What is the appropriate heat source to use

DIY_heat

I am new to this area and have done some research on the web, but still have many questions.

I have a 300 sq foot room addition that I have calculated the heat requirement at 15,000 BTU/H.  I have installed 27 linear ft of Slant/Fin model 30 baseboard, which should provide enough heat output for the room.  I intend to use a closed system isolated from the water source.  I have purchased a 3 speed 1/25 HP circulation pump, 3/4" ball valves, expansion tank, air seperator, thermostat, drain, pressure and temperature relief valves.  My questions concern the heat source.  I live in the Chicago area so I want to use natural gas.  I am space limited to a crawl that is 40" in height.  I am looking for suggestions regarding a tank type or tankless water heater. Is it possible to use a tankless heat source that is intended for an open system in a closed system?  Assuming not, the Takagi T_KJr appears to be rated for this type of application but is rated much higher than I need.  Any suggestions?

Larry Weingarten

How do you...

... heat the existing house?  Also, how do you heat domestic water?  You may already have your heater.



Yours,  Larry

EricAune

Good question Larry

It may be possible to utilize your existing domestic water heater as the heat source.  Taco makes a packaged product that works wonders for small to medium heat loads.  Your domestic water demand and heater sizing must be taken into consideration whether this will work for you. I've attached a photo of the Taco X-pump block from a recent install.



This single water heater takes the place of three.  Two 40's piped in parallel for domestic, and one 50 for the radiant (existing, by others).  All atmospheric.  The new homeowner contacted me with question of a tax credit and lowering their LP usage.  The recovery rate, the fact that is is condensing almost all the time, and the elimination of three 50-60% efficient units has been a blessing for the new owners and their LP tank levels.

Mark Eatherton

50 btu's per square foot per hour is a LOT of energy....

Are you sure about those numbers?



The average for an average home is around 30.



ME

TonyS

Try one of these

http://www.navienamerica.com/product/combi_01.aspx?skin=combi_01

DIY_heat

Sq Ft

Mark,

The room is 16' x 20' with 12' Cathedral ceiling. There are 7, 4' x 5' windows, 2 6' x 2' trapazoid windows and a 3' plus 5' steel insulated doors on each end.  All glass is thermopane.  The ceiling is R38, walls (what there is of them) are R21 and the floor is R21 above a 3' crawl.  I assumed -20F for my worst case low temp.

The house has a seperate forced air heat and 40 gal 40,000 BTU/H input hot water tank for domestic water.  My city tells me I can't tie into the existing hot water tank.  A contractor quoted adding a second 40 gal hot water tank and combine vents to be the heat source for the addition.  His estimate was 15,200 BTU/H. 

I would like the heat source in the crawl of the addition, since it would remove 60'+ of copper in the loop.

 

kcopp

a wall hung....

boiler is probably the best bet. Here is one example. it aslo can do HW. http://www.embassyind.com/ambassador/index.asp

I would not use a water heater, tankless or otherwise...simply the wrong application.

While your at it you could size it to run the gas furnace off a sep. zone through a hydro coil. Especially if the furnace is an older model.

Mark Eatherton

People who live in glass houses....

Can expect high heat losses...



How were you planning to deliver the heat to the room? I can tell you what won't fill the bill by itself. Radiant floors. They are limited to 30 btu/hr/sq ft.



Baseboard puts out around 500 btu/linear foot. Got 30' of bare wall?



You might have to do both!



Now, if you could make all the glass heat loss disappear... (Think radiant windows) the load would be significantly less :-)



ME

MIke_Jonas

Before you guys go too far..

I can't cite the exact code chapter and verse, but my understanding is, in the State of Illinois, you cannot use a water heater for space heating. I've seen what you guys are recommending get ripped out, due to code violation.



50 btu/sq. ft is not uncommon in my area.

EricAune

Code

Mike,



I know if what you speak, here in MN we have our own as well and it too states that a water heater may not be used as a heat source unless it is rated for such.  Until recently, finding one rated for space heating would land you upon equipment that was at boiler price-points, this has changed a bit as most manufacturers have them and the price is more comparable to a high end tank unit.



I stay away from tankless units for radiant sources, but on occasion, a tank/X-block combo fits the bill.

DIY_heat

heating the addition

I have 27' of baseboard rated at 610 BTU/H using 180 degree water. (16,470 BTU/H)  I derated it to 540 BTU/H using 170 degree water, which gets me close enough to the 15K BTU/H goal.  My issue is with the size of the heat source.  If it is very large (199K BTU.H) it will short cycle and the efficiency really goes out the window. For Chicago's current weather (18 - 30 degrees) I would need much less than 15K BTU.  4,500 BTU from an electric heater (1,500 W) currently gets me about a 40 degree rise, so the heat source should have the capability to modulate down into this range.  At 80% efficiency I would only need 18,750 BTU/H to satisfy the baseboard load.  Does anyone know of a 5K to 20K BTU/H heat source for NG?

DIY_heat

No replies

Well since no one could suggest a natural gas heat source for 5K to 20K BTU/H.

Can anyone recomment an electric heater in the 4500 to 5000 Watt range using 240 VAC for the heat source for this hot water heat system that is certified for the application?  It must not exceed 20Amps.

Thanks for all your help