Greetings,
I am in the process of making a decision in regards to a heat pump. Currently I have a hot air oil furnace. Can anyone give me any pros or cons with a heat pump? What about the air controller verses geo thermal? What questions should I make sure and ask? Are there any brands that I should specifically stay away from? Currently I am looking at Carrier, Trane, and Lennox.
Thanks in advance.
Adam
Replies
Where are you located?
Growing old is inevitable, Growing up is optional.
Central Pennsylvania
The Air to Air kind lose their efficiency when it drops
below freezing.
Some simple broad web searches will give you the basics, but
for our northern climates they don't seam to work that well.
The ground source heat pumps do work well but cost an arm and
a leg to install.
My house in Maryland has a 2 year old Carrier "Infinity" air source heat pump.
I'm very happy with it, although if money were no object, I'd have preferred a geothermal system (which, in our climate and for a fairly small house, simply is not cost effective).
The air source heat pumps are practical and popular in our mid-Atlantic climate. The chief benefit is that it combines cooling and heating in a single unit, one that makes relatively efficient use of electricity, which is a clean and convenient power source. A previous poster already mentioned one disadvantage. Another disadvantge is that in winter, the temperature of the heated air at the register is lower than what you get from gas heat. So even though the average ambient air temperature may meet the set point, the blowing air can feel cool, not toasty warm. I don't mind this because we also have a wood stove. Proper sizing and a variable speed air handler help, too.
Carrier/Bryant, Trane/American Standard, and Lennox all have their supporters. Correct sizing and quality installation are much more important than the brand (though I do like the controls on the newer Carrier systems.) So, focus more on the contractor not the label. A good contractor will carefully estimate your heating and cooling load, not just go with a SWAG based on square footage. An over-sized unit won't dehumidify in summer.
Whether a heat pump is a good choice in Central Pa, I don't know. Ask around your area and see if people are using them. If you decide you want one, get the most efficient unit you can afford. The more efficient units tend to come with other benefits such as quieter operation and more sophisticated controls. In my opinion the variable speed blowers and 2-stage compressors are worth the extra money (though some people may prefer a simpler system.)
I just had a Bryant system installed very much like Tom21769 recommended. I had an old Williamson gas fired unit that was functioning fine but the utility bills were getting bad. I live near Cincinnati Ohio and all people I trusted said go with a hybrid system which is what I did. The two stage outside unit stays on the lower setting most of the time. My wife told me last months utility bill was the lowest we ever had in 30 years. The Seer rating on the outside unit is 18. The gas unit in the house is a 90+ efficient system that has not even kicked on yet. I did a lot of duct sealing myself before having the system replaced. It took a lot of time to do it right and I think that helped a lot also.
There is one air/air heat pump (perhaps the only one) that is specifically designed for use down to -30 F. Do a search on the "Acadia" from Hallowell (I may have that spelling wrong). It is a two-stage affair, with all the defrosting done automatically.
Making a judgment about ground source heat pump being too expensive really depends on the particular situation. In many cases, there is a rather large cost associated with either drilling vertical wells or excavating a large area for horizontal loops. However, if you already have a well enough hundreds of feet deep for domestic water supply, AND the house is very well insulated so that the required heat load is not huge, AND groundwater is plentiful where you are, so that the well bore fills with water not too far below the surface (or is artesian), then you may be able to use the Standing Column Well GSHP design. You need something like 80 feet of water column per ton of heat load (12,000 BTU/hr). You'd certainly want to have a company experienced in doing these design and install one.
If your house is not well insulated, then you would be better off spending he first chunk of money on making it so. Reduce the heat demand before looking for a cheap source of heat.
I suppose Central Pennsylvania gets hot enough and cold enough that geothermal might make sense, but you have to do some homework to figure out if it saves enough on utility costs to recover the up-front costs in a reasonable pay-back time. Unless you just want bragging rights. Or you think the added comfort (or absense of an outside compressor, etc.) is worth any amount of extra money you're likely to pay.
Just wanted to say thanks to everybody. You gave me some good pointers to take into consideration. The one big thing that I keep asking myself is rather or not the extra money for geothermal is worth it. I have a tendency to go overboard sometimes but I usually am satisfied with the end results.
Thanks for your help.
go overboard on the insulation and air sealing first - the payback will be a lot faster
As Mr. Russell pointed out ... and I fully agree ... geothermal MAY OR MAY NOT be expensive to install ... depends on the site situation. Geothermal ... er ground source heat pump systems are very efficient.
