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Furnace BTU's

Old 09-12-2013, 10:01 AM
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Default Furnace BTU's

Building a 2,000 Sq. ft home in south Jersey on the water, for gas service I need to know the number of BTU's my system will produce. Any guess as to what that number might be? I don't yet have a contractor lined up so I cant ask him. Again just looking for a guess. It's a modular w 6" walls fully insulated but not over the top, R30 up top.
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Old 09-12-2013, 10:20 AM
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What gas appliances do you plan on having? Emergency generator, gas logs, gas fire pit, etc?
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Old 09-12-2013, 10:29 AM
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forced air? Water Baseboard? Using Natural Gas to heat your water, cook, etc?
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Old 09-12-2013, 11:06 AM
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Sorry I was on the run before and time was short. Forced hot air furnace, hot water heater (50gal.) nice stove but not industrial maybe a gas fireplace at some point but not now. I can est all items I need but the heat at this point, so any help will help. Time is an issue. there will be 3 sliders in the house with basic windows in every room. totaling 12 windows (plus sliders).
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Old 09-12-2013, 03:28 PM
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My boiler is 130,000 btu which came with the house. That's the largest consumer. A few years ago I switched to an indirect water heater so no additional gas there. Stove and dryer are minimal use.
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Old 09-12-2013, 03:35 PM
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I would go with 200,000 being on the water and heat loss from sliders. There are sights on line that you can enter your info about the house and area and get a heat loss and recommened BTU's
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Old 09-12-2013, 03:36 PM
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I want to say I previously had two 89 k btu furnaces for 3500 square feet in ri. I think if you used 100 k btu you would be safe. I have sliders, lots of windows and 2x6 construction.

Also note that you will likely need 1" pipe anyhow, as 3/4 is only good for about 100k assuming a 50 total run including fittings. 1 " is good to about 177 k. Now if you have a hig output stove you are already at 15 k per burner for total of 60, add in a 40 k fireplace and 100 k furnace you are already at 200k before water heater. That tells me they will likely need to upsize t 1 1/4" whic jumps to double btu capacity of about 350 k.

I would be very surprised if 2000' of new constructin needs more than 100 to 150k btus. Probably does not matter as I suspect you are jumping to 1 1/4 anyhow.

Talk to the gas company to see how close you need to be and what it means.
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Old 09-12-2013, 03:52 PM
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Originally Posted by BACKTOTHESEA View Post
I want to say I previously had two 89 k btu furnaces for 3500 square feet in ri. I think if you used 100 k btu you would be safe. I have sliders, lots of windows and 2x6 construction.

Also note that you will likely need 1" pipe anyhow, as 3/4 is only good for about 100k assuming a 50 total run including fittings. 1 " is good to about 177 k. Now if you have a hig output stove you are already at 15 k per burner for total of 60, add in a 40 k fireplace and 100 k furnace you are already at 200k before water heater. That tells me they will likely need to upsize t 1 1/4" whic jumps to double btu capacity of about 350 k.

I would be very surprised if 2000' of new constructin needs more than 100 to 150k btus. Probably does not matter as I suspect you are jumping to 1 1/4 anyhow.

Talk to the gas company to see how close you need to be and what it means.
Unfortunitly the gas company is why I'm here asking this question. No offense to any member here but I've got replies all over the place right now so I may have to call a contractor or maybe the builder will have some input.

Thanks
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Old 09-12-2013, 04:49 PM
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Less than 100,000 BTU's. When you buy, a 2 stage isn't a lot more $ and your system will run on 60K BTU most of the time.

For example, my house in CT was built in the 50's with little insulation. I added new windows and doors and an addition that doubled the sq ft that I built in the 90's with a total of 2800 heated sq ft. The boiler did the heating plus 2 indirect water heaters. The boiler input was 105,000 BTU's.

For the gas company, you'd be safe at 100,000 BTU. Let the experts chime in. BTW, I helped (in a small way) with the development of Wrightsoft http://www.wrightsoft.com/ and taught ACCA courses for manual J, duct and system design. But I'm sure there are many homeowner DIY's here that know more than me.
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Old 09-12-2013, 05:10 PM
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Originally Posted by 08087 View Post
Unfortunitly the gas company is why I'm here asking this question. No offense to any member here but I've got replies all over the place right now so I may have to call a contractor or maybe the builder will have some input.

