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Old 25-09-2018, 09:03   #1
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Diesel Heater Installation

I am in the process of installing a forced air diesel heater (cheap eBay unit) on my 31' boat. I am having difficulty finding a suitable duct for hot air distribution. Any ideas?

The specifications suggest the duct must handle temperatures of 130C/265F. The ducts that come in the brand name marine installation kits seem to be 60 mm / ~ 2.5" heat resistant ducts made of APK or three layers of aluminium, paper and plastic. They are typically 3' long and require plastic adapters to merge together. The duct looks and feels flimsy. The cost comes to something like $25/foot. In addition, certain areas would need an insulation sleeve, adding another $5/foot.

I have found an alternative duct on Amazon, called Hi-Tech Duravent. It comes in various sizes and temperature ratings, two examples are:

250F rating, 3", $3/foot: https://www.amazon.com/dp/B008XRAHOG/ref=biss_dp_t_asn

275F rating, 2.5", $9/foot:
https://www.amazon.com/dp/B008XR6X3A/ref=biss_dp_t_asn

Any experiences with these ducts? Any other alternatives for a reasonable hot air ducting suitable for boat installation?

Thank you for your thoughts.

Regards,
SV Pizzazz
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Old 25-09-2018, 09:14   #2
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Re: Diesel Heater Installation

Use the section that comes with the unit then here is what I used after that on the 5k unit I just installed on my 29 .
https://www.ebay.com/itm/New-Black-F...53.m1438.l2649
As to the need to insulate the duct why ?
I routed the duct thru compartments that I can store wet gear and use the heat from the duct to help dry the items.
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Old 25-09-2018, 09:14   #3
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Re: Diesel Heater Installation

I bought 4 meters of Webasto heater hose from these folk. Do you have a Webasto dealer near you? Adding external insulation to the hose made a huge difference too. Without the air was warm to the hand. With the insulation it was too hot to put you hand in front for more than a couple of seconds.

https://www.butlertechnik.com/instal...cessories-c122

https://www.ebay.co.uk/itm/EBERSPACH...UAAOxydlFS2U~P
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Old 25-09-2018, 12:08   #4
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Re: Diesel Heater Installation

Double-check the instructions. Are you sure that 265 degrees is not for the exhaust hose?

If I had it to do again, I'd make sure the exhaust hose was as short as possible. These things are made to exhaust downward out of a truck or RV, only a couple of feet. And they're not made to be near anything combustible like wood or fiberglass. They get dangerously hot, and I think the back pressure of a longer hose causes the unit to overheat and shut down sometimes.
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Old 25-09-2018, 12:17   #5
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Re: Diesel Heater Installation

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Originally Posted by CaptTom View Post
Double-check the instructions. Are you sure that 265 degrees is not for the exhaust hose?

If I had it to do again, I'd make sure the exhaust hose was as short as possible. These things are made to exhaust downward out of a truck or RV, only a couple of feet. And they're not made to be near anything combustible like wood or fiberglass. They get dangerously hot, and I think the back pressure of a longer hose causes the unit to overheat and shut down sometimes.
Yes, the exhaust is a stainless steel pipe and it will be around 2 ft long in my case, goes out to starboard 2 feet above the waterline, making sure it can handle a boat list up to 45 degrees. I believe the exhaust rating is for something like 700F.

I am sure that the 265F rating for the hose is conservative, hence I think a 250F will suffice and that is cheap at $61 for 25 ft. I need insulation not so much for heat loss but because the hot air hose will pass close to some wiring that I do not want to get hot/melt/etc. Otherwise it will be resting mostly against fiberglass which I think is fine with temperatures of 250F. May be someone with a diesel air heater can just measure the temp inside and outside of the hose they are using? That could help.

Thank you all for the comments so far.

SV Pizzazz
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Old 25-09-2018, 12:17   #6
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Re: Diesel Heater Installation

Quote:
Originally Posted by Pizzazz View Post
I am in the process of installing a forced air diesel heater (cheap eBay unit) on my 31' boat. I am having difficulty finding a suitable duct for hot air distribution. Any ideas?

