Running a small 5,000 BTU 115V Window Air Conditioning Unit

[littleharbor]

This previous quote doesn't seem to appear in this string, huh?
Originally posted by sdold
You know, if I was one of the professional engineers here who has volunteered to help you on his own time, I'd find that last statement to be pretty damned insulting. Calling the information you've received "meaningless calculations" is effectively telling them that the time and money they've invested in their education, years in training, and passing the PE amounted to nothing. This is how you thank them? Now I know why Dereck and Russ are the way they are.

[SunEagle]

This previous quote doesn't seem to appear in this string, huh?
Originally posted by sdold
....

The reason is it no longer available is because it was deleted by the person that posted it.

Not sure why sdold deleted it but I have to agree with him that some people just don't want to be helped by the professional engineers on this forum.

IMO for those that turn up their nose to this type of help is being a little pigheaded or jealous for not going out and getting their PE license.

[J.P.M.]

The reason is it no longer available is because it was deleted by the person that posted it.

Not sure why sdold deleted it but I have to agree with him that some people just don't want to be helped by the professional engineers on this forum.

IMO for those that turn up their nose to this type of help is being a little pigheaded or jealous for not going out and getting their PE license.

I try to avoid getting mouthy in/around areas where I don't know enough to have an educated opinion, and share what I think I might know when/if I think it may be correct, helpful and/r informative.

Often, I've observed those lacking self confidence are more easily offended than others more mature and comfortable in their own skin, regardless of the level of their technical knowledge.

When asking/seeking advice to reduce my ignorance about something, I say thank you for the consideration, ask clarifying questions as necessary and try to learn, remembering that none of us is as smart as all of us, and also that all of us act like assholes 1X/a while.

But, IMO, it's sad when an ignorant opinion must be considered equally as valid as an informed, experienced opinion simply out of misplaced political correctness that must make all opinions equally correct. The easily hurt feelings of immature snowflakes are one bane to knowledge exchange and progress we could all do without.

[sdold]

I deleted it because after reading it a few times, I decided it wasn't helping and that I was just venting frustration. But I still feel that way, where else can you get free professional help like this? If this was a legal forum populated by attorneys, would people be so quick to dismiss free legal advice? The answer is no, because people understand that sitting in their attorney's office for an hour will cost them $300 or more, but they have no idea what it takes to become a PE and therefore don't value the advice in the same way, but they should.

[Higher Voltage]

I ran my ac this summer.Only on sunny days was it needed and usually after lunch,when the batteries have had a good charge.Whats funny is that my 5000 btu 4.6a ac unit made by Gree ran almost completely off the panels and didnt even touch the batteries.It only cools for 20 min @ 4.6 a then 1.2a just fan for 20min . Its doable. I set up my solar differently then most.

[Higher Voltage]

The big thing is tring to run the heat in the winter. Its the oppiste. no sun run at night.

[bcroe]

Winter (where it get pretty cold) is a reason for grid tie. Bank in summer, withdraw in winter. Bruce Roe

[Higher Voltage]

Either way Id be cleaning off the panels.Grid tie or not

[max2k]

I ran my ac this summer.Only on sunny days was it needed and usually after lunch,when the batteries have had a good charge.Whats funny is that my 5000 btu 4.6a ac unit made by Gree ran almost completely off the panels and didnt even touch the batteries.It only cools for 20 min @ 4.6 a then 1.2a just fan for 20min . Its doable. I set up my solar differently then most.

not enough details; I can also state I ran my 36,000 BTU ACs this summer for 7 hrs on average daily off my solar but without details it would sound like bragging and not meaningful discussion. No matter how different your setup is the law of energy preservation still applies so 'doable' is not an argument.

If you had your AC on for only 40 min and it was enough for entire day it would mean you either live in relatively cool climate or have very efficient home or combination of both. Without context that statement doesn't mean much.

[J.P.M.]

not enough details; I can also state I ran my 36,000 BTU ACs this summer for 7 hrs on average daily off my solar but without details it would sound like bragging and not meaningful discussion. No matter how different your setup is the law of energy preservation still applies so 'doable' is not an argument.

If you had your AC on for only 40 min and it was enough for entire day it would mean you either live in relatively cool climate or have very efficient home or combination of both. Without context that statement doesn't mean much.

If anyone cares: Any HVAC unit will only run long enough to satisfy the load it sees. If a window shaker sees a small load, as when cooling a well insulated space, for example, it will not run much.

