Eberspacher heater circulation

[pcatterall]

I mess about with heaters for beer money. In the recent cold weather I noticed that heaters on test were failing my heat test (very scientific) where I see how long I can hold my in the hot air 6" from the outlet. It ususally gets a bit painful after 10/15 seconds but I noticed that I could do it indefinatly.
I reson that the heater can only 'add' so much heat to the air that passes through and the ambient temp was so low and my shed so badly insulated that the heater could not raise the shed temp to get warmer air passing through the system.
On my boat the heater is in the wheelhouse with ducting into the saloon. When it gets very cold I abandon trying to heat the wheelhouse and just use the outlet in the saloon. But, of course the heater is drawing the cold air from the wheelhouse warming it a fraction sending that slightly warmed air to the saloon but drawing more cold air in again.
It seems that I should have return ducting from the saloon to the heater which would be a bit of a pain.
Have I lost the plot here? please tell me that I dont have to make more holes in the bulkheads!!

 

[Heckler]

YES!
thats what i did so the eber sucks warm cabin air and recirculates it, strictly speaking i suppose if one was to burn warm cabin air it would be more efficient? however how safe it would be!
stu

 

[savageseadog]

I take the air from a cockpit locker. Not as cold as outside air but not stale air, some fresh and there are less noise issues

 

[uforea]

One of the Eber. manuals says to draw combustion air from the outside and to recirculate the heated air.

Ted

 

[Tidewaiter2]

Our Eber intake is in the cockpit locker- I think that location works well- engine compartment heat leaks in and takes the chill off the incoming air for quite a while- even if the engine only runs while berthing. Also risk of a build up of CO in the recycled air is reduced.
As a benchmark, we had loads of frost on the pontoons for 6 mornings last week.
Herself had the Eber on full or half chat all the time except when actually out sailing and actually took a layer off when below. Unknown event before we bought this boat!

 

[captainslarty]

Hi,
It depends on what type of eber it is, or more precicely the rating. Also the control unit fitted. On for example the airtronic d2 and d4, the heat is ramped up over a period of 3 minutes,, so try it after that period.
The heat output is dictated by the fuel input.. the metering pump.

2 kw in very cold weather is not great. thats the main reason we went for a D4.

I can send you the service manual if you like ? .. it has the ramp up graphs etc.
Joe

 

[pcatterall]

Thanks CaptainS, I have the data and only do my 'palm test' after the heater is really warmed up and on full pelt.
Yes, of course different heaters have different outputs. What I am saying is that the heater can only increase the temp of the air flowing through by X amount, if the air coming in is always at freezing and the warm air is being blown into another cabin then the heater will struggle to raise the temp in that cabin. But if the air is circulated back to the heater from that cabin the added value to the heat has more chance to make an impression.

 

[Ceejay]

The theory of recirculating the cabin air in order to increase the heating effect is sound. However one of the benefits of hot air blown heaters is that they reduce condensation and have a drying effect on the cabin and its contents. This will not occur if the cabin air is recirculated. One way round this I suppose would be to fit a divertor mechanism into the hot air intake pipe as fitted to many car heaters, which would allow air to be drawn from either inside or out.
CJ

 

[captainslarty]

Hi PC
Yes, exactly. same as gas boilers in house central heating.. however, I would think, that even in freezing conditions, you would not be able to keep the hand there for long ?.
Joe

 

[jimbouy]

My reading of Eber manuals is that you should recirc cabin air for the heated air.

If you heat fresh air from outside but have your heater controlled by a rheostat rather than an external thermostat you will get drier air (possibly but that will depend on out side conditions?) and you will probably be running the unit at full heat. Certainly on a cold day that could well be the case and I agree with the comment that the heater can only increase the temp of the air drawn in by X amount.

When I installed my eber I recirced air from with in the cabin and thought I had done the wrong thing as the unit cut out after ten minutes. I assumed this was because the unit was sensing the temp of the air drawn in.

Any way after connecting a fault code reader I discovered that in fact it was the main temp unit sensor that was giving the prob. Basically the whole unit was getting over heated. Cured the problem by opening the cock pit locker an inch.

I am in the process of redoing the installation as my first attempt was not very tidy. (also I picked up a D2 at a V good price and want to add an extra out let up front)

So I'll be insulating all the pipe work and may add a bit of ventilation to the locker. Any ideas on what to insulate the exhaust with?

Initially I'll stick to recirculating the cabin air and will see how that goes. The idea of a diverter to chose inside or out side air is a good one tho.

Oh and just as a point of interest I run mine form a small tank of paraffin ... it seems happy enough with that!

Cheers

Jim

 

[pcatterall]

I hate all that heat which goes flying up the exhaust. Trying to think of a simple way to capture it without the fumes. Drawing the returning circulating air over it?

 

[jimbouy]

Yes it does seem a bit contradictory I guess that any method of heat exchange would run the risj of exhaust fumes getting blown in with that nice warm air....



[ QUOTE ]
I hate all that heat which goes flying up the exhaust. Trying to think of a simple way to capture it without the fumes. Drawing the returning circulating air over it?

[/ QUOTE ]

 

[hlb]

Maybe you could raise the heat level a bit, by recirculating.

However my heaters running now, at just less than half power, it's about 80deg here. Theres glass all round and the curtains are open. I reacon I could easy push thye tempriture up to 100deg or more.

I've got weber now, but on occasions when the eber worked, got the same result. I can leave the patio doors open and heat the cockpit if I want.

Think you heater is just to small, mines D5 or equivelent.