Help with Replacement HVAC Proposals

RMund98RDecember 23, 2011

My home needs a new HVAC system because the 18-year old heat pump compressor locked up. The house is in Columbia, Maryland. It is a two-story colonial built in 1978. The unfinished block-wall basement, where the heating and air handler package is located, is 844 square feet. It has no air return and two operating registers cut into the single main trunk; those registers are opened in the winter and closed in the summer. The 844-square foot first floor has the larger air return high on one wall with floor registers throughout. The 972-square foot second floor has a return in the hallway ceiling that is about half the size of the first floor's, plus floor registers in the four bedrooms and two bathrooms. All windows are Anderson low-e, dual pane insulated. The house has a dark brown shingled mansard roof. The house front faces east. All windows are on the east and west sides.

As with many houses of this age and style, the second floor is hotter in the summer. This problem can be offset with constant operation of the air handler fan, keeping the temperature differential to 2 to 3 degrees.

This is an all-electric house; no natural gas in the neighborhood. All-in electric rate is 15 cents per kilowatt-hour.

The electric supply wiring to the indoor and outdoor units is aluminum.

It is possible that I will not stay in this house beyond 10 years.

In 1993, though it was operating relatively well, I decided to replace the original GE 2.5 ton heat pump and air handler/heat package on the theory that it had little useful life remaining and the local utility rebates for more efficient packages were enticing. The replacement units were Lennox: HP22-311 2.5 ton heat pump and CB19-31 air handler with 15 kW 3-element heating. A Honeywell Chrontrol III thermostat controlled it. Perhaps because the original thermostat cabling was short, more cable was spliced on the outside of the house, resulting in an electrical-tape-wrapped knot of wires exposed to the elements.

The 1993 installation was done in May. It was cooling season and, as soon as the system was operating, I started having indoor humidity problems. Humidity levels ranged from 60 to 70 percent. I was told that the old ductwork was not working well with the new high-efficiency units. In an effort to cure the problem, the manufacturer told the installer to replace the air handler's blower motor with one of lower horsepower. The theory was that the less powerful motor would run more slowly and allow the chilled air to lose more humidity. This had a negligible effect on the problem. No other help was forthcoming. My remedy was to run two dehumidifiers in the basement that brought the upstairs humidity down below 55 percent.

During heating season, the heat pump gave me ample heat without using the auxiliary heaters: 95-degree outlet air was quite welcome.

Over the years, in addition to the humidity problem, the Lennox system has suffered other problems: defrost control board died in first year; high-pressure cutoff has tripped at least 5 times, though the 6-month inspections showed no pressure problems; the air handler fan motor failed in year 15; the indoor and outdoor units' motor start capacitors have been replaced three times each; until I plugged it, a quarter-sized hole in the bottom of the heat pump allowed mice to take up residence in the unit. Thanks to having a all-inclusive and expensive maintenance agreement, these problems cost nothing extra to repair.

I have received replacement proposals from four companies and a fifth proposal is in the works. The state's energy fund rebate and the Federal tax rebate expire at the end of 2011, so I won't include them in pricing as it may be 2012 before the system is installed. Some manufacturers' rebates expired in the middle of December, just a few days after the heat pump died. I wasn't ready to make a quick decision and didn't have all of the proposals so I lost out on those rebates.

I told all of the representatives about the summer humidity problem and that I liked having a system that gave me ample heat in the winter.

Proposal 1 is from the company that has had the maintenance agreement for 13 years. It is rated best in the county by the local county magazine, though the ratings are based on reader (and, perhaps, employee) voting. Angie's List has no reports on it. The company has been in business since 1979. The person who visited did not inquire as to the square footage of the house or the number and type of windows.

This proposal said the existing 33-year old refrigerant lines would be kept in place, as would the existing thermostat wiring. I was told the manufacturer requires connections to the air handler be made with copper electric supply; a junction box would be mounted on the outside of the air handler and the aluminum wire transitioned to copper at that point.

Choice A) Carrier Infinity 16 25HNB636 two-stage heat pump; Infinity FE4ANF005 air handler; Infinity Control thermostat; 16.5 SEER; cost $8,850.

Choice B) Carrier Performance 25HCC530 heat pump; Performance FV4CNF002 air handler; Carrier Digital thermostat; 15.0 SEER; cost $5,790.

