Piping Size for 45K Mr Heater

[sasmith]

I just found this site and just registered, awesome site, couldn't have found it at a better time. Im in the middle of re-doing my attached 3 car garage.

I have bought and mounted up a 45k Mr Heater. I have NG appliances, furnace, water heater, dryer and range. They are all 1/2" copper from the meter, they all branch from there at the furnace after the regulator. I have run about 50' of the same 1/2" up from there through to the garage heater.

My question is, have I over extended my capacity? The reason I ask is a man from the local gas utility was over checking for a gas leak in the new house next door a few years ago and we were chatting about adding a gas fireplace down the road and he said if I remember correctly that if all of them were running at the same time it might not be enough.

My house furnace is a 55K btu and the stove doesnt get used much (my wife hates cooking). The dryer and water heater are about average use and we never did put in that fireplace. The garage heater wont be used very often.

Any advise would be of great help. Thanks in advance and again, the perfect website!

sasmith

 

[nate379]

I am guessing it is ok in the code where you live to have copper pipe for natural gas?

Here is a chart to go buy:

http://www.engineeringtoolbox.com/natural-gas-pipe-sizing-d_826.html

My piping is all 1" black pipe from the meter and it necks down to 1/2" at the applicances. I have the same stuff you do other than no water heater and my boiler is 90k BTU.

 

[sasmith]

I believe it is code to have all copper as when we built the house that's all they put in, in all the others near us as well.

I read a post about a man that had trouble with the black iron joints leaking, I used the same dope and black pipe connections made in China from Menards as well, I will do the soapy water to make sure.

Another concern I found on this forum is the older gas valves that are not code anymore, can anyone tell me what I'm to look for on these and what the difference is. While I'm doing all this I might as well do it all right. The house was built in 1992 if that helps.

Thanks again

 

[oNioN]

I just had a nat gas 60K Reznor installed in my garage. The installer teed off the high pressure side of the manifold at the furnace and put a regulator out by the heater. All of my gas lines are 1/2" OD copper and some black pipe here and there (house built 1994). The run out to the heater was 75'. We installed a 45K Mr Heater at my buddy's and did the same thing (come off high press side and put a regulator out by unit). So far both mine and my buddy's heaters work great. Good luck. Hope this helps.
Billw

 

[bochnak]

A ½” straight from the meter will support 53.6k BTU at 50’:

http://www.engineeringtoolbox.com/natural-gas-pipe-calculator-d_1042.html


I believe this value is input to the heater. For example, your heater has a 45k output at probably 80% efficiency, so 45k/.8 = 56.25k input to heater required.

I’m not sure what the ID of the copper is, so I used gas pipe ID.

 

[redsky49]

1/2" type K copper has an I.D. of 0.527".
1/2" type L copper has an I.D. of 0.545".

In most instances, especially at the end of a long piping run, it is better to size the piping for a 0.3" pressure drop, not the 0.5" shown on the chart indicated above.

Perhaps Hoosierbudy will chime in here. I believe that he is gas line installer/utility employee.

As always, offered only as opinion

 

[bochnak]

As always, offered only as opinion

That goes for me as well.

I ran 3/4" poly 130' or so and that same website says I will be borderline for an input of 75k.

The line was actually trimmed in today. I still have to pipe inside the garage and hang the heater.

 

[bochnak]

1/2" type K copper has an I.D. of 0.527".
1/2" type L copper has an I.D. of 0.545".

In most instances, especially at the end of a long piping run, it is better to size the piping for a 0.3" pressure drop, not the 0.5" shown on the chart indicated above.

Wow, those #'s do not help the situation.

 

[jrj3rd]

A ½” straight from the meter will support 53.6k BTU at 50’:

http://www.engineeringtoolbox.com/natural-gas-pipe-calculator-d_1042.html


I believe this value is input to the heater. For example, your heater has a 45k output at probably 80% efficiency, so 45k/.8 = 56.25k input to heater required.

I’m not sure what the ID of the copper is, so I used gas pipe ID.

Actually most unit heaters are rated on input. So 45K is actually ~36K output.

 

[bochnak]

Actually most unit heaters are rated on input. So 45K is actually ~36K output.

My heater lists both input/output at 75/60k. So this unit would sell as a 75k?

 

[redsky49]

Typically, all gas-fired appliances are listed at the input requirements of the device. For example, the SuperMegaheat Model 75, a 75,000 btuh input heater, will be labeled as such, with an output capacity of 60,000 btuh. This is an efficiency of 80%, or slightly less than many current code minimums of 82%.

The heater should be selected based on the output rating of the unit, in conjunction with the calculated heating requirements of the space or building. The gas line should be sized based on the input requirements of the unit. The flue should be sized per the heater manufacturer.

In general, if the calculated heating requirement of your space is *** btuh, my recommendation is to select a heater with an output rating of 120% of ***. This additional heating capacity allows a quicker pick up of the temperature when going from unoccupied to occupied mode, something that will occur frequently for garage applications. Additionally this allows some extra capacity for those rare times that outdoor conditions exceed the typical design temperatures. Heaters in excess of 120% of calculated demand are more likely to be inefficient in operation and are discouraged.

