Only 24k for 1800sqft?

[brianpgriset]

I am ready to purchase a conventional split system for my shop building. Houston TX area. 30 x 60 x 14 eaves with 3/12 pitch. Wood frame, slab on grade building with steel PBR panel exterior. 3" closed cell foam on roof deck, 2" wall. I then finished out the stud bays with R13 fiberglass both roof and walls. The building uses 2x4 lath between the studs and steel exterior and the foam fills the void between the stud and steel so there is very little thermal bridging. 3 panel doors, all R18 insulated. No Windows. Very tightly sealed.

Everyone keeps telling me I need 3 tons minimum. But right now I just have a 70 pint dehumidifier in there and that alone actually makes it pretty decent.

I used the loadcalc.net calculator for load sizing. It doesn't have options for my construction type so I used assumed stucco/siding R13 with R6 foam board as a best approximation. I then entered in the wall and door surface areas. When I set outside temp to 95 and inside to 70 I'm getting only about 12kbtu heat load. Of that about 9000 is the doors and only about 2000 is the gain from walls. Lighting would add another 1600btu.

This would suggest I could cool the space with a very small system. I understand there are some varying loads like opening the doors, etc but I don't plan to pull hot cars in very often.

From what I see it's very common to oversize. I wanted to buy a 2 ton heat pump. Is this reasonable? Are my load calc numbers reasonable?

I figure, using the loadcalc numbers it'll take about 14000btu to keep the building at 70 with the lights on in the hotest days of the year. That would leave me 10000btu of spare capacity for dropping temps from high, appliances, etc.

I'd probably rather underside than oversize. But I'm curious if anyone else has a very very tight building similar to this.

Because the building is so tight I'd probably rather underside than oversize.

 

[My Old Tools]

My building in east Texas is 30x40x12 with a 6/12 pitch, 22 feet to the peak. It has conventional roll insulation, 7 windows, man door and 12x12 overhead. I put in a 36k MrCool. It is pretty over sized by my estimation. It doesn't hurt anything as it throttles down, but I could have done a 24k easily I think. The first 2 days it ran hard and sucked a ton of moisture out. Once all the machinery stabilized to temperature, it just barely idles even on hot humid days.

 

[brianpgriset]

I see why people like mini splits in this application but I really want a conventional split system for the ducting and filtration. Tough call for sure. Thanks for the data point.

 

[Jackfre]

You can get filter boxes in woodworking stores, Rockler, Woodcraft, etc. I have a JDS that I run in my wood shop and it does an excellent job when combined with primary dust collection.

 

[PoorUB]

I would recommend 3 ton also, but you ran the load calc on it!

One thing to consider, are you leaving the AC on all the time, or shutting it off and back on when you plan on working out there? If you re not leaving it on I would lean towards oversizing the unit. You don't want to turn it on at 100F outside and wait 2-3 hours for it to catch up.

My 24x38x9 foot garage will cool fine on 12,000 BTU if I let it run 24-7. Start it up when the shop was hot and it would never catch up, or at least until evening. When I put in central air I went with 1-1/2 tons and it works well.

 

[kj_mustang]

I have a 32 x 52 x 16 with spray foam and batts. I cool almost half of it with a 1.5 ton central a/c. It works great. I plan on doing a 2 ton package unit for the other half some day.

 

[brianpgriset]

Thanks guys. My plan for use would be to keep it at high 70's on week nights then drop to low 70s on weekends. So somewhere between running all the time and only on weekends.

 

[American Locomotive]

20,000 BTU keeps my 250-year-old poorly insulated ~1800 sq.ft house cool enough on a 95 deg day. For a modern, well-insulated building, the rule of thumb is generally around 1000 sq-ft/ton.

 

[kelpaso1]

Why does everyone continue to use "ton" as a measure? That is so 90's. It's BTU's this century.

 

[PoorUB]

Why does everyone continue to use "ton" as a measure? That is so 90's. It's BTU's this century.

Because it is a standard in the industry?

I have worked in HVAC for twenty years and "ton" is used all the time. Even manufacturers websites list equipment by tonnage.

 

[BillK]

Not sure how hot it is in Texas but . . . . the 30x60 x 15 h unit that my business is in has a 5 ton unit on the roof and the air handler hanging below it on the ceiling. The flat roof has about 6 inches of foam and I am in one of the center units so pretty well insulated on the sides. It was in the low 90's here today and it was running most of the day which is pretty normal. I keep it set at about 73. I do have a large parts spray washer that generates some heat but I keep it closed most of the time and it has a vent up through the roof. I cant imagine a 2 ton doing the job.

 

[kelpaso1]

Because it is a standard in the industry?

I have worked in HVAC for twenty years and "ton" is used all the time. Even manufacturers websites list equipment by tonnage.

Sorry, but standards change and you are behind on the terminology. BTU's is what we use these day's.

