dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
11315
share rss forum feed

laserfan

join:2005-01-14
Texas

Do Air Conditioners and Heat Pumps cool equally well?

I know that Heat Pumps are A/C units with a reversing valve, to make Heat in the winter and Cool in the summer. But what I'm not clear on: is there any advantage one-over-the-other relative to Cooling? Is there anything about a "cooling only" A/C unit that is capable to make colder air than a comparable Heat Pump?

I don't care about relative costs, or costs-to-operate, only about cooling ability.

Maybe it's a dumb question but I wondered if A/C-only units might use different compressors or coolant...?



SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:3
Reviews:
·Verizon FiOS

1 recommendation

I don't think it's a dumb question because I wondered myself

My opinion was that something that's designed to do one thing well will do better than something designed to do 2 things.



cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to laserfan

In a way you can consider a "cooling only" unit as a stripped-down heat pump. All other things being equal, they will cool the same.
A 2ton, 15 SEER A/C unit will cool like a 2ton, 15SEER heat pump with the same cost.
The capacity of cooling depends on the BTU rating of the unit.


garys_2k
Premium
join:2004-05-07
Farmington, MI
reply to laserfan

They'll cool the same, a unit rated for (say) 36000 BTU/hr will move 36000 BTU/hr of heat, whether it has the extra valving required to make it a heat pump, or not.


neonturbo

join:2009-02-27
Lansing, MI
reply to laserfan

From what I know, a heat pump and an a/c unit are basically exactly the same except they run the pump "backwards" in the winter.

I doubt there is a noticeable difference from a plain A/C to a heat pump as far as comfort, or cooling ability. You can buy a cheap A/C only that sucks as far as cooling ability and energy use, and you can buy an expensive heat pump that is great for both cooling and energy use. It depends on the brand, and the quality.


Aranarth

join:2011-11-04
Stanwood, MI
Reviews:
·Frontier Communi..
reply to laserfan

I have noticed that our open loop geothermal produces much colder air than a lot of ac units I've seen.

But the real answer comes down to efficiency. Water is able to store huge amounts of energy compared to the air. AC unit consumes a huge amount of energy because it is trying to shift heat from inside to the outside where it is already hot. A geothermal unit is just pumping heat from hot air into 60F degree water.

You can easily double the efficiency of an ac unit by cheating and pouring cool water through the cooling coils.

In fact I have seen several houses and a restaurant cooled by running water from a Koi pond through a sprayer over the roof, and then returning it to the pond. Very cheap way to cool a house and keep the fish warm.



Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to laserfan

Like everyone else said standard air source heat pumps and A/C only units are basically the same thing when it comes to cooling costs as long as you are matching efficiencies between the two. Geothermal heat pumps are another matter entirely.



dolphins
Clean Up Our Oceans
Premium
join:2001-08-22
Westville, NJ
kudos:7
Reviews:
·Comcast
reply to laserfan

The heat pumps they had in Jamaica took 2 days to cool the rooms with the thermostat at its lowest setting. They were probably old, had a low BTU rating or both?
--
Stop The Mindless Killings Stop Over Fishing



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to Ken

said by Ken:

Like everyone else said standard air source heat pumps and A/C only units are basically the same thing when it comes to cooling costs as long as you are matching efficiencies between the two. Geothermal heat pumps are another matter entirely.

If the air temperature for an air source and the water temperature for a geothermal are equal then the efficiency for both are roughly exactly equal. A high efficiency air source may have an edge given it's larger coil surface vs the small heat exchanger surface area for a geothermal.

Here the ground water is around 58 degrees so anytime the air is warmer the air source is more efficient heating.


