New AC Troubles (Houston, West: house, contractor, calculation)

[Picketfence16]

Our house is 2200 sq ft.and originally had a 3.5 ton ac (Carrier), which worked fine for 15 years, but was starting to give out. We changed the AC, and put in a 4 ton unit thinking the previous ac was unable to keep up with the set temperature in the last few years because it was too small. That was the feedback we received from some of the service techs also.

With the new 4 ton ac, both the evaporator coil and the external compressor/radiator (York) was changed. The blower and the ductwork is unchanged. The problem we have is that the evaporator unit gets very cold and sometimes ice forms on it. Also the refrigerant return pipe freezes between insulation pieces. The AC stops cooling when this happens. If it is turned off, it starts to cool again. The Freon pressure is ok— checked twice, by two different companies.

What might be the problem? Weak AC? Loss of cold air? Bad blower motor?

Our windows are East and West facing. I am sure that doesn't help, but a brand new ac should be able to maintain a temperature of 74/75.

On good days, temperature hovers around 80-85. On bad days, when we see ice forming, it can go up to 95 as we have to give the unit breaks by turning it off!

Any ideas what could be the issue?

[Even Further]

That doesn't sound right. When I had my AC changed out, and increased to 4 ton, the air handler/blower, evap coil, coolant lines, condenser, were all changed out. The return duct was changed out to a much larger size, and the return grill/filter was changed out to a larger size. I'm not that knowledgeable about A/C, but it sounds like there is not enough air movement passing the coil, by a significant amount.

[aero100]

As Even Further said, coils generally freeze because there is not enough airflow. Using the old blower is concerning when the tonnage is being increased. More tonnage needs more airflow, which will be a combination of a larger blower and (possibly) increased size in the ductwork.

First, a long shot - if you are using an expensive pleated filter take it out and put in a cheap fiberglass one. That will increase airflow.

Second, another long shot - there has been an industry-wide problem with a rust inhibitor that was being used by a scroll compressor supplier (Copeland, who supplies many companies). The inhibitor caused the TXV (thermal expansion valve) in systems to gum up and fail. It happened on my new AC and as the TXV degraded it manifested itself in frozen coils. This was discovered with new units sold last year and there's been a lot of service bulletins (and a lawsuit) that have resulted. At least its something to ask about.

Third - did the AC company do any design work at all? In general, when HVAC is done correctly they will do a heat load calculation that takes into account square footage, windows, insulation, etc. They will also evaluate the supply and return ductwork and how many CFMs that can be delivered. Simply bumping up the tonnage by a half ton because the old system was struggling is what I would expect from some of the cheaper "rule of thumb" guys.

For some reason skipping the load calc is pretty common in Houston (probably because it is so hot it is really difficult to oversize systems) but many of the pros I've talked to tell me you should throw out any contractor who doesn't plan to perform one in the bid phase.

So...they may have misdesigned the system. Something is definitely wrong with your setup and you should stay on the installation company (and possibly hire a second contractor) to get it understood and corrected. Keep in mind this may involve a new blower/furnace and upgraded ductwork. I'm really skeptical of these guys if they just sold you a bigger compressor without advising you of the other things that may need to be done with the system. Is this a reputable company?

[DSL_PWR]

If you added tonnage you should have changed the ductwork.

I have a 3500 sq ft home and a 3.5 ton zoned system. It stays 72-74 in my home even in 100+ degree temps.

[Joe33]

Originally Posted by aero100

As Even Further said, coils generally freeze because there is not enough airflow. Using the old blower is concerning when the tonnage is being increased. More tonnage needs more airflow, which will be a combination of a larger blower and (possibly) increased size in the ductwork.

First, a long shot - if you are using an expensive pleated filter take it out and put in a cheap fiberglass one. That will increase airflow.

Second, another long shot - there has been an industry-wide problem with a rust inhibitor that was being used by a scroll compressor supplier (Copeland, who supplies many companies). The inhibitor caused the TXV (thermal expansion valve) in systems to gum up and fail. It happened on my new AC and as the TXV degraded it manifested itself in frozen coils. This was discovered with new units sold last year and there's been a lot of service bulletins (and a lawsuit) that have resulted. At least its something to ask about.

Third - did the AC company do any design work at all? In general, when HVAC is done correctly they will do a heat load calculation that takes into account square footage, windows, insulation, etc. They will also evaluate the supply and return ductwork and how many CFMs that can be delivered. Simply bumping up the tonnage by a half ton because the old system was struggling is what I would expect from some of the cheaper "rule of thumb" guys.

For some reason skipping the load calc is pretty common in Houston (probably because it is so hot it is really difficult to oversize systems) but many of the pros I've talked to tell me you should throw out any contractor who doesn't plan to perform one in the bid phase.

So...they may have misdesigned the system. Something is definitely wrong with your setup and you should stay on the installation company (and possibly hire a second contractor) to get it understood and corrected. Keep in mind this may involve a new blower/furnace and upgraded ductwork. I'm really skeptical of these guys if they just sold you a bigger compressor without advising you of the other things that may need to be done with the system. Is this a reputable company?

