dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
1193
share rss forum feed

boaterbob
Premium
join:2005-08-01
Moncks Corner, SC

Heat pump - inside temp 10 degrees higher than set point

I live in North Charleston, SC. Afternoon temps have been in the low 90s. House is approx 2500 sq.ft with one bedroom over the garage with its own t'stat. The main house has 12' ceiling everywhere except standard 8' in the 3 lower bedrooms and baths.

I have a Carrier Heat Pump Model 25HCA342A30 3.5 ton single phase, split system. The system is 5 years old (as is the house). SEER 14. The air handler is in the house attic.

Beginning the first of June (approx) the hp has been unable to maintain the 75 degree set point each afternoon. On the sun side (West side) of the house we have 5 windows that are ceiling to about 3 foot from the floor with blinds - with the blinds closed all the time. The inside temp gets to about 77 degrees by 3pm and goes to about 82 by 6pm - then remains at about 82 until about 8pm when the inside temp begins to drop and gets down to set point (75) about 10pm.

Does this sound like low refrigerant (Puron)? Or, could it be lousy insulation in the attic and/or walls as the major problem? The hp was last serviced about a year ago when the contactor was replaced because the service rep said it was pitted and could fail at any time.

I have a county electric company auditor scheduled to come check the house for energy efficiency - but, of course, he is not an AC person.

Thanks


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
If this is the first time your unit has not been able to maintain your 75 degree set point and nothing else has changed in your house figure on the "Puron" being low in the unit. Measure the air temperature from one of your vents closest to the air handler in the attic. It should be about 60 degrees or lower.


dandelion
Premium,MVM
join:2003-04-29
Germantown, TN
kudos:5
Reviews:
·Comcast
reply to boaterbob
Another thought, I have found heat pumps... particularly Carrier since I have one, are highly susceptible to dust/dirt. Has yours been cleaned recently? I would recommend getting a company familiar with heat pumps to look at your unit if haven't had one yet.

boaterbob
Premium
join:2005-08-01
Moncks Corner, SC

Re: Heat pump-inside temp 10degrees higher than set point UPDATE

Well, here's the deal. The hp required 5.5lbs of Puron. The tech did a leak test ($189) and found only a couple very small leaks (using a probe) - near the bottom of the coil. The coil was iced over for the bottom 1/4 of the coil.

The tech 'suggested' the icing up of the coil was due to restricted air flow which he said was probably due to the filters I used - 3M Filtrete 1500 Ultra Allergen filter.

He said not to use pleated filters, but to use the blue fiberglass inexpensive filter and change them every 30 days.

He also said he would contact Carrier about replacing the evap coil under warranty + $460 labor cost. This tech was not recommending Carrier but suggested Rheem 1st and Trane 2nd as to quality heat pumps.

Will see what Carrier says as to the warranty replacement of the coil. I am the original owner of the house and did my closing 4 yrs and 6 months ago. However, the tech says Carrier may demand to know when the heat pump was 'originally' installed during construction and try to use that date as the beginning of the 5 yr warranty on the coil.

Robert in SC


mattmag
Premium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3


If the system was low, which it apparently was given the discovery of leaks, then undercharge could also be the cause of the icing. Carrier should have a recommended filter chart for their products. If the Filtrete was present on that list, it should be OK to use, although reduced airflow is another cause of icing. The system should have been designed using the "Manual J" calculations, and the filter should be specified as well.

boaterbob
Premium
join:2005-08-01
Moncks Corner, SC
I'm considering using a Flanders
PercisionAire Pre Pleat 40 MERV 8
Replacement Furnace Filter Media
for Carrier HVAC systems - a 2" thickness - my filter holder presently has 1" filters but there is enough space for a 2" filter to be fit in.

Question - is a 2" filter any better than a 1" filter in my situation? Would a 2" filter cause any problems?

Lowe's and Home Depot both carry this brand.

boaterbob
Premium
join:2005-08-01
Moncks Corner, SC
Carrier will replace the leaking evap coil under warranty - I will pay installation costs only.

Kenbass

join:2007-05-10
Athol, MA
reply to boaterbob

Re: Heat pump - inside temp 10 degrees higher than set point

First of all Rheem equipment is much worse than Carrier. Second of all, 3.5 tons for 2800SF? Wow grossly undersized. Rule of thumb if you want to be comfortable is 4-500 SF per ton. You do the math.


jrs8084
Premium
join:2002-03-02
Statesville, NC
kudos:1
Reviews:
·AT&T U-Verse
said by Kenbass:

First of all Rheem equipment is much worse than Carrier. Second of all, 3.5 tons for 2800SF? Wow grossly undersized. Rule of thumb if you want to be comfortable is 4-500 SF per ton. You do the math.

Last I knew is that there are far more variables that determine proper sizing of HVAC equipment than square footage.


mackey
Premium
join:2007-08-20
kudos:12
reply to boaterbob

Re: Heat pump-inside temp 10degrees higher than set point UPDATE

said by boaterbob:

Question - is a 2" filter any better than a 1" filter in my situation? Would a 2" filter cause any problems?

I'm not familiar with the specific filters you're looking at, but in general for filters with the same filtering element, a 2" filter has more surface area and thus will not restrict airflow as much.

/M


Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to Kenbass

Re: Heat pump - inside temp 10 degrees higher than set point

said by Kenbass:

Second of all, 3.5 tons for 2800SF? Wow grossly undersized. Rule of thumb if you want to be comfortable is 4-500 SF per ton. You do the math.

All the old rules of thumb are dead. Yes in the past many installers went by that, but today it's impossible to have any simple formula to determine what the correct size system should be.

You build a 2800SF house with 2x4 walls, 3.5" of fiberglass in the wall, large windows with a low R value, and vinyl siding. I build a 2800SF house with 2x6 walls, 5.5" of spray foam in the walls, small windows with a high R value, and a brick exterior. Do you think our two houses are going to need anywhere near the same size system installed?

The only way to determine what size system you need is to take all the variables into account and then determine the correct size (manual J calculation). 3.5 tons could be grossly oversized for 2800sf under the right circumstances.