 

[kelpaso1]

1, 2 or 3 ton is irrelevant. It's BTU's in a system that matters as a whole. Building size, cooling/heating requirements etc.

 

[rawen2]

I believe that one ton = 12,000 BTU's.

 

[brianpgriset]

What about something like this?

2 to 3 Ton 20 SEER MrCool Universal Central Heat Pump Split System - Upflow/Horizontal

The 2 to 3 Ton 20 SEER MrCool Universal Central Heat Pump Split System is the innovative heating and cooling tool you need to stay warm in winter, cool in summer, and energy efficient every day of the year. Unlike other conventional heat pump split systems, the Universal relies on a DC inverter...

iwae.com

I honestly didnt know they made something like this. Seems like its best of both worlds.

 

[PoorUB]

Sorry, but standards change and you are behind on the terminology. BTU's is what we use these day's.

Um, sorry, I have only been out of the industry a couple months and Lennox listed their units by tonnage and BTU a couple months back. I doubt much has changed in the couple months.

I guess these guys are doing it wrong?

https://www.allied-commercial.com/products/packaged-rooftop-units/z-series/

 

[Jim greengo]

Who's we?
I've been in the trade for 30 years and still use ton also for cooling,BTU's is for heating.

Sorry, but standards change and you are behind on the terminology. BTU's is what we use these day's.

 

[Jim greengo]

1, 2 or 3 ton is irrelevant. It's BTU's in a system that matters as a whole. Building size, cooling/heating requirements etc.

Last time I checked 12,000 was still a ton,18,000 is 1.5 tons.
24,000 is 2 tons..........

 

[pizza]

Why does everyone continue to use "ton" as a measure? That is so 90's. It's BTU's this century.

on that note, why does everyone write BTU when they mean BTU/h?
BTU is a unit of heat, not power (heat per unit time).

"i drove 5 miles" vs "i'm driving 5 mph" -- different meaning.

1, 2 or 3 ton is irrelevant. It's BTU's in a system that matters as a whole. Building size, cooling/heating requirements etc.

what do you mean? it's not a different figure. both are units of heat rate (power).

1 ton of refrigeration = 12 kBTU/h

 

[PoorUB]

What about something like this?

2 to 3 Ton 20 SEER MrCool Universal Central Heat Pump Split System - Upflow/Horizontal

The 2 to 3 Ton 20 SEER MrCool Universal Central Heat Pump Split System is the innovative heating and cooling tool you need to stay warm in winter, cool in summer, and energy efficient every day of the year. Unlike other conventional heat pump split systems, the Universal relies on a DC inverter...

iwae.com

I honestly didnt know they made something like this. Seems like its best of both worlds.

Gree builds that unit for Mrcool. Nice unit. It comes in 2 to 3 TON and 4 to 5 TON.
Gree Flex

 

[kelpaso1]

what do you mean? it's not a different figure. both are units of heat rate (power).

1 ton of refrigeration = 12 kBTU/h

Must be a USA thing. Nobody in Canada uses the term "Ton". It's BTU's, which is the correct term. Do you use Ton for heating too?

 

[American Locomotive]

BTU/h and Ton are equivalent. 1 Ton = 12,000 BTU. Heating is sometimes specified in tons. MBH (1,000s of BTU/h) is pretty typical for boilers and furnaces.

But if you really want to be pedantic, BTU/h is also an archaic standard, with most of the world simply using "watts" or "kilowatts".

 

[pizza]

Do you use Ton for heating too?

probably not what you were asking, but i personally prefer to use SI (i calculate things in watts).

to actually answer your question, tons of refrigeration (TR) are just used to describe the power of cooling systems. that said, there's no reason you couldn't describe a heating system in TR since TR is just a unit of heat rate, but no one does. TR is old fashioned **** like horsepower. archaic but still used.

The ton of refrigeration is equivalent to the consumption of one ton of ice per day and originated during the transition from stored natural ice to mechanical refrigeration.

 

[u3b3rg33k]

I am ready to purchase a conventional split system for my shop building. Houston TX area. 30 x 60 x 14 eaves with 3/12 pitch. Wood frame, slab on grade building with steel PBR panel exterior. 3" closed cell foam on roof deck, 2" wall. I then finished out the stud bays with R13 fiberglass both roof and walls. The building uses 2x4 lath between the studs and steel exterior and the foam fills the void between the stud and steel so there is very little thermal bridging. 3 panel doors, all R18 insulated. No Windows. Very tightly sealed.

Everyone keeps telling me I need 3 tons minimum. But right now I just have a 70 pint dehumidifier in there and that alone actually makes it pretty decent.

