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  1. #1
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    Questions about bad old hvac installation

    Hello - just installed 2 new hvac systems today, and installer pointed out problems with the old equipment. I live just outside of Tucson, and we use our a/c from June through September, maybe 16 hours a day with a setting around 79 degrees or so. Our house is a newer, well insulated 2,300 square foot, single story model with R38 ceiling insulation, only one South-facing window, big shade trees on our West side, etc. I had a 2005 Trane 2 1\2 ton split system and another 2006 Trane 3 ton split system. It turns out that the old 2 1\2 ton condenser was hooked up to the larger inside air handler/furnace, and the old larger 3 ton condenser was hooked up to the smaller air handler/furnace. And the smaller system was hooked up to the 30 amp breaker, while the larger system was hooked up to the 20 amp breaker. Both old units died last week, within days of each other, and I'm wondering if the bad installation history of the two old systems contributed to their failure. We've been in the house 10 1/2 years, and it was an empty spec house for two years before that. Should the old Trane units have lasted longer than 12+ years, and would the bad installation have been very inefficient and contributed to their failure? Thanks in advance, for any help.

  2. #2
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    A 2.5 ton OD unit to a 3 ton indoor unit is quite common, been that way for many decades. 3 ton unit to a 2.5 ton not as common, and really should not be that way,... but I believe someone here said they have seen that situation as a matched system on rare occasions.

    OD units have breaker size that manufacturers want the installers to follow, typically it will be a minimum to a maximum overcurrent HVAC breaker/fuse. So certainly the 20 amprege breaker maaayy meet the minimum size. You do not mention if the breaker ever tripped repeatedly over the last 12 years..

    If you know the model numbers of the OD units of your old systems you can find the specifications sheets online to check what the breaker/fuse minimum/maximum overcurrent protection of both units are.

    You do not mention having regular or occasional preventive maintenance checks, possible you have improper duct design, kinked lineset, or incorrectly sized lineset. Oversized units on undersized ductwork is common so they tell me. etc.etc. One unit being mismatched. Combination of several things.
    Last edited by Bazooka Joey; 06-20-2019 at 08:08 AM.

  3. #3
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    Thanks Bazooka Joey! I checked the equipment spec sheet and it says that the old 2 1/2 ton unit should have "Min Cir Ampacity of 13" and a "Max Fuse Size Amps of 20", and it's been on a 30 amp circuit breaker. The old 3 ton unit spec sheet says it should have a "Min Cir Ampacity of 21" and a "Max Fuse Size of 35 amps, and it's been on a 20 amp circuit breaker. The tech who installed the new system told me not to run the larger unit until I had a 30 amp breaker installed where the 20 amp unit is now. The new 3 ton unit requires a minimum of 18.6 amps and a max breaker amps of 30. The units have not typically been tripping the breakers, but the larger unit did twice in the couple of days before it died. My ducts are insulated flex units, but don't appear to have been hung with a lot of care - they have some very tight angles and long, looping runs. I've had all the inside and outside hvac units on an annual maintenance contract since I bought the house in 2008, and we've never missed a maintenance visit. Both units had had hard start units installed during their lifetime by the maintenance guys. The last maintenance was on 5/6/19, when the tech added a total of 4 lbs of Freon to the two units. Nobody had previously mentioned any Freon leakage before.

  4. #4
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    As a Trane dealer I have seen matches for what would seem like a mismatch. For example Trane had a 31E (not the full number) air handler. It was rated for use with everything from 1.5 to 3 T and they had a 40E that was good for up to 4 T if I remember correctly. So from what I am hearing you say I would be more concerned with the flex duct with the tight bends than the supposed mismatch and breaker discrepancy. It would also seem odd to me that 4 lb was added to the units just a short time before the failure. They may have each had a leak or they may have been mis-diagnosed. Did they happen to weigh out the refrigerant when they recovered it for each unit?

  5. #5
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    Thanks BNME8EZ! When they removed the old units, there was no discussion of the amount of refrigerant in them. They just disconnected them and took them away - I didn't see any of that. It did strike me as odd that in 10+ years of maintenance contract, there was never any mention of a leak or a need for topping-off the refrigerant until last month, and then they added 4 lbs to the systems with a combined capacity of 11 lbs 13 oz.

