Heat Pumps for dummies (beginners guide)

[temper]

Erm, excuse me for butting in but isn't this thread a little location-centric?

Heat pumps are of great interest to me but in my part of the world the exercise is to get heat OUT of the house not IN it...

[Daox]

The beauty about this thread is it can always be updated and changed and it can grow. Its really just in the beginning stages and still being built.

[temper]

And, of course, the beauty of heat pumps is that they work both ways.

[Daox]

I'm bumping this for more info.

[jeff5may]

Common Refrigerants

Today, there are three specific types of refrigerants used in refrigeration and air-conditioning systems:

Chlorofluorocarbons or CFCs, such as R-11, R-12, and R-114
Hydrochlorofluorocarbons or HCFCs, such as R-22 or R-123
Hydrofluorocarbons or HFCs, such as R-134a.

All these refrigerants are "halogenated," which means they contain chlorine, fluorine, bromine, astatine, or iodine. In practice, halogenated refrigerants only contain chlorine or fluorine atoms, since bromine and astatine-containing substances are highly toxic.

Refrigerants are classified into groups. The National Refrigeration Safety Code catalogs all refrigerants into three groups:

Group I – safest of the refrigerants, such as R-12, R-22, and R-502
Group II – toxic and somewhat flammable, such as R-40 (Methyl chloride) and R-764 (Sulfur dioxide)
Group III – flammable refrigerants, such as R-170 (Ethane) and R-290 (Propane).

Refrigerants are also divided into two classes according to toxicity:

Class A: refrigerants for which toxicity has not been identified at concentrations less than or equal to 400 ppm
Class B: refrigerants for which there is evidence of toxicity at concentrations below 400 ppm


Traditional Refrigerants

R-12
Dichlorodifluoromethane, commonly referred to as R-12, is colorless and odorless in concentrations of less than 20 percent by volume in air. In higher concentrations, its odor resembles that of carbon tetrachloride (aka R-10). It is nontoxic, noncorrosive, nonflammable, and has a boiling point of -21.7°F (-29°C) at atmospheric pressure. One hazard of R-12 as a refrigerant is the health risk. Should leaking vapor come into contact with an open flame of high temperature (about 1022°F), it can decompose into phosgene gas, which is highly toxic.

R-12 has a relatively low latent heat value, and, in smaller refrigerating machines, this is an advantage. Due to its properties, the automotive industry fell in love with it. As a result, it was used almost exclusively for air conditioning systems in vehicles until just recently. R-12 is a CFC and has been banned because of its high ozone depletion potential.

R-20
Trichloromethane, commonly referred to as chloroform, is no longer used as a refrigerant, thank God! However, it shares the same properties as many of the lower-numbered refrigerants.

R-22
Monochlorodifluoromethane, normally called R-22, is a synthetic refrigerant developed for refrigeration systems that need a low evaporating temperature, which explains its extensive use in household refrigerators and window air conditioners. It is nontoxic, noncorrosive, nonflammable, and has a boiling point of -41°F at atmospheric pressure. Being an HCFC, it is an ozone depleter, and has been phased out by attrition. What this means is that no new units can be built that use it as the primary refrigerant. However, there are still millions of working R-22 systems in operation today.

R-32
Difluoromethane is commonly referred to as HFC-32. It has a boiling point of -62 degF at atmoshperic pressure. It has zero ozone depletion potential and relatively low global warming potential. Due to its high heat of compression, it has not been aggressively exploited as a mainstream refrigerant. Instead, it is blended with other refrigerants to avoid high compressor discharge temperatures.

R-125
Pentafluoroethane is commonly referred to as HFC-125. It has a boiling point of -55.3 degF at atmoshperic pressure. It is considered to be the polar opposite of R-32 in the HFC family of refrigerants. Besides being blended with other compounds, it is also used as a fire extinguishing agent, and has replaced Halon in this realm.

R-134a
Tetrafluoroethane is very similar to R-12 in operation. The major difference is that it has zero ozone depletion potential. Noncorrosive, nonflammable, and nontoxic, it has a boiling point of -15°F at atmospheric pressure. Used for medium-temperature applications, such as air conditioning and commercial refrigeration, this refrigerant is now widely used in automobile air conditioners.