I used the loadcalc.net calculator for load sizing. It doesn't have options for my construction type so I used assumed stucco/siding R13 with R6 foam board as a best approximation. I then entered in the wall and door surface areas. When I set outside temp to 95 and inside to 70 I'm getting only about 12kbtu heat load. Of that about 9000 is the doors and only about 2000 is the gain from walls. Lighting would add another 1600btu.

This would suggest I could cool the space with a very small system. I understand there are some varying loads like opening the doors, etc but I don't plan to pull hot cars in very often.

From what I see it's very common to oversize. I wanted to buy a 2 ton heat pump. Is this reasonable? Are my load calc numbers reasonable?

I figure, using the loadcalc numbers it'll take about 14000btu to keep the building at 70 with the lights on in the hotest days of the year. That would leave me 10000btu of spare capacity for dropping temps from high, appliances, etc.

I'd probably rather underside than oversize. But I'm curious if anyone else has a very very tight building similar to this.

Because the building is so tight I'd probably rather underside than oversize.

your dehumidifier ADDS heat(temperature) to the space, so if it's running and not a furnace in there yeah you are likely fine.

FYI: a typical 3 ton 2 stage is 1.98 tons on stage 1. you can have both.

or you could get something like a 3T ODU bosch bova 2.0 system and just pick an airflow target, and let the ODU adjust it's RPMs to match your load. it's basically a minisplit in traditional clothing meant for regular thermostats.

 

[brianpgriset]

Purchased the Mr Cool universal split today from Ingrams. Seems like the best of both worlds; variable output, high efficiency, conventional air handler, and DIY friendly.

Only drawback was it cost a few hundred more than a comparable traditional split heat pump but im willing to sacrifice that for the benefits.

We'll see how it goes.

 

[dcg9381]

I have 48,000 BTU of mini split cooling a 40x60x16 in central Texas. Open cell foam all the way around, maybe R-12 - R-15. 3 huge crappy insulated doors.
Nice thing about mini-splits is you can always add another..

 

[Yankeefarmer]

Purchased the Mr Cool universal split today from Ingrams. Seems like the best of both worlds; variable output, high efficiency, conventional air handler, and DIY friendly.

Only drawback was it cost a few hundred more than a comparable traditional split heat pump but im willing to sacrifice that for the benefits.

We'll see how it goes.

I think you’ll be happy with it. I installed the 4-5 ton model (based on heating needs) and am very satisfied. Just yesterday I saw a video from Ingram’s affirming that the warranty is valid with a DIY installation if you use their precharged line set.

 

[brianpgriset]

Thanks. Just showed up on the truck this afternoon.

 

[kelpaso1]

Why do you guys keep saying "tons"? Mini splits are rated in BTU's (at least up here). I don't care if 1 ton equals whatever BTU's. Use the correct terminology.

 

[SALIV8]

you keep repeating yourself but nobody cares.
And they are not talking about mini splits anyways. Lol

 

[Selkirk]

Purchased the Mr Cool universal split today from Ingrams. Seems like the best of both worlds; variable output, high efficiency, conventional air handler, and DIY friendly.

Only drawback was it cost a few hundred more than a comparable traditional split heat pump but im willing to sacrifice that for the benefits.

We'll see how it goes.

Please keep us posted on how the install goes, and you thoughts on the Mr Cool universal quality. I have a weekend place that needs a new split system, Mr Cool universal and maybe Bosch heat pump split are on my short list.

 

[Bert_]

Why do you guys keep saying "tons"? Mini splits are rated in BTU's (at least up here). I don't care if 1 ton equals whatever BTU's. Use the correct terminology.

Why do you keep talking about BTU. Down here the standard is "ton".

If I talk to my wholesaler and ask for 30,000 btu he's going to say "how many ton is that?"

 

[kelpaso1]

Why do you keep talking about BTU. Down here the standard is "ton".

If I talk to my wholesaler and ask for 30,000 btu he's going to say "how many ton is that?"

Opposite can be said here. I could ask for a 3 ton unit and they will ask how many BTU's?

 

[like2wheel]

Anybody know the setting to ignore a poster on this new format?

 

[haveissues]

Anybody know the setting to ignore a poster on this new format?

Hover over their name and click ignore.

 

[like2wheel]

Hover over their name and click ignore.

Thanks.
Problem solved

 

[Bert_]

Opposite can be said here. I could ask for a 3 ton unit and they will ask how many BTU's?

That just went right over your head...

Nobody else in this thread is going to talk to a supplier in Canada. In this thread it doesn't matter what unit of measure you use... It's that simple

 

[kelpaso1]

WT.. are you talking about? There are a lot of Canadian members here reading this.

 

[Trock03]

Hey OP I'm in the Houston area and an curious to know how this works out for you so please let us know how it goes. Knowing your results might help me out a TON on my project.

kelpaso1 - I hope my use of ton didn't offend you. Enjoy your BTUs and your round bacon.

TC

 

[man00]

I been looking at a 96000 oz mini split