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-   -   Portable Ac with heat single hose for winter heating ? (https://ecorenovator.org/forum/showthread.php?t=5430)

ecomodded 09-23-17 02:46 PM

Portable Ac with heat single hose for winter heating ?
 
Edit ~ To get to modifications implemented and required follow the link to post # 91
http://ecorenovator.org/forum/geothe...eating-10.html

Going try using a single hose portable 14,000 Btu Honeywell ac with 11,000 Btu heat for the fall and winter heating season.

The usual day and night low winter temperature is between 1*c / 33*f and -5 / 22*f

The unit I picked up has a Cop of 2.75 and has no cold temperature limit mentioned assume because its a single hose unit. It says is good for winter heating and ends there with no temp info.

As it scavenges heat from the warm inside air and exhaust cold air the outside temp can be much lower then a dual hose unit if my understanding is correct

The single hose units are reported to output about 30% of the air it conditions threw the rear vent. The Honeywell unit in question airflow is 245 cfm 30% of that is about 75 cfm so that's its loss threw air infiltration.

I'm thinking the single hose will allow me to run it all winter well that's my expectation.

It will be placed in the basement of a split level home with a open stairway so air natural convection will heat the upper floor or so I'm hoping.


Should mention the basement has its own cracks to feed it with as well as the rest of the house has its little cracks and air infiltration being a mid 70's split level house.

In this case what do you think ? will the single hose Ac/ heater save me money on heating or will draw to much cold air from cracks to make it transfer the heat upstairs ?

I'm thinking the single hose would allow me use it in colder winter weather including at night.

I have not found any info on people using a single hose unit as I described I have read that single hose units are best for one room cooling due to the negative pressure I'm hoping that with it in heat mode its convection will heat the upper floor despite the units negative pressure.


Am I being way too hopeful or what you think offhand ?

Im second guessing myself for buying it and not dual hose i was thinking the dual hose would not work well during the night and on cold days due to its poor cold weather performance. I payed $350 for it delivered or about 1/2 price.

jeff5may 09-23-17 11:11 PM

I ran a few of this type of unit while I was trying out the same concept. There are two ways to approach this concept:

1. put the unit in the cold and blow in warm air
2. put the unit in the warm and blow out cold air

I found that method 2 works very well with the portable aircon units. The things recirculate a lot more warm air than they do cold air. The one I ended up using all winter was a non-reversible, cooling-only model. It was pointed towards a window, and the cold air exhaust was sealed up with xps foam boards against the cracked open window opening. I toyed with trying to recirculate some outdoor air into the evaporator, but found it made the evaporator frost up. The family called it "the wolf" because the squirrel cage condenser blower howled (quietly). It did a good job of keeping the inefficient gas furnace shut off until temperatures dropped below maybe 40 degF.

oil pan 4 09-24-17 11:10 AM

Those things are junk.
But better than nothing, but only by a little.
So glad I replaced mine with a 2 ton inverter split.

ecomodded 09-24-17 12:12 PM

That is reassuring to hear , I should be fine with this units reduced outlet flow

It was a rush purchase they were almost sold out of the single hose units with just 1 left so bought it haphazardly spuriously after quickly deducing it would be better of the two styles for winter heating.

I'm hopeful it will work fine its good to get some input on heating as most people cool with these it seems.

A electric heater down in the rec room heats up the top floor real nice. If I don't heat the basement room the stairway and front door area are chilly all winter long. That air mixes with the living room kitchen and dinning room air.

So with it will be heating 1/3 the basement and the 2/3 of the top floor with 1200w of juice.

That works out to $55 @ 12hrs use or $110 @ 24hrs continuous use.
The coldest months pay as much $300 per month with baseboard heating , $1200 a yr

The owners of the dual hose models defend them strongly for summer cooling I have to agree with those arguments as the temp difference is only 20 to 30 degrees.
Where as winter temps are more like a 60 to 70* difference.

It will be vented from a pellet stove outlet left in place from the previous owners. Currently has a 4 inch vent the AC vent is 5.9 inches.


First thought was to use a 6 to 4 reducer after reading up on it appears it may cause too much of a restriction

In my head I deduced a 4 inch outlet would reduce the airflow by about 1/3 which should reduce the air infiltration by the same amount.
A win win I thought before reading papers on airflow vs pipe diameter.

