HVAC question

[Wolf mom]

Just moved into an older home with a new HVAC system - or two as I'm told. It's a heat pump with a gas heat backup -
If the outside temp goes below 40 degrees, the gas heat kicks in otherwise it's an electric heat pump. I've never heard of this before. Is it normal? Is it really cost saving? The house was advertised with gas heat. Upon inspection, it was found not to work & the former owners installed this set up - all new.
My second question is this. The compressor on the heat pump is outside the house. BUT it runs (at least the fan runs) whenever the heat goes on. Being from Arizona, I've lived with heat pumps for 50 years and never had the compressor or compressor fan go on with the heat. Is this something new? I've had a guy out once already & he told me that's the heat pump - Nope - that's the compressor for the air conditioner. I think the heat pump is under the house with the gas heater...
Am I right in calling the the company out again to fix it so the compressor or compressor fan is off when the heat goes on with the heat pump?
Could someone educate me, please?

[ninny]

Originally Posted by Wolf mom

Just moved into an older home with a new HVAC system - or two as I'm told. It's a heat pump with a gas heat backup -
If the outside temp goes below 40 degrees, the gas heat kicks in otherwise it's an electric heat pump. I've never heard of this before. Is it normal? Is it really cost saving? The house was advertised with gas heat. Upon inspection, it was found not to work & the former owners installed this set up - all new.
My second question is this. The compressor on the heat pump is outside the house. BUT it runs (at least the fan runs) whenever the heat goes on. Being from Arizona, I've lived with heat pumps for 50 years and never had the compressor or compressor fan go on with the heat. Is this something new? I've had a guy out once already & he told me that's the heat pump - Nope - that's the compressor for the air conditioner. I think the heat pump is under the house with the gas heater...
Am I right in calling the the company out again to fix it so the compressor or compressor fan is off when the heat goes on with the heat pump?
Could someone educate me, please?

The heat pump is your air conditioner. A heat pump is a reverse cycle air conditioner. Instead of cold air blowing inside and the warm blowing outside, the cycle is reversed, the warm air blows inside and the cold outside. From your description it sounds like your system is working properly. The fan running outside is also normal.

.

[Sawmill Jim]

Yep sorry you just were told you had a heat pump at the other house
What you have now is one of the latest and greatest ever units called duel fuel heat pump . As has been said it is a AC unit with a reverse valve . Big difference in this new unit once balance point is near it switches to gas heat instead of the older style strip heat that made the meter spin at near ,the speed of sound .

Balance point is where air is the same temp on both sides of a heat pump = no heat and no cool or near about for anyone with charts and graphs .

Note if this unit does have a defrost mode don't freak out if you catch it in that mode

[Harry Chickpea]

Yep, all entirely normal and good. To the best of my knowledge, all heat pumps have a defrost mode so that ice doesn't build up on the outside coil. How often it cycles varies.

[1shotwade]

Yes to every reply. You're Ok. It'll freak you out when it goes into defrost so don't get alarmed when it looks all froze up and doesn't sound right. That's all part of the process.Having the backup heat source is also a good Idea.Just enjoy it!


Wade

[billinwv]

Great system. You can switch over to emergency heat on your thermostat and run the system with a generator if you are wired for it. In this gas only mode you are only running the fan. Basic heat pump is too much energy pull for most generators.

[michael ark]

These guys is shooting it to you straight . At your last house sounds like you had electric heat strips or a broken heat pump or both.

[Wolf mom]

Thanks everyone. I will enjoy it now that I understand what I've got.

[agmantoo]

What is your source for the gas, natural gas from pipeline or propane from a tank?

See if you can determine the SEER rating of the new heatpump.

I suggest that you do not jockey the thermostat up and down. Find a comfortable level and leave the thermostat alone.

Make certain that you change the air filter frequently. Use the cheap filters and toss the old ones often. You want to keep the coils clean year round. You should find the heatpump to be very economical.

[Nevada]

I'm not a big fan of heat pumps. Heat pumps can be an efficient way to heat a home, but only under certain conditions. The colder it gets outside the more expensive heat pump operations becomes, thus your 40 degree changeover to gas.

Moreover, the cooling efficiency of heat pumps is not optimized. The design is a compromise to have acceptable efficiencies for both heating and cooling, but not optimized for either. That means you take a hit on power costs during the summer.

Heat pumps also have a reversing valve, which is prone to sticking. Changing out a reversing valve is a lot of trouble, so it's expensive.

For climates around here (Las Vegas) the best systems are split air conditioner systems with gas heat. I stay away from roof units, since they have to fight heat from the sun constantly. You're better off with a split system with the condensing unit on the north side of the home for shade. I have a 15 SEER split AC unit with gas heat. The share of the gas bill for winter heat is never more than $35/month for a 1,000 sq ft home. That's the way to go.

[Harry Chickpea]

Moreover, the cooling efficiency of heat pumps is not optimized. The design is a compromise to have acceptable efficiencies for both heating and cooling, but not optimized for either. That means you take a hit on power costs during the summer.

