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Old 01-04-2014, 09:41 AM   #1
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Choosing a thermostat


Hi all,

Happy New Year! All the best!

Up here in Montreal, Canada we have great swings in the winter temperature... can go from -20C (-4F) one day to +5C (41F) the next. We also can have very windy days that make it feel much colder, which can greatly affect the heating of the house. More than have of the houses (including mine) were built in the 1960's and earlier. Not much insulation in the walls.

And in the summer it can get very hot. 30C (86F) and higher with extreme high humidity.

Currently I have a fancy Honeywell RTH9580 wifi thermostat. I have read a lot of complaints about this unit and I am on the fence. Maybe mine is wonky, not sure.... the temperature on the display rarely changes.

the problem with these "smart" thermostats is that they don't seem to have enough advanced setting. There is no cycle per hour setting, etc.

We have a heat pump and oil furnace. Given all the combinations of heating/cooling; indoor and outdoor temperature; outdoor wind chill or humidity.... how can this thing really make smart decisions?

Whats the best thermostat out there to use for max comfort (avoid temperature swings) in summer and winter in this crazy place ?

Thanks!
Terry

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Old 01-04-2014, 11:16 AM   #2
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Choosing a thermostat


i have a honeywell stat. the temp never changes. the furnace cycles on/off too much for my liking. the the room temps stay very steady.

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Old 01-04-2014, 11:23 AM   #3
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Choosing a thermostat


1) Get yourself a accurate digital stick thermometer and place it on top of the tstat to see if it is actually working.

2) These "learning" thermostats work well in a stable environment. they use a algorithm which samples/records the length between heating cycles and how long it takes to drop and recover more than 1 deg F and basically averages them out and calculates a run time and swing. Carrier did that 15 yrs ago with 2 stage furnaces so it is nothing new. No thermostat in the world can compensate for drastic swings or how the human body feels with drafts and changes in humidity so they are a compromise at best. Heat pumps are slow to recover so one of those tstats may not be a good idea either.
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Old 01-04-2014, 11:36 AM   #4
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Choosing a thermostat


Honeywell IAQ(YTH9421). Its not wifi. But you can set the CPH. Plus with an outdoor temp sensor you can set a compressor lock out, furnace lock, and then use 2 degree droop. This will help on those windy days/nights when the wind causes the house to lose heat faster then normal and the heat pump can't keep up. It will switch to the furnace if the indoor temp drops 2 degrees.
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Old 01-04-2014, 12:39 PM   #5
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Choosing a thermostat


The 9580 is not dual fuel compatible to start with!
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Old 01-04-2014, 05:53 PM   #6
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Choosing a thermostat


Quote:
Originally Posted by hvactech126 View Post
The 9580 is not dual fuel compatible to start with!
It's not dual fuel, but in Quebec we let the electric company decide... see my next post down below.

Cheers!
Terry

Last edited by tls1; 01-04-2014 at 06:29 PM. Reason: I was incorrect.
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Old 01-04-2014, 06:08 PM   #7
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Choosing a thermostat


The thermostat is not dual fuel capable because it does not have a heat pump balance point setting. That thermostat will run the hp and oil furnace at the same time and can ruin the heat pump.
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Old 01-04-2014, 06:28 PM   #8
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Choosing a thermostat


Hydro Quebec has a special rate for customers that have oil or gas with some form of electric heat. it's a dual meter with a thermometer built in, a red light inside the house and a relay to control the heating.

DT: 4.4 cents/KWH when warmer than -12C (red light off, use electric heat), otherwise 21.26 cents/KWH (red light on, use oil/gas)
D: 5.41 cents/KWH always (20% more)

Until recently I had a heat pump and the oil furnace and it was controlled by the thermostat to switch from electric to oil at -10C according to the thermostat. But Since I have the DT rate I should switch according to the red light, but the house was not heating properly at -10C. But most people theoretically don't really need the dual fuel t-stat here in Quebec, they let hydro decide when to turn off the HP with the relay which is coordinated with the red light.

So in my house we would switch to expensive oil ($1.20 a liter tax included) at -10C when I theoretically could still be using cheap electric heat down to -12C when the red light turned on and only then use oil.

I purchased an electric plenum heater. It has a 4KW and 8Kw heater. ANd a very special controller that has temperature sensors in the return duct and outside. if you search ABC hybrid you will find the controller.

When the famous red light is off, we use the heat pump always to bring the temp as high as it can (around 35-38C)! And then depending on conditions we use 4/8/12 KW electric heat to make it even hotter. I can get the air temperature up to 45C. Now these electric elements don't run continuously... when it's -11.5C outside, it might run 8Kw coil on and off.... at 4.4 cents a KWH we're looking at 8 KW x 30min (half the time) x 4.4 cents = 16 cents an hour.

sorry for the confusion...

terry
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Old 01-04-2014, 06:36 PM   #9
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Choosing a thermostat


I'm looking at my 9580 t-stat manual:

There is a button:

Emergency Heat (heat pumps with aux. heat): Controls auxiliary/emergency heat. Compressor is locked out.

I think this t-stat when used is the traditional way as you describe has it's own algorithm when to use backup heat. I guess it can sense based on desired temperature, time elapsed and current indoor temperature to switch to backup/aux heat. I do see the this t-stat occasionally display "Aux heat" and that's when my electric coil kicks in with the HP.

cheers!
terry
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Old 01-04-2014, 07:54 PM   #10
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Choosing a thermostat


It would be a lot easier to just move to Winnipeg and build/buy a house like mine. R40 in the attic/3 pane low-E argon windows/2x6 walls with R20. It has been -35 and lower for the last week with the windchill and going to stay for another week. My 70,000 BTU furnace runs 10 mins every half hour and I am comfortable as heck. Other than the odd roaming polar bear it's a great place to live. We have St. Boniface and the Festival du Voyageur which is a lot of fun with the snow sculpture contests and Park etc. MB Hydro is cheap also so why go thru all the complications of a heat pump and duel fuel and whatever. NO freezing rain either.

No le Habs but the Jets may get better in a few yrs.
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Old 01-04-2014, 08:00 PM   #11
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Choosing a thermostat


Naw, I'd rather live in Quebec where we have...

separatism
language laws
pasta gate
charter of rights
language police
problems in the economy
pot holes
freezing rain
scorching summers
cheap electricity
being treated like second class citizen
Charbonneau commission
wish we had Rob Ford
etc

If I move... it will be SOUTH! where there is no snow!
Maybe Costa Rica or Panama

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