You will need a backup heat source for your heat pump as someone pointed out (e.g. natural gas).
A air source heat pump is not a good choice in cold winter locations ... feel out what other people are using ... The guy in Maryland is good to go it sounds like, but PA ... not sure. If your average winter temp is say higher than maybe 38-40, then the heat pump will likely be a good bet ... under 32, it starts becoming marginal.
Quick question here.
Why is a back up heat source always spec ed for heat pumps?
Power outages knock out several other forms of heat, what's
so different about this ?
What may be implied is that more typical air-source heat pumps, in mild climates rather than in really cold winter areas, are designed/optimized to run with air temperatures down into the 30s. If the climate is mild enough, that covers most of the time. For those once-in-a-while cold snaps, when either there isn't enough surface area in the evaporator coil to move heat from the outside air to the evaporating refrigerant at the reduced temperature difference, or even cold enough that the outside air is colder than the refrigerant evaporating at its minimum temperature, then backup heat is needed. This usually is in the form of electric resistance heating on the exit of the blower.For an air-source heat pump in a cold winter climate, it really needs to be designed to work in really cold air temperature. Either that, or put in a combustion-based system, to be used when the heat pump won't cut it. Then you at least have A/C when needed, plus heat-pumped heating for a good part of the cooler times of year.Of course, GSHP is largely independent of time of year. Nice when it's a good fit for the situation.
In the heating mode ... for when it's too cold ... see Mr. Russell comments. The refrigeration cycle (reversed) only works down to e.g. 30 degF where the efficiency begins to take a nose dive ... not to mention the condenser freezing up.
Beauty of the GSHP is the constant temp of 'outside' (i.e. the ground). Rather than trying to extract heat out of e.g. 30 degF outside air, it is doing it from 55 degF ground temp ... so you maintain high efficiency even when it is below zero outside. The GSHP system is good in the colder climates for this reason. Otherwise, the air source is not a good choice for that application.
This is a reply for Mr.Russell also.
Well I was thinking in terms of a GSHP ( because that's what we have).
The unit itself has a backup resistance heat mode. Is it really that common for the bottom of a pond to drop below freezing? or three
feet in the earth if that's the case?
I wonder if it's necessary or just that these are unusual and
cause worry.
When the heat pump craps out from a freon leak or ineffective heat transfer, you don't want to have anything to keep DW from ripping off the possibility of future children?
BTDT. They always die in December when it's 10 below outdoors. Always. Expect it to happen at the worst time. Cause it will.
I hear you, but that's true of any heat source.
We've got a wood stove so I'm not worried but curious.
2 heat pumps.
Wood furnace and 10 cords of wood.
4 rooms with electric baseboard (not been turned on in ten years)
10kW standby gen and a month's fuel
Coupla a' feather beds.
Shop with wood stove and couch.
Do I need anything else for heat, other than DW?
Trying to hijack this thread a bit. My father-in-law is hard bent on a GSHP for an old house he has inherited. I've talked insulation and windows and sealing and he is agreeable to that but "I want geothermal!" must be something about the free heat.We are on the shore of lake superior and can tap lots of 45-55 degree water from very shallow wells (sandpoint) year-round. I can't find information on the flow rate and temperatures required for an open system. I'd like to do some of the work myself. Can you or someone out there on the internets point me in the the right direction for info? Products?
Books?Ted
flow rate
Figure on 10 GPM capability needed minimum.
Lots of web info, google GSHP, etc. Water furnace, et. Al. adds will be on the right hand site. good surfing.
Water source heat pumps typically have cataloged performance data ranging from 1.8 to 3.4 gpm/ton for both heating and cooling, with cooling entering water temperatures ranging from 45 to 120 degF, and from 25 to 86 for heating. At least that is the data we publish for our units. For sizing pumps and pipes, I use 3 gpm/ton. In the cooling mode (which dominates selections most of the time), lower entering water temperatures and higher water flow rates yield greater efficiency. There is a point of diminishing return with greter flow rates. If the difference between 17.7 SEER vs 19.7 SEER requires twice the water flow rate, the additional efficiency might offset the additional pumping costs. But then agian, it might not.
As with any HVAC equipment selection, it begins with a required capacity. How much heat is needed and how much cooling is desired?
Most manufacturers provide performance tables in their equipment catalogs and most are availlable online.
