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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.


DEnd 09-25-17 02:49 AM


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


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.


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


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.

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.

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