BTU calc

[yeldogt]

Or you could use the free one I posted earlier. It did not require much in the way of RTFM.

I'd be interested to hear from people familiar with manual J how well that calculator represents manual J. It tells me I would need about 19k btus to maintain my set heat in my planned 32x48x12 shop, at the 98% coldest outside temp. Other simpler calculators have ranged from half that to 50% more.

(so people don't have to scroll back, it's https://www.loadcalc.net/load.php)

Well if 15k can keep my 1600+ sf shop warm in PA with cold temps .. 19k could easily work for you.

When central heating came in there was no insulation -- big heaters. After WWII makers kept making the big heaters -- that's what was going into all those old houses. People don't understand how much coal was still being used in the 50's .. there was huge market for retrofitting. So what if the units were too big for newer houses with more insulation -- fuel was cheap.

It really did not change at all until the later 70's and not by much .. still 140k heaters in 2500sf houses.

It's a mind set .... how can 20k be enough. It's impossible ..

 

[cosmopedro]

Yep.

I have been doing nothing but heating here in Montana for 29 years. Most of my customers have large commercial shops. If I spent my time overthinking and doing all kinds of calculations like some of you do I would never get any work done. The KISS method works great for both large/small shops.

You guys are what keep me employed! Explaining to folks why their big-ticket HVAC systems don't work and proposing systems that do - by doing heat-loss calculations and on-site visual inspection and building audits!

keep it up - I'm not ready to retire yet!

 

[cosmopedro]

The KISS method I use does not result in overkill.

There are 2 top reasons I have seen in my experience that explains overkill. #1 the engineer, seller, installer, etc goes overkill to cover there own ****. They get to caught up in worrying the customer will complain so they go unnecessarily big. #2 unfortunately we have a very small number of people who are just out there to make as much $$$ as they can without any regards in doing the job right.

ShopSpecialties, I'd never make the assumption that you don't know what you're doing - I don't know you, but I know a ton of other folks who claim their KISS solutions and 25+ years experience mean they know what they're doing only to have major issues a few years down the road, after the install warranty expires. Condensing boilers installed in old facilities when the heating coils weren't changed and the installers just set the supply temp of the boiler to 185 to keep up. Other end of spectrum: boilers short-cycling like a leaky air compressor.

I'm not saying you don't know what you're talking about - I'm saying a lot of folks who follow 'rule of thumb' and/or KISS methodology only care about making it through the installer warranty period.

 

[Shop Specialties]

ShopSpecialties, I'd never make the assumption that you don't know what you're doing - I don't know you, but I know a ton of other folks who claim their KISS solutions and 25+ years experience mean they know what they're doing only to have major issues a few years down the road, after the install warranty expires. Condensing boilers installed in old facilities when the heating coils weren't changed and the installers just set the supply temp of the boiler to 185 to keep up. Other end of spectrum: boilers short-cycling like a leaky air compressor.

I'm not saying you don't know what you're talking about - I'm saying a lot of folks who follow 'rule of thumb' and/or KISS methodology only care about making it through the installer warranty period.

Well you made that assumption in your previous post that I am keeping you in business. That is totally false. I own a specialized business here in Montana where I have been the only one doing it for 29 years. I talk to my customers in person and we discuss real world data. My products provide ROI in as little as 1 month. I provide service after the sale and in fact personally extend the mfg warranty. I do that because I know what I am doing and put customer service as a priority over sales.

 

[yeldogt]

cosmopedro: There is also a lot of -- This is what I did and it works. W/O any real discussion of the building or its insulation/ construction ..or possible shortcomings


This is very common with radiant .... mine has worked for x years and this is what I did. Well -- when the original Levittown got built. They buried copper pipe in the slabs and hooked them up to oil boilers with fin tube on the second floor. Fuel was cheap .. and hay we never get any snow build up around the foundation and the daffodils always bloom early.

God I love my radiant heat .... it worked -- but was it efficient?

