recomendations for programmable thermostat, must have NV backup, think I want RS232 interface

[Rusty Carruth]

I currently have a Honeywell Chronotherm III here at the house, and I'm really tired of its not quite doing what I want.

So, I'm looking for 2 replacements (one upstairs, one down).

First, a bit of info:

Here in AZ where I live, we have a time-based energy cost thing that has 2 schedules: noon-9pm in the summer (or 1-8, or whatever they decide each year), and 5am-9am/5pm-5pm during the winter, for the expensive times. So, I want either for the 'periods' for heat set points and cool set points to be independent, or I need enough set times to handle the situation we had a few years ago where my set (change) times were 5am, 9am, noon, 5pm, 8pm, 9pm!

However, there are times during the 'summer' schedule when i actually want to run the heater, and vice versa. And I really don't want to re-program the stupid 'morning/afternoon/evening/night schedule of some thermostats I've seen at each schedule change.

And I absolutely insist that either the thing has an absolutely non-volatile (no battery needed) memory of my schedule, OR be remotely-controllable and/or remotely-settable (probably just remotely-settable) **with a protocol that is documented** and that I can write my own software for (since I use linux and not windows). (Of course, both would be really nice)

Oh, and it would be really really nice if it cost me no more than around $100 per (which I have every intention of installing myself).

So, how far away from reality am I? Do I need to go design this thing myself since the closest I found was either the HAI (which does not seem to have a publically-available protocol) for $127 (lowest price I found); the enerzone (about which I have basically only been able to find pricing) for around $170 or so; and the RCS for around $200 (which seems to do exactly what I want). Each. And, like I said, I need 2. Now, it appears that the RCS will do what I want/think_I_need, but I could be all washed up there (and its too pricy anyway - if it comes to a $200/per situation I'll buy 2 cheapo units with NV program storage and design my own system that does precisely what I want)

Or should I punt on the remote computer control idea and just find a good multi-time thermostat with true non-battery-reliant nonvolatile memory? And where in the world ARE such beasts?

Thanks all!

rc

reply to r u s t y c < a t > d e s c o m p < d o t > c o m for best chances of my seeing it! (But I will also monitor the newsgroup)

(the email from which this posting came *will* work, but I rarely check it)

[Joseph Meehan]

Sounds like you just had a bad day.

I have a Hunter Auto Temp Plus 44422. I would tend to believe Honeywell has much the same kind of features available.

You set the programming manually, not difficult fair interface. After that you have two kinds of manual control. You can reset the temp and it will stay until the next program change, or you can set the temp to manual so it stays until you turn it back to program operation

It does have batteries, I replace mine every couple of years. It also has a batter warring indicator so letting them die is really your fault. As I recall the batteries can die and it will not loose the program, unless you want for months and a power outage.

Frankly if it dies I would like to go back to the technology that lets you set the temp you want during the day on one day and then over the next six days make any changes needed for those days. After that it takes care of it for you, including anticipating the lead time to get it to the desired temp at the desired time by measuring the response time through the day so if it is colder out it will start heating sooner or cooling later.

[Rudy]

Sorry your chronotherm isnt doing the job for you. I'm curious, are you at home during all these period/time settings or are you typically away 'at work' with the house vacant during the day ? We had a 2700+ sf. home in Tucson until last Spring. It was 'all electric' with Tucson Electric Power (TEP)- no gas heat or H/W.

We had 2 Carrier Heat pumps with Chrono III's ( it was a long house- 2 zones) and found them to work well. I checked out the rates offered (sounds like you re on the 'nite-low rate like after 9 pm for laundry etc with the rate for 'prime time' 6-9Am and

5-9PM being higher) but since we were retired and the chance of us being 'home' using the A/C and other electric items "during the day" was high, we decided to not go with that plan. Instead we were elegible for the Guaranteed Rate plan ( new home with several "how to build it" rules applied mandated by TEP) which was a flat 20% off the normal rate. Their engineers determined from our plans (before the house was built) what the average yearly heating/cooling would be ( $ 665.00 yr/ $ 1.75 day) and guaranteed it wouldnt go over that for 5 years. Well they were right, it never did. Our highest monthly electric bills were in the range of $ 144.00 in August (when the air ran the most) down to $ 45.00 in April/ Nov. I was quite pleased with that. I dont know where in AZ you are or if your home can qualify for the "guaranteed rate" but we found the daily "high/Low" changing rate to not be an advantage if anyone was going to be at home. On days when we went out for most of the day (once or twice a week) we just set the Chronos on hold @ 78 oF for A/C and in the winter 68 oF for heating.

[Rusty Carruth]

approx 3200 sf home, Tempe. Family is there most of the time. All electric. So its very similar to your situation, except that we're with SRP.

similar - we're 2 story, so have upper and lower units.

Wow. That's cool (no pun intended!). We bought the house about

1.5 years ago. The previous owners' average bill was around $200 / mo!

78 is the lower end for my comfort. Usually I like 79-80, and when we leave we set for 85+ for cooling. (When we are doing it manually). I forget what we set for heat, its been too long ;-)

Back to the original topic, more or less: I've just about decided to go back to my original plan, which is to design and build my own thermostat. In the meantime I'm looking for a moderatly inexpensive unit with true nonvolatile storage (yes, I change batteries, however my chrono 3 (for example) has a habit of dropping batteries out, thus losing backup power. SRP is busy fiddling around in the neighborhood doing wiring, and we've had 3 or more power failures in the last 2 weeks.... (well, ok, it doesn't drop the batteries, but it DOES lose the program even with good batteries (and if you take it off the wall for any reason the downstairs one *does* drop batteries - now I have to go dig it out from under the piano!). Also, the LCD is almost totally unreadable - certain numbers you can know only because you could (barely) read the previous digit!)

Also, to answer Joseph Meehan's comments:

More like a bad week or two, not just a bad day ;-) I've been planning to make my own thermostat now for around 3 years, so the ideas are mosly congealed in my mind (when I can get my mind to remember them ;-). And unfortunately our schedule is 'way too 'semi-random' for me to believe that a thermostat could automatically figure out the right thing to do ;-) However, I can see that it might be able to remember how you've tweaked it... Hmm.

And, finally, my last thought/challenge for the day - its too bad that the choices seem to be visit Lowe's/HomeDepot/Ace and browse their offerings, spend hours and hours having 'fun' on the web chasing down all sorts of options, or call in some kind of high-priced contractor (see alt.hvac ;-) (some of whom seem to have no small problem being polite - fortunately not many). Well, at least we have the web... (and real honest-to-goodness usenet! Wow, I'd almost forgotten...)

rc