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foojin · 10-02-2014, 21:41

I am considering installing some Hardie concrete backerboard to provide extra insulation behind my stainless liner, but not sure it's necessary.

The heater will sit about 2.25" from a bulkhead with the stainless liner between. From all the photos of installed Dickinsons I have seen (and can see what's behind the liner) not many have extra insulation. And I had no problem not having extra insulation on the bulkhead-mounted Refleks diesel heater I installed on my last boat.

The backerboard is heavy and hard to work with. Is it overkill?

Strait Shooter · 11-02-2014, 05:13

I used the backer board as well. Yes, it's probably overkill, but it gives you some options in regards to what you can use over that, i.e. tile etc.
I also don't think of overkill and hot things on my boat as a bad thing.

Dale Hedtke · 11-02-2014, 05:30

I agree with SS's comments. We mounted our with the concrete board covered with ceramic tile. I put teak trim around both (like a picture frame) to cover the raw edges. It was easy.

I note that you have a SST liner. Good idea, as it will reflect heat; that helps with heat distribution and keeps the substrate cooler. It does NOT insulate BTW.

psneeld · 11-02-2014, 05:36

The Hardie backerboard I used was the thin stuff and easy to work with and cut.

....often the stainless shields depend on airflow between them to be effective...make sure the backerboard isn't effecting that.

LakeSuperior · 11-02-2014, 06:30

Quote:

Originally Posted by Dale Hedtke

I note that you have a SST liner. Good idea, as it will reflect heat; that helps with heat distribution and keeps the substrate cooler. It does NOT insulate BTW.

Your first sentence above contradicts your last sentence above. The metal liner, which is reflective, will act as a radiation shield and therefore insulates or retards the heat transfer through the liner.

For example, radiation shields are commonly used in cryogenic insulations and it is the reason for the foil on some of the insulations used in the building industry.

Dale Hedtke · 11-02-2014, 06:48

I'm sorry if my statements were confusing. My meaning is that the SST liner will reflect radiant heat, it does not insulate (reduce) conductive heat transfer.

LakeSuperior · 11-02-2014, 06:48

The manufacturer will provide guidance on the installation of the heater. I would follow this to the letter. A change from the guidance requires an analysis of the proposed installation and in many cases the results could be counterintuitive.

For example, installing concrete board on 3/4 in plywood potentially is of little benefit in terms of actual temperature reduction on the back of the concrete board. That is the delta temperature between the front and back surfaces may be minimal. This is because the 3/4 in plywood is also insulating thus reducing the temperature drop in the backer board.

**GordMay** · 11-02-2014, 06:53

Dickinson specifies a 1/4" high heat insulation board with a stainless sheet on ½" standoff; and a minimum of 2" separation twixt heater and insulated wall.

Diesel ➥ http://dickinsonmarine.com/Manuals/D...ual-2011-2.pdf

Propane ➥ http://dickinsonmarine.com/Manuals/P...2%20Manual.pdf

LakeSuperior · 11-02-2014, 07:00

The standoff posts should be at the corners and edges farthest from the heater/standoff minimal distance. If possible use non heat conducting fasteners. A thermal short circuit is created if metal bolts are used in the standoffs.

foojin · 11-02-2014, 10:57

Thanks for the responses.

SS, is your backer board also the concrete version?

As Gord points out, the Dickinson manual does specify 1/4" high heat insulation board. I have called almost everywhere I can think of in the Vancouver-Bellingham-Seattle area, but not found 1/4" board.

The closest I have been able to find is the 1/2" Hardie concrete backboard which weighs a ton. Even the Sigmar/Dickinson factory in Surrey was unable to suggest a supplier. Seems to me that no one is actually expected to follow the manuals, but the small print is there to protect the firm's a$$. But maybe I'm just suspicious.

There is one product (Kaowool) made in MA that seems to the bill, made from ceramic and alumina bits, but I would have to get a whole carton shipped to the West Coast to get one small piece.

Thus my question about how others have insulated.

foojin · 11-02-2014, 11:07

Quote:

Originally Posted by LakeSuperior

A thermal short circuit is created if metal bolts are used in the standoffs.

LS, excuse my ignorance, but are you suggesting that if I bolt the standoffs to the liner, as well as to the wall, instead of welding, say, that this will short circuit or limit the amount of heat that flows through the standoff?

If so, would this effect be increased by adding washers to the connection, or using aluminum standoffs instead of stainless?

LakeSuperior · 11-02-2014, 11:18

Quote:

Originally Posted by foojin

LS, excuse my ignorance, but are you suggesting that if I bolt the standoffs to the liner, as well as to the wall, instead of welding, say, that this will short circuit or limit the amount of heat that flows through the standoff?

If so, would this effect be increased by adding washers to the connection, or using aluminum standoffs instead of stainless?

If we are talking about the same thing, a stand-off panel, then to make the panel stand off the liner (effect an air gap between the liner and panel)
one would want use posts and fasteners that do not conduct heat.

So if you used a heat conductive or metal carriage bolt to hold everything up you could end up with hot spots on the liner. This is because the metal bolts would get hot and conduct the heat to the liner.

Aluminum conducts heat better than stainless. Only marginal benefit if the washers are steel (or any other material) because the bolt head would still be a source for heat flowing down the bolt.

foojin · 11-02-2014, 11:51

Quote:

Originally Posted by LakeSuperior

If we are talking about the same thing, a stand-off panel, then to make the panel stand off the liner (effect an air gap between the liner and panel) one would want use posts and fasteners that do not conduct heat.

So if you used a heat conductive or metal carriage bolt to hold everything up you could end up with hot spots on the liner. This is because the metal bolts would get hot and conduct the heat to the liner.

Aluminum conducts heat better than stainless. Only marginal benefit if the washers are steel (or any other material) because the bolt head would still be a source for heat flowing down the bolt.

Ok, we were probably not talking about the same thing. I was referring to a liner/panel that is both connected to the heater and to the bulkhead. I seem to have misunderstood, and you were actually suggesting that using bolts increases rather than decreases the heat transfer.

And quick googling after my last post showed, as you suggest, aluminum is a better heat conductor than stainless. It is surprising in that Dickinson provides aluminum mounting bars for the heater.

AnchorageGuy · 11-02-2014, 14:42

Quote:

Originally Posted by GordMay

Dickinson specifies a 1/4" high heat insulation board with a stainless sheet on ½" standoff; and a minimum of 2" separation twixt heater and insulated wall.

Diesel ➥ http://dickinsonmarine.com/Manuals/D...ual-2011-2.pdf

Propane ➥ http://dickinsonmarine.com/Manuals/P...2%20Manual.pdf

This was our Dickinson Diesel heater. The backer is fireproof board, covered with a SS sheet and in a teak frame, mounted with 1/2 inch stand offs at the corners and center edges. we used this extensively for years.