| New thermostat, no C-wire I really want to install a programmable thermostat in my new house, and was really excited about the 3m50 WiFi, but don't have a C wire  I read that you can get an external power supply / transformer for it, but really don't think a wire hanging from the thermostat would go over with the other half.
Should I get someone to run a new 5 wire connection and install something like the 3m50, or should I find a good battery operated programmable one? What are some good ones with 7 day programming?
I was reading the PDF manual for the Honeywell RTH8500D, but couldn't tell if it required the C wire for power or not. |
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 jack bGone FishingPremium,MVM
join:2000-09-08
Cape Cod
kudos:1 | What (if any) other wires do you have coming to the existing thermostat?
If it's only one pair, (a red and a white) there is not much else you can do with the 3M stat except rewire it to provide a C wire, or install a power supply transformer.
The RTH8500D works on batteries, and doesn't use a C wire.
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Vitanic
join:2006-10-06
Rockville Centre, NY Reviews:
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| reply to talz13
2 of my 16 year old programmable Honeywells failed within weeks last year. For one I got a Carrier Edge programmable thermostat on a gas boiler with baseboard heat - no AC. The thermostat requires a C common line, which my relays (a Honeywell 832 or something) don't provide. I have 2 wires to my thermostat (mostly - they sometimes change in-wall to 2wire from 3-5 wire).
The interesting thing about the Edge thermostat is that the switching relays are part of a sort of base module & the display/temp sensor module is connected to the base by 2 wires. You can (and I did) split the units to be in separate areas. The base is in the basement connected to the display via the existing in-wall 2wire connection. The display module is maybe 1/2" thick sitting on the wall & *utterly silent*.
For the 24vac the thermostat requires, I bought a separate transformer: a honeywell 24vac 50va wall-wart. The transformer is connected to Rc & C; the boiler relays attach to Rh & W. The Rh & Rc are bridged internally (or by a jumper manually). Works perfectly.
The second thermostat I got was a Honeywell VisionPro 8000 (its in the same family as the model you mention). The thermostat drives me nuts. I removed the 5minute compressor protection - otherwise it waited 5 minutes before letting me change the temp & flashed "wait". So now it clicks in triplicate & is far from being considered quiet - its louder than my 42db diswasher.
The Bryant Preferred T6 series is virtually identical but with a white bezel - the Carrier has a metallic gray bezel. I've seen them on ebay for about the price as my Honeywell - that sucketh so much. |
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| reply to talz13
said by talz13:I really want to install a programmable thermostat in my new house, and was really excited about the 3m50 WiFi, but don't have a C wire I read that you can get an external power supply / transformer for it, but really don't think a wire hanging from the thermostat would go over with the other half.
Should I get someone to run a new 5 wire connection and install something like the 3m50
I've got a Radio Thermostat (Same maker as the 3M-branded) WiFi tstat, and their firmware has come a long, long way since I started experimenting with it last winter. I ran it "alpha", connected to nothing, and ran megabytes of WireShark traces for about two months before they issued an upgrade that made it stable enough to actually control the furnace.
That said, it's still got some quirks in the programming and fit-and-finish department. It's nowhere near as refined as my Honeywells. As far as I'm concerned the 3M-branded units are still geeky hobbyist units. Even though I'd consider myself a geeky hobbyist, there are times when I've wanted to "fix" it with a hammer.
I have my tstat cable in ENT to a junction box inside an access panel, so I considered putting in a remote transformer at the junction box, but I didn't like adding another layer of stuff to break. I also have 2-stage, so I already needed another conductor for that. So, it wasn't too tough a decision to replace the tstat wire with, I think, 9-conductor and be done with it.
The biggest compromises for me with the 3M units:
1. Can't see the display unless I press a button.
2. Every time the power goes out, the keyboard beep turns back on.
3. When the power goes out (usually when I shut it off once a month for filter cleaning), it's a crap shoot whether the stat will sync its clock properly.
4. There is something really screwy with their thermistor algorithm. After boot-up the temp readings are low by 8+ degrees (F), often causing the furnace to start until things have been running for a bit. For example, it shows a temp of 58 when the actual temp is 66. So the furnace might run until it gets to 62 on the stat, which is actually more like 70 in the real world. Then the temp on the display will magically increase from 62 to 70 over a period of, I don't know, maybe one minute.
5. Mounting screws are lousy. There is no standard box mount option like with the Honeywells.
6. Fit of the wiring access panel does not hide the wires very well.
7. There is no heat anticipator.
8. There is no intelligent recovery.
9. No fan programmability.
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| reply to talz13
Ok, I ended up picking up the Honeywell rth7600d. Install was very simple, and probably took under 20 minutes, including the repeated trips downstairs to get another tool that I forgot in the basement.
Now comes the challenge of programming it to save some energy! My GF and I work very different work schedules, so it may be that the only time we can have savings is overnight (~10pm-6am on weekdays, ~11:30pm-7:30am on weekends) |
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jack bGone FishingPremium,MVM
join:2000-09-08
Cape Cod
kudos:1 | One quick thought: try to be careful with any of these digital thermostats to avoid a static electricity discharge when touching the thermostat. Ground yourself on a light switch cover screw before touching it.
I've wiped out two after inadvertently zapping them, and unless it was "professionally installed" good luck getting any manufacturer warranty coverage.
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| said by jack b:One quick thought: try to be careful with any of these digital thermostats to avoid a static electricity discharge when touching the thermostat. Ground yourself on a light switch cover screw before touching it.
I've wiped out two after inadvertently zapping them, and unless it was "professionally installed" good luck getting any manufacturer warranty coverage.
Good call out, should be something familiar to those who work with the internals of electronics in general! |
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