Thanks
The point I was trying to make is there may be a significant btu range before it makes a difference in the pipe size. If ou give the gas company your estimates ask them the size pipe and how much room there is +- before the pipe size is impacted. They may say that based on your numbers without the furnace, your furnace btu can range from 50 to 200 k before it makes a difference. The btu sizing charts are online to give ou an idea of what I am trying to explain.
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Old 09-12-2013, 05:40 PM
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Gas load for 2000 sq for purpose of filling out a gas app?
Furnace 120k btu is plenty
Water heater 45-60k btu
Range 50k
Dryer 45k
If you plan on continuos use water heater the btu load is no less than 199 ,000
Outdoor grill 75k
These are all avg. On normal btu loads some ranges can be much higher depending on gas delivery as high as 200,00
You have any other question pm me I do this for a living
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Old 09-12-2013, 06:58 PM
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A standard residential meter for natural gas is 325,000 btu's around these parts. I'm sure your house will be at 200 or less for full load. The furnace will probably be in the 70,000 range.
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Old 09-12-2013, 07:19 PM
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I think you're looking for the gas line size needed. Most applications use high pressure to the meter where it is stepped down to a lower, yet somewhat high pressure where it is then delivered to your gas appliance. Each appliance will then have a regulator that steps down to the usable pressure. If this is the case, 3/8 copper line will deliver plenty of gas to each appliance.
If you're looking for the size furnace necessary to heat your house, a heat loss calculation (such as Wrightsoft as discussed before) can calculate that and is probably mandatory for permitting purposes. Also, as stated before, a two stage system is the only way to go. Heat gain calculations are based on the average coldest day of the year but since you rarely reach that temperature, your furnace is oversized the majority of time. During more moderate cold temperatures, the furnace is running on first stage albeit running longer but using a proportional amount less gas. You have the benefit of a more consistent temperature and the longer run time allows for better air filtration and humidification.
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Old 09-12-2013, 08:26 PM
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Thanks guys, I'm going to fill out 120,000 BTU for the furnace, I grabbed the rest off line tonight. 200,000 should do the trick, I'll see if I can get someone on the phone that knows something and may up the est. for future use/load.
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Old 09-13-2013, 04:22 AM
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Originally Posted by cooldude View Post
I think you're looking for the gas line size needed. Most applications use high pressure to the meter where it is stepped down to a lower, yet somewhat high pressure where it is then delivered to your gas appliance. Each appliance will then have a regulator that steps down to the usable pressure. If this is the case, 3/8 copper line will deliver plenty of gas to each appliance.
I was with you until you mentioned the copper. Before you use it, better make sure your local building codes allow use of copper tubing for natural gas distribution.
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Old 09-13-2013, 01:07 PM
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Wow you can get a lot of advice on one post. I can see where you would get confused
Good decision on the 200 number I would have. Gone 250. But you should be fine not all appliances run at once
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Old 09-13-2013, 01:50 PM
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Originally Posted by yarcraft91 View Post
I was with you until you mentioned the copper. Before you use it, better make sure your local building codes allow use of copper tubing for natural gas distribution.
I've never seen copper in any of my properties. Copper, really sounds scary?
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Old 09-13-2013, 03:49 PM
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You likely need a 140-150,000 btu boiler for a single story 2,000 sq ft house in NJ.
Keep in mind with gas service the difference between 1", 1-1/4" or even 1-1/2" isn't much money - once you get it from the gas meter inside you will be splitting and reducing it. You have to look at max load and be under that with everything that can be on at the same time: stove, oven, boiler, water heater, dryer, fireplace, bbq - although it is unlikey you will have the bbq and fireplace on at once. It is better to oversize now than to have to upgrade later.
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Old 09-13-2013, 04:49 PM
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the Utility has a department that comes out and adds all the BTU together to determine the size of the service you will need i am assuming you are a high pressure gas service area and most likely a 1.25" service would be plenty to do a house your size. i have run 100's of gas services low pressure to high pressure you take a static and load test and a 1.25" service i have ran to huge commerical buildings with 2 stage boilers and never an issue
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Old 09-13-2013, 04:54 PM
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Originally Posted by 08087 View Post
Thanks guys, I'm going to fill out 120,000 BTU for the furnace, I grabbed the rest off line tonight. 200,000 should do the trick, I'll see if I can get someone on the phone that knows something and may up the est. for future use/load.

and 1.25" service will do more than you can put in your house
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