After checking it looks like a 4 inch vent might reduce the airflow by 50% to 70% if I understand it correctly.

So its looking like I will use the same size vent outlet to keep the units efficiency up.

ecomodded 09-24-17 12:33 PM

Quote:

Originally Posted by oil pan 4 (Post 55645)
Those things are junk.
But better than nothing, but only by a little.
So glad I replaced mine with a 2 ton inverter split.


Im not staying in my house for much longer 1 yr tops so this is a quick fix for this fall winter heating season and I'll leave in place for the next owners.

If this crappy unit cuts my electric bill in half or there about I will call it a complete success and a worthy purchase.

If it doesn't do that I would have to agree they are junk as I bought it save money not spot heat

I will update the thread as its usefulness or lack thereof unfolds over the upcoming months starting next week.

It will make good use of a vent that's in place if its successful it might pay for itself in the next 3 months, time will tell

ecomodded 09-24-17 01:43 PM

My latest deduction is this

The unit is 275% efficient vs baseboard it draws in 1/3 cold air from air infiltration

So it has a added loss of 1/3 that is re warmed at 275% efficiency rate

So its worse feature is padded by the high efficiency making for a win win no matter how I look at it as compared to baseboard heating.

I could not find one person who thinks along those lines on the internet the HVAC guys know little about these crappy units so their input was always flawed in some way.

A good discussion I found was on "the straight dope" forum - Portable air conditioner - one hose or two?

I learned how not to look at it by reading that forum more so could see the errors in the logic even though it was talking about cooling not heating. I had to reconvert the discussion to my heating needs.

This thread may well gain some attention as there is practically no info on heating with a portable ac with heater on the web not in my search results anyways

A simple query turned into a confusing topic.

Although still not 100% if the negative pressure will or will not hold the warm air in the downstairs room.

That is going need to be tested directly to see if this thing is a win or loss

I'm assuming the first few paragraphs I wrote are correct

Ormston 09-24-17 03:28 PM

1 Attachment(s)
I like the idea but struggle to see it working.
The only way i see it heating the house by more than the power consumption is if the air expelled from the outlet hose is colder than the outside temperature.

Assuming the outlet hose expels air at 0C and the outside temp is 0C, take a look at the attached sketch (I used a cop of 4 to make it easier to see)

Steve

Attachment 7907

oil pan 4 09-24-17 04:02 PM

The problem with these units when heating or cooling is the air they draw into the house to move heat.
They work alright cooling since they are drawing in air that is maybe 10 to 30F degrees warmer than what they are trying to cool. The real problem comes when the temperature difference is 50F or more.

ecomodded 09-24-17 04:44 PM

Im not sure you have it correct in the diagram ?

its not what I expect from a heat pump it may well be correct , I don't feel its correct as you left out the input COP which turns that 1kw of cold into heat and the output with its heat stripped out

the unit will turn 2/3 of the interior warmth back on its self at a hotter temperature expelling 1/3 cold and bringing in 1/3 more for a continuous cycle.

The air that comes in allows the cycle to repeat gaining 2/3 the Btu it expels out the back.

As long as the interior is within working temp it will scavenge the heat and reject the 1/3 of colder conditioned air.

So it will heat more then it cools while in heat mode.

1kw in gets turned to 2.7 kw in heat with 1 kw back out for a gain of 1.7 kw


As its a heat pump it must do better then the 1 to 1 performance the diagram has.


Im thinking ( yikes) the chart needs adjusting , the air expelled has 2000w of Cop of heat removed and saved in the house using a 2.7 Cop cycle and a 1200w power draw.

Its the heat concentration that makes the gains or what am I missing ?

ecomodded 09-24-17 05:00 PM

Quote:

Originally Posted by oil pan 4 (Post 55650)
The problem with these units when heating or cooling is the air they draw into the house to move heat.
They work alright cooling since they are drawing in air that is maybe 10 to 30F degrees warmer than what they are trying to cool. The real problem comes when the temperature difference is 50F or more.

When in cooler mode the manufactures suggest the owners of the two hose models plug the intake outlet and use it as a one hose unit if the temperature difference is high and / or if the humidity is high to get the unit to work more effectively.

