Home A/C issues

[wyliesdiesels]

Yes, i realize this forum is geared toward garages and this is for my house. I rent so I'm hoping someone here can help me before i go barking at my landlord just to discover im wrong.

Moved into a new to me house(1056 sq. ft, built in 1932; very poor insulation) last november and i just started using the A/C today as the temps reached 97 deg. The furnace is a bryant 80 plus and the condenser is a bryant 563cn030-b, which is supposedly a 2.5 ton unit, according to several google search results. I have no idea how old the system is but i would guess about 10 yrs.

I turned the system on at about 2:30-3pm when the house was at 94 deg and it took approx 4-5hrs to get the house down to 84 deg. Seems like it should be able to get the house cooler faster. As it is now, the condenser is just gonna run all day long and never kick off causing my electric bill to be through the roof, with the thermastat set to 75 deg, which doesnt seem unreasonable to me.

Now, you're probably thinking- why didnt he turn the system on earlier. And that's because i was actually working outside and didn't realize how hot it had gotten inside. Also, we usually try to let just the breeze keep our house cool and we HATE high electric bills.

The last house(1200 sq ft, built 1973) i rented in town had a slightly larger(3 ton) roof mounted combo unit(all in one, probably newer) and was able to cool down the house about 10 degs in a few hrs and the compressor would cycle on and off with a good time lapse in between. Both houses have ducting in attic and current house also has the furnace in the attic. I have checked the ducting and there is only a few small leaks mainly at the plenum. During the winter, the heater performed great and heated the house 5-10 deg in an hour. I tested the register and return air vents and got a 20 deg difference which ive read is what u want

The system seems a little oversized for the sq ft of the house so thats why I'm thinking something is wrong.

Questions:

1) Based on the above, should i be getting better, quicker cooling with this system meaning there is something wrong?
If so, what could it possibly be? (I dont want to go all summer with the compressor running non stop, hiking up my electric bill through the roof(our rates are insane here- 16 cents/ kwhr over 500 kwhrs!!)

2) If it sounds like the system is running about normal, then would installing an attic fan help improve performance(seeing as the furnace/evap and ducting is in the hot attic)?

3)Is there some kind of tangable performance rating to go by, such as degrees cooled per hour? I know there's SEER ratings but as i said, thats not really a tangible measurement, unless theres some formula used in conjunction with SEER ratings!

Thx for the help in advance! Im considering calling an HVAC shop but would like some ideas first before i spend money i may not get reimbursed for!

And please dont tell me to just call the landlord as my slumlord wont even fix leaky faucets and sagging tubs!

 

[pattenp]

Just on the face value of what you're saying it seems to me that the house does not have enough insulation. You need to be careful about adding a power vent in the attic it can cause negative pressure in the house and actually **** cool air out of the house. You need to do some searching on the web for the pros and cons of attic power ventilation.

 

[Falcon67]

Have the system checked by an HVAC expert. If the system parameters are all in line, then your issues are all with the house. Air leaks, insulation, windows, etc. Our old house was built in 1926 and once I got it reworked 2.5 tons would keep that 1600 sq/ft cool easy. Shop is the same way - 960 sq/ft and I can keep it nice with only 16K BTU and warm it with 24K BTU.

 

[pseudorealityx]

You said it yourself.... very poor insulation. Of course it worked fine in the winter, Mondesto rarely if ever gets below 40 degrees.

Waiting till 2 in the afternoon when the entire house's thermal mass was 90+ certainly didn't help. You really got yourself outside of the happy place for that unit. If you don't like high electric bills, rent a house with better insulation, or just deal with sweating a lot. There's no way around not having A/C in the central valley. There's no quantifiable "degrees per hour" measurement. A 2.5 ton unit is typically rated at 95 degrees, and should produce ~30,000 btu of cooling. In general, to test how well the unit is working, measure the air going into the return, and the discharge temperature coming out of the supply vents. Most HVAC systems are only capable of giving you ~22 degree change. If you've got 90 degree air going in, it's not going to get much better than 68 degrees coming out.




Off-topic, I'll be driving through your area in a few weeks on vacation, from SF to Yosemite.

