Ductless minisplit brands, options, info

SWEI

I would suggest re-running the calcs with 12-16" (or whatever seems practical up there) of new attic insulation. Could be interesting.

Harvey Ramer

Why is your latent load so low?

ChrisJ

Harvey Ramer said:

Why is your latent load so low?

I don't know?
What would you have expected for a loose house like mine?

SWEI

Harvey Ramer said:

Why is your latent load so low?

RH assumption looks like 50%.

ChrisJ

Generally is around 50-55% in the summer with the window units going.

I have a 50pt dehumidifier in the basement that runs nonstop from spring to fall as well maintaining about 40-45% down there.

Harvey Ramer

I just wonder if all the sources of latent were accounted for. The load looks off to me. Do you have a complete breakdown of all building component loads. First floor having a higher load looks a bit strange as well assuming equal square footage. Unless you have a lot of glazing.

3 tons for 1500 sf is out of control. I am not saying it's wrong. Just saying I'm not used to seeing that.

ChrisJ

Harvey Ramer said:

I just wonder if all the sources of latent were accounted for. The load looks off to me. Do you have a complete breakdown of all building component loads. First floor having a higher load looks a bit strange as well assuming equal square footage. Unless you have a lot of glazing.



3 tons for 1500 sf is out of control. I am not saying it's wrong. Just saying I'm not used to seeing that.

House has a total of 20 windows, 24 if you count attic and basement. Most windows are 2.5' x 4' and 150 years old.

No insulation in most walls, no sheathing just clap board with aluminum siding over it.

The 68,000 figure at 0F is very close according to the Ecosteam run times.

Just doing the math in my head, first floor is 122sqft of glass, second is 110sqft of glass.

First floor also has 3 exterior doors.

Also keep in mind, that's a 70F inside temp with 95F ambient.

Harvey Ramer

I don't think 70 deg. with 50% rh is very comfy. 50% rh would be good for a 74 deg. indoor temp. If you want 70, I would shoot for about 43 to 45% rh.

Harvey Ramer

Remember, the purpose of air conditioning is just that. Making it cool inside is just one part of the equation.

ChrisJ

Harvey Ramer said:

I don't think 70 deg. with 50% rh is very comfy. 50% rh would be good for a 74 deg. indoor temp. If you want 70, I would shoot for about 43 to 45% rh.

43-45% would be wonderful, but is that possible with the typical R410 system? Won't I be looking at 50F evap temps?

Harvey Ramer

It certainly is possible. No problem with 410 at all. You just have to select the correct coil and airflow.

JUGHNE

Why do you use 95 design day when you posted earlier you design for your area is 89. That 5-6 degrees can make a fair difference in sizing.
I believe I read that design days were based on 97.5% of actual averages. The other 2.5% (unusually and rarely very hot or cold) is not figured as it would oversize all equipment.
So when it is 95plus outside and it seems that the house is warmish, then you just go outside for 15 minutes and come back in and the house feels great. It is the same logic for heating when you hit 29 below zero, one day in 20 years for me, (with -10 HDD) and the house might be only 65. A quick trip to the mailbox and back will put things in perspective.

ChrisJ

JUGHNE said:

Why do you use 95 design day when you posted earlier you design for your area is 89. That 5-6 degrees can make a fair difference in sizing.
I believe I read that design days were based on 97.5% of actual averages. The other 2.5% (unusually and rarely very hot or cold) is not figured as it would oversize all equipment.
So when it is 95plus outside and it seems that the house is warmish, then you just go outside for 15 minutes and come back in and the house feels great. It is the same logic for heating when you hit 29 below zero, one day in 20 years for me, (with -10 HDD) and the house might be only 65. A quick trip to the mailbox and back will put things in perspective.

Good questions.

We've had several weeks of 92-95F this year, in a row.
The wife said she wants the house cold on those days. I tend to agree. And we all are more then familiar with the phrase "happy wife, happy life".



As far as going outside for 15 minutes when it's 95+ out, that's just silly. Everyone knows that would surely kill me.

We're going to mess with the numbers tonight, both outdoor temp and indoor temp as well as attic insulation and humidity and see what we get.

There's also kitchen load to consider and we kept that on the low side to be honest. Either way I won't be going over 3 tons, but I'd like to see how far 2.5 will take me.

JUGHNE

95 amb is good for the AC business, most of the repairs are outside and take more than those death inducing 15 minutes.
Some people will pay anything to get the AC back on at that time because the house is up to 80 inside.
Then wonder (a day later)why it cost so much for a new cap or contactor change out.

Another question for all: Do the sophisticated heat gain programs take into consideration of the location of the supply registers in the structure? As I said above my office high side wall supplies give me a head chill at 74 and I reset to 75 or 76.
Going to the portion of the house with floor supplies that does not happen.
All of your supply air will be coming down on your head towards the floor, stacking the warmer air up towards the ceiling and heading up your stairwell.

I have had customers get the head chill while in bed, and this was from just one 6" flex run with the round ceiling diffuser.

Techman

Going w/ a 25TD out vs indoor temp is a smart move if you do indeed want below 70*F indoor temp. what happens when the "big" comp is working against the ambient of 80-85*F? The humidity is no longer "in ratio" so the RH% will change. A 2stage comp would help, or a digital scroll.

ChrisJ

Techman said:

Going w/ a 25TD out vs indoor temp is a smart move if you do indeed want below 70*F indoor temp. what happens when the "big" comp is working against the ambient of 80-85*F? The humidity is no longer "in ratio" so the RH% will change. A 2stage comp would help, or a digital scroll.