Thanks Tim. The capacity requirement will depend on how much insulating and sealing, new window efficiency etc gets done. is there a ton to BTU conversion? This is primarily a heating application. What units do you make/sell in N. IL? Thanks again . Ted
One ton of "refrigeration" is the equivalent of 12,000 btu/hr of energy transfer.
The reason I used quotes, is that a heat pump is a reversible refrigeration cycle.
I work for the Trane Company in Wisconsin. I live just south of the border, in front of the "cheddar curtain".
I, too, live just across at the cheddar curtain (the northern or white cheddar curtain). Thanks for the info and the smile.
Great input ... just what this discussion needed.
Done properly a GSHP should need no backup heat at all. The ground has a huge capacity at a great temperature ... no need for 'backup' because it should always work for you.
If your pond is small, it may not have the capacity you need ... and the temp (due to convective currents in the water) may end up at 32 degF ... still better than outside air temp if it's cold. Horizontal buried loops are typically down at 4-6 ft where you should have plenty of capacity to stabilize the source temperature for the system.
If the pond is small, you could actually cause it to freeze. Normally you would look for a larger body of water ... although I don't think it has to be too large.
Thanks for the feed back.
The pond was made to the manufacturer's specs.
Minimum 1/4 acre
At least 8' deep They ran extra coil horizontally in the ground for
paranoia's sake.
The systems been working fine for twelve years now.
You confirmed my suspicion, that there's no more
reason then any other kind of system.
They are building McMansions at the local lake and running lots of pipe out into the lake for HP's. I wonder what will happen when Bubba's anchor on his jon boat gets to it.
Hate to think of all that anti-freeze in the lake.
A non-toxic anti-freeze, such as used in RV, would be used for that. I think that it would also be used in a closed loop burried or drilled system..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Yeah my "Geothermal" guy told me that.
He also said you never have to change it.
You'll have to pardon my sceptacism.PS
You wouldn't believe how I tried to spell
sceptacism! Thank the lord for spell check.
Air source heat pumps have been installed in Whitehorse, Yukon. We have a -40 design temperature which needs no converting (-40 C. = -40 F.). It is generally not cost effective to operate the hp below -20 C (-4 F). I recently inspected a new installation at the home of a heating and refrigeration contractor. He wants to have real life data he can use to help sell the units but at $25k a pop, it will be tough sell.
It helps to understand how much heat is in the air if you use the Kelvin scale instead of the (useless) Farenhite scale. That is, water freezes at +273 K (0 C.) and absolute zero is 0 K. So -20 C (-4 F) is +253 K.
If your average winter temp is say higher than maybe 38-40, then the heat pump will likely be a good bet ... under 32, it starts becoming marginal.
The efficiency of a heatpump drops when the temperature falls below 0F, but above that (e.g. 32F) they are fine. Heat pumps are commonly used in Western and Central PA, because the temperature rarely falls below 0F.
The pros to heat pumps are that they can be more energy efficient and that one unit does both heating and cooling. The cons are that they tend to have shorter lives and that some people feel the heat is "cold" and less comfortable. However, a properly sized humidifier will moisturize the air to overcome the second objection.
I've seem many graphs that show heat pumps are cost effective well below freezing point. Of course efficiency drops with outside temperature. 60F would be more efficient than 50F and so on, but as long as the cost to operate is lower than resistance heat then it is "more efficient".
A thousand watts of resistance heat gives approx 3500BTU's of heat and a heat pump using 1000 watts of electricity (compressor,fans etc) should give you over 10,000Btu's of heat in optimum conditions. When outside temp drops and the air becomes moist(a bigee) your heatpump BTU's will start to drop. As long as you get more than say 3500 BTU's of heat per 1000 watts you are ahead of the game.
Of course, how you figure all that out is a problem:)roger
Right ... and usually this break even point is around 32 degF ... that and the freezing factor ... if you have to defrost often, that is accounted for in the drop in efficiency as well ... e.g. if your COP is say 1.5 at 32 degF, but you have energy expended for defrost, then it may have a net below 1.0.
Certainly systems can be designed to maintain efficiency at lower temps, but systems aren't designed like that ... they have to balance the heating and the cooling and the cost of the equipment, so generally most manufacturers provide some optimized designs that perform down to around 32.
