furnaces/MPD%2033179%20SP%201.08.pdf
My 8500 11 manual has a better thermostat drawing. It shows "Terminal R- common" and Terminal W where the two wires go-- I have to go out and look at which colour goes where.
โNov-29-2017 11:38 AM