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I didn't see this mentioned anywhere.
When we moved in to this house, PSCO did a free energy audit.
Maybe you can go that way. You might have your power company check the meter too.
When we moved in to this house, PSCO did a free energy audit.
Maybe you can go that way. You might have your power company check the meter too.
If it were me, I would find out my delta t from the supply/return based on the type of system you have installed. I would expect around 15-20 degrees. That could mean your system is doing the best it can for the current conditions (outdoor/indoor). If the delta T were struggling, I would check the evaporator coil for blockage, check filter, then I would look at condenser coil and make sure it is clean and free of debris, and open to fresh air. I would then have a refrigeration tech check the sub-cooling and pressures. If they are out of design, could be blocked expansion valve, or something fouled in the piping.
And how would you come up with these computations\know what it's specs are?
If it were me I'd call some who knows what they're looking for...in the business......:-$
Well I am a mechanical guy, so I can get the answers I need by finding out for myself. Not everyone is like that, and doesn't care to understand how an A/C system operates and that is fine. However, a set of refrigeration pressure gauges, and a temperature gauge (a thermistor or thermocouple style) will tell you a lot of what you need to know about the refrigeration cycle and the condition of the standard split system. By reviewing a refrigeration chart crossing it with the pressure gauges and measuring sub-cooling, will tell you the health of the system.
It all comes down to a price of some sort...everything we do everyday costs money. I would pay for someone to analyze my unit. If it was not performing up to par, see what it costs to get it to working as design. If the contractor says the unit is doing all it can do, then I would ask for him to provide a quote on replacing with a unit that will accomplish my heat loads, and ask if he will waive the cost of analysis of the old unit if you use him to install the new unit.
Something to remember on split systems, the tonnage is based on CFM of Air flow as well...if you try to increase your tonnage and your ducts are not able to handle the extra flow, then the blower fan slows down, and you get a large delta T on the supply/return, and sometimes that can cause performance issues. As others have stated a short-cycling will cause extra wear on the motors, but also cause humidity issues within the home. A system, in my opinion is properly designed if it needs to run +60-70% of the day when the outdoor temperature is above 95F. Just think about how long the average cooling season is, and the amount of days we are really in the +95F. why size for the higher temps when we are in them less than the average temps of around 90F for the remaining summer.
A contractor will know if the system is over/under charged on refrigerant, or if there is a stuck valve or blockage. You pay for what you get with this type of technical evaluations...you will need to find a competent contractor.
Most of the time in the middle of the summer and the +95F we are getting here...the units are just doing the best they can as they were designed to do. I have seen some engineer around town size their units for 100F because of the few weeks we can have of +100F ambient weather.
Absolutely correct. By saying undersizing can be acceptable or good, I mean a slight difference. Say your house calculates out to need a 3.25ton unit; well, they are typically sold in .5ton increments, so you would be better off with the slightly undersized unit vs the oversized unit.
However, that is also based on older units that did not have variable speed fans. If your system can run at a lower speed when maximum capacity is not needed, then slightly oversizing would not be a negative attribute anymore.
LOL!!!!
So we now see that the only valuable advice you have is "call a pro"
Delta-T is the difference in temperature. Measure temp going in (at intake) and exit (exhaust (cold air) vent closest to blower unit).
The specs are printed on the labels shown earlier in the thread.
when sizing a non-spec build it's better to round up a 1/2 ton vs down. reason is simple .. a bit of headroom for extreme temps can be a good thing. you just don't want to be way off .. like say installing a 5 ton on a 1500sf home. but if you are that close rounding up or down, both will probably work fine.
to explain why one constantly sees .. "call a pro" .. HVAC work can get very complex in a hurry. correctly diagnosing what's actually wrong can make a HUGE difference in costs to fix. below goes into a tiny portion of what a competent HVAC tech does ...
for instance your example above of variable fan speed and sizing really has little to no relevance. variable speed fans are controlled by newer units with electronic boards. low speed to keep air constantly moving .. medium speed for heater which needs slower air speeds .. high speed if needed to achieve air flow needed to meet AC mfg spec's or what ever ...
your AC is spec'd by the factory for XX CFM airflow to keep coils from freezing up. then we get into metering devices .. TXV or piston .. superheat is the amount of heat removed by refrigerant after it passes through A coil or evaporator. a thermal expansion valve will open or close depending temperature. a fixed orifice or piston meters a set amount of refrigerant controlled by piston size.
dialing correct amount of refrigerant for TXV is different vs piston. with TXV using subcooling one needs to insure a full stream of liquid refrigerant just before TXV but not so full system slugs liquid to compressor which can kill it ... to properly charge a piston unit one needs to measure superheat ... measure wet bulb temperature at intake duct. then measure outside temp by condenser. the correct superheat range can be found using a chart for fixed metering devices.
then factor HVAC work is one of the most equipment intensive or all the trades ... a competent/honest tech is an asset! you cannot blame a pro for not wanting to explain how to fix your HVAC unit .. it might have taken him years to figure out .. not to mention the very expensive/on going costs for equipment. then factor all the new equipment coming out ... for instance above explanation for variable fan speeds can be thrown out for ductless mini-splits .. which can use DC driven variable speed compressors and fans.
here's my latest equipment purchases .. Appion G5 recovery unit and Digicool AK9000
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The reason I asked was to show that the average home owner ....won't have a clue
Good advice was given
The reason I say call someone that knows is to save money and time
LOL, I'm an ICC licensed mechanical inspector with 35 yrz experience in the field
So, instead of trying to buzst someone's balls , why don't you just try to help
Thanks and Good Luck
Good advice was given
The reason I say call someone that knows is to save money and time
LOL, I'm an ICC licensed mechanical inspector with 35 yrz experience in the field
So, instead of trying to buzst someone's balls , why don't you just try to help
Thanks and Good Luck
Yea those are cool cy
Imagine going from slugging a unit to measuring weight to charge a unit
Then some of the newer refs on the market that are charged in liquid,
I don't mean to upset anyone, like was said ...bad info can be Really bad
But I'm still learning....Thanks......:-)
Imagine going from slugging a unit to measuring weight to charge a unit
Then some of the newer refs on the market that are charged in liquid,
I don't mean to upset anyone, like was said ...bad info can be Really bad
But I'm still learning....Thanks......:-)
Having extra tonnage is like 4 wheel drive.