The problem with EFFICIENCY at cold weather is not that much of a problem. It is EFFECTIVENESS.Heat pumps can have a COP (effiency) well above 100% below zero.And one needs to compare the cost of alternate heating to see when to replace or supliment the heat pump with the other source.However, the real limitation is that as it get colder the heat pump puts out less and less heat.At the same time the house requires more and more heat as it gets colder.The point at which the heat pump can't supply all of the house requirements is called the balance point.And the heat pump needs to be sized for the AC loads and that limits the amount of heat that it can produce unless you have multiple stage equipment.While it will vary I have heard that the balance point is typically around 30-35.So below that pump you need to supliment the heat pump..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks for some good clarification there, Bill. Good stuff.
However, the real limitation is that as it get colder the heat pump puts out less and less heat.
At the same time the house requires more and more heat as it gets colder.
The point at which the heat pump can't supply all of the house requirements is called the balance point.
It's certainly true that as it gets colder, a heat pump puts out less heat. However, the decline in heat output is minimal, down to 0F.
What you have named the "balance point" is below 0F. If you look at the specs for a heat pump, this becomes clear.
As an anecdotal reference, I have lived in several houses with heat pumps. The only time the emergency heat came on was during a freak winter when the temperature dropped to -20F. At our normal 0F or so low for the winter, the heat pump was just fine and could readily heat the house to 75F.
"It's certainly true that as it gets colder, a heat pump puts out less heat. However, the decline in heat output is minimal, down to 0F."COMPLETELY FALSE.http://www.arthurhewett.com/id26.htm#copLook at this data.30* - 38,800 BTU
20* - 35,100
10* - 29,800
0* - 23,300Basically a stright line reduction in heat output."What you have named the "balance point" is below 0F. If you look at the specs for a heat pump, this becomes clear."Again compeltely FALSE.The heat pump specs don't have that information.You also need to know the heat load requirments for the building.This shows the balance point for ONE example.http://www.arthurhewett.com/id26.htm#hp_balance_chartIt comes out at 32. And numbers in the range of 30 to 35 have been what I have typically heard. But again it depends on the house load and the sizing of the heatpump.If the suppliment heat source is one that can operate in conjuction with the heat pump then the heat pump can still supply a significant amount of the heat well below the balance point.That is show in the table below the chart..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"It's certainly true that as it gets colder, a heat pump puts out less heat. However, the decline in heat output is minimal, down to 0F."
COMPLETELY FALSE.
Sorry, Bill, but your opinions don't change physical law. The information I posted is correct.
You also need to know the heat load requirments for the building.
This statement I agree with. Whether or not a heat pump will supply sufficient heat at any temperature, including between 0F and 32F, clearly depends on the heat requirements and therefore the heat loss of the building. Taking extremes, no heat pump could heat the world, while essentially any heat pump could heat a thermos bottle.
As the chart on the Canadian site you linked in another message shows, for a typical situation (whatever that is - they don't really say) the decrease in efficiency of a heat pump is minimal between 32F and 0F. I realize that's not what their text says, but it is clearly what their chart shows. I'm guessing the engineers did the chart and the marketeers did the text.
""It's certainly true that as it gets colder, a heat pump puts out less heat. However, the decline in heat output is minimal, down to 0F."COMPLETELY FALSE.Sorry, Bill, but your opinions don't change physical law. The information I posted is correct."As referenced in the other message for a 5 ton Lenox CHP16(R-651-653 heat pump here is the heat output vs OAT.30* - 38,800 BTU
20* - 35,100
10* - 29,800
0* - 23,300I will let the other people viewing this thread decide a decrease in output from 38,8000 BTU to 23,300 or 40% is MINIMAL or not.", for a typical situation (whatever that is - they don't really say) the decrease in efficiency of a heat pump is minimal between 32F and 0F. "As some one that claims to be an engineer I find that it is surprising that you don't understand that changes in effiency does not affect when the balance point.Rather it is the heat capacity of the unit with does decrease by a MINIMAL AMOUNT of 40% from 30 to 0F for this example..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
guess I got mixed up who was saying what ...
While the output 'only' decreases by 40% 30 to 0 degF ... personally, I think a drop in output of 40% is significant. But as I think someone pointed out ... the load in the graph must be accounted for as well ... to establish the balance point. So while the output of the equipment goes down a whopping 40%, the LOAD on that equipment INCREASES by 75% over that same range!