 

[wyliesdiesels]

You need to be careful about adding a power vent in the attic it can cause negative pressure in the house and actually **** cool air out of the house. You need to do some searching on the web for the pros and cons of attic power ventilation.

There is 4 gable vents already in the attic so i doubt an attic fan would cause little if any negative pressure in the house!

 

[acmikee]

check your temp differential. is your condenser coil clean. if you need to clean if use simple green and water wash it.

 

[digdug18]

Is any of your ducting running through the attic? How about the condenser, and the cooling unit.

Like the others have said, seeing how old the house is, I'd say something to your landlord about the lack of insulation in the house. See if you can work something out that if you add insulation, you can forgo a month's rent, or something like that.

 

[Milton Shaw]

For a quick check of the units operation, is the suction line(the big one) cold and sweating with condensation at the outside unit. If that line is hot and not sweating then the unit is probably very low on freon. Get an HVAC expert out there ASAP. If that line covered with frost, the unit is slightly undercharged most probably. HVAC expert is needed. (This is to be checked after the unit has run for an hour or more)

 

[danielzig]

Dropping the temp of the whole house 10 degrees in that amount of time does not seem unreasonable. As someone stated, the unit should be designed to run 100% of the time to maintain 75 degrees inside when it is 95 outside.

Sent from my DROID X2 using Tapatalk 2

 

[wyliesdiesels]

Totally forgot about this thread as i got caught up in the electrical section where i always hang out!

Just on the face value of what you're saying it seems to me that the house does not have enough insulation. You need to be careful about adding a power vent in the attic it can cause negative pressure in the house and actually **** cool air out of the house. You need to do some searching on the web for the pros and cons of attic power ventilation.

Well now Im not sure if the insulation plays as much of a part in this as i originally thought because the other day i got the house down to 75f deg(outside was 95f deg), at which the system shut off(thermastat was set to 76f deg). I turned the temp up to 79 deg and it took several hours to heat back up!

You said it yourself.... very poor insulation. Of course it worked fine in the winter, Mondesto rarely if ever gets below 40 degrees.

Waiting till 2 in the afternoon when the entire house's thermal mass was 90+ certainly didn't help. You really got yourself outside of the happy place for that unit. If you don't like high electric bills, rent a house with better insulation, or just deal with sweating a lot. There's no way around not having A/C in the central valley. There's no quantifiable "degrees per hour" measurement. A 2.5 ton unit is typically rated at 95 degrees, and should produce ~30,000 btu of cooling. In general, to test how well the unit is working, measure the air going into the return, and the discharge temperature coming out of the supply vents. Most HVAC systems are only capable of giving you ~22 degree change. If you've got 90 degree air going in, it's not going to get much better than 68 degrees coming out.

Off-topic, I'll be driving through your area in a few weeks on vacation, from SF to Yosemite.

Modesto actually got into the lower 20s for several weeks this year. With wind chill and humidity, that equals brrrrr! That's why i said the heater did pretty good considering the temps!

So what do u mean by a 2.5ton unit is typically rated for 95f deg??

I did test what i think is called 'delta t', the temp difference between the return and the register vents, and it was exactly 20f deg difference. So, is there anything else i should check, like refrigerant pressures(i would have to buy a set of gauges!!)?

check your temp differential. is your condenser coil clean. if you need to clean if use simple green and water wash it.

I did check it, which i said in my first post. And yes, i already cleaned the gunk out of the condenser!!

Is any of your ducting running through the attic? How about the condenser, and the cooling unit.

Like the others have said, seeing how old the house is, I'd say something to your landlord about the lack of insulation in the house. See if you can work something out that if you add insulation, you can forgo a month's rent, or something like that.

Yes, the furnace/air handler is in the attic along with the vents!! The condenser is outside.

My landlord wont even fix a trickling toilet that costs me money, so theres no way he will give a squat about insulation!

For a quick check of the units operation, is the suction line(the big one) cold and sweating with condensation at the outside unit. If that line is hot and not sweating then the unit is probably very low on freon. Get an HVAC expert out there ASAP. If that line covered with frost, the unit is slightly undercharged most probably. HVAC expert is needed. (This is to be checked after the unit has run for an hour or more)

The suction line IS cold however its not sweating. Does that indicate an issue since its not sweating? The high side is warm BUT not hot!