Ken
Premium,MVM
join:2003-06-16
Markle, IN

Maybe like 2 weeks a year would the geothermal cost the same as an air source, but the other 50 weeks the geothermal is going to be much cheaper to operate. Especially an open source geothermal.



linicx
Caveat Emptor
Premium
join:2002-12-03
United State
Reviews:
·TracFone Wireless
·CenturyLink
reply to laserfan

Heat Pumps don't work well above 80F or below 20F - at least in the Mid-US. Swamp coolers do not work in humid areas. If you want to be warm and cool you use a device that heats and a device that cools or a single device that can do either.
--
Mac: No windows, No Gates, Apple inside



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom

1 edit
reply to Ken

said by Ken:

Maybe like 2 weeks a year would the geothermal cost the same as an air source, but the other 50 weeks the geothermal is going to be much cheaper to operate. Especially an open source geothermal.

The average temperatures match the ground water temp more than 2 weeks per year. Additionally they have clamped down on open source as too many people were drawing water from wells and just dumping it. That only leaves people living in coastal areas. I live on the coast but the water is much too cold in winter to use.

quote:
Does an open loop system cause environmental damage?

No. They are pollution free. The heat pump merely removes or adds heat to the water. No pollutants are added. The only change in the water returned to the environment is a slight increase or decrease in temperature.
I don't know of or heard about anyone around here getting a permit for an open source. All are closed loops systems.
How can they say this when they are pulling water out of aquifers and dumping it. Water depletion in aquifers in most areas in the country is a big problem and wasting it this way is environmentally unsound.

Advantages

In both commercial and residential installations, geothermal heat pump systems typically have lower maintenance costs than conventional systems as all equipment is installed inside the building or underground. This means that there is no outside equipment exposed to weather and vandalism. All refrigerant systems are sealed, similar to household refrigerators.

Open loop systems have less loss in heat transfer
Open loop systems have lower heat pump energy costs

Geothermal systems are very flexible. They can be easily and inexpensively subdivided or expanded to fit building remodeling or additions. They are particularly well-suited to "tenant finish" installations.

In commercial installations, systems can save money by recovering excess heat from building interior zones and moving it to the perimeter of the building. They can also save money by allowing management to isolate and shut down unoccupied areas of the building.

Disadvantages

Problems associated with disposal of the water after once-through the heat pump, disposal wells can be costly,
Water which has suitable qualities could change with time to poor quality that causes problems of corrosion later in time,
Costs associated with the drilling of the water well can be high and unknown at the outset,
Water tables and well output can change over time and cause future problems,
Permitting and its costs are usually required,
Open-loop systems have more potential problems than either conventional systems or closed-loop geothermal systems because they bring outside water into the unit. This can lead to clogging, mineral deposits, and corrosion in the system.
Open-loop systems require a large supply of clean water in order to be cost effective. This often limits their use to coastal areas, and areas adjacent to lakes, rivers, streams, etc. In addition, there must be an acceptable method of returning the used water to the environment. This may be limited not only by environmental factors (such as no place to dump that much water), but also by local and state regulations.
Since accessibility to terminal units is important in geothermal systems, architects and mechanical and structural designers must carefully coordinate their work.
Each unit requires both electrical and plumbing service.
Duct systems must be installed to bring outside air to each space.
Secondary or backup heat sources are required in cooler climates.


iknow
Premium
join:2012-03-25

said by Jack_in_VA See Profile

How can they say this when they are pulling water out of aquifers and dumping it. Water depletion in aquifers in most areas in the country is a big problem and wasting it this way is environmentally unsound.

matter can neither be created, nor destroyed, only changed. in this case only the temperature of the water is changed, so the water is not wasted, it either seeps back down into the aquifer, or evaporates into the atmosphere, and comes right back into the aquifer as rain!. either way it goes back into the aquifer!. unless they use electrolysis to break down the water into hydrogen and oxygen, that is. the problem with aquifer depletion is too much water being used at one time by so many people that it can't be replenished fast enough, an open source heat pump won't do this.


Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to Jack_in_VA

I don't know who "they" is in reference to clamping down on open source, but here at least open source is still perfectly legal. Our aquifer in this area is more than capable of keeping up with a few people who use pump and dump systems.