Im not sure how that relates to energy savings , it does increase its effectiveness or ability if you exhaust them and let them draw in air from cracks etc

NiHaoMike 09-24-17 05:39 PM

Direct the cold air up towards the ceiling.

ecomodded 09-24-17 05:50 PM

I did read manufactures say these portable AC heaters were to be used for heating between 40 and 50*F


My thinking was they were talking about the dual hose Models well that was my assumption , you know what they say about those ..

the facts are a heat pump moves heat from once place to another

The way its placed it will move cold from the room and expel cold out the back at a Cop of 2.7 bringing in new air to run continuously.

Hopefully it heats for me this winter or its Junk as far Im concerned as Jeff suggests
I feel pretty good about it Im hopeful anyways as that 75 cfm air coming in and out allows 245 cfm of air to be conditioned

ecomodded 09-24-17 06:13 PM

Quote:

Originally Posted by NiHaoMike (Post 55653)
Direct the cold air up towards the ceiling.

Do mean the cold intake air ( probably just a typo and you mean Hot air) anyways the intake comes in threw cracks and out the back of unit and out the vent.


I will be directing the hot air up to the ceiling so we are thinking similar just different criteria, I want heat upstairs

Thinking I will sit the unit on a table so the vent will go straight out a old pellet stove vent , then tape a cardboard duct to the units cold intake that leads to the exhaust and extend it down low to the floor so it will draw cooler floor air out the back of the unit and out of the rear vent. Then direct the front heat vent upward toward the the rooms roof and out the doorway that leads to the stairway and upper floor.

Might hang a blanket in the rec room doorway with 18 inches of space at the top of the door and 12 inch gap at the bottom so the house will have good convection.

As right out that doorway two flights of stairs are leading to the upstairs where I hang out.

So the downstairs room will be like a breathing and heating room for the house

The house is a open concept so the stairway and front door has no walls upstairs just a iron railing to separate the stairs from the living room etc.


Its good to get input as its a challenging premise using a little unit like this

Ive invested money into this thing so have a little tunnel vision going not too much I hope.

I guess worse case scenario is it can be use in the milder weather if so I'll call it a wash.

I will put it on a power meter and see what kind of economy it provides as it is the house uses $20 to $25 a month in electricity without heat so the bills will be easy to decipher.

NiHaoMike 09-24-17 10:46 PM

The idea is that since heat tends to rise, directing the cold air up in heating mode offsets that and reduces losses through the ceiling. You'll have to experiment to see if it's more efficient than directing it outside after accounting for leakage.

jeff5may 09-24-17 10:55 PM

Ok, here's my take on what you're figuring. The compressor uses maybe 1000 Watts up from the power line. Some of this is radiated from the compressor shell directly and some superheat is added to the cool refrigerant as it passes by the motor coils. The rest is used up as work of compression. As the preheated and compressed refrigerant condenses, all of the added superheat is dissipated before the gas condenses. So there's your standard resistance heating component. The fans don't count, as they are not using lots of power, and are either both adding to indoor heating or subtracting heat from each other.

As the refrigerant condenses, it gives off lots of heat. It is then subcooled a few degrees. Due to the high surface area and high airflow, heat recovery is effective. Lets say that x amount of airflow heats up 9 degrees F in one pass through the condenser. The warm air rises naturally away from the unit. Between the compressor radiation and forced air convection, there's your 14K BTU of raw heat gain.

On the other side, the room air is sucked through the evaporator at a slower rate and is cooled by the evaporating refrigerant. Let's say that x/3 amount of airflow is cooled 30 degrees F. This cold air is exhausted outside. Let's say 12K BTU makes it outside. So you lost 2K BTU in leakage between everything everywhere. That's 12K BTU NET HEAT GAIN.

This arrangement works well because the x/3 amount of infiltration (make-up) air is not always as cold as the exhaust air, especially in spring and fall. When it is warmer outside than your exhaust air, let's say 35-40 degrees F, the system is gaining BTU from your make-up air. With a 1-pipe setup, the delta T is always going to be low, as both heat exchangers are being fed room temperature air. As a result, the evaporator is not going to frost up on you (more latent energy rejection down the drain as condensed humidity), and the unit COP remains high. Even when it is frosty outside, the recirculated BTU (drawn into the refrigerant in the evaporator and rejected into the house) is much more than the power drawn from the power line. The gradients from (the make-up air minus exhaust air) and (outdoor air minus exhaust air) subtract from the overall refrigerant heat transfer.