Dropping the temp of the whole house 10 degrees in that amount of time does not seem unreasonable. As someone stated, the unit should be designed to run 100% of the time to maintain 75 degrees inside when it is 95 outside.

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When it was 106f deg outside a few weekends ago, the darn thing ran constant for hours and couldn't get the house below 80f deg! It seems that sometimes the system works pretty good and other times it has trouble just maintaining!

On another note, does it help to cool down the house quicker by spraying the condenser with a water hose while its running?

 

[theoldwizard1]

check your temp differential. is your condenser coil clean. if you need to clean if use simple green and water wash it.

Best, cheapest way to improve A/C efficiency. Even just hosing down without cleaner works well.

 

[brewchief]

When it was 106f deg outside a few weekends ago, the darn thing ran constant for hours and couldn't get the house below 80f deg! It seems that sometimes the system works pretty good and other times it has trouble just maintaining!

Modesto shows a 98 degree summer design temp in my heat load program, if the unit is perfectly sized 98 degrees should be the point that it runs 100% of the time to maintain temp, any hotter and the temps might start climbing inside.

 

[wyliesdiesels]

Ok, that makes sense. Its been 102f deg most of the day and it has been on constantly maintaining 77-78f deg.

On another note, do happen to have any answers to my previous questions in comment # 10? Such as the no sweating on the suction line?

 

[Falcon67]

It was 106F yesterday and we had family dinner. The Goodman had a hell of a time keeping the place at 78F. It finnaly hit the set point around 12:30AM. It was 104 today and it was 76 (on a 73 temp set) when we got home. Ours is 12 years old, just ate it's second cap in a year and seems to be donw on power a bit. I think we're going to be financing a heat pump here in the next 12~24 months.

Spraying the condenser can sometime help - I should have tried that since there is a sprinkler head right next to the condenser here. Well water is cold. But you'll not be very cool standing outside spraying water on your condenser

 

[brewchief]

Ok, that makes sense. Its been 102f deg most of the day and it has been on constantly maintaining 77-78f deg.

On another note, do happen to have any answers to my previous questions in comment # 10? Such as the no sweating on the suction line?

You may not get sweating on the suction line depending on outdoor temp and dewpoint.

20 degree delta T is pretty much where you want to be.

Make sure the suction line is insulated well, the cool gas that comes back to the unit cools the compressor, if a bunch of insulation is missing in the attic you won't get much cooling for the compressor.

It sounds like it's doing it's job, without a set of gauges on it to check superheat or subcooling it's hard to be 100% sure.

The situation you are in with a properly sized unit that can't quite keep up due to temps above design temp is why there are so many oversized units out there, as a HVAC contractor you want the sizing spot on but when it is you will get angry customers coming out of the woodwork any time you get conditions above or below(in heating) design temp. The next generation of variable capacity A/C units will provide a little bit more forgiveness in this area in the future.

 

[wyliesdiesels]

You may not get sweating on the suction line depending on outdoor temp and dewpoint.

20 degree delta T is pretty much where you want to be.

Make sure the suction line is insulated well, the cool gas that comes back to the unit cools the compressor, if a bunch of insulation is missing in the attic you won't get much cooling for the compressor.

It sounds like it's doing it's job, without a set of gauges on it to check superheat or subcooling it's hard to be 100% sure.

The situation you are in with a properly sized unit that can't quite keep up due to temps above design temp is why there are so many oversized units out there, as a HVAC contractor you want the sizing spot on but when it is you will get angry customers coming out of the woodwork any time you get conditions above or below(in heating) design temp. The next generation of variable capacity A/C units will provide a little bit more forgiveness in this area in the future.

Thats a good point. I know the insulation is missing in a few spots as rats chewed threw it. Will the missing insulation effect the performance as well or just the life of the compressor?

 

[wyliesdiesels]

Do any of the A/C pros on here know of a decent manifold gauge set that will work with R-12, R-22, AND R-134a? I was looking at a model by 'BACHARACH' that will work with all 3 but couldnt find any reviews on it. I would like to test the refrigerant levels in my house system and i also have to work on the A/C in one of my cars!!