All of the above refrigerants are single compounds. When pressure is released or applied, they don't separate into fractions or decompose. Most of all, they do their job very well over a wide range of conditions. Until recently, they represented over 95% of all refrigerant used in consumer products of any type (refrigeration, heating/cooling, automotive, etc). However, they all have targets on their backs, marked by the EPA as bad for the Earth. They either eat the ozone layer, or are potent greenhouse gases, or both.

Modern / Retrofit Refrigerants

R-410A
R-410A is a non-ozone-depleting blend of two HFC refrigerants, R-32 and R-125. It has a boiling point of -55.3°F at atmospheric pressure. Due to this low boiling point, systems run at much higher pressures and refrigeration capacity than R22, and these in turn deliver performance benefits. It offers a better Energy Efficiency Ratio (EER) than R22. It is a suitable replacement for systems previously operating with R22. Many refrigeration and air-conditioning manufacturers have equipment specifically developed for R-410A. Chances are, if your existing R-22 system quits today, it will be replaced by a new system running on R-410A.

R-422A/B/C/D
The R-422 series of refrigerant blends are only approved for certain systems, and R-422A does not appear on EPA's list of approved HFCs. They are a retrofitting blend, designed to replace R-22 in refrigeration and air-conditioning applications. There is a sizable drop in efficiency from R-22. R-422B, C and D are all on EPA's approved list for use in new and retrofitted systems.

There are many more modern refrigerants being used today. These fall into the R-4xx or R-5xx numbering standard, and are all blends of previously developed refrigerants. They all have been invented to replace a particular traditional refrigerant that has been phased out of existence. Lucky for us, not much of this stuff is used in the residential sector. The only exception is R-410a.

Natural Refrigerants

Natural refrigerants are naturally occurring substances, such as hydrocarbons (propane, propylene, iso-butane), CO2, ammonia, water and (believe it or not) air. In general, they have zero ozone depletion potential, very low global warming potential, and operate well in a wide variety of systems. However, most natural refrigerants are not considered for retrofits in existing systems. Hydrocarbon refrigerants are extremely flammable or explosive, so extra safety measures must be integrated into products to prevent catastrophic failures in case a leak occurs. CO2 systems operate at extremely high pressures, so the refrigeration circuit must be made heavy enough to contain this high pressure. Despite the risks, many have been in use since the 1850's when refrigeration was invented.

R744 (Carbon Dioxide)
R744 can be applied in most heating and cooling systems such as mobile air-conditioning in vehicles and buses, vending machines, coolers, commercial cabinets for supermarkets, containers and climate control systems for residences. CO2 technology has also shown to be extremely efficient in heating water. This explains the success of the Japanese "Eco Cute" heat pump water heaters, which can also be combined efficiently with floor heating. In Japan, more than 300,000 CO2 based Eco Cute water heaters were sold in 2006.

R717 (Ammonia)

Ammonia refrigeration is the backbone of the food industry for freezing and storage of both frozen and unfrozen foods in many parts of the world (including fruits, vegetables, meat, poultry, fish, dairy, ice cream, beverages). In the range of 50 kW to 200 kW ammonia may be used, and for larger freezers ammonia is almost always preferred due to improved energy efficiency and reduced leakage.

Hydrocarbons (Propane, Propylene, Butane, Ethane, Ethylene)
R600 - Butane
R290 - Propane
R1270 - Propylene
R170 - Ethane
R1150 - Ethylene

By far the largest application for hydrocarbon refrigerants to date has been in domestic refrigerators and freezers. For example, R-600a (isobutane) is used in more than 400 million so-called Greenfreeze fridges and freezers worldwide. R-290 (propane) is used in commercial freezers & refrigerators.

Although largely ignored by policy makers to date, hydrocarbons have a long track record of safe, efficient and high performance use in mobile air conditioning systems in North America, Australia, many parts of South East Asia and other countries around the world. This strong empirical evidence of the suitability of hydrocarbons for use in servicing existing systems cannot continue to be overlooked in the urgent search for emissions abatement opportunities.

EDIT: In 2015, the EPA added Ethane (R–170), HFC–32 (R–32),
isobutane (R–600a), propane (R–290), and the hydrocarbon blend R–441A to its list of approved refrigerants. There are limits to this approval in residential refrigeration, air conditioning, and heat pump systems, but the approval itself is a testament to the future direction of the industry.