The specifications suggest the duct must handle temperatures of 130C/265F. The ducts that come in the brand name marine installation kits seem to be 60 mm / ~ 2.5" heat resistant ducts made of APK or three layers of aluminium, paper and plastic. They are typically 3' long and require plastic adapters to merge together. The duct looks and feels flimsy. The cost comes to something like $25/foot. In addition, certain areas would need an insulation sleeve, adding another $5/foot.

I have found an alternative duct on Amazon, called Hi-Tech Duravent. It comes in various sizes and temperature ratings, two examples are:

250F rating, 3", $3/foot: https://www.amazon.com/dp/B008XRAHOG/ref=biss_dp_t_asn

275F rating, 2.5", $9/foot:
https://www.amazon.com/dp/B008XR6X3A/ref=biss_dp_t_asn

Any experiences with these ducts? Any other alternatives for a reasonable hot air ducting suitable for boat installation?

Thank you for your thoughts.

Regards,
SV Pizzazz
the warm air outlet at the plenum / outlet should be no more that 120 to 130 degrees.
You are definitely talking temperatures of the combustion exhaust. Not the warm air run.
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Old 25-09-2018, 12:20   #7
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Re: Diesel Heater Installation

Quote:
Originally Posted by Pizzazz View Post
Yes, the exhaust is a stainless steel pipe and it will be around 2 ft long in my case, goes out to starboard 2 feet above the waterline, making sure it can handle a boat list up to 45 degrees. I believe the exhaust rating is for something like 700F.

I am sure that the 265F rating for the hose is conservative, hence I think a 250F will suffice and that is cheap at $61 for 25 ft. I need insulation not so much for heat loss but because the hot air hose will pass close to some wiring that I do not want to get hot/melt/etc. Otherwise it will be resting mostly against fiberglass which I think is fine with temperatures of 250F. May be someone with a diesel air heater can just measure the temp inside and outside of the hose they are using? That could help.

Thank you all for the comments so far.

SV Pizzazz
I will be at my boat next week I will take a couple temps for you and let you know.

Btw what unit did you install ?

Pictures?
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Old 25-09-2018, 13:15   #8
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Re: Diesel Heater Installation

These guys have ducting a d fittings listed online. They are in Seattle
Welcome - Sure Marine Service Inc
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Old 25-09-2018, 13:18   #9
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Re: Diesel Heater Installation

Quote:
Originally Posted by Paul L View Post
These guys have ducting a d fittings listed online. They are in Seattle
Welcome - Sure Marine Service Inc
but Paul have you seen their prices?
I can find most of what I needed at an rv dealer.
The same stuff just without the marine price.

One spot to not scrimp is the thru hull exhaust fitting.
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Old 25-09-2018, 13:25   #10
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Re: Diesel Heater Installation

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but Paul have you seen their prices?
I can find most of what I needed at an rv dealer.
The same stuff just without the marine price.

One spot to not scrimp is the thru hull exhaust fitting.
Yep, not a discount place. But good to see specs on what is considered equipment for a quality install.
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Old 25-09-2018, 14:14   #11
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Re: Diesel Heater Installation

Hi. If you havn't all ready cut the hole for your exhaust. I would suggest getting it as high as you can on either side of the hull. If you go out through the transom you can get fumes back into the boat. Forced air is worth every penny it costs.
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Old 25-09-2018, 17:03   #12
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Re: Diesel Heater Installation

Quote:
Originally Posted by Kalinka1 View Post
Hi. If you havn't all ready cut the hole for your exhaust. I would suggest getting it as high as you can on either side of the hull. If you go out through the transom you can get fumes back into the boat. Forced air is worth every penny it costs.


Thank you, Kalinka. I agree with you that the exhaust should be on the side. I thought about the transom and decided against it for the same reason you mention regarding the fumes. I will summarize my install once I source all the parts.
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Old 25-09-2018, 19:11   #13
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Re: Diesel Heater Installation

Be careful not to shorten the exhaust hose without checking the spec for a minimum.

A certain back pressure is required.

RTFM carefully
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