Choice C) Carrier Comfort 25HBC530 heat pump; Comfort FB4CNF030 air handler; Carrier Digital thermostat; 13.0 SEER; cost $4,550.

Proposal 2 is from a company that got an "honorable mention" in the county magazine. I know nothing about it except that it exists and that it is a Trane dealer. Angie's List has no reports on it. The person who visited did not inquire as to the square footage of the house or the number and type of windows. I mentioned that I had read that Honeywell made Trane's thermostats and he said I could save a few dollars by using Honeywell instead of the Trane model. When the proposal arrived by e-mail days later, it said:

Remove all old equipment from jobsite.

Install a Trane XL15i 2�-Ton Heat Pump. Heat Pump to sit on new pad with pump ups.

Install a variable speed Air Handler with new auxiliary Heater.

Revamp ductwork to accommodate new Air Handler.

Run refrigerant lines connecting Air Handler and Heat Pump.

Re-wire high and low voltage at Air Handler and Heat Pump.

Install Honeywell Programmable Thermostat.

Start and check system.

Cost $6,485.

When I asked for the models numbers associated with the above proposal I received the following:

Trane Heat Pump - 4TWX5030A1000A

Trane hyperion Air Handler - TAM7A0B30H21SA

Honeywell Thermostat - TH8320U1008


Proposal 3 is from a larger company that bought out the company that installed the current Lennox. It got an honorable mention in the county magazine. Angie's List gives it a grade of B. The person who visited did not inquire as to the square footage of the house or the number and type of windows. He used to work for the bought-out company. 13 years ago, I was not impressed by the abilities of the technicians who serviced my system after the buyout and switched to the Proposal 1 company for service. This person said no changes were necessary to the aluminum electric supply cable and that the coolant lines would be replaced. The proposal was printed by hand and is hard to read.

"Good" Option) Trane XL15I; Outdoor Unit 4TWX5030; Indoor Unit TAM7A0B30; Thermostat TCONT802AS320A; 15.75 SEER, 9.5 HSPF; cost $8,570.

"Better" Option) Carrier 16; Outdoor Unit 25HNB636; Indoor Unit FE4ANB003; Thermostat Infinity Control; 16 SEER, 9.1 HSPF; Cost $8,938.

"Best" Option) Carrier Inverter; Outdoor Unit 25VNA036; Indoor Unit FE4ANF003; Thermostat Infinity Control; 19.2 SEER, 10.5 HSPF; Cost $13,704.

Proposal 4 is from a company that was recommended to me by someone who knows some of the employees but may not be familiar with the quality of their work. Angie's List gives it a grade of A but lists only three reports. It has been in business since 1969. The representative took the time to ask about the square footage of the house, measure the windows, and count the number and type of doors. The proposal was e-mailed to me the next day and also (not expected) dropped off at my house in a tote bag with a company logo. A follow-up phone call came two days later. This company won't change the aluminum electric cable, will install a fused outdoor disconnect, will replace the thermostat wiring to the outdoor unit, and will replace the coolant lines.

Level 1) Lennox Heat Pump XP21-36; Air Handler CBX40UHV-42; Thermostat CS7000; Air Cleaner HC16; "EvenHeater" 4-level heat package; LSOM package; 18 SEER, 12.5 EER, 8.5 HSPF; cost $8,720.

Level 2) Lennox Heat Pump XP16-36; Air Handler CBX40UHV-30; Thermostat CS7000; Air Cleaner HC16' "EvenHeater" 4-level heat package; 16 SEER, 12.5 EER; 8.5 HSPF; cost $7,156.

Level 3) Lennox Heat Pump XP14-30; Air Handler CBX40UHV-36; Thermostat CS7000; 15 SEER, 12.5 EER, 8.5 HSPF; Cost $6,578.

Proposal 5 is from a company that had all A grades on its 11 reports on Angie's List. Otherwise, I know nothing about it. The company owner was at my house 20 minutes after I called him. I have not yet received the written proposal. The person who visited did not inquire as to the square footage of the house or the number and type of windows. This company will reuse the aluminum wire and install a fused outdoor disconnect. The owner said the 33-year old existing coolant lines are of far better quality than what is available today and he would reuse them. The information listed is from our discussions so I may not have specific model numbers.