Put the two together and you have a significant potential defficiency in equipment capacity whereby your backup heat MUST be used and that will affect the net COP of the heat pump ... that is, the COP drops below 1.0 ... and as it gets colder, the reversal/defrost must be used more frequently ... also adding to the affective drop in COP. Yes, you could oversize the HP, but standard practice does not do that ... it's simply not economical.
Bill's chart and the explanation is clear. We aren't saying a heat pump won't work below the balance point ... just that the benefits of the heat pump (i.e. high COP) drops off and it becomes uneconomical to use the heat pump.
This chart is commonly used in the HVAC industry to illustrate the points being made. To say or imply a HP works perfectly fine to 0 degF is, I feel, misleading. Below the balance point you should have your backup heat running (regardless of whether the HP is running or not). That is why you don't use HPs in cold climates w/ average winter temps below 30 degF.
Edited 7/19/2008 1:52 pm ET by Clewless1
As some one that claims to be an engineer I find that it is surprising that you don't understand that changes in effiency does not affect when the balance point.
I don't "claim" to be an engineer, I AM an engineer. You have claimed to be an engineer, but have said you aren't licensed - which is required, by law, to practice engineering in the US.
Furthermore, based on your profile posted on another forum, your background appears to be digital electronics and DSP - so this is outside your area of claimed expertise. From prior discussions, I have learned that you have never submitted a product to UL for approval and don't understand that process, that you don't understand op amp circuits and virtual grounds, and that you don't understand inductive coupling. I guess I will need to add heat pumps to the list.
I could take your tack and post a bunch of inane, poorly written links that support my points, but you would just post more obscure, contradictory links, and that could go on forever. One of the problems with the internet is you can find a link that says almost anything. In any event, it seems pointless to argue with you or try to educate you. As I have said before, I cannot teach you to be an engineer via this forum.
For those considering a heat pump, the best advice is to talk to a knowledgable local professional. There are many factors that affect the comfort and success of a heat pump installation. While heat pumps are commonly used in areas with temperature ranges within 0 F - 110 F, that doesn't necessarily mean that it's the right choice for your area, even if it is within the range. In addition, HVAC folks often have biases - against heat pumps, for example - for reasons such as past customer complaints that may have more to do with customer misunderstanding than equipment insufficiency.
Edited 7/19/2008 7:33 am ET by woodturner9
So's you ARE an engineer. What type? Civil , Mechanical, nuclear, there's all types.
In the real world, where people have to interact with real people, sometimes those with excessive education wear that education on their sleeve. They believe everyone HAS to know it. And everyone better DAMN well respect it.
This is a well known condition with those that must work with PhD's. Oh, they're smart and well informed, but they have absolutely no common sense in the pursuit of their being right.
You may very well be correct about the efficiencies and performance - in theory.
But, if'n I needed a HP, and some overly confident engineer type told me it would be fine down to zero, one of two things would happen:
1. I would swallow his line. But I would be watching the subsequent electic bill and performance of that machine like a freakin' perv at a strip club. And once that thing failed to perform like he said, he'd be out there nonstop, making it do so - under warranty - until DW was as happy as a clam. If he couldn't, I'd be finding another overly educated and arrogant type (lawyer) to "discuss" the situation with him.
2. I'd laugh like a hyena and throw his #### out the door.
Sometimes, the educated make fools out of themselves in the real world. Sometimes they don't.
I've had to fire several engineers for behaving as such. They think they know all, but when the tire meets the road, I get rather upset with paying them their fee while I educate them.
I'd suggest your intense support of your position is indicitive of other issues.
But I would be watching the subsequent electic bill and performance of that machine like a freakin' perv at a strip club. And once that thing failed to perform like he said,
Ahh, but you are making the assumption the engineer was wrong. If a competent engineer specified the system, and it was implemented to his or her specifications, it would be fine.
As you implied, every trade and profession has it's biases. Techs and contractors often feel that engineers "wear their education on their sleeve" and "lack commonn sense". So they do what they think is correct rather than what the engineer designed. That's why we have bridge collapses, failing decks, collapsing buildings, etc.
I don't mean to belittle the trades - they are every bit as important as the engineer. It works best when we work together - and not well at all when either side thinks they "know better".
To answer your question about my background, electrical and mechanical.
"If a competent engineer specified the system, and it was implemented to his or her specifications, it would be fine.""So they do what they think is correct rather than what the engineer designed. That's why we have bridge collapses, failing decks, collapsing buildings, etc."I have a lot of respect for engineers, but your comments make it sound like an engineer is never wrong. Do you want to rethink that?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
I have a lot of respect for engineers, but your comments make it sound like an engineer is never wrong.