Finally, carefully select the design conditions when calculating your heat loss. Do not select a max heating outdoor design temperature that occurs only once every ten years. Most designers use a 97.5% or 99% number. This is a minimum temperature that is not exceeded 97.5% or 99% of the time, as based on annual weather data. For Washington, DC for example, the respective temperatures are 17 degrees and 14 degrees, even though this area has occasionally reached near zero. And remember, you can always put on a sweater.

As for gas piping, only select the service piping after the heating calc's are performed and a heater is selected. Several of the posters on this board are installing piping prior to thinking through this issue, and are finding that they have guessed incorrectly. Seek professional help if you are unable to confidently perform these tasks yourself.

As always, offered only as opinion

 

[Joel 67]

Redsky (or others),

Any insights on how to determine the btuh requirements for a given space? Is there a site or calculator I can use to determine this?

thanks
Joel

 

[sasmith]

I just had a nat gas 60K Reznor installed in my garage. The installer teed off the high pressure side of the manifold at the furnace and put a regulator out by the heater. All of my gas lines are 1/2" OD copper and some black pipe here and there (house built 1994). The run out to the heater was 75'. We installed a 45K Mr Heater at my buddy's and did the same thing (come off high press side and put a regulator out by unit). So far both mine and my buddy's heaters work great. Good luck. Hope this helps.
Billw

oNioN,
Thats a great idea, right now the start the run of the Mr Heater right next to the high pressure side, but on the regulated side there, I can tee into the high side if I have to. I have tried the unit, exceptionally quiet).

Thanks to you all for the info, Ill let you know how it goes after the sheetrock and insulation are in.

sasmith

 

[duaneb9729]

"L" copper is the only code approved copper for gas lines, K is considered water line or refrigeration line copper.

There currently are no minimum efficiency codes the require 82% or higher, currently manufactures are required to build furnaces that are not less than 80%.

One thing I would caution folks to consider when putting in a garage heater, is how you will use it. By this I mean, will you go out to your garage when its -20 and fire it up cause its cold out?

This sort of use will wreck your heater, the heat exchanger will tear its self apart, and not be covered by warranty.

I do this for a living, and have to be the bearer of bad news often in this regard.

In my own garage, I insulated it well, R-50 in the attic (over bought insulation) R-13 in the walls and an insulated garage door.

one other thing I installed a thermostat that goes down to 38 degrees, and i find it almost never runs, the heat from the car engines keep it warm.

In order to protect your heater and have it live a long life, let it run, its a small price to pay for the long life of heater.

I get a lot out of this site, if i can give back, so to speak just pm me I am glad to help

 

[redsky49]

"L" copper is the only code approved copper for gas lines, K is considered water line or refrigeration line copper.

There currently are no minimum efficiency codes the require 82% or higher, currently manufactures are required to build furnaces that are not less than 80%.

I was incorrect as to the current minimum energy requirements for a furnace.

Official requirements:

"Table 503.2
Minimum Equipment Performance
Equipment Category Subcategory e Referenced
Standard Minimum
Performance

Air-cooled heat pumps, Heating mode < 65,000 Btu/h cooling capacity Split systems
Single package ARI 210/240 6.8 HSPF a, b
6.6 HSPF a, b

Gas-fired or oil-fired furnace < 225,000 Btu/h — DOE 10CFR Part 430, Subpart B, Appendix N AFUE 78% b
Et 80%c

Gas-fired or oil-fired steam and hot-water boilers < 300,000 Btu/h — DOE 10 CFR Part 430, Subpart B, Appendix N AFUE 80% b, d

Air-cooled air conditioners and heat pumps. Cooling mode <65,000 Btu/h cooling capacity Split systems
Single package ARI 210/240 10.0 SEER b
9.7 SEER b

For SI: 1 British thermal unit per hour = 0.2931 W.

1. For multicapacity equipment, the minimum performance shall apply to each capacity step provided. Multicapacity refers to manufacturer-published ratings for more than one capacity mode allowed by the product's controls.
2. This is used to be consistent with the National Appliance Energy Conservation Act (NAECA) of 1987 (Public Law 100-12).
3. These requirements apply to combination units not covered by NAECA (three-phase power or cooling capacity 65,000 Btu/h).
4. Except for gas-fired steam boilers for which the minimum AFUE shall be 75 percent.
5. Seasonal rating."

Note that 78-80% does not qualify for "Energy Star" listing (must be 90% or better), and that both the minimum and Energy Star requirements will likely be much more stringent in the next year or two.

Regarding copper pipe:

Type K, the heaviest wall tubing, is used primarily for underground water service, fuel oil, and gases where high temperatures or pressures are anticipated. Any buried application should be Type K. Pipe has a green marker.

Type L is used primarily for interior water service, gases, fuel oil, and some underground drainage applications. Pipe has a blue marker.

Type M is the lightest of the three types and is primarily used in interior water service and some drain applications. Pipe has a red marker.