With a 2-pipe setup, the evaporator is fed cold outdoor air. The delta T works against outdoor temperature, and so does COP and condenser discharge temperature: as outdoor temperature drops, they all get worse. As outdoor temperature approaches freezing, the evaporator can frost up fast, then the unit loses its advantage. Efficiency really depends on lots of stuff that is usually not included in these rigs, like variable expansion valves and hot gas defrost. That's why the makers discourage 2-pipe use below about 40 degrees F: passive defrost using ambient airflow to thaw out the evaporator is slow, plus the compressor is shut off.

ecomodded 09-25-17 12:56 AM

NiHoaMike that would be a easy install plug it and let it run , where do see the heat gains coming from ? is it in the refrigeration cycle ?

I know of heat gain by enthalpy of moisture vapor in the room , not sure where other gains are made , Where or what are you thinking it will make gains in a closed loop system ?
Maybe enthalpy in the cooper tubing ?

Im thinking the trick is to scavenge the heat from the room and blow out condensed cold air to the outside vent leaving the condensed heat in the house.

Like this

70* house air gets cycled and exhausted back to the house at say 110*

With a 2/3 smaller volume of air being chilled down from 70* to say 35* on the cold side and expelled.

The heat gained is scavenged from the outlet air with a bit more from the enthalpy of water vapor to liquid.