Option 1) Carrier Heat Pump Infinity 20; Air Handler FE4ANF005; Thermostat Infinity Control; cost $8,462.

Option 2) Carrier Heat Pump Infinity 16; Air Handler FE4ANF005; Thermostat Infinity Control; cost $6,735.

Option 3) a basic unit yet to be specified.

My initial reaction is that Proposal 5 Options 1 and 2 are bargain priced.

Thank you in advance to those who comment and provide guidance me. I know this post is lengthy but I tried to be as thorough as possible.

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Yes, you have way too many quotes and really expect too much from a forum like this.

I would insist on a load calculation for your home, in writing, and on the software letterhead. Numbers not to be transposed. You and dealer should agree on the design temperature to use both inside and outside temp.

Ductwork should be thoroughly inspected. I would ask about adding a return in basement and if not recommended, the reason why.

I can't see your home from here. The humidity issue bothers me and needs further evaluation. Where is it coming from?

Reusing and flushing a refrigerant lineset is a big deal if lineset is not to manufacturer specs to the condenser/system selected. Size is important and this is not a small detail to toss aside.

I would not purchase a new system for your location/climate that did not have electronic demand defrost.

Any other heating source in your home other than the HP system?

New system should be installed and updated to all codes. Do dealers quoting intend to pull a permit from the local governing authority?

Here are my minimum specs for a new HP system.

these are the minimum specs you should be looking for.
both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset
10 yr warranty on parts and compressor

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

My personal recommendation is Trane/AmStd, Rudd/Rheem, and Carrier/Bryant.

Depending on your location, I would not purchase a new system that did not have electronic demand defrost.


    Bookmark   December 24, 2011 at 10:41AM
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I think I like the Trane XL15 quote from proposal 2 for the price of $6,485. I like the fact they are running new refrigerant lines. The 2.5 ton size seems appropriate for your house. I don't understand why your old unit was de-humidifying. It is possible it was fan speed related. Unless 2.5 tons is too big for your home and you didn't get long cycles during the hot humid weather your old unit should have dehumidified just fine unless the fan speed was to fast.

The carrier comfort 15 quote from proposal 1 for $5700 isn't bad either but I would like a new lineset, and I think I prefer trane over the carrier since it has demand defrost.

    Bookmark   December 24, 2011 at 12:19PM
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I want to see load calc.

2 1/2 ton may be borderline.


    Bookmark   December 24, 2011 at 12:26PM
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After reading many other posts to this forum, I thought this the right place to ask my questions. You suggest it is not the proper forum. Can you recommend other forums that may be more suitable?

You say I have way too many quotes. How many quotes would be the right number?

You say my dealer and I should agree on a design temperature. Can you give me an example?

The system has never had a return in the unfinished basement. What would I gain from having one? It seems to me that the lack of one allows me to create a basement-only zone. That zone can be warmed and dried by a dehumidifier during the summer and does not contribute cold return air that must be heated during the winter.

Indoor humidity was not an issue with the original 1978 GE 2-1/2 ton heat pump. It became an issue when that system was replaced with Lennox in 1993. The only source of humidity of which I am aware is the sump pit in the basement but that hasn't changed in all these years. I live alone and don't cook. Except for showers, little humidity is added to the upstairs.

You say I should buy a system with electronic demand defrost. I have brought that up with every representative and all tell me that all the systems they proposed have this feature, be they Trane, Carrier, or Lennox.

Beside the heat pump, the other source of heat for the house is the auxiliary/emergency electric strip heat built into the air handler.

Only one of the proposals specifically mentioned obtaining proper permits.

You say that a 2-1/2 ton unit may be borderline. Is that borderline too much or too little? Most of the systems proposed to me have a two-stage compressor with low stage being around 2-1/2 ton and high stage being 3 ton.

You say your personal recommendation is Trane/AmStd, Rudd/Rheem, and Carrier/Bryant. In that order or are they equal? Why? How does Lennox rate?

    Bookmark   December 24, 2011 at 9:04PM
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Not all brands have demand defrost. Carrier doesn't. Their version is an improved version of the basic time/temperature.

Trane/Am. Std, York/Luxaire/Coleman, Rheem/Ruud, have demand defrost. Their might be another brand.

I thinking 2.5 tons is the right size. You don't want to go bigger for sure.

