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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8389
Experience:  Furnace, A/C and heat pump specialist.
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I live in a 1880's two story (approximately

Customer Question

I live in a 1880's two story (approximately 3500sqft)Victorian Home with a metal roof. I have two floors....each having their own separate HVAC systems. The home originally had a 3 ton ac unit downstairs running Freon. It never ever had a problem cooling the entire downstairs. The air handler was/is in the basement and the condensing unit outside under the porch. After the compressor went bad this year, we replaced it with a new 3 ton unit running R410A. We also replaced the inside condenser coil. The unit does the job but not nearly as well as the old unit. We have the digital thermostat set at 70 during the summer and on hotter days (90 degrees or so in VA) the temp moves up to 73 or 74 during the day. Again, this never happened with the freon unit. This disturbs me but I can deal with it.
The real issue is the upstairs unit. Ironically, the upstairs unit went bad about 2 months after the downstairs (lucky me). I had the original upstairs heatpump/ac unit installed in 2002 and it never really cooled the upstairs well when it was hotter (above 85) outside. The company that installed the unit (there was nothing upstairs previously) placed the air handler and venting in the attic so the vents are coming through the ceiling upstairs. I've never had a problem with heat ...but it constantly kicks on the aux heat. When the upstairs AC went bad a few months ago, we replaced it with the same size unit (a 2 ton). They looked at the indoor condensing unit and said as long as we replaced the unit outside with the same size unit we could keep the indoor condensing unit. So ...surprise...the upstairs unit still doesn't' cool well...but now its worse than before. Our high today was 86. At today's high, the indoor temp was 78 ...again, the thermostat was set at 70. At the moment, it is 10PM and 75 outside. The indoor temp is 76. I placed thermometers at the air return (I have one main one and another smaller return in my bedroom) and it mimics the indoor temp:75. I placed a thermometer at a vent where the AC is coming out and it reads 60. I have two ac vents per room, and one in each hallway. My question first is: Does this temperature difference between return and ac vent seem normal or should it be more? I'd surmise the temp difference gets closer and hotter during the day 2. I can't call the installer back for various reasons ...the main being he doesn't do that work anymore. so I am kinda stuck. Im fairly sure that I have enough r410a in the system as it was checked late fall but if I didn't would this be a reason for the difference? 3. Any suggestions? Im at a loss after spending a good amount of money for what I thought should be newer better systems. HELP
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

I. We should have 17 to 20 degrees difference in supply and return.Possibly slightly low on refrigerant.

2. If charge is correct they might not have changed metering device on indoor to work with the R410A properly causing refrigerant to flash too late and therefore not pick up enough heat .

3.My suggestion would be to get a new tech in to first of all check the charge and then make sure metering device is correct.

Both of these will be identifiable by connecting gauges and watching pressures.

Customer: replied 1 year ago.
Ok I can do that. I'm more worried that the system just isn't adequate in general . The air handler again is in the attic which is insulated only with paper insulation. There is no insulation on the venting itself in the attic. The vent work just lays on top. Does this play a factor? I have even debated putting aux fans into the venting to force more air but to be honest, I closed a few vents in not used rooms and there has been no temp difference although air flow feels good in the rooms that are still open. Thought about an attic fan too but if it wouldn't make a difference I don't want to spend the money. At this point...I almost would be tempted to install an additional heatpump and let it cool and heat 1/2 the upstairs and the current do that rest. Just looking to fix it the most cost effective way possible.
Expert:  airheatman replied 1 year ago.

1. How many square feet upstairs ,how high are ceilings and are there a lot of windows?

2. Ductwork definitely needs to be insulated

Customer: replied 1 year ago.
About 1150 sq feet or so; ceilings are about 8 feet. As far as windows, i'd have to say yes a good amount of them. My bedroom has 4, other rooms two each. Halls 1 each. They all have wooden blinds which stay closed all day. The duct work itself appears to be wrapped in a layer of insulation with a silver exterior. Are you referencing blowing additional insulation or wrapping it differently?
Customer: replied 1 year ago.
Feelings about the attic exhaust fan? Additional 3rd system?
Expert:  airheatman replied 1 year ago.

I am speaking of wrapping.Ducts should be wrapped with a 2" vapor bearing .I am thinking also the 2 tons is slightly small.The only way to know that is to run a load calculation on the structure but as a rule of thumb a two ton unit is good for about 800 to 1000 square feet.

An attic exhaust fan would probably help some.If you can get the attic air down from 120 to 130 on a hot summer day to 95 to 100 will make a tremendous difference.

AS for a third system, you might consider installing what is called a mini split to help out on these hotter days

Customer: replied 1 year ago.
Well the attic fan might be a fairly doable alternative and i have no issue wrapping the ductwork with more insulation if needed as well. Is the insulation something I can get at a local store. I looked into minisplit systems a bit yesterday but since the house is in a historic district, I have to be careful because you'd have to mount the unit in a room and they frown on that becuase of historical significant. I was thinking since the duct work was already in the attic that maybe I could just add another heatpump outside and air handler up there but then again...if thats horribly more expensive then a mini split to install...perhaps I could get an allowance. Maybe I should just put in a brand new bigger system.....IDK
Expert:  airheatman replied 1 year ago.

Here is my suggestion.Have another contractor come to give you an "estimate" on replacing system.Ask them to do a load calculation for you to determine what size is actually needed .If indeed a 2.5 or 3 ton is needed,ask about a trade allowance on your 2 ton system. Also have them do an analysis and evaluation of the ductwork.

Expert:  airheatman replied 1 year ago.

If you have further questions, please let me know.

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