Hi @Techman
My issue is I don't like the fact a two stage compressor by nature is less efficient in low stage, exactly where it's going to spend most of it's time. I also don't like that no efficiency ratings reflect this as they're all done in high mode.


So, my solution is a whole house dehumidifier combined with a single stage unit. It will likely cost more to run, but it will also do quite a better job. It also gives me the option to bring in outside air when it's cool and muggy outside and squeeze the extra moisture out without cooling the air.

What are your thoughts?

ratio

Have you given any thought to a science fair project? An old condenser, some copper, a few small compressors, or maybe a VFD on one compressor? It would be a lot of fun, & while it wouldn't be as cheap as a plain condenser, you should be able to get something that does exactly what you want as efficiently as current technology allows.

I built a frankencondenser for my brother-in-laws parents out of spare parts I had demo'ed out a few years ago. It lasted a couple've years, but I started out with old, used pieces. Worked fine while it lasted.

ChrisJ

ratio said:

Have you given any thought to a science fair project? An old condenser, some copper, a few small compressors, or maybe a VFD on one compressor? It would be a lot of fun, & while it wouldn't be as cheap as a plain condenser, you should be able to get something that does exactly what you want as efficiently as current technology allows.

I built a frankencondenser for my brother-in-laws parents out of spare parts I had demo'ed out a few years ago. It lasted a couple've years, but I started out with old, used pieces. Worked fine while it lasted.

Hi @ratio
While I like experimenting and playing around, I wouldn't like doing it on something I depend on to cool the house, as well as it could be a serious safety risk as well. What if something failed while no one was home? Could burn the house down etc.

I'd rather have equipment that is known to be reliable in the industry as well as UL (or equivalent) approved.

A few guys have pushed me in the direction of American Standard / Trane and a TAM7 airhandler.

ChrisJ

Hatterasguy said:

ratio said:

, a few small compressors, or maybe a VFD on one compressor?

I know of a compressor that is sitting in his kitchen that he can harvest for this project......................

Can you imagine, 75 monitor top compressors all running together to produce 36,000 btu/h of cooling?

It'd certainly sound beautiful, all chugging along at 1725 rpm.

If only I had $100 to start the project..........

ChrisJ

Hatterasguy said:

ChrisJ said:

Hatterasguy said:

ratio said:

, a few small compressors, or maybe a VFD on one compressor?

I know of a compressor that is sitting in his kitchen that he can harvest for this project......................

Can you imagine, 75 monitor top compressors all running together to produce 36,000 btu/h of cooling?

It'd certainly sound beautiful, all chugging along at 1725 rpm.

If only I had $100 to start the project..........

Is that fridge actually less than 500 BTUH? Doesn't seem possible.................???

My 3 are 480 btu/h with 100°F ambient, 80F dewpoint.
The 1935 models in the same size got bumped up to 500+.

However, keep in mind most modern 18-20 cubic foot models are only around 490 btu/h and I doubt that's at a 100°F ambient. Most modern refrigerators, if not all, cannot cope with temperatures even close to 100°F.

The 1930s machines are grossly oversized by modern standards, you just don't realize how small refrigerator cooling systems are. The 1930s models are expected to run a 30-50% duty cycle while modern ones are expected to run 50-100%.

1933-1934



1935+

ChrisJ

Keep in mind, if you look at the pressures on the 1933-34 machines, if building something modern with that you'd likely use R-11 or R-123 with it.

ChrisJ

Here's some temperatures
July 2016


August 2016

Bob Bona_4

I was forced to design equipment around an ASHRAE "standard" of 84 outdoor in CT to meet Energy Star 3 criteria for several jobs. Ng.

One lady in New Canaan, when she was made aware of the ES3 parameters when she was looking into the tax benefits, said no @$*# way. Still did ground source geo, but sized for her requirements.

Techman

So, with those daily degree # you can pick and choose your desired indoor temp at those ambients and size for the btu/comp load. But,come on ChrisJ, think with your mechanical heart and become one with the comp then decide.

ChrisJ

Hatterasguy said:

Techman said:

But,come on ChrisJ, think with your mechanical heart and become one with the comp then decide.

He really needs to become intimate with this new compressor in similar manner as his intimacy with the steam boiler.

One for each season.

njtommy

Not sure how any one can really cool there house with a 50 degree evap coil. Ran into this with a rheem/ Rudd system at a coworkers house he just bought. He gets 60- 62f supply air. Can't get his house below 75f and 53% Rh. Unit is sized correctly we double checked every thing and made sure every thing was matched. He call rheem/ Rudd and they said yup that's what we want to run at 50 degree coil. I'm not sure the logic behind it.

I like to see 55f supply air or lower. With a 34-40f coil no matter what.

ratio

Annnnd, efficiency trumps comfort.

njtommy

13 seer is bottom of the barrel for a new unit when it comes to efficiency.

ChrisJ

@njtommy do they offer a different metering device for it? Or can you substitute one?

ChrisJ

You know what I don't get?
If any of us vents into the atmosphere we face huge EPA fines.

A few years back my dad's R-22 system with I think a 2007 York blue coated evaporator dumped it's entire load and York fought them over the warranty. Apparently, this was a huge problem with that evaporator according to my dad's HVAC guy and yet York doesn't get fined for ignoring them until they leak? Had it been replaced ahead of time it wouldn't never dumped all of that R-22.

I don't get that?
Am I looking at this wrong, or?

njtommy

I'm not sure if that's really a York evap coil or someone else's labeled York. I know guys where conplaining about them to and I always complain about yorks condenser coils. Lol