I don't know the cycles well at all , can you explain your Theory ?

~~~~~~~~

After reading Jeff5mays post again I see the magic is right there in front of us

Quote Jeff5may

The compressor uses maybe 1000 Watts up from the power line. Some of this is radiated from the compressor shell directly and some superheat is added to the cool refrigerant as it passes by the motor coils. The rest is used up as work of compression. As the preheated and compressed refrigerant condenses, all of the added superheat is dissipated before the gas condenses. So there's your standard resistance heating component.

So its condensation in the unit that makes up the mystery heat , if I understand it correctly

ecomodded 09-25-17 01:14 AM

Jeff5may I am following you on your understanding its the one I guess I need to work with and pretty much convinced that's how it will work for me as a few People have had the same suggestion.

It will be depended on the intake temp vs outlet temp.

Unless part of the refrigeration cycle makes up more heat then air infiltration would cause in losses

I don't know of what cycle that would be if it exists , Maybe NaHoemike has a idea

jeff5may 09-25-17 01:33 AM

The main idea is this: as long as the evaporator doesn't freeze up, the one pipe setup will work as best it can. The reducer coupling on the exhaust pipe may or may not keep the evaporator from freezing. Rig it up and see if the unit short cycles. It might not do it until it gets pretty cold outside. If it does, a bigger exhaust pipe will probably keep the unit going, but by then the make-up air will already be eroding at your net heating factor. Trial and error will figure it out. Compared to a baseboard heater, the little heat pump has a long way to fall before it is less efficient, watt for watt.

Ormston 09-25-17 01:53 AM

We are talking about a heat pump, it doesn,t create, destroy, amplify, magnify, concentrate or otherwise pull heat from the ether.
It's only purpose in life is to move heat from one place to another.

In your case it is pumping heat from inside the house and blowing it back inside the house for a gain of nothing.
Some chilled air gets blown outside, so long as this chilled air is colder than the outside air that infiltrates the house there will be a net heat gain.
Once the outside air temperature drops to equal the temperature of the outlet duct the gain will be nothing.
When the outside temperature is below the outlet duct temperature you will be pumping heat out of the house.

Virtually all of the electric consumed will degrade into heat and end up in the house.

What you need to test is what is the temperature of the outlet hose when the device is sat in a room at the temperature you maintain during the winter.

As the only gain is the temperature difference between the outlet duct air and the external air this is where your answers are.

Steve

ecomodded 09-25-17 02:00 AM

The idea is 1200w will make 11,000 BTU of heat at a 2.7 COP gain
In practice this may well not work as its a semi closed loop ?

Part of the heating equation is heat loss by conduction threw walls making the house part of the systems usefulness of it.

So the interior air needs heat added on a regular cycle as the house cools by conduction and air infiltration.

Its sounding like both jeffs are thinking the same as you Ormston thats 3 people so far sounds like we have this dog figured out

ecomodded 09-25-17 02:18 AM

I read and like your updated explanation on post #15 jeff5may , it has the info that was evading me

Ormston 09-25-17 02:42 AM

The COP and amount of heat output are measured/calculated under a certain set of test conditions.
As there test setup likely did mot involve exactly what you are looking at doing then the ratings are meaningless.

My guess is that if inside your house is 20C and the outside air temp is 20C you will likely achieve a COP of 2+ or whatever the rating says.
As the outside temperature falls you will get a lower and lower the COP will also fall until it is cooling not heating the house.
What you need to figure out is what outside temperature this will work down too before becoming useless.

Steve

DEnd 09-25-17 02:49 AM

Quote:

Originally Posted by ecomodded (Post 55659)
NiHoaMike that would be a easy install plug it and let it run , where do see the heat gains coming from ? is it in the refrigeration cycle ?


The issue is the heat doesn't stay in the house. You are basically adding energy to the air and it will move as fast as it can outside the house. A major path of this energy escape is the stack effect. And that combined with outdoor air temps is what determines how well your unit will be able to add heat to your house cost effectively.

Basically the unit works because of the Delta-T (difference in temperatures) between the inflitrated air and the unit's exhaust air. At some point when the inftrated air is still a bit warmer than the discharge air it effectively becomes a house exhaust fan with a resistance heater attached (all electrical devices are in effect resistance heaters). Where the point of cost effectiveness is depends entirely on how much leakage your house has. Remember the stack effect pushes out warm air and pulls in cooler air that then needs to be heated. That cooler air accounts for between 30% and 66% of the BTUs needed to heat your home. Fans can easily overpower your stack effect, so when you end up pulling more than ~2.7 times the amount of natural air infiltration then you are automatically at the point of it's cheaper to use resistance heat. But that's not the actual point it doesn't become cost effective. Where it looses cost effectiveness (against resistance heat) is at the point where the recoverable BTU's in the infiltrated air is less than 2.7 (or whatever the COP of your unit is) times the amount of BTUs to bring that air up to room temperature.

