This SOLAR PLAN MUST be Possible>>

Blackcherry04 · July 2011

Re: This SOLAR PLAN MUST be Possible>>

drees wrote: »

There's nothing special about high SEER AC units being worse than low SEER AC units at removing moisture. If it's not removing enough moisture that's likely a setup problem where you've got too much AC so AC cycle times are not long enough to remove the moisture (your AC unit is too big).

I have to agree with this one. I just replaced a 4 ton heat pump with a 3 ton. Not only has my electric bill dropped, but the house is much more temperate and comfortable. 15 years ago they used much different heat load calculations and I'v made improvements in windows and insulation, that said the company wanted to put a 4 ton unit back in and be safe and for me to pay for it for the next 15 years. Today I have a 20 + degree temperature differential between in and out and the unit is cycling.

ggunn · July 2011

Re: This SOLAR PLAN MUST be Possible>>

Blackcherry04 wrote: »

I have to agree with this one. I just replaced a 4 ton heat pump with a 3 ton. Not only has my electric bill dropped, but the house is much more temperate and comfortable. 15 years ago they used much different heat load calculations and I'v made improvements in windows and insulation, that said the company wanted to put a 4 ton unit back in and be safe and for me to pay for it for the next 15 years. Today I have a 20 + degree temperature differential between in and out and the unit is cycling.

The thinking used to be that there was no such thing as an A/C that was too big, so home builders would typically oversize A/C units "to be safe". As it turns out, though, an A/C that is too big for a house will start and stop more times in a day (more surge current) and not mix the air adequately for comfort. Go figure.

drees · July 2011

Re: This SOLAR PLAN MUST be Possible>>

Blackcherry04 wrote: »

I have to agree with this one. I just replaced a 4 ton heat pump with a 3 ton. Not only has my electric bill dropped, but the house is much more temperate and comfortable. 15 years ago they used much different heat load calculations and I'v made improvements in windows and insulation, that said the company wanted to put a 4 ton unit back in and be safe and for me to pay for it for the next 15 years. Today I have a 20 + degree temperature differential between in and out and the unit is cycling.

I had to argue and argue with multiple HVAC contractors when I was having my heat-pump put in. They all wanted to put in 4-ton units. Got one to agree to install a 3-ton after running the load calcs. It still cycles - I think a 2 or 2.5 ton would have been plenty - longer cycle times, less noise and less power and lower humidity.

GreenerPower · July 2011

Re: This SOLAR PLAN MUST be Possible>>

drees wrote: »

There's nothing special about high SEER AC units being worse than low SEER AC units at removing moisture. If it's not removing enough moisture that's likely a setup problem where you've got too much AC so AC cycle times are not long enough to remove the moisture (your AC unit is too big).

The hi SEER design is quite different from the traditional design in the past. The refrigerant flow rate, evap. temp, air flow are all tuned to apply the heat extraction to air (edit, I meant) sensible heat removal and minimal on moisture condensation (latent heat). That's how they've got hi SEER. Those units in ~100% humidity climate as ours would get the air out at low temp but still high in humidity. As the result, home owners would set lower thermostat temp to get more "comfortable". Installers can tweak to some degree to get more moisture out but that would result in an overall lower SEER system. Putting extra money to get a hi SEER (> 20) in our climate is a waste, IMHO.

GP

drees · July 2011

Re: This SOLAR PLAN MUST be Possible>>

GreenerPower wrote: »

The hi SEER design is quite different from the traditional design in the past. The refrigerant flow rate, evap. temp, air flow are all tuned to apply the heat extraction to air latent heat removal and minimal on moisture condensation. That's how they've got hi SEER. Those units in ~100% humidity climate as ours would get the air out at low temp but still high in humidity. As the result, home owners would set lower thermostat temp to get more "comfortable". Installers can tweak to some degree to get more moisture out but that would result in an overall lower SEER system. Putting extra money to get a hi SEER (> 20) in our climate is a waste, IMHO.

While a high SEER design may be capable of cooling the air more without removing as much latent heat (moisture), what that really means is that it's more critical to properly choose properly sized equipment.

Your typical way too oversized AC unit will simply not remove enough moisture from the air. Multi/variable stage units may help hide the drawbacks of an oversized system, but way too many HVAC techs insist on installing an oversized system when a much smaller system will be more efficient and provide more effective humidity control thanks to longer cycle times.

GreenerPower · July 2011

Re: This SOLAR PLAN MUST be Possible>>

drees wrote: »

While a high SEER design may be capable of cooling the air more without removing as much latent heat (moisture), what that really means is that it's more critical to properly choose properly sized equipment.

Your typical way too oversized AC unit will simply not remove enough moisture from the air. Multi/variable stage units may help hide the drawbacks of an oversized system, but way too many HVAC techs insist on installing an oversized system when a much smaller system will be more efficient and provide more effective humidity control thanks to longer cycle times.

I'm talking about all properly sized systems here, all else equal. Otherwise it would be comparing apple and orange (even though it's common practice to oversize for most AC installers). Even with a properly sized hi SEER system, the discharged air has higher humidity level (even with long run time) than lower SEER system that is designed to remove more moisture (at the cost of lower BTU/Watt). This is the aspect of our high humidity climate that the SEER standard can not address. People tends to lower the thermostat set-point when humidity level is high to get comfortable whereas they can let it at higher set-point when humidity level is low. Oversize hi SEER system makes it worse - MOLDY environment.

There is a good section about AC and SEER in this - http://consensus.fsu.edu/FBC/ac/Why_People_Florida_May08.ppt

GP

drees · July 2011

Re: This SOLAR PLAN MUST be Possible>>

GreenerPower wrote: »

There is a good section about AC and SEER in this - http://consensus.fsu.edu/FBC/ac/Why_People_Florida_May08.ppt

Yep - very informative.

Mangas · July 2011

Re: This SOLAR PLAN MUST be Possible>>

We decided to run two smaller 2.5 ton variable speed high SEER A/C units rather than one large one. Also at night when the A/C is running, we use fans in our bedrooms to circulate the air.

Splitting the house into two zones conserves power without sacrificing cooling and provides redundancy. In a solar set up like ours, maintaining one temperature setting 24/7 (81 summer) seems to use less power than varying the settings e.g. day vs night.

In addition to Rastra construction, we have retractable shutters on all doors and windows as well as triple pane which significantly reduces how hard the A/C units have to work during the day. These conservation building materials are very important.

Sidebar, after observing power consumption, we disconnected the frequently running heat pumps as they used a large amount of power.

solar_dave · July 2011

Re: This SOLAR PLAN MUST be Possible>>

This looks like an interesting AC setup:

http://www.fafcosolar.com/go-solar/hybrid-solar-air-conditioning/

Uses solar Thermal to help the AC system.

One in action:

http://sensitivedentistry.net/green.html#a18

This SOLAR PLAN MUST be Possible>>

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