Many multinational corporations have adopted natural refrigerants as part of their business development plans. Coca Cola, Pepsi, McDonalds, Wal-Mart, and many others have begun changing their "old" equipment out with modern systems that use natural refrigerants. Literally millions of vending machines, display cases, and unit coolers have been installed worldwide. Due to this massive demand, natural refrigerants are gaining traction in an industry who has shunned them for decades.

The bottom line is this: if you have an existing heat pump or air conditioner, it probably runs off R-22 and it's living on borrowed time. If you purchase a new one, it will most likely be filled with R-410a. If you look hard enough, new units are available that use natural refrigerants.

[NiHaoMike]

And there's an emerging trend of "natural" refrigerants like hydrocarbons, water, and carbon dioxide. The latter two require special parts and would not be suitable for DIY use, but hydrocarbons are very good for DIY use.

Most common is R290 (refrigeration propane or dimethylmethane) and mixtures based on it such as R433b. (Note that it is much higher purity than camping propane, though there have been some attempts at purifying camping propane into refrigeration propane.) Main disadvantage is the flammability, but as the oil makes all refrigerants flammable, it's actually a much lesser problem than you might think for the small systems we typically work on. The interesting part is that hydrocarbons are actually very popular overseas.

Eco-friendly cooling | Global Ideas - YouTube

Hydrocarbon Referigerants VS Freon Gas - YouTube

R433b (often sold as ES22a) is designed as a general replacement for R22 in air conditioning, but it does work for heat pumps as well. R433a and R433c (often sold as ES502a) is somewhat better tuned for heat pump and refrigeration applications.

[jeff5may]

Choosing A Heat Pump That Works For You

If you are like most regular people, all of this information is rather foreign and confusing. You say, "Who cares what's inside the box? All I want is to be comfortable indoors! What's wrong with what I have now? Who knows, this setup might outlive me!"

Others may be more interested in improving what they already have for one reason or another, but there are SO MANY choices out there. How can one tell what's what? How can one be sure that a selected choice will work well?

There is a simple plan to follow to make sure the system you have is what you need after all is said and done:

1. Site survey
2. Realistic planning/budgeting
3. Proper installation and commissioning
4. Wise use and maintenance

[jeff5may]

The most important part in ensuring that your heat pump will do its job well is a thorough site survey. There are many systems operating inefficiently as we speak as a direct result of an insufficient site survey. Not only are these systems providing a lower level of comfort, they are wasting energy every day. Extra time, effort and money spent identifying what you have to begin with will pay for itself many times over during the life of the system.

A good site survey always begins with an energy audit. Even if your home is brand new, you cannot assume that there are no opportunities to save energy. Many power utility companies will perform an energy audit on your home for free. Others will refer you to a certified third party who may do the audit for free. Even if it costs you something, the information gleaned from the audit will provide you with valuable information.

Before the energy auditor visits your house, make a list of any existing problems such as condensation and uncomfortable or drafty rooms. Jot down a quick estimate describing the dwelling (square footage of heated spaces, number of occupants, which rooms are in use, typical summer and winter thermostat settings). Have copies or a summary of the home's yearly energy bills. (Your utility can get these for you.) Auditors use this information to establish what to look for during the audit, and having this information available beforehand will allow the auditor more time to focus on taking measurements.

When the auditors arrive, they will begin by assessing the outside of the property and/or asking you questions mentioned above. Your answers may help uncover some simple ways to reduce your household's energy consumption. Walk through your property with the auditors as they work, and ask questions. They should be using equipment to detect sources of energy loss, such as blower doors, infrared cameras, leak checkers, furnace efficiency meters, and surface thermometers. Simple "rule of thumb" calculations from sketchy measurements are not what you want.

Make sure the auditors are granted access into anywhere they ask. Equipment closets, roofs, attics, crawl spaces, and other usually unoccupied areas should be accessible. The more places they can look, the more information they can gather. The less places they look, the more gaps your audit will have in it, raising the uncertainty of the audit.

The energy audit should also include an appraisal of your existing heating and cooling system, if equipped. The overall heating and/or cooling efficiency should be measured. Ducting on both supply and return side should be evaluated. Airflow should be measured or calculated. They will also look at you water heating system.

Once the auditors are done gathering information, they may want to sit down and talk about their preliminary findings. If you are offered this opportunity, do not pass it up. These highly trained professionals are a valuable source of information. The whole experience may seem to be a sales meeting, and in a way, it is. That doesn't mean you're going to hurt anybody's feelings if you turn down their offer. But it will help you realize your goals and begin to form a plan.

