AC Question

[mikester]

Let me start off by saying I have no real experience with HVAC stuff but I have a question.
Back in 2000 I had AC put in the upstairs of my 119 year old house. Its a combination setup. Forced air heat through an air handler thats a separate zone on the boiler and AC for the warm months. Never had an issue.
The main floor has baseboard heat and a separate AC setup that was installed by the same guys 4 years ago.
Two years ago the upstairs unit has an issue. Turned out the problem was the condenser outside.
The guy replaced the condenser/compressor with a new Fridgidaire 1 1/2 ton unit. Not sure about the specs.
The old one was a 2 ton 10 seer unit.
Long story short, it seems since the unit was changed its never really cool upstairs. Had the company come back and the guy said it was because the thermostat needs to be set at one temp. You cant expect it to be 50 just because the thermostats set at that. He told me to leave it at 70 and it should keep that temp all through the summer. This is an attic conversion. The ceiling is the roof but well insulated.
Since Im not into this stuff does this sound like **** ? My daughters bedroom and a bathroom are the only rooms up there and some days its pretty hot.
Now that I looked at the receipts Im wondering if he replaced the unit with one thats undersized for the area.
What do you guys think ?

 

[brewchief]

It's possible that it's undersized, is the new unit r-22 or r-410a? Was the airhandler replaced or just the condenser outside?

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[American Locomotive]

Condensing units must be matched the coil. You can't just stick a 1.5 ton condensing unit on a 2 ton coil and expect it to work right.

The thermostat just sends a signal "On" or "Off" to the condensing unit. If the room is above the set temperature, it turns on. When it drops below the set temperature, it turns off.

 

[mikester]

It's possible that it's undersized, is the new unit r-22 or r-410a? Was the airhandler replaced or just the condenser outside?

Sent from my SM-G965U using Tapatalk

Its an R-22 and no, just the condenser was replaced. The air handler is still the original.

 

[American Locomotive]

I don't get why they would replace a 2 ton unit with a 1.5 ton. Best case, you just lost 6,000 BTU of cooling capacity. Worst case you lost more because now you have a mis-matched system.

 

[LS6 Tommy]

X3 on the mismatch. You should have had them correct it right away. Unfortunately, there's probably no way they'll ever make good on it 2 years later.

Tommy

 

[bonneyman]

I don't get why they would replace a 2 ton unit with a 1.5 ton. Best case, you just lost 6,000 BTU of cooling capacity. Worst case you lost more because now you have a mis-matched system.

Probably because of the higher efficiency horse ****. The newer unit is more efficient, therefore we can put a smaller (lower cost) unit in and it will still do the job.
They did this back in the day with the "short" 3-ton condensing units. (You old timers might remember these. I can't remember the letter designation. It was after the YAC units - I think it was the Cool Cube model). I think Carrier/Payne did it. There was a standard 3 ton unit, and then what they called a "short" 3 ton. Was a bit smaller height wise, and alot of folks didn't want to see the whirling fan - or the HOA wouldn't see the thing poking above the roof line. It was gently pushed as a short unit concerning height (and less money).
But it was actually short on capacity! The standard 3 ton unit had 36,000 BTUH (or more) compressors in them, but these things had as small as 33,000 or so comps in them. Sooooo - on the hottest days, it was "short" on capacity. A call about insufficient cooling during the first year got a tech visit and excuses. Once out of the years warranty a real technician came out and told them what was up and they were outta luck.

 

[MattT]

The main floor has baseboard heat and a separate AC setup that was installed by the same guys 4 years ago.

Was the downstairs air conditioned before they installed that new system? If not they might have thought that change had reduced the upstairs load enough to drop half a ton.

This is an attic conversion. The ceiling is the roof but well insulated.

What about the knee walls? Are they sealed and well insulated?

One other thing to check would be the air handler and duct work if they're in the attic. The tech could have knocked a duct loose, or forgot to put insulation back, when he re-commissioned the system.

 

[SGKent]

filters changed every 3 months? Ducts all open? That is a must. A good AC will stay on considerable time in hot weather rather that frequently cycle. If it cycles too much and cools too fast it is over sized. I'd set it somewhere between 72 F and 74 F and leave it alone. See what it does*. I will add - on more than one occasion I have seen ducts that fell apart just sending air into the basement or attic.

*Then consider setting a programmable unit so it more closely follows your habits and budget.

 

[99LeCouch]

Was the inside coil replaced, or did they reuse the old coil? And, did they make sure the amount of refrigerant was correct?

 

[mikester]

Was the inside coil replaced, or did they reuse the old coil? And, did they make sure the amount of refrigerant was correct?

The coil wasnt replaced. Just the unit outside due to it rotting out. They filled the system and checked it again a year later.

 

[mikester]

filters changed every 3 months? Ducts all open? That is a must. A good AC will stay on considerable time in hot weather rather that frequently cycle. If it cycles too much and cools too fast it is over sized. I'd set it somewhere between 72 F and 74 F and leave it alone. See what it does*. I will add - on more than one occasion I have seen ducts that fell apart just sending air into the basement or attic.

*Then consider setting a programmable unit so it more closely follows your habits and budget.