  6. #6
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    Quote Originally Posted by bslocum View Post
    Thanks Bazooka Joey! I checked the equipment spec sheet and it says that the old 2 1/2 ton unit should have "Min Cir Ampacity of 13" and a "Max Fuse Size Amps of 20", and it's been on a 30 amp circuit breaker. The old 3 ton unit spec sheet says it should have a "Min Cir Ampacity of 21" and a "Max Fuse Size of 35 amps, and it's been on a 20 amp circuit breaker. The tech who installed the new system told me not to run the larger unit until I had a 30 amp breaker installed where the 20 amp unit is now. The new 3 ton unit requires a minimum of 18.6 amps and a max breaker amps of 30. The units have not typically been tripping the breakers, but the larger unit did twice in the couple of days before it died. My ducts are insulated flex units, but don't appear to have been hung with a lot of care - they have some very tight angles and long, looping runs. I've had all the inside and outside hvac units on an annual maintenance contract since I bought the house in 2008, and we've never missed a maintenance visit. Both units had had hard start units installed during their lifetime by the maintenance guys. The last maintenance was on 5/6/19, when the tech added a total of 4 lbs of Freon to the two units. Nobody had previously mentioned any Freon leakage before.
    So this company is changing like tonnage for like tonnage and not doing a load calculation? No modifications to your existing duct system?

    So if you have the existing 20 AMP. Breaker on the new 3 ton OD unit and the minimum overcurrent breaker required is 18.6 amp. Why can't you run your unit and use your A/C?

    Did they replace the other unit yet? Why couldn't they swap out the existing breakers as another option? I'm guessing they do not have the license to get into your main distribution panel?

    Your new system may have the same fate as your old system, if you have ductwork issues..

  7. #7
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    Quote Originally Posted by bslocum View Post
    Thanks BNME8EZ! When they removed the old units, there was no discussion of the amount of refrigerant in them. They just disconnected them and took them away - I didn't see any of that. It did strike me as odd that in 10+ years of maintenance contract, there was never any mention of a leak or a need for topping-off the refrigerant until last month, and then they added 4 lbs to the systems with a combined capacity of 11 lbs 13 oz.
    How do you know the combined capacity of both system was 11 lb. 13 oz. you take that number from the electrical data plate on the OD units? If so that number is not necessary the correct amount. For many years now, that number is for the OD unit, a matching ID unit and 15' of correctly sized lineset, so if either or both units have longer than 15' lineset then you add a certain amount of refrigerant for every foot above the 15' then dial in the final field refrigerant charge to manufacturer spec. such as subcooling or whatever is listed in the OD unit install guide.

    You should request a commissioning report from the Installing Contractor as to what the subcooling/superheat number is, your static pressure ( sounds like you got iffy sized duct system ) doesn't hurt to check amprege draw of both ID and OD fan motors and compressor etc.etc. are all within manufacturer specifications.

    Make sure to register your system as the manufacturer warranty decreases significantly if you never register it.

    If you had high efficiency SEER rated equipment ( around 16+ SEER and a certain EER ) installed and your state or local utility company offers rebates you would need a AHRI number to prove matching energy star rated equipment was installed.

  8. #8
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    Quote Originally Posted by bslocum View Post
    Thanks BNME8EZ! When they removed the old units, there was no discussion of the amount of refrigerant in them. They just disconnected them and took them away - I didn't see any of that. It did strike me as odd that in 10+ years of maintenance contract, there was never any mention of a leak or a need for topping-off the refrigerant until last month, and then they added 4 lbs to the systems with a combined capacity of 11 lbs 13 oz.
    It is not out of the question that a 10 year old unit to need some refrigerant. However an A/C is suppose to be a sealed system, the only way it need refrigerant is if there is a leak somewhere. Now it is possible that if they put the gauges on the system every time they service it over time there will be a natural loss from connecting/disconnecting the gauges but even in 10 years I would doubt 4 lb. If it was low on refrigerant they should have at least mentioned looking for the leak otherwise it will just keep leaking out. Had you noticed they were not cooling as well as in the past or had you not run them yet?

  9. #9
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    Quote Originally Posted by bslocum View Post
    Thanks Bazooka Joey! I checked the equipment spec sheet and it says that the old 2 1/2 ton unit should have "Min Cir Ampacity of 13" and a "Max Fuse Size Amps of 20", and it's been on a 30 amp circuit breaker. The old 3 ton unit spec sheet says it should have a "Min Cir Ampacity of 21" and a "Max Fuse Size of 35 amps, and it's been on a 20 amp circuit breaker. The tech who installed the new system told me not to run the larger unit until I had a 30 amp breaker installed where the 20 amp unit is now. The new 3 ton unit requires a minimum of 18.6 amps and a max breaker amps of 30. The units have not typically been tripping the breakers, but the larger unit did twice in the couple of days before it died. My ducts are insulated flex units, but don't appear to have been hung with a lot of care - they have some very tight angles and long, looping runs. I've had all the inside and outside hvac units on an annual maintenance contract since I bought the house in 2008, and we've never missed a maintenance visit. Both units had had hard start units installed during their lifetime by the maintenance guys. The last maintenance was on 5/6/19, when the tech added a total of 4 lbs of Freon to the two units. Nobody had previously mentioned any Freon leakage before.
    We ( company I'm involved with ) actually like to install breakers more on the lower side or mid side than at the maximum side as an example if the OD unit does not have any pressure safety controls or the OD fan fails or the OD unit gets plugged up and the refrigerant pressures continue to rise which raises the amprege draw, to me the breaker may trip before it just sits there and bypasses the refrigerant internally, heating up the compressor and tripping the internal overload, kind of gives it a somewhat added safety device IMO.