Sometime after the audit is done, you should receive a written report detailing the findings of the audit. It should contain calculations of your heating and cooling loads, the relative energy efficiency of your home, and the condition of your equipment, among other things. It should contain recommendations of areas that need repairs or upgrades. It may or may not contain some kind of estimate as to the cost of labor and equipment.

Do not ignore the findings of this audit. Pay attention to any structural, health or safety issues found during the audit. Take heed of the items high on the list, as the auditors prioritize their analysis by what will pay for itself first. By recognizing these issues before any work is done, you may end up with a much more comfortable and valuable house in the end. In any case, the sooner problems with the home's energy efficiency are dealt with, the sooner you can start saving money. Addressing simple issues like adding insulation and sealing leaks can save you from needing a larger heat pump system, saving hundreds or thousands of dollars up front.

[jeff5may]

Now that a site survey has been performed, we have a clue as to the condition of the home, the heating and cooling loads, and any issues with the home. Now we can begin to put a plan together.

Take out your site survey and energy audit from the previous step. Look up your existing heat loss and load at the home's design temperature. This will serve as a baseline for consideration of options. With these figures, it becomes easy to compare heating and cooling systems and their relative cost vs. efficiency ratios.

Now is the time to decide whether to improve the existing structure or not, and how much. Take note of any recommendations in the energy audit and decide what to do or not to do. Estimate the cost and time frames of improvements and write them down. Depending on the home, this work may end up costing more than the HVAC work, but that's OK. This type of improvement has the potential to drastically alter the way your home feels and acts when the weather gets nasty. If the work drastically reduces your energy needs, you may not even need to upgrade your HVAC system in the end.

If it was decided to improve the structure, write down new heating and cooling load estimates for the modified structure. Use these figures for the lower limit of capacity for your heat pump system. If you figured correctly, a system sized to meet these needs will perform well for 98 to 99 percent of the year. For most, that's the best you can do economically. For those 5 or less awful days a year, the system should fight hard to keep up, running constantly. The temperature may deviate from the desired setpoint for a while if the system loses ground against mother nature. You need to decide if this is acceptable or not.

If it was decided that the Comfort Control system must cover 99.99 percent of the load, the heating or cooling side will most likely need a backup source. In most every home, there will be a particular area that suffers the most during extreme weather. This area tends to affect the rest of the home. If the area cannot be modified or isolated to avoid the effect, the backup source should pour its energy into this area. For heating, a natural gas unit or a single-zone, sub-zero rated mini-split is most cost effective. For cooling, a window air conditioner or mini-split unit can be installed to serve the extreme needs of the area. This backup source may be oversized to eliminate all doubt. Since it will only run in a temporary fashion, the most efficient design is usually overkill, as it will be much more expensive than a run-of-the-mill source, and not save that much energy overall.

That being said, every home is different, so a creative solution may be effective and viable. Many ecorenovators have devised simple mods to their existing systems to improve performance. It may be possible to eke out a few extra percent of efficiency that allows the system to cover temporary peak loads. This option may reap great savings or may not be possible at all.

After settling on design goals for the system, you may now begin to compare equipment. If you did your homework up to now, choosing equipment will be simple. Deciding which way to go is an exercise in personal preference and overall system goals as well as pricing. Reputable manufacturers publish all the data that you will need to determine suitability of their units in whatever conditions you may need to cover. They also publish tons of pictures of their units in various settings and describe the operating behavior and what makes their units unique. Some hype is always included, but if you do a fair amount of shopping around the hype will become obvious.

Once you have chosen equipment, you can assemble a system blueprint and assign dollar values for equipment and labor. If much of the work will be performed by contract labor, you can submit this plan to contract firms and begin to consider estimates for the job. If much of the work will be DIY, it is recommended to seek estimates anyway. This way, a professional can critique your plan and suggest other options you may or may not have considered. The pro may discover problems with the plan that cannot be ignored. If no estimates are requested, at least have a professional building inspector or engineer review your plan. The value of having your plan checked before the fact far outweighs its cost.

[student]

i have not done much work because i need to find out about the energy audit on the house i am planing to build (i have changed from stick construction to insulated foam block) once i know that i will re-ask the question of how long a ground loop i need and what size push pull pumps i need, but a great many thanks to all who write here, and the site operator.