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Old 07-11-2013, 03:47 PM
 
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Just bought a new house and it has a multi-zone, multi-thermostat heating and cooling system. So one A/C unit outside and 3 thermostats that all work independently of each other inside. The house is one story and only 2200 sq foot so not a mansion here!

In the evenings when all the thermostats are programmed to the same temperature because the family is home, it means the A/C unit is running 3 times as often as it should. Needless to say, my A/C bills have been rather high. I keep the A/C between 83 and 84.

Any feedback on a way to deal with it?
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Old 07-11-2013, 03:51 PM
 
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That seems odd, I've never heard of multi thermostats for 1 A/C units. Are you sure there is only one unit?
How does it know which thermostat to take the reading from...does it just go by which ever one is set to the lowest temp?
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Old 07-11-2013, 04:49 PM
 
Location: Phoenix AZ
6,039 posts, read 11,201,848 times
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Quote:
Originally Posted by HX_Guy View Post
That seems odd, I've never heard of multi thermostats for 1 A/C units. Are you sure there is only one unit?
How does it know which thermostat to take the reading from...does it just go by which ever one is set to the lowest temp?
A true "multi zone" setup uses dampers to send conditioned air to different areas of the home - you can actually have part of the house be cooler or warmer than another part of the house.. some setups just "average" the temps between different thermostats, without actually diverting the airflow based on the actual temp..

To the OP, do you actually want your house to be 84 degrees in this weather? You may find that lowering the temps doesnt really cost much more, because the efficiency of the unit increases with longer run times.. you might also want to make sure of the billing plan you are on with the power company - the wrong rate plan could easily jack your bill by $100+

The "standard" plan with APS is only like 1000kw, if you go above that usage, they nick you pretty hard. You would definitely want to be on one of the "time of use" plans with a 2,000+ sq ft house.

You might also want to dig into the programming of those thermostats - there are probably some "swing" settings there that would help with short-cycling , like allowing the variation to be "x" degrees before the thermostat triggers the hvac system..

Last edited by Zippyman; 07-11-2013 at 04:58 PM..
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Old 07-11-2013, 05:03 PM
 
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I always wonder if we are on the right rate plan with APS. We're on the Combined Time Advantage Noon - 7pm time plan and we work from home, so is that the best plan? We do try and limit use of dishwasher and washer/dryer during those times but A/C, computers, microwave etc are running.
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Old 07-11-2013, 05:28 PM
 
Location: Buckeye
533 posts, read 838,435 times
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I am off-peak between 7 pm and noon. Don't know if it's good or bad. I am wondering too about the multi-zone thermostat. I would understand with a 2 story house and 2 units. We had a 2200 sq ft house and one thermostat was plenty enough. Geez I would melt at 84.
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Old 07-12-2013, 06:27 AM
 
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HX_Guy, yes, absolutely sure it's one unit with 3 thermostats. =)

Zippyman, thank you for the suggestions. I was already at $300 for the month of June. I know many have much higher electric bills but considering the size of the home, that it's brand new and that it's billed as extremely energy efficient, it seems pretty nuts when it's kept at 83/84 all day.

By the way, this system does seem to run directly to the temp in that particular area of the house as I leave the master bedroom / bath even warmer during the day and close the door. It's most definitely hotter in there then the rest of the house. What it does is cycle on/off constantly. There are 3 zones, so zone 1 runs for 5 minutes, turns off, then zone 2 triggers it to turn on, then off, then zone 3 for 5 minutes, then off. By then, zone 1 is warmer and triggers it again. Sometimes it's hard to sleep at night it runs so often. I can't imagine this is good for the unit.

I will have to look at time of use again (SRP). I work from home full-time. Although I'm an AZ native I've just moved back from living out of state for a few years. I'm not sure how it all works so I'm off to research. I'm also calling the Customer Care department of the builder to have them schedule someone to come out and check it just in case. I've read where people have found out it was wired incorrectly. This particular model had two units, and then, I am guessing, as a cost saving measure, the builder decided to build ONLY this model with one unit and this multi-zoned system. Yeah for me.
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Old 07-12-2013, 08:48 AM
 
Location: Phoenix AZ
6,039 posts, read 11,201,848 times
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Quote:
Originally Posted by webrighton View Post
HX_Guy, yes, absolutely sure it's one unit with 3 thermostats. =)

Zippyman, thank you for the suggestions. I was already at $300 for the month of June. I know many have much higher electric bills but considering the size of the home, that it's brand new and that it's billed as extremely energy efficient, it seems pretty nuts when it's kept at 83/84 all day.

By the way, this system does seem to run directly to the temp in that particular area of the house as I leave the master bedroom / bath even warmer during the day and close the door. It's most definitely hotter in there then the rest of the house. What it does is cycle on/off constantly. There are 3 zones, so zone 1 runs for 5 minutes, turns off, then zone 2 triggers it to turn on, then off, then zone 3 for 5 minutes, then off. By then, zone 1 is warmer and triggers it again. Sometimes it's hard to sleep at night it runs so often. I can't imagine this is good for the unit.