Cooling efficiency is primarily dictated by the refrigerant characteristics, compressor and fan efficiencies, and coil size. I think that you are confusing optimal SIZING with optimal efficiency. Optimal sizing of AC units is primarily to prevent a damp cold clammy interior space. In the southeast, where humidity can reach 90% or more, that is a somewhat valid point, although sizing is commonly based upon cooling load not heating load so it is a moot point. In a dry climate like LV it simply is not an issue unless you have an indoor hot tub.

I have been using heat pumps for 30 years and never run into a problem with the reversing valve. Compressors and A coil fan motors, yes. However, both of those are AC problems as well.

In LV, a swamp cooler could be much more efficient than an AC for much of the year.

[Nevada]

Originally Posted by Harry Chickpea

Cooling efficiency is primarily dictated by the refrigerant characteristics, compressor and fan efficiencies, and coil size. I think that you are confusing optimal SIZING with optimal efficiency. Optimal sizing of AC units is primarily to prevent a damp cold clammy interior space.

Compressor & fan efficiency characteristics are what are used to calculate SEER. In a standard split AC unit the SEER rating is only calculated for the condensing unit. But a complimentary A-coil in installed, which is not part of the SEER calculation. The A-coil acts as the condensing coil when running in heat mode, so it has to be included in the heat pump SEER calculation. I think you'll find that you don't do as well with the A-coil exchange area.

Originally Posted by Harry Chickpea

In LV, a swamp cooler could be much more efficient than an AC for much of the year.

That used to be true, before 2 million people moved here and installed swimming pools & lawns. Today the added humidity makes swamp coolers only work for a small part of the summer. Some people still have them but they're mostly used in "piggyback" systems that can switch to AC when needed. I don't fool with a swamp cooler.

[arabian knight]

It is not the humidity that is counted when figuring when you can use your swamp cooler.
It is the Dew Point.
Above 55º DEW POINT the evap cooler is not good anymore.
Even in Phoenix you only got a very few weeks to use one. When the monsoons come around and the Dew Point reaches that 55º and higher you shut them off and turn on there AC.
It sure was nice to have a swamp cooler when I lived for all those years in Tempe. Especially when that day it reached 122º Yikes.
Out horse barns we estimated that inside it was Over 140º.~!
My pony never left his spot Standing in front of his fan~!
I even had a portable swamp cooler for my Great Pry. LOL


Here was my set up evap cooler on top AC unit just below it.

[Nevada]

Originally Posted by arabian knight

It is not the humidity that is counted when figuring when you can use your swamp cooler.
It is the Dew Point.

Dew point is just a way of expressing humidity.

[arabian knight]

You still go by what the Dew Point is when considering when and if to use a evap not the humidity level
52°
SUN AND CLEAR SKIES
FEELS LIKE: 52°
SKY COVER: 1%
DEW POINT: 24
HUMIDITY: 33%
WIND: NW AT 1 MP
PHX right now.
They are two different things. Measured differently.

Even in my area where the hum it is a lot higher.
There is a new hog barn 1/2 mile from me and the sides of those Huge Barns is a Evaporative Cooler Pads. Neat Not sure how this will work out but being NEW they must know something.
One barn is two football fields long.
Total amount of ground under cover is 5.7 acres~! Those are some huge buildings.
Those are some mighty huge evap cooler pads. LOL

[coolrunnin]

Been using evaporative coolers several years in chicken houses in Arkansas and Missouri.

And you can't measure relative humidity without measuring dew point.

[Nevada]

Originally Posted by coolrunnin

And you can't measure relative humidity without measuring dew point.

The data that AK posted as "humidity" was in fact relative humidity. Relative humidity is calculated from dew point (absolute humidity) to show the saturation percentage of air. Dew point is an expression of absolute humidity, relative humidity is not.

[1shotwade]

All that and nobody mentioned "wet Bulb"?

Wade

[Nevada]

Originally Posted by 1shotwade

All that and nobody mentioned "wet Bulb"?

Wade

Wet bulb is an important property, but not a direct expression of humidity. Indoor wet bulb temperature is commonly used by HVAC technicians to determine one if the properties for how much superheat a suction line should have when charging a split AC system with refrigerant.

I have a meter that reads both temperature and relative humidity. It looks something like this.

http://www.ebay.com/itm/Digital-LCD-...item2a461ed813

I place it inside the home near the intake register. When I know the temperature and relative humidity I calculate the wet bulb with a free app on my smart phone, that works like this (use 29.92 in Hg for pressure, it doesn't matter).

http://www.srh.noaa.gov/epz/?n=wxcalc_rh

For the temp & rel humidity on the meter in the ebay ad (82.9F and 85%), wet bulb temperature is 79.2 and dew point is 77.93.

[Nevada]

Originally Posted by arabian knight

Even in my area where the hum it is a lot higher.
There is a new hog barn 1/2 mile from me and the sides of those Huge Barns is a Evaporative Cooler Pads. Neat Not sure how this will work out but being NEW they must know something.

Well, that's for a hog barn. I prefer AC. LOL

I used an evaporative cooler when I lived in Arizona. In fact that's all I had. In the remote AZ desert it worked well for all but a few weeks in August. I ran away to Laughlin when that happened.

I can always tell when I walk into a home with a swamp cooler. It's livable under the right conditions, but not as comfortable as AC.