I believe the issue without dehumification occuring properly on your second unit was caused by fan speed since you say your original system dehumified fine. I think the Trane quote is good. If you want to go cheaper you can ask and independent installer for a brand like Luxaire/Coleman. They make good equipment too and are typically considered less expensive.

    Bookmark   December 25, 2011 at 7:54PM
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"You say I should buy a system with electronic demand defrost. I have brought that up with every representative and all tell me that all the systems they proposed have this feature, be they Trane, Carrier, or Lennox"

Factually, the above statement is not correct. Carrier does not have it. Lennox high end systems do. Trane/AmSTd also have true electronic demand defrost.

I again would insist on a load calculation. I also like Trane's XL15i HP-one of the best sgl stg HPs on the residential market. If Trane, I would elect Trane's two stg 7/12 KW heat strip which would be more than adequate for a home your size.

The Carrier GreenSpeed quoted is overkill and simply not cost effective due to it's price. Have never been a fan of Lennox HPs.

With a 15 cent KWH cost, I want a new system that has minimum 9 HSPF AHRI rating.

Going back to the Trane quote, I would want the Tam7 036 air handler size and the 8321 thermostat for better AC humidity control.

Refer back to my initial post.


    Bookmark   December 26, 2011 at 7:39AM
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A two stage heat pump will help control your summer humidity problems. The Carrier Infinity controller has a cool to dehudify feature. The AC will continue to run up to 3 degrees below the set point in order to reach the target humidity level. It works very well in my house.

I don't understand the comment about your duct work not working with the high efficiency equipment. The duct work needs to be proprely sized and sealed. In my opinion it doesn't matter if the air flow is being pushed by an efficient or inefficient system.

What are the typical low temperatures in your area and how ofter do they occur? I don't own a heat pump, but from what I read the demand defrost is a nice feature where temperatures are often below freezing.

    Bookmark   December 26, 2011 at 3:47PM
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Neohioheatpump said, " I thinking 2.5 tons is the right size. You don't want to go bigger for sure." The problem is that most of the proposals I have received are for two-stage units of 3 tons (as they only come in even number tonnage). The single-stage units can be had at 2.5 tons. I wonder if I will be giving up features I might need if I go with a single-stage unit.

I was told by one of the Carrier contractors that the first stage runs at 63 percent of maximum, which would be 1.89 tons (22,680 BTU). Given the summer humidity problems in the house, perhaps that would be a better choice than a single stage running at 30,000 BTU.

I used an online calculator and got a heat gain below 22,000 BTUH.

Mike Home asked, "What are the typical low temperatures in your area and how ofter do they occur?" According to the Trane website, the average cold weather low temperature is 32.4 degrees with 91 days below 40.

Tigerdunes suggested, "...elect Trane's two stg 7/12 KW heat strip which would be more than adequate for a home your size." I worry about putting in less than the 3-strip 15 kW I have now. That same online calculator told me I had 9233 BTUH of heat loss. Is 7/12 kW sufficient to make up for that loss if necessary?

I inquired earlier, "The system has never had a return in the unfinished basement. What would I gain from having one?" Would I be better off treating the unfinished, uninsulated basement as part of the total system or should I keep it relatively isolated and served by a dehumidifier in the summer?

    Bookmark   December 26, 2011 at 10:22PM
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It is true that 2-stage models only come in even size tonage. If you were to get a 3-ton model and run it the vast majority of the time on the low stage that would work.

If your old heatpump worked fine in heating mode, and it cooled fine but didn't dehumidify your fan speed was probably wrong.

Was your old unit blowing alot of air and making duct-noise when it was on?

    Bookmark   December 27, 2011 at 7:55AM
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If you add a return to the basement, then you need to keep the registers in the basement open all the time. Closing them may cause a negative air pressure problem. I would be cautious about this due to your humidity problems. You may be drawing up more humid air from the basement and adding to the problem. I would not feel comfortable about adding the basement return with a single stage AC.

I noticed in your original post you mentioned you kept the fan running during the summer in an attempt the even out the upstairs and downstair temperatures. This also contributes to the humidity problem. I think you will be more comfortable in the summer and winter if you purchased a two stage heat pump with a variable speed air handler.

How much insulation do you have in the attic? Have you considered increasing it?