Even discounting that and assuming a closed loop, geothermal is still much cheaper to operate than a conventional air source heat pump for the majority of the year. It's not even a close comparison.



FiReSTaRT
Premium
join:2010-02-26
Canada
Reviews:
·Velcom

Most of the questions have been answered, so I will reiterate what's important.

1) A heat pump unit can reverse the refrigeration cycle, so it rejects the heat into the occupied space. Otherwise, it will typically be as efficient as a cooling only unit.

2) Geoexchange might be an anal rape to get up and running, but the big money items can stay for about a century (probably more) and you WILL experience major energy efficiency benefits. In most of Europe/Norh America/Asia, in the winter, the medium will be much warmer than the outside air and in the summer it will be much cooler.

3) They are working on pretty exciting stuff these days including really boosting the performance of geoexchange boilers. Keep an eye on this technology and consider it next time you have a few bucks to spare on major home improvement. We're at the point where some of this stuff can already be cheaper to operate than gas in most of occupied Canada - but I'm talking cutting edge technology.
--
If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.
—George Bernard Shaw



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom

1 edit
reply to Ken

said by Ken:

I don't know who "they" is in reference to clamping down on open source, but here at least open source is still perfectly legal. Our aquifer in this area is more than capable of keeping up with a few people who use pump and dump systems.

Even discounting that and assuming a closed loop, geothermal is still much cheaper to operate than a conventional air source heat pump for the majority of the year. It's not even a close comparison.

The AHJ's regulate it. We have problems with so much water being removed the land is sinking.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to iknow

said by iknow:

said by Jack_in_VA See Profile

How can they say this when they are pulling water out of aquifers and dumping it. Water depletion in aquifers in most areas in the country is a big problem and wasting it this way is environmentally unsound.

matter can neither be created, nor destroyed, only changed. in this case only the temperature of the water is changed, so the water is not wasted, it either seeps back down into the aquifer, or evaporates into the atmosphere, and comes right back into the aquifer as rain!. either way it goes back into the aquifer!. unless they use electrolysis to break down the water into hydrogen and oxygen, that is. the problem with aquifer depletion is too much water being used at one time by so many people that it can't be replenished fast enough, an open source heat pump won't do this.

Only the temperature is changed? How about removing it from aquifers that are thousands if not millions of years old and dumping in on the ground and contrary to your description it does not just filter right back into the aquifers. True one doesn't make too much difference but many will.

Closed loop is the only viable environmentally friendly method of geothermal heating and cooling.


boogi man

join:2001-11-13
Jacksonville, FL
kudos:1

and closed loop is far more efficient. the reason being that a well pump is usually min 1/2hp and frequently far more than that. vs a closed loop system that maybe uses a 1/4hp at most.

yes the water cycle is endless but it is not very quick at all when it comes to the kind of water you'd like to drink.
--
my site



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom

said by boogi man:

and closed loop is far more efficient. the reason being that a well pump is usually min 1/2hp and frequently far more than that. vs a closed loop system that maybe uses a 1/4hp at most.

yes the water cycle is endless but it is not very quick at all when it comes to the kind of water you'd like to drink.

Agree and the most important thing no water is wasted by dumping.


boogi man

join:2001-11-13
Jacksonville, FL
kudos:1

yes. even though i am in florida i am very sensitive to water. piss poor planning down here is leading to shortages in s. florida that is impacting me here in n. florida via the desire to take up to 200mil gal of water a day out of the st johns river. also there is a huge desal plant on tampa bay.

if the gf and i buy the house we're renting the air/air unit is being ditched and we're going geo asap we have a pond in the back yard which makes the loop placement stupid easy.
--
my site


laserfan

join:2005-01-14
Texas
reply to laserfan

Thanks you guys, I have wondered about our heat pumps for a long time and now I know: they are just more complicated than cooling-only units but provide the same cooling.

I suppose they're susceptible to more maintenance issues (especially leaks) because they run all winter too. Vibration, expansion/contraction etc.