I did not intend to imply that at all. Engineers are human, and like all humans, sometimes make mistakes. There are checks and balances, though, that SHOULD catch most mistakes before they are implemented. The trades are an important part of those checks and balances - they often will ask when something doesn't "seem right", and find errors the engineer overlooked. Sadly, some engineers circumvent those checks and balances and "look down" on the trades (just as some tradespeople look down on engineers).
It's a system, involving engineers, tradespeople, inspectors, etc. to (in theory) ensure that nothing "falls through the cracks". When the system works, quality construction results. When one person in the chain has an attitude, the system doesn't work so well.
required, by law, to practice engineering in the US.
Not 100% true. In the commercial building field, maybe yes.
There were very few registered engineers on the teams who designed the space station and commercial aircraft. State regualtors would not have a clue how to formulate a 'test' for most of aerospace applications. Engineering registration mostly a 'protect my legal butt' and to raise revenue by the states mostly.
I think the reference was to building technology and applies to both residential, commercial, and idustrial. I've had to have a professional stamp on my residential project.
I assume the talk about engineers ... the guy says he's a mechanical engineer ... I assume that mechanic experience is in HVAC vs one of the other many fields of mechanical engineering. Few HVAC engineers were actually trained (i.e. educated) in building technologies; unfortunately. Hopefully they were lucky enough to mentor with someone that was actually skilled and knowlegeable in HVAC. This tends to be an on-going problem in the HVAC industry.
Few HVAC engineers were actually trained (i.e. educated) in building technologies; unfortunately. Hopefully they were lucky enough to mentor with someone that was actually skilled and knowlegeable in HVAC. This tends to be an on-going problem in the HVAC industry.
I'm curious what led you to that conclusion. Not sure exactly what you mean by "building technologies", but to become a licensed PE in ME requires a thorough knowledge of HVAC.
That's not to say there aren't a LOT of contractors and engineers working outside their field of expertise. If you find a PE working outside his expertise, report him - one of the legal requirements for a PE is NOT to work outside their expertise.
At the same time, if you have an HVAC contractor that can't or won't do a manual J calculation, get another contractor - that contractor will be unable to install an efficient system.
Experience led me to that conclusion. I've met very few HVAC engineers that had an HVAC mechanical engineering degree ... very few colleges/universities offer HVAC based engineering degrees. Most HVAC interns (college graduates) have little knowledge of the building design or construction process when they first start out.
By 'building technologies', I'm referring to building design science and engineering as opposed to engineering that may relate to many other disciplines that have little to do with building design. The typical mechanical engineering degree may have a handful of classes (if they are lucky) associated with building design science.
In the Northwest where I hail from ... I understood that an engineer could (legally) practice engineering in whatever area of engineering he was comfortable with regardless of what discipline he took the exam in. Much like architects generally can practice and stamp any part of any building design that he is comfortable with (e.g. electrical, HVAC, structural). Most don't choose to do that, but I've seen many regularly do structural and/or HVAC systems design.
While I respect your comment about Manual J ... just because he can't or won't do manual J doesn't mean he is incapable of installing an efficient system ... he's just unable to design one. I know ... symantics. I know a lot of trades people who do very good work ... if they are told what needs to be done ... they just know very little about how to actually design and choose equipment.
In the Northwest where I hail from ... I understood that an engineer could (legally) practice engineering in whatever area of engineering he was comfortable with regardless of what discipline he took the exam in.
That is my understanding as well.
While I respect your comment about Manual J ... just because he can't or won't do manual J doesn't mean he is incapable of installing an efficient system ... he's just unable to design one.
I agree. However, in many areas, it's common practice for the HVAC installer to select the equipment, particularly for residential replacements. In those cases, the installer's ability and willingness to accurately determine the building load will directly impact efficiency and comfort of the system.
absolutely agree
required, by law, to practice engineering in the US.
Not 100% true. In the commercial building field, maybe yes.
Don't really want to reopen that debate, which we have had many times on these boards, but some state have an "industrial exemption" that allows people to be titled as engineers if employed by a company that manufactures a product. Otherwise, engineers must be licensed to practice "engineering" - and engineering is a term defined by law.
