Comments on: How NOT to Use Your Heat Pump Thermostat

By: Allison Bailes

Allison Bailes — Mon, 21 Jul 2014 16:15:23 +0000

Kelly Y.:
Kelly Y.: In addition to what David said about the frost on heat pumps, you might want to read the articles below. The first is just about how a heat pump works. The other two are about frost and the defrost cycle.

How the Heck Does a Heat Pump Get Heat from Cold?!

Why Does My Heat Pump Frost Over?

Why Are Heat Pumps So Dumb About Frost?

~ ab3

By: David Butler

David Butler — Mon, 21 Jul 2014 07:26:45 +0000

@Kelly, frost is normal and
@Kelly, frost is normal and unless it turns into a solid coat of ice, has on minor impact on performance. Heat pumps are designed to go into a defrost cycle to melt the frost. Early heat pumps didn't do this very well, which is one reason they got such a bad rap. Today's heat pumps have intelligent defrost control, so that if there's little or no frost present, the defrost cycle will terminate quickly, typically in less than a minute. That said, it's important that the defrost settings be adjusted for your particular climate.

Sadly, it sounds like the former owner spent a LOT more money on heat than was necessary. The fact that she was on her 3rd heat pump within 12 years suggests there may be problems that still need to be resolved. I recommend that you try to talk with the tech that did the last replacement to see if you can find out the cause for the failure.

By: Joe Marchione

Joe Marchione — Mon, 21 Jul 2014 06:42:21 +0000

Kelly,

Kelly,

I understand your concerns. Many people who have never had a heat pump before get confused on the most efficient way to use it. You can go to my web site at http://www.thebesthvac.com and click on the “Heat Pump” link to learn more about how the heat pump works and how to get the most efficiency from it.

I hope that helps you and if you have any other questions, please post back here so that others can benefit from the information.

Also, I would like to understand what you mean when you say that the previous owner went through 2 heat pumps in the last 12 years. Normally, 12 – 15 years is the life expectancy of a heat pump (just my experience). In order to properly diagnose the issue we will need more information.

By: Kelly Yager

Kelly Yager — Mon, 21 Jul 2014 05:45:49 +0000

I have just bought a home
I have just bought a home that is equiped with a heat pump, it was installed in May of this year. The former owner said if the fins on the outside of the heat pump become frosted more then about two thirds then I need to switch the heat over to emergency. She has also went threw two units in the past 12 years with this being the third. My question after reading your info and knowing not to use the emergency heat unless its an emergency is do I need to be concerned with frost and if so what do I need to watch for,how do I need to fix it?

By: David Butler

David Butler — Mon, 09 Jun 2014 22:43:50 +0000

@Sara, an A/C (or a heat pump
@Sara, an A/C (or a heat pump in cooling mode) can operate well below 20C, and in fact, capacity and efficiency increase as outdoor temp drops. That said, if it's too cold, low refrigerant pressure can cause problems.

Different manufacturers specify different low limits. For example, York specifies a minimum of 10C in cooling mode. I'm not aware of any AC or HP that won't operate safely down to at least 13C.

Sounds like your duct system is poorly designed. Having a single system serve upstairs and downstairs without zone control doesn't work well because the load balance between up and down is very different in summer vs. winter, requiring different amounts of air. Unfortunately, this is common practice. Some states are now requiring zoned equipment or air distribution in multi-story homes.

However, indiscriminately closing off vents is a bad idea. It not only redirects airflow, but also reduces system airflow due to the additional back pressure, which can lead to problems (e.g., coil ice), especially if duct system and/or filter is undersized. I suggest you call a mechanical contractor with NATE or National Comfort Institute certification to balance your duct system and install a damper that can be used to adjust upstairs / downstairs flow rates between seasons. That's the only way you can ensure system airflow remains within an acceptable range.

By: Sara

Sara — Sun, 08 Jun 2014 19:14:51 +0000

We have a constant dispute in
We have a constant dispute in our house about the cooling function of our HP. The house heats up during the day and when the outside temp cools down at night my father believes we should shut the HP off. In his opinion the system cannot cool the air outside if it's below 20C outside.
The issue is that the exterior and the upper floor has been heating up all day and unless the cool air is actually blowing, the second floor is extremely uncomfortable.
There are 8 floor vents on the first floor and only 4 ceiling vents on the second floor though the square footage is the same so I have blocked 4 of them downstairs. I think that should even out the air flow better and make the cooling much more effective upstairs.
The question I have for you is what is the lowest outdoor temperature that an air-air heat pump can tolerate while in the cooling function?

By: David Butler

David Butler — Thu, 20 Mar 2014 23:31:14 +0000

@Dave H: assuming your system
@Dave H: assuming your system has electric supplemental heat, it's a bad idea to turn it OFF at night. Your thermostat will undoubtedly rely on supplemental heat to recover in the AM, more than offsetting any savings.

It's OK to setback your thermostat a few degrees at night during milder weather (e.g., overnight lows in 40's), but you'll need some way to keep your strips off during the recovery period. The best way to accomplish that is with an outdoor thermostat. Some hp thermostats support an outdoor temperature sensor for this purpose. Otherwise, special outdoor thermostats are available for this purpose (see 3024-6881/D). During colder weather you're better off reducing or eliminating setback.

By: Dave Higgins

Dave Higgins — Thu, 20 Mar 2014 05:11:02 +0000

I've been having pretty good
I've been having pretty good luck with my HP as far as performance goes. My question is: at night I turn the unit completely off just before I go to bed, 10:00 pm. Then turn the unit back on in the morning around 7:00 am. Does it save on electricity to do it this way or is it more efficient to leave it on all night?

By: WC

WC — Sun, 16 Mar 2014 21:54:10 +0000

Thanks for the info! I just
Thanks for the info! I just moved across country due to a foreclosure & rented a room in someones house. The elec. bill came & it was DOUBLE what my old house used & Im only renting a SINGLE room. Sure enough I looked at the stat & the emerg. heat was on. I been here 60 days & feel like room mate ripped me off with her stupidity!

By: David Butler

David Butler — Sat, 15 Mar 2014 22:01:26 +0000

@Francis, the majority of
@Francis, the majority of furnaces, A/C's and heat pumps operate at a single capacity. They're either on or off. That's considered a single stage.

So 'stages' refer to how many discrete steps in capacity a particular model has.

Variable capacity (or modulating in the case of a furnace) means a system can vary its capacity continuously within a certain range.

Multi-stage and variable capacity equipment is more expensive, but generally has a higher efficiency rating.

The XP14 is a single-stage heat pump. Technically speaking, the supplemental electric heat installed in the air handler provides 2nd stage heating capacity but it would be incorrect to call the XP14 a 2-stage heat pump.