I love the idea that water might improve efficiency. Last year in Texas we had 110 days of 100deg plus temps. This year notso bad but we're in a period of 100+ again w/no end in sight. We also have a severe water problem--I have only rainwater and it hasn't rained in a month so water is an issue. But it seems SUCH a good idea that I wonder why no condensing units have been designed with water in mind i.e. pipes/holes on top and a pan/return pump at the bottom. Hmm gotta build such a thing!

Would have loved to do geothermal but it's rock, rock, and more rock where I live and so finding a contractor (and a home builder willing to work w/same) was problematic when we built.



cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
kudos:7
reply to boogi man

said by boogi man:

and closed loop is far more efficient. the reason being that a well pump is usually min 1/2hp and frequently far more than that. vs a closed loop system that maybe uses a 1/4hp at most.

Depending on the installation, even considering the additional energy requirements, a GWHP has a better efficiency rating then a GLHP due to a more constant water temperature (cooler then return water in the summer and warmer in winter).


Ken
Premium,MVM
join:2003-06-16
Markle, IN

1 recommendation

reply to boogi man

said by boogi man:

and closed loop is far more efficient.

Absolutely not! Open loop is more efficient than closed in every single unit I have ever looked at. Here are just 2, but I have looked up other brands and they are all more efficient as open loop.

Bryant
Up to 4.6 COP (closed loop)
Up to 27.0 EER (closed loop)
Up to 5.1 COP (open loop)
Up to 31.5 EER (open loop)

Water Furnace



whoaru99

join:2003-12-17
reply to dolphins

said by dolphins:

The heat pumps they had in Jamaica took 2 days to cool the rooms with the thermostat at its lowest setting. They were probably old, had a low BTU rating or both?

Could be either or both. In some ways they're the same.

BTW, the temp setting of the thermostat doesn't affect the rate of cooling or heating.


boogi man

join:2001-11-13
Jacksonville, FL
kudos:1
reply to laserfan

overall system efficiency not just the heat pump itself.
--
my site



Ken
Premium,MVM
join:2003-06-16
Markle, IN

Open Loop still comes out ahead. Open loop pumps water lets say between 50 and 300 feet depending on your water table, closed loop pumps the same volume of water 600 feet. So you start with a more efficient heat pump and add half the pumping capacity and you are in even better shape. A closed loop which is less efficient to begin with, and on top of that you have to add basically 2 to 3 times the pumping capacity.



boogi man

join:2001-11-13
Jacksonville, FL
kudos:1

i don't see how you're coming up with 2-3x's pumping capacity. if that were the case the pumps needed for a closed loop system would be larger than the pumps needed for a well. 2.5gpm per ton in residential systems according to FHP is what's needed. now i can tell you that if you through the loops in contact with each other in the hole then yeah you'll lose some efficiency however a properly planned and executed closed loop system won't have that issue.

so if it takes 1/2hp to move say 5gpm out of the ground and takes 1/4hp to push 5gpm through a loop. which takes less energy?
--
my site



boogi man

join:2001-11-13
Jacksonville, FL
kudos:1
reply to Ken

I'd also like to point out that chart is not complete there is no mention of the EWT on the closed loop system.
--
my site



cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
kudos:7
reply to Ken

said by Ken:

Open Loop still comes out ahead. Open loop pumps water lets say between 50 and 300 feet depending on your water table, closed loop pumps the same volume of water 600 feet.

It requires less power to circulate water around a closed loop then it does to pump it out of a open loop (presuming typical installation)


Ken
Premium,MVM
join:2003-06-16
Markle, IN

Closed loop has much more pipe, and the pipe is much smaller leading to much more friction. I don't see how pumping water up 150 feet through a 1.5" pipe is going to cost more than pumping water horizontal 600 feet through a series of 3/4" pipes. However even if I am wrong, the fact that the open loop heat pump is more efficient you are still going to come out ahead. This is why people choose open loop, it's cheaper to install and cheaper to operate. I have never heard anyone try to say a closed loop is cheaper to run than an open loop.