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Heating & Air Conditioning

Heat pump and thermostat setbacks

10 years ago

My new condo has a heat pump that uses a water source. The water is supplied by a master boiler for the building in the winter and a cooling tower in the summer.

My question is should I be using the setback mode on my thermostat. I find conflicting answers on the internet, but they all talk about air source heat pumps and never using a setback.

My system does not have an auxiliary heating coil.

I want to run this system the most cost efficient way.

What are your thoughts?

Thanks.

This post was edited by icucwec on Thu, Jan 16, 14 at 19:59

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Comments (17)

mike_home
10 years ago
Who is paying for the heating and cooling of the water?

Who is paying for the electricity to run the heat pump?
icucwec
Original Author
10 years ago
Heating and cooling of the water paid out of HOA fees. The cost to run the heat pump is paid directly by me.
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I think you both raise good points & I appreciate the feedback. Intuitively, I would think that the ramp up is from the heat strips while coming back from being setback or idle for prolong periods of time thus causing the aux strip heat to be used. However, I would think that the installer should have set-up some sort of smart recovery to slowly ramp-up from setback to comfort & limiting any heat strip usage under fairly normal condition (i.e. waking up in the AM). In the XL950 installation guide page 13 - there are these entries: can you all tell me what it's saying? Aggressive Recovery: This option disables the 10 minute inhibit anytime the thermostat sees more than a 2ÃÂ° change (such as moving from one program time frame to another). This applies to heating & cooling modes. Heating Aggressive Recovery: This option disables the 10 minute inhibit based on outdoor temperature in heating mode only. The value for outdoor temperature can be set from 0ÃÂ°-70ÃÂ°. * Heating Aggressive Recovery can only be enabled if Aggressive Recovery is disabled. * There is a 10 minute Ã¢ÂÂinhibitÃ¢ÂÂ period between first and second stage compressor as well as compressor heating & supplemental strip heat. * This 10 minute inhibit period minimizes the cycling of higher capacity request due to drafts around the thermostat or marginal load conditions. Here is a link that might be useful: XL950 Comfort Link Installation Guide
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If something is wrong with the thermostat preventing it from shutting off, then the room temp would rise above the setpoint while it keeps running ... but that's not what's happening, right? It apparently is "keeping up" enough to almost-but-not-quite reach the setpoint. What probably is happening when you raise the setpoint is the auxiliary is triggering to raise the temp 1°F higher, which then prompts the system to shut off when you drop it back down. If this is a recent change in operational characteristics at 40°F-ish outdoor, then you should have the system checked for a problem as mike_home suggests.
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mike_home
10 years ago
Since you don't have auxiliary back up heat strips, then I don't see any negatives by doing a set back.

The same is true for cooling. Be aware it takes much longer to come out of a cooling set back than one for heating. A heating set back of 6-8 degrees is fine, but for cooling I would suggest 3-5 degrees F. There is no harm in experimenting.
tigerdunes
10 years ago
I generally agree with Mike although I think both setbacks he suggested for cooling and heating are too large. If the hp condenser runs continuously on recovery for any length of time, I think at some point the setback defeats the purpose.

One question I will throw back at you. Since you are sharing the boiler hot water cost through homeowner fees, would it not be cheaper for you to just heat with the hot water coil and forget the HP condenser except possibly in shoulder months?

Just a thought.

Do you mind sharing location?

IMO

This post was edited by tigerdunes on Fri, Jan 17, 14 at 11:53
icucwec
Original Author
10 years ago
I don't think I have any way to stop the compressor from running.
tigerdunes
10 years ago
If it's not already set up that way, it should be. Emergency heat setting on your thermostat should be the heat produced from hot water coil only.

If it's not, that's what I would want. The hot water coil heat replaces the heat strip.

IMO
icucwec
Original Author
10 years ago
There is no emergency heat setting on my thermostat. Simple 4 wire system. Y W R G
tigerdunes
10 years ago
If this is new install, your dealer did you a disservice. All heat pump thermostats have an auxiliary and emergency setting as well as on/off , heat, cooling, along with fan setting. Dealer apparently looked out for himself, not you.

Sorry to report that.

IMO
icucwec
Original Author
10 years ago
My system wiring
tigerdunes
10 years ago
Not interested in wiring.

Post model and brand of thermostat please.

BTW, it would be nice to get model number of HP condenser and air handler.

IMO

This post was edited by tigerdunes on Fri, Jan 17, 14 at 12:22
mike_home
10 years ago
How do you control the heat pump without an O or B wire? You need a wire to reverse the condenser from heating to cooling.

Do you have any model numbers of the equipment?
Elmer J Fudd
10 years ago
I'm the ignorant voice speaking, but could this be simply a heat exchanger in each unit running with heated or chilled water from the building's central system (like in an office building) and not a heat pump?
tigerdunes
10 years ago
Could be....he may not even have a HP although he seems to think that's what he purchased.

Something fishy here.

IMO
icucwec
Original Author
10 years ago
Unit is a Florida Heat pump. Model fhp024

It does have an O/B wire. Mistake in not listing that. Also has a common to power the thermostat.
tigerdunes
10 years ago
Not familiar with Florida HP.

The obvious question is whether you are cooling exclusively with chilled water and heating exclusively with hot water.

IMO
icucwec
Original Author
10 years ago
This might help.
icucwec
Original Author
10 years ago
page 2

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