Check the filter and make sure all your vents are open.

Going from 3.5 to 4 ton shouldnt be a problem with ductwork or the blower in the furnace. Especially in the summer.
Go to all of your registers and make sure that plenty of air is coming out of them.

If it started right after they installed the unit, It is either they left something in the evaporator which is blocking airflow (packaging) or the fan motor speed was turned down.

If it is the TXV problem as mentioned above, just the evaporator itself would collect some ice but it will not travel back down the suction line. It dosent generally ice up the entire evaporator.

Try some other service tech. Neither one of the ones who said the charge was correct know what they are doing.

[Picketfence16]

Thanks.

First, a long shot - if you are using an expensive pleated filter take it out and put in a cheap fiberglass one. That will increase airflow.

We downgraded the filters to the No. 2 to help with the airflow.

Third - did the AC company do any design work at all? In general, when HVAC is done correctly they will do a heat load calculation that takes into account square footage, windows, insulation, etc. They will also evaluate the supply and return ductwork and how many CFMs that can be delivered. Simply bumping up the tonnage by a half ton because the old system was struggling is what I would expect from some of the cheaper "rule of thumb" guys.

Our guys didn't do the calculations. It seems that the blower might be the problem. They didn't change the blower motor speed, as far as I know. The airflow from the vents seems weaker in the day compared to night, at least subjectively. Although it could be just my imagination/the air isn't cold enough.

If it started right after they installed the unit, It is either they left something in the evaporator which is blocking airflow (packaging) or the fan motor speed was turned down.

It started about two months after installation. The weather was not as hot before, and that may be why we didn't notice the problem. We are trying to insulate the house for now- just so that the AC doesn't have to be on as much so it would ice up. It also should save us some electric bill. It appears to help.

Does anyone in Houston have a mechanic/company they can recommend?

[aero100]

I wish I could recommend a company. I won't recommend mine. I had the same sort of problems on a new system that I paid five figures for and it took the better part of a year (and over a dozen visits) to get right, but they did.

While (hopefully) someone gives you a good recommendation, I'm not sure how far you've escalated with the original installing company. They clearly screwed something up, there's no way that a new 4 ton unit should be freezing up and leaving your house in the 80s when the old 3.5 ton system was cooling adequately. Joe33 had a few other good ideas of things they may have not done right.

If you haven't done so already, it's time to call the installing company and insist on speaking to the operations manager or the owner. This troubleshooting is probably beyond their standard issue tech and I'd insist on a senior person. Be professional but firm - the system you purchased has not been installed/commissioned correctly. Keep a log of every communication with them. Every time the tech is there, you need a DETAILED receipt on the work performed/what they did/what they checked. I bought a data logger for $80 at Fry's and started keeping a record of the temps in the house.

Another resource forum you can try is the forum at hvac-talk.com. There is a section there for homeowners to post questions and only professionals are allowed to answer. That forum was invaluable when I was fighting my issues and I know there are Houston techs there, that would be a good source for a company recommendation. I found the guys on that forum really had a passion for the business and customer service (after all, they were helping people online for free) so I'd trust their opinions.

[Picketfence16]

Thanks for recommending this site.

Originally Posted by aero100

Another resource forum you can try is the forum at hvac-talk.com. There is a section there for homeowners to post questions and only professionals are allowed to answer. That forum was invaluable when I was fighting my issues and I know there are Houston techs there, that would be a good source for a company recommendation. I found the guys on that forum really had a passion for the business and customer service (after all, they were helping people online for free) so I'd trust their opinions.

We will definitely not be using the guys that installed the new unit. It is very clear they are way in over their heads. This is a small self-owned company, so unfortunately we may not get very far with raising the issue with them.

At this time, we want to consult with a reputable company that can actually perform the work. We asked another big name off Beltway 8 to come out and take a look and their tech wasn't able to tell us anything.

It seems like on hvac-talk most of the guys responding are professionals. It looks like a great tool.

I would also like to get some input from the residents here on which companies they went with and liked.

[DSL_PWR]

I would suggest that if you have a sincere care about the AC system in your home that you contact the TDLR with Texas and file a complaint should you close on the house. Voice your concerns and document everything and then you will have a case to have your system fixed at their expense and the state will make them correct everything until you are completely satisfied and the state has verified that all concerns are addressed and rectified.

Trust me as I just went through this not to long ago.

The state made the installing ac company spend approximately $15k to remedy the issues and bring my system up to code as well as to solve the airflow, return air, and zoned issues my system was having. It's a lengthy process but was well worth it in the end.

Good luck.

[txdemo]

I don't have any experience with this at all but we had our entire system changed out (not the ductwork) and we used NRG Home Services. We've had no complaints and have had great responsive service. 8 years labor and 10 years parts warranty.