DEnd 09-25-17 02:58 AM

Quote:

Originally Posted by Ormston (Post 55665)
As the outside temperature falls you will get a lower and lower the COP will also fall until it is cooling not heating the house.
What you need to figure out is what outside temperature this will work down too before becoming useless.

Steve

Not quite in this instance. Since the unit is working solely indoors, it is also using heat from other sources. That outside air is first warmed before it hits the unit. It's measured COP should be about what it is rated at.

ecomodded 09-25-17 10:17 AM

That's how I see it too DEnd ( with my uneducated mind )

I try to put a like by the posts that could guide us / me and future readers to the correct theory / data ( as I figure at the time )

All the replies deserve a thanks , Thanks as posting theories leads to more questions and understandings

ecomodded 09-25-17 10:28 AM

The unit should run at near peak efficiency 24-7 due to the constant warm air it breaths.

Everyday is a warm day with it inside so its in peak efficiency while it works any air in is mixed and cycled threw in the house in peak efficiency.

So that 30% cold air out allowed 70% to be Super heated

The next 30% cold air in/out repeats the cycle endlessly , gaining 70% threw the heat pumps conversion of a kw of electricity to 2.7 COP of heat energy 24-7

Hope my understanding is sound or Im as lost as ever !

Please do point out any errors in that premise as I would like to fully understand the cycle

ecomodded 09-25-17 11:24 AM

I have anemometer / wind meter so will be able test the units rear vent airflow and post real numbers to play with.

It may well exhaust closer to 20 or 25% then 30% as some web info suggests.

I will try the unit using a 6 to 4 inch reducer to fit the current vent and see how it runs.

I have the reducer already it a quality one with a smooth transition so flow will be less impacted.

Thinking the velocity will increase and noise when the reducer is in place so flow losses will be minimized. In a HVAC set up they use branches and vent size to control air flow to different areas of the building so those flow rate reductions do not apply to this set up or so I now deduce.

I'll test the flow differences when the unit arrives and post the difference.

As a bonus we will get some actual numbers to compute with. the web posts say 30% flow out for the last 10 yrs of posts , things may well of changed for the 2016/ 17 models.

Ormston 09-25-17 12:47 PM

Quote:

Originally Posted by DEnd (Post 55667)
.... Since the unit is working solely indoors, it is also using heat from other sources. ......

Unless those other heat sources are outside the thermal envelope of the house you're stealing heat from one part of the house to give to another.
So no net gain.

ecomodded 09-25-17 01:30 PM

The gains come from the COP it will always be there 24-7 the small influx of air will not cancel out the heat pumps Cop.

This might help clarify losses vs gains

Many houses have a heat exchange for fresh air intake that can run as high as 70 CFM

People heat their house fine with or without COP from a heat pump to supplement the heat exchanger losses.

I look at it as the air infiltration is just one loss to overcome and part of the heating bill as is conduction threw the walls floor and roof it all has to be overcome.

Which is why the heater is used in the first place. In short it will run more often but still save money over electric baseboard heat.

To overcome any losses by air in or conduction out the heat pump runs *longer* to heat the space the saving grace is the 2.7 COP it has while running

Again if I understand it correctly

ecomodded 09-25-17 02:08 PM

an example of how much a family of four living in a typical 1970’s 2-storey house with a full basement and three bedrooms could save in ventilation costs by replacing an air exchanger with a high efficiency ENERGY STAR rated HRV. A typical air exchanger for a house of this size, providing ventilation to the whole house would use 960 to 1080 kWh a year.

Replacing it with a high-efficiency HRV that uses 340 to 400 kWh a year results in a 65% reduction in energy costs associated with ventilation.

https://www.cmhc-schl.gc.ca/en/inpr/...images/3_3.JPG

That's a years costs above the non energy star models are around 50% efficient


The air in and out is not a big source of loss compared to the COP gains of this little one hose ac heat pump
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Will operating costs increase my electric, heating or cooling bill?

An HRV/ERV requires service and electricity to run the fan but it provides an opportunity for heat recovery. All homes need ventilation air that must be heated in winter and may be cooled and dehumidified in summer. John Bower (1995)1 calculated the cost for 80 CFM of continuous balanced ventilation in several U.S. cities, including Minneapolis, Minnesota, with and without heat recovery. A typical annual cost of 80 CFM of continuous ventilation was calculated at $86 with heat recovery and $188 without heat recovery. Of these amounts, approximately $42 is the cost of the electricity to run the 60 W fan).2 Systems requiring the furnace fan to run continuously will have additional costs for operation. Continuous operation of a typical furnace fan for heating or cooling and circulation would range from $0.40 to $1.00 per day.

ecomodded 09-25-17 02:59 PM

If after reading the previous post if you still don't have a understanding of how this could work read Jeff's #15 post again.

It helped me to understand that the theory that it works is actually a fact.

Quote:

Originally Posted by jeff5may (Post 55658)