 

[danski0224]

Yes, the furnace/air handler is in the attic along with the vents!! The condenser is outside.

When it was 106f deg outside a few weekends ago, the darn thing ran constant for hours and couldn't get the house below 80f deg! It seems that sometimes the system works pretty good and other times it has trouble just maintaining!

Ductwork and HVAC equipment in an unconditioned attic is just about the worst thing you can do.

Duct or equipment air leakage on the return side can easily erase 30% of the system capacity when 100*+ air is introduced to the system.

Duct leakage on the supply side means you lose conditioned air to the attic. Leakage at the supply registers means you draw hot attic air into the airstream around the boot in the ceiling.

Typical residential duct leakage is 20%.

Pleated "high efficiency" air filters restrict airflow.

Most common HVAC duct insulation or flex duct is R4.2-R8, depending on region, local codes and installation date. Those R values are for properly installed (non-compressed and no gaps) insulation. Installed R values are typically lower, much lower.

Cool air in the ducting is fighting 100+ degree attic conditions while your home at ~75 is fighting the same at the ceiling. The duct air is cooler, so it loses more heat and your attic ceiling probably has more than R4.2 to R8, so what chances do you think the duct has?

Use a good quality digital thermometer (airstream, not one of those point and shoot infrared laser ones) to measure supply air at the equipment and supply air at the register. Do the same for return. That is called heat gain.

 

[danski0224]

Do any of the A/C pros on here know of a decent manifold gauge set that will work R-12, R-22, AND R-134a? I was looking at a model by 'BACHARACH' that will work with all 3 but couldnt find any reviews on it. I would like to test the refrigerant levels in my house system and i also have to work on the A/C in one of my cars!!

Unless you know what superheat and subcooling are (and how to get them), a manifold gauge set will be useless to you. Hint: you will need some more tools. There is more to it than shooting for 70 on the low side.

Most newer cars have variable displacement compressors, so once again, without training and a troubleshooting guide, a gauge set by itself is useless on most cars. The only accurate way to ensure the proper amount of refrigerant is to recover what is there and then weigh in new based on the data tag.

 

[JakeKohl]

Do any of the A/C pros on here know of a decent manifold gauge set that will work R-12, R-22, AND R-134a? I was looking at a model by 'BACHARACH' that will work with all 3 but couldnt find any reviews on it. I would like to test the refrigerant levels in my house system and i also have to work on the A/C in one of my cars!!

Don't bother - the oils in these refrigerants are incompatible. You do not want to take a manifold set and connect it between different systems even if you find one. You need a manifold set for each different refrigerant - they all have their own thread types as well (except for R-12 and R-22...I believe those are the same). R-410 (the new one) is also a new style thread.

 

[brewchief]

Don't bother - the oils in these refrigerants are incompatible. You do not want to take a manifold set and connect it between different systems even if you find one. You need a manifold set for each different refrigerant - they all have their own thread types as well (except for R-12 and R-22...I believe those are the same). R-410 (the new one) is also a new style thread.

Oil issues aside you can buy adapters for 134a as used on autos for a normal manifold set.

410a is the same fittings as all the others, 1/4" flare.
A r-410a manifold set has higher pressure rated gauges and hoses then the older refrigerants(some of the r-22 hoses may now be rated for the higher pressures now however).

Most of my manifold sets are yellow jacket, I've got one imperial set that I don't care for that much but it's a 4 valve set so it is nice for pulling a quicker vacuum on large systems.

As danski pointed out unless you know how to read superheat and subcooling and which one to use based on your system gauges won't help a lot.

 

[JakeKohl]

410a is the same fittings as all the others, 1/4" flare....

The threads are not a standard thread on 410 minisplits.

 

[dbonne]

Unless you know what superheat and subcooling are (and how to get them), a manifold gauge set will be useless to you. Hint: you will need some more tools. There is more to it than shooting for 70 on the low side.

Most newer cars have variable displacement compressors, so once again, without training and a troubleshooting guide, a gauge set by itself is useless on most cars. The only accurate way to ensure the proper amount of refrigerant is to recover what is there and then weigh in new based on the data tag.

I'm with Danski, Unless you know what you are looking at, or if the charging chart is still inside the electrical cover of the condensing unit, gauges will not tell you much.