    Bookmark   December 27, 2011 at 8:59AM
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I have read this post for the first time today with much interest. Just some observations..... You did get a lot of proposals.. not really a problem but it can make it very confusing with different contractors pulling you in different ways because everybody has different things they value more than others.

I also as most on here like the trane 15 seer proposal you got. Price is good and system is good.
I am not sure what the humidity problem you have is caused by and there is no way for me to tell from here. But I would be very interested if I was you on having some of the contractors you had give you proposals figure that out before you decided on a replacement system. Humidity control is real important to comfort. It may be determined you need a 2 stage system but then again there may be something none unit related that can be done.

I am suprised that no one seemed to quote you a 2 stage trane 16 Seer XLi system. I know tigerdunes does not like them but We have put in a bunch and I put one in for my dad and grandad with no problems and they love it. might be a thought.

    Bookmark   December 27, 2011 at 2:53PM
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Going back to the size of the heat strip.

Trane's 2 1/2 ton XL15i produces around 17 KBTUs at 17 degree fah.
Each KW of heat strip yields about 3400 BTUs of heat. So on the two stg 7/12 KW heat strip that I recommend, 7 KW yield about 24 KBTUs of heat, 12 KW about 40 KBTUs of heat. More than enough for a home your size.

And to Harlem,

It's not that I am necessarily opposed to 2 stg condensers. However the benefit of added comfort and possible operating cost savings is marginal at best especially when the additional cost is considered. And Trane's XL16i has poor dehumidification properties compared to the XL15i model. Plus, the XL16i's low stg is close to 70% of high output. In this homeowner's situation, he would need to go up to 3 ton which raises another issue about the adequacy of his ductwork system.


    Bookmark   December 27, 2011 at 3:46PM
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While you are at it you should also give the trane 20 XLi a look. It is a little pricey...... Cost for the efficiency could be questioned but the comfort can not. People that are used to running there units on 73 degrees are just as comfortable at my house at 77 because the humidity is around 40%....... humidity is comfort.


I wasn't questioning your opinion on the trane 16 XLi units.... there is even a few differing opinions even in our company on the value. A lot of the dehumidification of the 16 seems to depend on size and the air handler that it is matched up to.Also on how you set up the fan selections. there is a bunch of different ways. My dads humidity runs closer to 51% in the summer but my grandad's runs closer to 44 to 45 % both 16 xli in the georgia humidity. One a 3 ton one a 4ton. Ductwork is actually worse on grandads unit. But dollar for dollar the 19XLi that i have keeps it closer to 39% in the middle of the summer with 95% outside..... I almost need a humidifier for the summer.

    Bookmark   December 27, 2011 at 7:55PM
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I said in my previous post that a Carrier dealer told me that low-stage on the two-stage heat pump was 63 percent of maximum. I found in the Carrier literature that it's 67 percent. Then it says, "NOTE: 67% compressor capacity translates to approximately 80% cooling or heating capacity at the indoor coil." That would mean a 36,000 BTU unit would give 28,800 BTU in low-stage.

Neohioheatpump asked, "Was your old unit blowing alot of air and making duct-noise when it was on?" No, no duct noise. "Alot" of air is subjective and I would say when the system was changed there was no difference in airflow. When first installed, the Lennox was surprisingly quiet compared to the 15-year old GE it replaced.

Mike Home asked, "How much insulation do you have in the attic? Have you considered increasing it?" It's been years since I was up there and I don't remember measuring it. I remember it had the original 1978 pink blanket insulation plus more loose blown-in. After all these years, I'm sure it has settled and could use more. Maybe I'll increase it when I get a new roof and have them put in baffles to prevent the soffit airflow from being blocked by the increase.

I went to the Trane website for a list of local dealers and then to Angie's List for ratings of them. The best had some B grades and most had a lot of Cs, Ds, and Fs, with one being called a house butcher. The two Trane proposals I received came from contractors not even listed on Angie's. So, no Trane dealer I can find is considered outstanding.

I'm trying to give Trane a chance. I read in other posts on this forum that the installer may be more important than the equipment. But, if that's the case, and I have a proposal from a Carrier dealer with exceptional ratings on Angie's and a good price, then I may go with him.

A lot of the day was spent reading Carrier info on their website. I'll try to do the same with Trane. I like to learn....