Type ACR tube is the trade name for copper tubing for refrigeration use. It can be hard or soft temper, and has the same wall thickness as Type L. Also referred to as 'cleaned and capped', it is (usually) purged with oxygen.

Maximum allowable working pressure ratings range from 75 to 1750 psi depending on wall thickness, though normal working pressures rarely exceed 700 psi.

As far as I can tell (haven't seen the 2009 NFPA 54, Fuel Gas Code), types K,L and ACR are permitted for low pressure gas applications. The exception would be any western states/jurisdictions where the old UPC codes were adopted. These codes prohibited all copper gas piping due to corrosion as a result of contaminants in the gas. Denver was one such area. All gas piping was threaded black steel.

Anyone contemplating a gas system using copper (or any other material) should consult their local jurisdiction for approved methods and materials.

As always, offered only as opinion

 

[Schrodingers Cat]

what is he delivery pressure on the load side of the meter?
the unit needs 5" WC, they recommend 7" WC...
there is also an adjustment for manifold pressure, basically a regulator...
factory set at 4...

 

[bochnak]

Several of the posters on this board are installing piping prior to thinking through this issue, and are finding that they have guessed incorrectly.

My line was sized based on a heater size I should be running, not based on the larger heater I got for free. I don't even know if the darn thing works.

 

[HoosierBuddy]

Let me "chime in".

First of all, regarding copper for natural gas lines. Before using copper, make sure you check with your gas company and/or local building inspection people if they allow it. Although it's pretty standard for propane, as far as I understand, some gas companies prohibit copper. If they do or don't generally traces back to the fact that "natural" gas, being a naturally occuring product of nature, is not identical in every town and hamlet in the universe.

Some natural gas may contain (or at least may not be guaranteed NOT to contain) sulpher dioxide in enough concentration that it would pose a risk to copper piping. If you look at specification for the use of copper line by copper manufacturers they cover that concern with a standard number of grains of SO2 per unit of volume above which copper can't be used.

Our company recommends black iron in all cases and requires it from the meter into the structure. We allow CSST if used according to manufacturers requirements inside the structure. We recommend against using copper but don't prohibit it for customer piping. We allow for the use of PE gas line underground, but prohibit any other plastic. But, every utility will differ here....so check before you spend money. The OP indicates other piping in his home is copper so it's probable that copper is allowed. One other point about copper, I've got a 120 year old gas light at my house and the copper tube has occaisionally stopped up with black fines. I've seen that several times over the years and attribute it to corrosion in the copper. You don't get that with black steel pipe. That stuff can work its way into an orifice and cause problems fairly easily.

On load...on natural gas...most gas meters in the U.S. for homes are rated at about 250,000 BTU's hour on low pressure. The normal delivery pressure at sea level is 7" water column. As you go higher in altitude, delivery pressure is increased to compensate for lower atmospheric pressure...so if you are in Denver, your gas company likely gives you a lot more than 7 inches w/c. Other pressures are available.

Your meter should be stamped with a number like 175, 250, 275, 415 etc. on the nameplate that designates it's BTU in capacity in thousands of BTU's per hour (250 meter=250,000 BTU's hour at base pressure). If you're worried about overloading your meter, check your meter vs your load. A gas meter will not normally LIMIT your gas supply to its rated capacity. The 275 on my house will deliver 400,000 BTU's per hour all day long if I need it to. HOWEVER, it will not meter properly at delivery volumes over its rated capacity. As you pull on it harder and harder, the absolute pressure in the meter will drop lower and lower, below the pressure the meter is supposed to be delivering. What does that do? It makes the meter spin faster than it should. So, you end up paying for more gas than you actually got.

Your meter should be sized to carry the maximum load it sees or you will cost yourself money. Now, at some point, the meter will actually be so much too small that it (or the regulator in front of the meter) will limit gas supply below what is required. Typically I see this where a big pool heater or a backup generator is added. Backup generators expecially are the bane of all gas companies, because they will often represent more load than the rest of the home combined. Large homes with big backup generators will need a large gas meter like you'd normally see on a commercial operation. If the gen-set is sized to carry the a/c load, it will typically draw twice what the entire house would draw by itself.
Your load would triple in that case and your gas meter, regulator (and maybe even your whole service line) would need to be bigger.

Phil

 

[redsky49]

If I recall correctly, at one time the copper manufacturers were producing a "lined" copper pipe for gas applications with high levels of hydrogen sulfide or other contaminants. I think that the pipe was lined with tin. I don't recall many jurisdictions accepting this due to the likelihood that installers or contractors would try to cheat with unlined pipe.

Thanks for the input Hoosierbuddy, though this thread is going off topic

Now if I could only figure out how to format the quoted energy standards in Post #15 I will be fine

As always, offered only as opinion

 

[bochnak]

My line was sized based on a heater size I should be running, not based on the larger heater I got for free. I don't even know if the darn thing works.

My 3/4" run is sufficient for my 75k unit. I have used it several nights with no issues.