Filters changed frequently. Probably less than 3 months. Ducts are open. The air handler is behind the knee wall. Theres an access door to service it. Plenty of air coming from the vents.

 

[mikester]

Was the downstairs air conditioned before they installed that new system? If not they might have thought that change had reduced the upstairs load enough to drop half a ton.



What about the knee walls? Are they sealed and well insulated?

One other thing to check would be the air handler and duct work if they're in the attic. The tech could have knocked a duct loose, or forgot to put insulation back, when he re-commissioned the system.

We had the upstairs done first since it was an attic conversion. Theres only two windows, one at each end so we didnt want to put in a window mount and block any egress. The original setup seemed to cool the upstairs without any issues. Its a small area. One 12x26 room thats being used as a bedroom and a small bathroom.
The knee walls are 2x4 framed and well insulated. I know this for a fact since I did the majority of the work. The air handler is in the middle of the attic behind the knee wall with a metal access door for servicing. Nothing was knocked loose.

 

[mustangacman]

They should have also changed the metering device in the evap. coil to match the new condenser.

 

[yeldogt]

Probably because of the higher efficiency horse ****. The newer unit is more efficient, therefore we can put a smaller (lower cost) unit in and it will still do the job.
They did this back in the day with the "short" 3-ton condensing units. (You old timers might remember these. I can't remember the letter designation. It was after the YAC units - I think it was the Cool Cube model). I think Carrier/Payne did it. There was a standard 3 ton unit, and then what they called a "short" 3 ton. Was a bit smaller height wise, and alot of folks didn't want to see the whirling fan - or the HOA wouldn't see the thing poking above the roof line. It was gently pushed as a short unit concerning height (and less money).
But it was actually short on capacity! The standard 3 ton unit had 36,000 BTUH (or more) compressors in them, but these things had as small as 33,000 or so comps in them. Sooooo - on the hottest days, it was "short" on capacity. A call about insufficient cooling during the first year got a tech visit and excuses. Once out of the years warranty a real technician came out and told them what was up and they were outta luck.

The small carrier units were great -- think they were called "Cube" . I used them all the time ... they were r22. And you could get the odd sized unit -- that unit was perfect with some homes where you could change the fan speed for better humidity control. Don't think that's the OPs problem.

 

[yeldogt]

Let me start off by saying I have no real experience with HVAC stuff but I have a question.
Back in 2000 I had AC put in the upstairs of my 119 year old house. Its a combination setup. Forced air heat through an air handler thats a separate zone on the boiler and AC for the warm months. Never had an issue.
The main floor has baseboard heat and a separate AC setup that was installed by the same guys 4 years ago.
Two years ago the upstairs unit has an issue. Turned out the problem was the condenser outside.
The guy replaced the condenser/compressor with a new Fridgidaire 1 1/2 ton unit. Not sure about the specs.
The old one was a 2 ton 10 seer unit.
Long story short, it seems since the unit was changed its never really cool upstairs. Had the company come back and the guy said it was because the thermostat needs to be set at one temp. You cant expect it to be 50 just because the thermostats set at that. He told me to leave it at 70 and it should keep that temp all through the summer. This is an attic conversion. The ceiling is the roof but well insulated.
Since Im not into this stuff does this sound like **** ? My daughters bedroom and a bathroom are the only rooms up there and some days its pretty hot.
Now that I looked at the receipts Im wondering if he replaced the unit with one thats undersized for the area.
What do you guys think ?

Sadly -- I think you are dealing with an undersized system now. If the old system worked and the new one never did --- that's your problem. Maybe with the end of the old refrigerant and equipment your installer was trying to help you out and all he could get was a 1.5? Many systems got replaced when replacements ended.

An attic space, even with spray foam may need a tad more BTU's -- conventional with any of the equipment in the attic -- will need more BTU's.

I think your installer was praying that by lowering the thermostat the system would "catch up" and be able to maintain. Often this is the case ... or worst case the system will only fall behind a bit in the heat of the day. Top floors can be a challenge and it's not unusual to have to keep them running as whenever you allow a space to overheat a properly sized system is going to take a while to bring it down

If it only had problems on odd hot days at 2pm -- I would say it's properly sized. Sounds like this is all the time.

 

[mikester]

I was going to call the guy this week but Im on the fence. Ive had the guy do three installs at my house. The AC in the attic and main floor and also the Hot Dawg in my garage. He did a clean install on all three.
The one issue is I worked with his brother for close to 20 years. Theyre both nice guys. I think I should have called him on it the first time it felt like the unit wasnt cooling the upstairs. Like Tommy said in his reply, 2 years is too long. Looks like Im living with it. Live and learn.
Thanks for all the replies and info though. GJ always has answers !

 

[bonneyman]

The small carrier units were great -- think they were called "Cube" . I used them all the time ... they were r22. And you could get the odd sized unit -- that unit was perfect with some homes where you could change the fan speed for better humidity control. Don't think that's the OPs problem.

I saw them mostly on track homes. A whole line of houses (same floor plan) but one or two of them had the short 3 tonners on there. Every July and August they'd be calling us because "the unit isn't as cold as it should".