    Bookmark   December 27, 2011 at 9:59PM
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Proposal 5 came through in written form as follows:

Option 1) Carrier Infinity 16, Model 25HNB636A003; Infinity Fan Coil FE4ANF005T00 with 15 kW heat; Infinity Controller Thermostat SYSTXCCUID01-B; Cost $6,735.

Option 2) Carrier Infinity 20, Model 25VNA036A003; Infinity Fan Coil FE4ANF005T00 with 15 kW heat; Infinity Controller Thermostat SYSTXCCUID01-B; Cost $8,462.

    Bookmark   December 27, 2011 at 10:59PM
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It is very apparent that a large majority of homeowners do not understand the benefits of "electronic demand defrost" feature on heat pumps versus time/temp. Not only is this a cost and comfort issue but also one of wear and tear.

Here is a post on the subject by one of the wise men on HVAC forums.

Posted by baldloonie (My Page) on Sat, Dec 24, 11 at 11:45
A timed defrost will defrost every so many minutes of the coil is below freezing, which it will be if the outdoor temp is below about 40. Usually the longest interval is 90 minutes which means every 90 minutes of run, the
unit goes into cool mode and pours cold air into the house til the outdoor coil gets warm. Backup heat will come on to temper this. A defrost could last several minutes up to the max if cold & windy. My unit has a timer which I've been meaning to get rid of since it rarely needs defrosting when I hear it switch.

Demand defrost has coil & ambient sensors and defrosts only when conditions say it needs to. On a Trane, it can go up to 6 hours with no defrost. Not sure what Rheem's board does. So these boards can eliminate 100s of unnecessary defrosts each winter.


    Bookmark   December 27, 2011 at 11:09PM
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I was just thinking. If you were letting your fan run all the time during the summer that would add to the humidity. Even after your A/C shuts off there is still water in the coil, and if the fan were to continue running you would be humidifying the house.

When your old A/C would run, was it producing water? It either goes thru a pipe on a floor or drains into a condensate box and then gets piped up and out to a drain.

If it was producing water then your unit was de-humidifying.

    Bookmark   December 28, 2011 at 8:24AM
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If one lives in a high humidity area, it is best to run AC in auto mode.

Carrier and Bryant high end systems have a delay feature which allows homeowner to run fan "on" without reintroducing humidity into the home that evap has just removed.


    Bookmark   December 28, 2011 at 8:34AM
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Its unfortunate that you don't have any good trane dealers in your area but it happens that way sometimes. There is nothing wrong with carrier equipment. They do not have demand defrost to my knowledge, which would be very helpful to you in your location. But the dealer is the most important part for sure. Because if you have a problem with the system you will want a good dealer that will stand behind the system they installed.

Pretty much all 2 stage compressor heat pumps only trim the refrigerent pumping to somewhere between 60 to 70%. But the fan is only trimmed to 80%.That is why you get the cooling capacity closer to 80% on a 2 stage compressor system. Any fan trim that is too much more than that and you run into coil freezing issues.

The only true 50% cooling on 1st stage comes with a 2 compressor system that has 2 seperate physical compressors (such as trane xli 20)or one with a variable speed compressor. That being said they really are a lot of overkill for your location probably.

    Bookmark   December 28, 2011 at 8:50AM
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There is a summer humidity problem which requires two dehumdifiers to be in operation during the summer. With a electricity cost of 15 cents per KWH that translates into a big expense. In my opinion solving this problem would be the highest priority. Running the fan constantly in the summer contributes to the problem, but it is not clear by how much.

You stated in an earlier post that you run the fan in the summer because the upper floor is 2-3 degrees hotter than the lower floor. I think adding the attic insulation will help this. You could also zone the first and second floors, but this is expensive and probably not feasible with your current duct work.

My thinking is go with the best contractor with a 2 stage heat pump. If this is the Carrier dealer, then you may have to give up the demand defrost feature. It may cost a little more to operate, but you should save quite a bit of money not running the dehumdifiers in the summer. If there is a concern about the wear and tear of a time defrost, then purchase the Carrier 10 year labor warranty. You will have no worries for the next 10 years.

