Vermont Casting 2477 사용자 설명서

10

Procedure:
1.  Convert specifications to R-value:

i.  R-value given - no conversion needed.
ii.  k-factor is given with a required thickness (T) in 

inches:  

iii. K-factor is given with a required thickness (T) in 

inches:

iv. r-factor is given with a required thickness (T) in 

inches:  R = r x T 

2.  Determine the R-value of the proposed alternate 

floor protector:
i.  Use the formula in Step 1 to convert values not 

expressed as R.

ii.  For multiple layers, add R-values of each layer to 

determine overall R-value.

3.  If the overall R-value of the system is greater than 

the R-value of the specified floor protector, the alter-
nate is acceptable.

EXAMPLE: The specified floor protector should be 7/8-
inch thick material with k-factor of 0.84. The proposed 
alternate is 4” brick with an r-factor of 0.2 over 1/8” 
mineral board with a k-factor of 0.29
Step a: Use formula above to convert specification to 

R-value:

Step b: Calculate R of proposed system. 
  4” brick of r = 0.2, therefore:
   R

brick

 = 0.2 x 4 = 0.8

  1/8” mineral board of k = 0.29, therefore
   R

mineralboard

 =         x 0.125 = 0.431 

   R

total

 = R

brick

 + R

mineralboard

 = 0.8 + 0.431 = 1.231

Step c: Compare proposed system Rtotal of 1.231 to 

specified R of 1.04. Since proposed system Rtotal is 
greater than required, the system is acceptable.

Definitions

To install the heater without legs as a fireplace insert, 
the floor must be completely noncombustible, such as 
an unpainted concrete floor over earth.
Many fireplaces do not satisfy the “completely non-
combustible” requirement because the brick or con-
crete hearth in front of the fireplace opening usually is 
supported by heavy wooden framing as in Figure 13.  
Because heat passes readily through brick or concrete, 
it can easily pass through to the wood. As a result, such 
fireplace hearths are considered a combustible floor. 
You may not install a heater on a combustible hearth 
without legs. Standard leg installations must include the 
bottom heat shield.  The  floor protector must also meet 
standard requirements for freestanding installations.

Fireplace installations with the standard legs and the 
bottom heat shield must have a floor protector of the 
same construction as that specified for freestanding 
installations: an approved 7/8” (22mm) noncombustible 
hearth pad with K = 0.84 BTU/in ft

2

 hr. °F or equivalent 

material with an R-value of at least 1.04 (Refer to “How 
to Determine if Alternate Floor Protection Materials are 
Acceptable” section) The floor protector must extend at 
least 16” (406 mm) [18” / 457 mm in Canada] from the 
front of the stove and from the left (loading door) side, 
and at least 6” (152 mm) [8” (203 mm) in Canada] from 
the right side and rear.  It must also provide protection 
beneath any horizontal runs of the chimney connector, 
including 2” to either side.
Many raised hearths will extend less than the required 
distance from the front of the heater when it is installed.  
In such cases, sufficient floor protection, as described 
above, must be added to extend the hearth 16” (406 
mm) [18” (457 mm) in Canada].
Hearth rugs do not satisfy the requirements for floor 
protection.  
Fireplace insert installations also have specific clear-
ance requirements to the side walls, side decorative 
trim, and fireplace mantel.  This information is found in 
“Fireplace Installation Clearances” in this section. 

The Dutchwest Model 2477 has a reversible flue collar 
to allow for either top exit or rear exit installations.
You may install your Dutchwest Model 2477 in an exist-
ing fireplace as a fireplace insert with no legs, or with 
the standard legs attached.

R =             x T

1

K x 12

R =   x T

1

k

R =    x T  =          x 0.875 = 1.04

1

k

1

0.84

1

0.29

 

R = (ft

2

)(hr)(°F)

Btu

 

k =                   = K x 12

(Btu)(in)

(ft

2

)(hr)(°F)

(Btu)(ft)

(ft

2

)(hr)(°F)

 

K =                

r =

(ft

2

)(hr)(°F)

(Btu)(in)

1

k