If an A/C unit, window, central or otherwise is oversized, it may well produce less than desirable comfort levels in a conditioned space by not running long enough to knock enough moisture out of the dwelling air, resulting in cooler air in the dwelling that's more damp than a smaller unit running longer would produce. That happens a lot when older houses are retrofitted with a lot of insulation and building sealing without consideration of the HVAC equipment, particularly in the SE part of the U.S. and especially when a dwelling is tightened up and air leakage is reduced.

[max2k]

If anyone cares: Any HVAC unit will only run long enough to satisfy the load it sees. If a window shaker sees a small load, as when cooling a well insulated space, for example, it will not run much.

If an A/C unit, window, central or otherwise is oversized, it may well produce less than desirable comfort levels in a conditioned space by not running long enough to knock enough moisture out of the dwelling air, resulting in cooler air in the dwelling that's more damp than a smaller unit running longer would produce. That happens a lot when older houses are retrofitted with a lot of insulation and building sealing without consideration of the HVAC equipment, particularly in the SE part of the U.S. and especially when a dwelling is tightened up and air leakage is reduced.

some of us still care, thanks for pointing to HVAC size/humidity relation, I bet this gets regularly missed.

[J.P.M.]

some of us still care, thanks for pointing to HVAC size/humidity relation, I bet this gets regularly missed.

Missed my butt. I bet most are clueless about most of it.

[Higher Voltage]

I live in a cooler climate.Think we passed 30 C 5 times this summer. Honestly anything is doable but at what cost. I dont have a big system and it definity isnt professional. Just conversation

[max2k]

I live in a cooler climate.Think we passed 30 C 5 times this summer. Honestly anything is doable but at what cost. I dont have a big system and it definity isnt professional. Just conversation

it's not about just absolute max, it's about relative humidity as well: 25C at 95% feels 'hot' simply because there's not enough temp difference for the body to cool down so you start to sweat but due to high humidity that doesn't work either so you end up having sauna for free. Canadians have special expression for this: 'sticky weather'. If you have oversized AC it will cool air too quickly leaving most of the air moisture where it was and actually bringing relative humidity practically to 100% making air very 'dump' inside the house, that's what JPM was pointing to.

[J.P.M.]

it's not about just absolute max, it's about relative humidity as well: 25C at 95% feels 'hot' simply because there's not enough temp difference for the body to cool down so you start to sweat but due to high humidity that doesn't work either so you end up having sauna for free. Canadians have special expression for this: 'sticky weather'. If you have oversized AC it will cool air too quickly leaving most of the air moisture where it was and actually bringing relative humidity practically to 100% making air very 'dump' inside the house, that's what JPM was pointing to.

Actually Max, it's more about about dew point temperatures, how oversized HVAC systems do not lower the dew point temps. as much or as effectively as less oversized systems will, and the difference between dewpoint and skin temp. At a given (probably elevated) body temp., the hypothalamus gland will tell the sweat glands to produce liquid to, in effect, turn the body's surface into an evaporative cooler to reduce or regulate the body's temp. For the most part, and to a 1st approx., but not exactly, for the same activity level, the body will produce as much sweat in an environment that has a 20 deg. C. dewpoint as it will in an environment that has a -5 c. dewpoint. The difference is that in a lower dewpoint environment most, or all of the sweat will evaporate, while in the higher dewpoint environment, it will not. That non-evaporation will not cool the body as effectively and cause sweating to continue as the hypothalamus attempts to maintain homeostasis. This is usually a not too comfortable situation for most folks.

On the HVAC side, oversized systems, in a counterintuitive way, do not wring as much moisture out of the air as smaller capacity systems, mostly but not entirely because their compressors do not run as long, and so don't have as much moist air going through them. That means the dew point of the air in the conditioned space says high(er) - the air tends to stay more humid - making the temp. difference between the dew point and the skin less, with the dew point temp. and what's called the dry bulb temp, closer together. Since the difference between the dew point and the skin temp. is what drives the rate of sweat evaporation, less sweat will be evaporated, with the ensuing discomfort as described above as a result.

The ways Psychometrics and physiology interact are quite interesting but one of the less precise fields of engineering endeavor,

FWIW, the actual condensate load (how much moisture is "knocked out" of the air in the cooling process) can be anywhere from zero to maybe ~ 20% - 30% of the load the air conditioner sees.

Take what you want of the above. Scrap the rest.