Diesel Heater Setup

[skatun]

We got an old sailboat(42 feet in horrible shape) that we currently are installing a diesel heater in. We already have a ventilation system(230V) installed, and it will beneficial to install the diesel heater in series with this unit to save ducting. We have ordered a chinese heater, thrown away evrything except of the heater itself. When it comes to the instalation we have a few questions:

The air inlet for the burner, can that be bleed off(25mm/1") from the air inlet(100mm/4"), air inlet is coming from outside(through the ventilation unit)

In the exhaust bend,we have seen exhaust bend with drain pipe(pig tail) attached to it, when is that needed?

On the air outlet we want to place a radiator to produce hot water for floor heating, heating in forward cabin and hot water tank, is that a bad idea?

[MWGDVC]

I would be concerned about using the fan drawn/pushed air for the combustion intake upsetting the fuel/air mixture of the heater.
The pig tail drains off water due to condensation from humid ambient air.
There are Chinese diesel heaters manufactured with both an air heating capability and a water heating capability. I would think this would be a better choice for your water heating needs.

[Dockhead]

Originally Posted by skatun

We got an old sailboat(42 feet in horrible shape) that we currently are installing a diesel heater in. We already have a ventilation system(230V) installed, and it will beneficial to install the diesel heater in series with this unit to save ducting. We have ordered a chinese heater, thrown away evrything except of the heater itself. When it comes to the instalation we have a few questions:

The air inlet for the burner, can that be bleed off(25mm/1") from the air inlet(100mm/4"), air inlet is coming from outside(through the ventilation unit)

In the exhaust bend,we have seen exhaust bend with drain pipe(pig tail) attached to it, when is that needed?

On the air outlet we want to place a radiator to produce hot water for floor heating, heating in forward cabin and hot water tank, is that a bad idea?

Is it a hydronic heater? It's not quite clear from your description.


Or are you proposing to transfer heat from hot air to an air to water heatex? If that's the idea, then it is a terrible idea. You will not harvest enough heat to heat water.


You need a hydronic heater for this application. You put a fan coil in line with your other ventilation system, and then radiators or more fan coils in other locations where you need heat. Pipe the water return through your calorifier and you get hot water. If you also heat that from the engine, then you will want a calorifier with two coils in it.


Drains in exhaust pipes are for condensation.

[skatun]

I made a simple system sketch

[GordMay]

Originally Posted by skatun

I made a simple system sketch
Attachment 295804

So, you're drawing combustion air, from the boat's interior living space?
In which case, IIRC, the space should provide a room volume of at least 50 cubic feet, per 1,000 btu/hr combined input rating, of all open combustion appliances, in that space.
Using inside [combustion] air can depressurize the living space [causing cold air draughts], and [perhaps] even backdraft that appliance. It, also, reduces the overall efficiency of the heater.

Direct vent, sealed combustion, with outside combustion air intake is much preferred.

[skatun]

Originally Posted by GordMay

So, you're drawing combustion air, from the boat's interior living space?
.

No I draw combustion air from the air coming from the outside. Most of the air from outside gets to the inlet of the diesel heater, i just take out a small amount of this air for the combustion instead of having to make a seperate hole in the hull for this. I could take the air on the cold side of the ventialtion unit instead of the warm side, it just requires a bit longer hose.

I updated the sketch with colorscheme to show temperatures as well

[Dockhead]

OK, so you've got an air heater, not hydronic.

You can forget harvesting heat from the hot air flow into water. If you do calculations of heatex areas required you'll see.

If you want hot water and radiators then you need a hydronic heater. Just use a separate hydronic heater for that and leave your hot air system the way it is. Except that you should, as Gord suggested, NOT take combustion air from the interior. Take that from outside.

[HeinSdL]

If still possible, put the warm air outlets as low as possible near the cabin floor

[GordMay]

Originally Posted by skatun

No I draw combustion air from the air coming from the outside. Most of the air from outside gets to the inlet of the diesel heater, i just take out a small amount of this air for the combustion instead of having to make a seperate hole in the hull for this. I could take the air on the cold side of the ventialtion unit instead of the warm side, it just requires a bit longer hose.

I updated the sketch with colorscheme to show temperatures as wellAttachment 295805

Thanks, for clearing MY confusion!
My remarks stand, for those using inside combustion air.

[Kelkara]

If you haven't already done so download the Espar (Eberspächer) installation guide ... it's an almost identical installation for the Chinese copies, but unlike whatever documentation came with your chinese heater, it is actually helpful ...

https://ca.binnacle.com/pdf/Espar%20...LG6n1lFGctZbcK

[skatun]

I will take some photos and share with you guys when i get tarted on it

[fourlyons]

So there are companies selling air to water heat exchanger kits for these forced air heaters, but they are for producing domestic hot water. Here is an example, https://www.bobilvans.co.uk/product-page/new-bobil-air-hybrid

However, almost half the heat produced by these heaters goes out the exhaust. So there are people scavenging that heat to heat water and putting it to work, that might be enough to do some heating. Google it.

[intervivos]

Haven't installed one in my boat (yet) but did install one in my sprinter van. In your schetch you are pulling in outside air for both combustion (good) and circulation (bad). This would create positive pressure in the cabin, which i don't think is bad as negative pressure but still not ideal.

Use outside air for combustion intake only, and exaust goes outside. You can draw this as a simple linear line through the boat with the heater in the middle. No need to warm the intake air, unless you are going to the artic/antartic.

The air warming circuit should be exaust to vents (skip the water heat exchanger, it will cause too much back pressure. Air volume flow is key) and the intake air should also be inside the cabin. Just like a/c and reverse heat systems.

[Leighpilot]

Do not draw the combustion air from inside the boat. Think about it. The combustion air becomes the exhaust air and is vented over the side. So as much air is exhausted outside, as much air , cold outside air , must be drawn into the boat. So while you are warming the air inside the boat , you’re continually drawing in cold outside air , not terribly efficient. So make sure you draw combustion air from outside.

[nofacey]

Most every diesel stove on the coast (most commercial tugs & fishing boats) pulls combustion air from inside the cabin, as do many espar style heaters. The dry heat they generate far exceeds the heat loss due to cold air intake. The effort required to run an external fresh air intake is not returned unless you’re in artic like conditions. Assuming you’re not in the artic…..an internal air supply cycles the air supply inside your boat, which I consider a positive.

I live in the Pacific Northwest, and have owned & occasionally lived aboard in the water thu winter, with various diesel stoves/heaters. Biggest issue is usually related to running them on the lowest setting. Presently using a Chinese forced air in 32 ft powerboat - we frequently have to open windows to keep temp comfortable.

But forget trying to heat water via inline radiator, just won’t get enough heat transfer.