I will have to look at time of use again (SRP). I work from home full-time. Although I'm an AZ native I've just moved back from living out of state for a few years. I'm not sure how it all works so I'm off to research. I'm also calling the Customer Care department of the builder to have them schedule someone to come out and check it just in case. I've read where people have found out it was wired incorrectly. This particular model had two units, and then, I am guessing, as a cost saving measure, the builder decided to build ONLY this model with one unit and this multi-zoned system. Yeah for me.
I think your issue is mostly with the rate plan, if you're on the "same price all day" plan - that rate plan is great for small houses & apartments, but the "penalty" rate adds up quick for bigger houses. I haven't dealt with SRP in a while, but I know APS was quite nice in regards to running an "estimated" bill with different plans & suggesting the low cost option, based on the actual use we were experiencing.

As for the HVAC unit - the short-cycling is a problem mostly because for the first 10-15 minutes of run time, it's drawing 100% of the energy, but not producing 100% of the cold it is capable of. If each thermostat will trigger the unit, it probably isn't wiring - more likely it's a programming issue. If there's a brand and model on your thermostat, you can post that here, and I'd be glad to look for an "installer's" manual for you - there are usually several adjustments that can be tinkered with to make the units run when you want them to. Usually the "consumer" settings lock out all the juicy bits that actually control the function of the unit.

If you talk to the builder, I'd be asking for the HVAC installer to come out & have some real data for them - I.E, "it was 105 today, and I timed the unit for one hour at noon- it cycled 8 times, and ran an average of 4 minutes per cycle".. if they don't instantly know something is wrong, they can call the thermostat manufacturer's tech support & get talked through adjusting the settings. Most of the HVAC manufacturers won't talk to a retail customer, but they'll chat for hours with a tech solving an issue.

If you don't have real data about how often the unit is cycling, I'd expect to get blown off. $300 isn't a high bill for Phoenix, but it seems a little high for 85 degrees in a new house. I'm sure you'll get resistance from them if you just say "high bill"...

As for cycling at night, other than adjusting the settings, there isn't much you can do - the heat load is lower - running all night isn't necessary, and letting the house run "wild" will make it even more uncomfortable.

Not sure why so many HVAC guys seem to have a fetish for setting up compressors under a bedroom window, but it is incredibly common.. it's one of those things you learn to look for in the second house you buy.. "If you could just put *my* a/c compressor under the neighbor's bedroom window, that would be great!"...
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Old 07-12-2013, 10:19 AM
 
9 posts, read 18,431 times
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Zippyman, Thank you for being such a wealth of information!! You do this community a great service.

I will start tracking times / temps by zone over this weekend and into next week (so I have both scenarios). I don't expect they'll come out right away as it's not an emergency (and understandable). I just timed it now, current temp is 91 outside, interior temp is set to 83, it ran for 7 minutes. I removed thermostat from the wall to get the model number. After reattaching it, 7 minutes after it stopped (the previous reading) it started up again. I'm assuming that's because I removed it?? ARGH.

All three are Honeywell TH6110D1021. Since this model looks to be for a single unit, I'm assuming there's a control board somewhere in the attic.

What is the clicking noise in the thermostat right before it starts up? Is that the relay turning on the air?

By the way, the unit is on the other side of the house than the Master Bedroom. It keeps me up due to the thermostat click and then how hard it blows the air into the room. It goes from OK temp to Ice Box in two seconds.

Edited to add: Does it matter that none had the battery back-up installed? Shoot, bet I need to reprogram them after re-attaching.

Thank you again!!!
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Old 07-12-2013, 11:13 AM
 
Location: Hard aground in the Sonoran Desert
4,654 posts, read 8,627,010 times
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Quote:
Originally Posted by HX_Guy View Post
I always wonder if we are on the right rate plan with APS. We're on the Combined Time Advantage Noon - 7pm time plan and we work from home, so is that the best plan? We do try and limit use of dishwasher and washer/dryer during those times but A/C, computers, microwave etc are running.
There is a feature on the APS website that will tell you what you're going to pay, based off your usage, with each plan. Pick the cheapest one and that's the right plan for you. Assuming you're going to continue with the same usage pattern.
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Old 07-12-2013, 11:47 AM
 
Location: Phoenix AZ
6,039 posts, read 11,201,848 times
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looks like that model doesn't allow you to set a "differential" temperature..it holds to plus or minus one degree..

The manuals for it are here:
FocusPRO 6000

Click the tab that says "manuals"..

The White-Rogers/Emerson thermostat in my house allows you to choose to let the house temp "swing" a little more to allow for longer cycles..

you might try calling Honeywell directly to see if there's a hidden menu for that somewhere -
it doesn't look like they are as "locked down" as White Rogers/Emerson is regarding retail calls.. They actually advertise a phone number - 1-800-468-1502

As for that "clicking" noise.. all the new ones do that..
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