Ok, here's my take on what you're figuring. The compressor uses maybe 1000 Watts up from the power line. Some of this is radiated from the compressor shell directly and some superheat is added to the cool refrigerant as it passes by the motor coils. The rest is used up as work of compression. As the preheated and compressed refrigerant condenses, all of the added superheat is dissipated before the gas condenses. So there's your standard resistance heating component. The fans don't count, as they are not using lots of power, and are either both adding to indoor heating or subtracting heat from each other.

As the refrigerant condenses, it gives off lots of heat. It is then subcooled a few degrees. Due to the high surface area and high airflow, heat recovery is effective. Lets say that x amount of airflow heats up 9 degrees F in one pass through the condenser. The warm air rises naturally away from the unit. Between the compressor radiation and forced air convection, there's your 14K BTU of raw heat gain.

On the other side, the room air is sucked through the evaporator at a slower rate and is cooled by the evaporating refrigerant. Let's say that x/3 amount of airflow is cooled 30 degrees F. This cold air is exhausted outside. Let's say 12K BTU makes it outside. So you lost 2K BTU in leakage between everything everywhere. That's 12K BTU NET HEAT GAIN.

This arrangement works well because the x/3 amount of infiltration (make-up) air is not always as cold as the exhaust air, especially in spring and fall. When it is warmer outside than your exhaust air, let's say 35-40 degrees F, the system is gaining BTU from your make-up air. With a 1-pipe setup, the delta T is always going to be low, as both heat exchangers are being fed room temperature air. As a result, the evaporator is not going to frost up on you (more latent energy rejection down the drain as condensed humidity), and the unit COP remains high. Even when it is frosty outside, the recirculated BTU (drawn into the refrigerant in the evaporator and rejected into the house) is much more than the power drawn from the power line. The gradients from (the make-up air minus exhaust air) and (outdoor air minus exhaust air) subtract from the overall refrigerant heat transfer.

With a 2-pipe setup, the evaporator is fed cold outdoor air. The delta T works against outdoor temperature, and so does COP and condenser discharge temperature: as outdoor temperature drops, they all get worse. As outdoor temperature approaches freezing, the evaporator can frost up fast, then the unit loses its advantage. Efficiency really depends on lots of stuff that is usually not included in these rigs, like variable expansion valves and hot gas defrost. That's why the makers discourage 2-pipe use below about 40 degrees F: passive defrost using ambient airflow to thaw out the evaporator is slow, plus the compressor is shut off.


Ormston 09-25-17 03:40 PM

Sorry my understanding of heatpumps does not allow for heat to be created from nothing.

Please don't waste any money on this.

Steve

ecomodded 09-25-17 04:14 PM

Please enlighten us with your understanding of heat pumps particularly the refrigeration cycle.
I love learning its my favorite past time

Ormston 09-25-17 04:24 PM

Quote:

Originally Posted by ecomodded (Post 55689)
Please enlighten us with your understanding of heat pumps
I love learning its my favorite past time

It's in the name "Heat Pump" it pumps heat from one place to another.

A GSHP pumps heat out of the ground into the house.
A ASHP pumps heat out of the external air and into the the house.
A Fridge or freezer pumps heat from inside the appliance to the radiator on the back.

Your idea involves pumping heat from inside your house to inside your house:eek:

ecomodded 09-25-17 04:39 PM

O.k So I can deduce from your answer that you are not familiar with the Refrigeration cycle. Until you delve into it on your own and teach yourself how it works you will be ignorant as to how the COP is made

ecomodded 09-25-17 05:07 PM

Jeff's explanation explains pretty elegantly and clearly and his numbers are damn close

The 14000 BTU ac I picked up makes only 11,000 Btu in heat 14,000 in cool mode.

The loss Jeff explained in his post (his estimate was 12,000 Btu ) account for the lower heating efficiency of the unit in heat mode same as the manufacture claims.

Jeff5may knows his refrigeration , I mean did you get what he said ? Its real information that accounts for the 2.7 COP

That 2.7 Cop turns 1200 watt input power into 3240 watts of heat energy.

Hence the gains from "nowhere"

ecomodded 09-25-17 05:54 PM

How I got the COP number of the portable ac heat pump

Rated input power 1200 watt
Rated Btu (heat) 11,000 Btu

1200 watt to Btu = 4095 Btu

Divide 4095 Btu into 11,000 Btu = COP

11,000 Btu divided by 4095 Btu = 2.68 COP

The unit will more then likely draw 1150 to 1175 watts pushing the COP up past 2.7

1150w draw puts the COP at 2.8

ecomodded 09-25-17 07:56 PM

With this indoor heat pump I should buy a cheap HRV / heat recovery vent and put it in the same room as the AC.

It would work great with this pump , it could be wired off the Ac's fan power line to run at the same time. Im going to scout one out right now.

I love that idea

edit - They are too costly new about $750 to $1000

NiHaoMike 09-25-17 08:16 PM

Quote:

Originally Posted by Ormston (Post 55690)
Your idea involves pumping heat from inside your house to inside your house:eek:

Still a net gain if you take from where it's not needed and send it to where it is needed.

ecomodded 09-25-17 08:32 PM

To clarify it makes heat and rejects cold

It doesn't just move it around that would be a Vent its more complex then a Vent.

That pesky 2.7 COP has to come from somewhere and its the refrigeration process and Enthalpy.

You will get it


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