Thursday, August 2, 2007

Informal Review: Honeywell RTH7500

Honeywell RTH7500 Thermostat

Following up the RiteTemp GMPG808C review...

This thermostat is actually simpler to describe. It has no character. You don't notice it.

Actually, one might take it as a compliment - this is exactly what you want from an appliance - all you need of it is to perform its function and not struggle for getting a piece of your attention all day.

But it'll sure make you work to get to that point and will punish you if you try to upset the status quo.

First of all: don't lose the manual.

The rest of installation is simple - just follow the installation manual. It would be a good idea to read all of it beforehand - there's a couple of quirks you need to be aware of, in particular, configuring the thermostat to work with your exact HVAC system configuration.

Configuration takes a while - again, it's better to have the unit on the desk before you, and not in th wall cradle, when you do it. Can't do it without the manual - options are numeric. Did I mention - don't lose the manual?

That's basically it - unless you are really off with setpoints and schedules, you won't have to touch it again.

A few observations:

  • It is nice to be able to move period boundaries. Different people, different schedules.
  • You may want to think twice if you really want to use the "recovery" option (the one that makes sure that if you set the period starting at 9PM having setpoint of 78°F, you will have the room at 78°F at 9PM, instead of HVAC unit starting to struggle to cool it down at 9PM) - this option will throw a wrench into your energy savings if you are on a time of day usage plan. The worse is your HVAC (or, should I say, the more properly it is sized), the less useful this option is.
  • Have to imprint it in your mind that all you need to do to change the temperature temporarily is to press up/down arrows a few times. There is no need to press "hold" - this makes the thermostat hold the temperature forever. Kind of counterintuitive in the context of other interaction patterns - closure is expected, but missing.
  • I absolutely hate the fact that the only way to see the screen in the dark is to actually press the button, and, it does something just as you press the button.Watch what you're doing. The only way not to screw things up is to learn what button is idempotent when pressed twice, and find it in the dark (oh, by the way, it is not the temperature up/down arrows... they invoke a "temporary temperature change" context, which you have to explicitly get out of or let it time out - of course, not before the light goes off). Or just forget it and switch on the lights - to me, this option eventually won the argument. In other words, if you're specifically looking for a backlit LCD thermostat, have a chuckle and move on.
  • Summarizing the above, one could say that the user interface design violates the principle of least astonishment and thus may not be well suited to people who still have their VCRs blinking at 12:00.
  • There is no apparent way to adjust hysteresis, so if you are big on energy savings, you'd better consider thermostat that can do that - GMPG808C is not the worst other choice.
That's basically all. I can make an educated guess (but it is a guess nevertheless, please let me know if it is correct) that other thermostats of the same product line are probably identical to this except for different scheduling options:

  • RTH7500 supports 7-day programming (for $100);
  • RTH7400 supports 5-1-1- day programming (for $80);
  • RTH6300 supports 5-2 day programming (for $60);
  • RTH3100 doesn't support any programming at all (for $50).
Bottomline: brand name may be overrated and overpriced.

The only other consideration is - it's been less than a year since both Honeywell and Rite Temp thermostats have been installed, so let's see which one lives longer, and by how much.


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