  10. #10
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    The new system is the same tonage as the old, 2 1/2 and 3 tons. The old units were 13 SEER but the new ones are 16 SEER, single speed compressors. The company didn't do a manual J calculation, and they're the same guys who did the original install in 2006. My house is a typical model in a development with about 4,500 homes, and I probably got the same system as hundreds of identical models with no modifications for extra insulation, orientation on the lot, etc. I don't know why the tech didn't swap the breakers for the new unit. Both of the old units have been replaced. I'm going to have somebody inspect the ductwork, but I'm a little concerned if the original company reviews their own work from 2006 - can they be objective, and if problems in their 2006 work are found, should I expect them to correct the work without charge? The new units nearly tapped me out financially for the year (I'm 72 and retired), and I worry about the extra cost of revised ductwork if not done for free by the original installer.

  11. #11
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    Quote Originally Posted by Bazooka Joey View Post
    How do you know the combined capacity of both system was 11 lb. 13 oz. you take that number from the electrical data plate on the OD units? If so that number is not necessary the correct amount. For many years now, that number is for the OD unit, a matching ID unit and 15' of correctly sized lineset, so if either or both units have longer than 15' lineset then you add a certain amount of refrigerant for every foot above the 15' then dial in the final field refrigerant charge to manufacturer spec. such as subcooling or whatever is listed in the OD unit install guide.

    You should request a commissioning report from the Installing Contractor as to what the subcooling/superheat number is, your static pressure ( sounds like you got iffy sized duct system ) doesn't hurt to check amprege draw of both ID and OD fan motors and compressor etc.etc. are all within manufacturer specifications.

    Make sure to register your system as the manufacturer warranty decreases significantly if you never register it.

    If you had high efficiency SEER rated equipment ( around 16+ SEER and a certain EER ) installed and your state or local utility company offers rebates you would need a AHRI number to prove matching energy star rated equipment was installed.


    Bazooka Joey - I know the combined Freon capacity was 11 lbs and 13 oz because I got it from the Trane General data product specification sheet for the 2TTB3031 and 2TTB3036 units. The refrigerant lines are probably closer to 20' (a guess) than 15'. I didn't receive anything called a commissioning report from the installer, and nothing else with the data you listed on it - just a receipt and list of system components. I'll ask for the report - hope they comply, but what do I do with that data once I have it? No current rebates from my utility company unfortunately.

  12. #12
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    Quote Originally Posted by Bazooka Joey View Post
    So this company is changing like tonnage for like tonnage and not doing a load calculation? No modifications to your existing duct system?

    So if you have the existing 20 AMP. Breaker on the new 3 ton OD unit and the minimum overcurrent breaker required is 18.6 amp. Why can't you run your unit and use your A/C?

    Did they replace the other unit yet? Why couldn't they swap out the existing breakers as another option? I'm guessing they do not have the license to get into your main distribution panel?

    Your new system may have the same fate as your old system, if you have ductwork issues..
    Bazooka Joey - The new system is the same tonage as the old, 2 1/2 and 3 tons. The old units were 13 SEER but the new ones are 16 SEER, single speed compressors. The company didn't do a manual J calculation, and they're the same guys who did the original install in 2006. My house is a typical model in a development with about 4,500 homes, and I probably got the same system as hundreds of identical models with no modifications for extra insulation, orientation on the lot, etc. I don't know why the tech didn't swap the breakers for the new unit. Both of the old units have been replaced. I'm going to have somebody inspect the ductwork, but I'm a little concerned if the original company reviews their own work from 2006 - can they be objective, and if problems in their 2006 work are found, should I expect them to correct the work without charge? The new units nearly tapped me out financially for the year (I'm 72 and retired), and I worry about the extra cost of revised ductwork if not done for free by the original installer.

  13. #13
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    Quote Originally Posted by BNME8EZ View Post
    It is not out of the question that a 10 year old unit to need some refrigerant. However an A/C is suppose to be a sealed system, the only way it need refrigerant is if there is a leak somewhere. Now it is possible that if they put the gauges on the system every time they service it over time there will be a natural loss from connecting/disconnecting the gauges but even in 10 years I would doubt 4 lb. If it was low on refrigerant they should have at least mentioned looking for the leak otherwise it will just keep leaking out. Had you noticed they were not cooling as well as in the past or had you not run them yet?
    BNME8EZ - No one ever mentioned anything about a leak until the day the tech added 4.4 lbs of Freon. We hadn't had the A/C on since probably mid-Oct of '18 and I can't say that I noticed any fall-off of the cooling the previous summer, but a gradual decrease over the years would probably not have been noticed.

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