How often does anybody get to see the same building -- with different services? That's why it's cool to see a development where they are doing spray foam in some homes and walk through both types. Or experience different building with different equipment -- or different types of radiant

 

[yeldogt]

Well you made that assumption in your previous post that I am keeping you in business. That is totally false. I own a specialized business here in Montana where I have been the only one doing it for 29 years. I talk to my customers in person and we discuss real world data. My products provide ROI in as little as 1 month. I provide service after the sale and in fact personally extend the mfg warranty. I do that because I know what I am doing and put customer service as a priority over sales.

Are you the company in Bozeman

 

[Shop Specialties]

Are you the company in Bozeman

I live in Grass Range but we cover the whole state.

 

[yeldogt]

I live in Grass Range but we cover the whole state.

There is a radiant company there that I have purchased from and will again in a couple weeks once this shut down is lifted.

 

[Shop Specialties]

There is a radiant company there that I have purchased from and will again in a couple weeks once this shut down is lifted.

I bet you are talking about Radiant Engineering or actually the new correct name which is Radiant Design & Supply.

 

[LS6 Tommy]

Come on now. Engineers know everything. And everything they do is well thought out and discussed with all of the other disciplines. So when we get the drawings it's all perfect.

And after it's all installed and running, the tech spends the next few weeks on the site figuring out how to make it work.

Seriously, not all engineers are "bad", but it sure seems like the ones in HVAC have the highest frequency.

Tommy

 

[toyotadriver]

No need to overthink heater sizing for a shop. If you are doing the typical hanging heater most of us use, you don't really have a lot of options in sizes anyway. If your calculation comes up with a recommended 60k furnace, you'll most likely install an 80k. If it comes up with a recommended 30k furnace, most likely you'll install a 50k.

If a Manual J comes up with a recommended 50k and you install a 140k....yes it'll short cycle. If it recommends a 50k and you install an 80k, it'll still work fine.

Garages that aren't heated full time (which is most of them) need more BTUs since they have to heat up everything in the shop. Also, garage doors (even insulated ones) lose a lot of heat compared to an insulated wall. And, when you open a garage door, you have just opened a huge hole to the outdoors. You need quite a few BTUs to make up for the huge (but temp) heat loss.

Garage/shop heater over sizing isn't nearly as important as properly sizing a house furnace.

 

[Mike007]

No need to overthink heater sizing for a shop. If you are doing the typical hanging heater most of us use, you don't really have a lot of options in sizes anyway. If your calculation comes up with a recommended 60k furnace, you'll most likely install an 80k. If it comes up with a recommended 30k furnace, most likely you'll install a 50k.

If a Manual J comes up with a recommended 50k and you install a 140k....yes it'll short cycle. If it recommends a 50k and you install an 80k, it'll still work fine.

Garages that aren't heated full time (which is most of them) need more BTUs since they have to heat up everything in the shop. Also, garage doors (even insulated ones) lose a lot of heat compared to an insulated wall. And, when you open a garage door, you have just opened a huge hole to the outdoors. You need quite a few BTUs to make up for the huge (but temp) heat loss.

Garage/shop heater over sizing isn't nearly as important as properly sizing a house furnace.

I agree. One of the big problems in oversizing is undersized ductwork for size of the installed appliance. That's obviously of no concern with a hanging heater without ductwork.

 

[cosmopedro]

Well you made that assumption in your previous post that I am keeping you in business.

No, I said companies like yours so yes

That is totally false.

Don't be so testy... and I appreciate that you're the one firm I've been able to determine (by your accounts, not mine) that is the exception to the rule. I was/am just trying to help the OP with a problem I might know more about than he does.

Enjoy your day!

 

[Shop Specialties]

No, I said companies like yours so yes

Don't be so testy... and I appreciate that you're the one firm I've been able to determine (by your accounts, not mine) that is the exception to the rule. I was/am just trying to help the OP with a problem I might know more about than he does.

Enjoy your day!

I take my business personal and to be honest I do not like people who throw weak shade. If you want to come at me then do it instead of the silly imply ****. Taking shots at how I run my business is not helping the OP especially since they are not even a customer of mine.

This thread is about helping the OP with his BTU calc so lets try to stay on topic.

 

[Bert_]

I think it's safe to say that while an experienced professional may be able to select the right size heater for the conditions without doing a full heat load calc, an average homeowner can't. Many guys who do it for a living can't either.