    Bookmark   December 28, 2011 at 10:18AM
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Tigerdunes brought up demand defrost versus timed defrost. For the past 18 years, I have dealt with my Lennox defrost scheme. The only times I heard it go into defrost mode were when the unit was first running in heat mode. The unit would switch over from heat to defrost, the defrost cycle would complete and everything would turn off. I never heard it run a defrost cycle when it was not first heating. I rarely heard it go into defrost. I never heard it defrost on a fixed cycle such as every 90 minutes.

Am I to understand that a Carrier will just go into defrost mode every X minutes whether it needs it or not and is not in a heating cycle; just turn on and defrost itself?

I found this information in the Carrier 25HNB6 heat pump installation instructions:

AUTO defrost adjusts the defrost interval time based on the last defrost time as follows:
When defrost time When defrost time 3-5 minutes, the next defrost interval=90 minutes.
When defrost time 5-7 minutes, the next defrost interval=60 minutes.
When defrost time >7 minutes, the next defrost interval=30 minutes.
The control board accumulates compressor run time. As the accumulated run time approaches the selected defrost interval time, the control board monitors the coil temperature sensor for a defrost demand. If a defrost demand exists, a defrost cycle will be initiated at the end of the selected time interval. A defrost demand exists when the coil temperature is at or below 32_F (0_C) for 4 minutes during the interval.

From that description, if the time interval elapses and the coil is not at 32 degress, then no defrost will take place. That, to me, sounds like a form of demand defrost. Is Baldloonie saying that the coil could be at 32 degrees or less without frost and, therefore, a defrost cycle would be unnecessary? What kind of ambient sensor detects presence or absence of frost?

Neohioheatpump asked, "When your old A/C would run, was it producing water?" It was producing water and I saw it dripping from the condensate drain. One weekend I went out of town and came back to find water on the floor around the return box that the fan coil sits on. I opened up the access and found the interior insulation of that box soaked. Turns out the condensate line was plugged. Took awhile for that to dry out.

On the other hand, this past summer I did not see water dripping from the condensate drain. The drain line was not plugged and the drip pan seemed dry. I thought it was because I had dried out the air so much with the two dehumidifiers that there wasn't enough remaining for the A/C to remove. Cooling was normal.

Running the fan on manual started with the installation of the Lennox and an associated Honeywell Electronic Air Cleaner. The house suddenly became dusty and I blamed the EAC for not doing its job. The Honeywell zone representative came to my house, sized up the situation, and told me to run the fan on manual so that the dust would remain suspended in the air and available to be captured by the EAC. I did that and it was of no help for the dust situation but it did help reduce the temperature differential between the first and second floors during cooling so I kept doing it as a matter of routine. Thus, I cannot say that not running the fan reduced the humidity.

Though I complained about humidity, the heat pump contractor never told me that I was humidifying the house by running the fan (on orders from the Honeywell rep).

I will continue to run at least one dehumidifier in the completely below grade basement during the summer because I want that area to be warm and dry to avoid mold and mildew. I've been in the basements of other houses in the area that don't use dehumidifiers and they stink.

Mike Home said, "You stated in an earlier post that you run the fan in the summer because the upper floor is 2-3 degrees hotter than the lower floor. I think adding the attic insulation will help this." I agree that adding attic insulation could help. But, having a Dutch Colonial house with a barn-like roof that is covered in dark shingles on the east and west sides causes a lot of heat gain through the second floor walls. I'm not keen on opening the walls to determine the amount of insulation or add to it. Changing to a light-colored roof would make the house look out of character with the neighborhood. There are newer shingles that reject heat gain that I will investigate.

Mike Home also said, "You could also zone the first and second floors, but this is expensive and probably not feasible with your current duct work." There is but one main feed duct and it runs through the basement. There is no way to segregate the room feeds in this scheme without doing each one individually. I'll leave that expense to the next owner.

    Bookmark   December 28, 2011 at 5:54PM
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Which option did you choose?

    Bookmark   October 22, 2012 at 4:20PM
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I am thinking to replace my york heat pump, 3.5 ton, 2 zones.
1 st option: Lennox XP14-042, with CBX48MV variable speed air handler.

2nd option: XP 16-48, with CBX 48MV variable speed air handler.

My questions:

1. Do I need 4 ton unit for XP 16? My current system is 3.5 ton.

2. Which option is more efficient in long run considering I have two zones?

    Bookmark   March 20, 2014 at 2:10PM
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