So, an unlicensed person cannot (legally) say "I am an engineer". If they fall under the industrial exemption, they can say "my job title is engineer". However, if they do any work that affects public safety, they must still be licensed.
http://www.oee.nrcan.gc.ca/publications/infosource/pub/home/Heating_and_Cooling_with_a_Heat_Pump_Section7.cfm?Text=N&PrintView=N
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Methinks someone is confusing F with C.
Methinks someone is confusing F with C.
It appears he is confused about more than just that.
I've been taught/told otherwise ... below around 30-32 degF the efficiency drops dramatically (and you get freezing on the condenser). I'd be surprised if it was otherwise.
below around 30-32 degF the efficiency drops dramatically (and you get freezing on the condenser). I'd be surprised if it was otherwise.
You are welcome to be surprised, but if you read the specs on a heat pump, you will see that the efficiently drop between 32F and 0F is only a few percent.
Alternatively, ask an engineer, if you are not comfortable with this engineer's experience and knowledge.
BTW, heat pumps operating below 32 F periodically reverse the cycle briefly. This keeps the coils from freezing.
Heat pumps can be nice, BUT ....
The Achille's heel of the heat pump is winter. Simply put, they fall short on the 'heating' side of the equation. The colder your winter, the more you will need supplemental heat. The heating units that come with heat pumps tend to be very expensive to operate.
So, don't skip the step of also providing for winter heating.
I just took a brief look at the Hallowell site, describing the Acadia cold climate heat pump:
http://www.gotohallowell.com/vsheatpump.htmlA technical paper mentioned there shows that the theoretical COP for pumping heat from 0 F to 70 F is over 7. Of course, with refrigerant evaporating somewhat below 0 and condensing somewhat above whatever hot air temperature is desired (say over 100 F), plus mechanical losses, then the actual COP is going to be less. The site gives some measured info.What's interesting is that, as oil heat cost goes up, while a lot of power generation in the US remains via coal, not dependent on crude oil cost, then the cost of oil heat is approaching that of electric resistance heat, and so any type of heat pump ought to be way ahead of oil heat in terms of cost.Side thought: I was thinking about the cost of crude, $140/barrel, and all those barrels of crude pumped. Are those "deposit" barrels?
Another vote for the Air to Air heat pump. All of the pros and cons have been listed already. Everyone told me what a fool I was when i replaced my heat pump with another 5 years ago. They had (have?) a bad rap for awhile. I made the choice based on my needs in my home and the heat pump wins hands down. I am in central MD with electric resistance backup. My wife stays home and keep the woodstove going when temps drop below 20 or so (which is not often)Meanwhile the cost of oil and propane are going through the roof. And all those same people that are paying big $$ for their heating oil and propane are crying the blues. My electric rate is still 4.4 cents per kWh. About to double to 8.8 cents. But my electric heat will still be cheaper than propane or diesel if current trends hold. To say central PA is a bit misleading. Central PA can be VERY cold in the winter or fairly moderate. Central PA is a term that covers a wide area geographically with some fairly drastic differences in winter climate. One poster mentioned to put your $$ into insulation and air sealing versus a GSHP. I agree 100%. I've spent the past few years sealing ducts and wiring holes in the wall top plates. Last year replaced all windows and wrapped house with Tyvek when replacing the siding - the difference has been noticeable and dramatic.
I'm not an expert but I can give you an end user point of view. We lived in Wisconsin for a while and there were no heat pumps. To cold.
The thing I liked about the heating in Wisconsin was that after a snow it was quiet outside. And that was in town. If it was a snow day all the kids ( and some grownups) would come out and play. In the evening after a snow it was just magical some times.
In Kansas we lived out in the country and had a heat pump. It didn't work very well at all when it got cold. Cheap noisy piece of junk imo. Underline cheap.
Going outside after a nice snow is something I will always like to do and one of the reasons is because of the sounds, or lack there of.
Edited 7/17/2008 5:22 pm ET by popawheelie
i reside in central pa and have an all electric house with a lenox heat pump and air handler, was kinda of concerned when i bought the place 8 years ago. However I find it heats the house well even on the coldest days but it is very dry heat. I did have a problem with a part in the heat pump which they claimed cost 900 dollars in labor (was able to get off for 450 since they failed to give me an estimate as i requested) for a 35 dollar part (saved the 35 dollars cause it was under warranty) and a problem with the air handler and this was approximately 5 years after the house was build. By the way my electric bill as averraged about 70 per month.
Dan