Diesel heater - fuel supply arrangements

[cheesegas]

Hi all. I'm fitting a Planar diesel air heater into my boat hopefully before it starts to get chilly. Taking all the usual precautions - using branded stainless clips and a marine sealed silencer instead of the non-sealed automotive silencer included in the kit, loop in the exhaust between silencer and skin fitting, marine skin fitting, metal fuel lines/filter in the engine bay, fat wires from the batteries etc.

 

However, the thing that's got me is the fuel supply. Some people have a plastic day tank out of the engine bay which I don't like, or have a metal one in the bay, some with a pump to top up from the main tank which adds a degree of complexity. I'd never want to run it on heating oil, only diesel.

 

What's the best way to neatly get access to the tank? It's a cruiser stern with the engine being gravity fed and the tank forming the back wall of the engine bay down to the uxter plate. The top of the stern is the top of the tank. Options I can see are a dip tube in the top of the tank, but then it would need to be outside the engine bay and prone to being caught on stuff. Or taking a T off the engine's supply after the filter/water seperator, but then there's the possibility of air being drawn into the engine if the heater's dosing pump doesn't have a perfect non return valve. Maybe this is a non issue? I don't like the idea of drilling in the side of the tank as the penetration is below the fill line...

 

Any more ideas? How's it done with other diesel Webasto/Eberspachers? Thanks.

[David Mack]

Why not T off the engine feed pipe immediately after the shut off valve, and fit a separate filter for the heater supply. As the engine is gravity fed the feed pipe will always be under positive pressure (unless you run out of diesel completely) and so the heater shouldn't be able to push air back into the engine feed.

[Alan de Enfield]

I have seen eber supply pipes T'd into the engine supply, I've seen them connected into the fuel filter (most filters have 2-oulets so it can screw straight in) but I have always been told the 'proper way' is to have a dip tube that is at least 2" higher that the outlet / dip pipe for the engine to ensure that you do not use all the fuel running the heater and have insufficient left to start your engine.

[MarkH2159]

I have just changed my heating system fuel supply set up.

Originally there were two Lucas Cav type filters.

One was fed from a low tank suction and fed the engine and the Mikuni Diesel heater.

The other was from a higher suction and fed only the Kabola Diesel Stove.

I kept the two filter arrangement and swapped the feed to the Mikuni over to the spare outlet on the filter that was feeding only the Kabola.

So now I have engine on low suction with its own filter and the heating units on higher suction with their own filter. This, I believe is the correct way for two supply set up.

 

If you have only one supply from the tank then it is quite normal to use the second outlet from the engine filter, if available, to feed the heater.

This would be much better than trying add another fuel supply line from the tank.

If no second outlet on filter available, I would T into the engine supply, preferably before the filter so as to be able to add a second filter for the heating system, but remember to add in a stop valve.

Failing that, just T into the engine supply after the first filter and add a stop valve to supply the heater.

 

 

[Tony Brooks]

3 minutes ago, MarkH2159 said:

I have just changed my heating system fuel supply set up.

Originally there were two Lucas Cav type filters.

One was fed from a low tank suction and fed the engine and the Mikuni Diesel heater.

The other was from a higher suction and fed only the Kabola Diesel Stove.

I kept the two filter arrangement and swapped the feed to the Mikuni over to the spare outlet on the filter that was feeding only the Kabola.

So now I have engine on low suction with its own filter and the heating units on higher suction with their own filter. This, I believe is the correct way for two supply set up.

 

If you have only one supply from the tank then it is quite normal to use the second outlet from the engine filter, if available, to feed the heater.

This would be much better than trying add another fuel supply line from the tank.

If no second outlet on filter available, I would T into the engine supply, preferably before the filter so as to be able to add a second filter for the heating system, but remember to add in a stop valve.

Failing that, just T into the engine supply after the first filter and add a stop valve to supply the heater.

 

 

 

I am a bit concerned over the red bit, if the injector pump uses a transfer pump. What I fear may be possible with any sort of lift pump and a system with a high volume return (self bleeding) system

 

The filter will cause  some kind of restriction and as it gets partially clogged that restriction will get worse. Despite most NB tanks providing a head, I fear that there may be a potential for the engine to suck air in via the boiler. In some cases, it may need frequent bleeding.

 

If you must tap into the engine fuel system, then certainly go before the filter and fit another boiler fuel filter.

[Alan de Enfield]

6 minutes ago, Tony Brooks said:

I am a bit concerned over the red bit, if the injector pump uses a transfer pump. What I fear may be possible with any sort of lift pump and a system with a high volume return (self bleeding) system

 

 

I also mentioned this earlier in the thread - I have seen many diesel heater feeds taken from the 2nd filter outlet - maybe it is because its easy to pick up a feed, but is it really 'bad practice' ?

[Tony Brooks]

19 minutes ago, Alan de Enfield said:

 

 

I also mentioned this earlier in the thread - I have seen many diesel heater feeds taken from the 2nd filter outlet - maybe it is because its easy to pick up a feed, but is it really 'bad practice' ?

 

I have had maybe two questions since about 2006  implicating the heater feed introducing air into the engine fuel system so It's probably not a major problem. I would be much more concerned about the ease with which you could run out of fuel, especially if you are iced in etc.

[Alan de Enfield]

44 minutes ago, Tony Brooks said:

 

I have had maybe two questions since about 2006  implicating the heater feed introducing air into the engine fuel system so It's probably not a major problem. I would be much more concerned about the ease with which you could run out of fuel, especially if you are iced in etc.

 

Agreed - I made the same point earlier.

It's a case of always making sure you have a FULL jerry can of fuel JIC (Just In case) so you can at least get the engine running to charge batteries or go and fetch diesel etc.

[MarkH2159]

1 hour ago, Tony Brooks said:

 

I am a bit concerned over the red bit, if the injector pump uses a transfer pump. What I fear may be possible with any sort of lift pump and a system with a high volume return (self bleeding) system

 

The filter will cause  some kind of restriction and as it gets partially clogged that restriction will get worse. Despite most NB tanks providing a head, I fear that there may be a potential for the engine to suck air in via the boiler. In some cases, it may need frequent bleeding.

 

If you must tap into the engine fuel system, then certainly go before the filter and fit another boiler fuel filter.

Agreed, hence my wishing to seperate my engine fuel set up from my heating set up, with seperate feeds, filters etc. Short of having a seperate tank, it was the best option.

Also the heating draws from higher so I should always have engine fuel when the heating runs out.

[cheesegas]

Thanks for the advice, I think I'll take a feed off the Lucas CAV water seperator to a filter for the heater, I dip the tank regularly to check the level so I'm not too concerned about running out of fuel. Reckon the tank's around 250 litres based on my highly unscientific calibrated dipstick.

 

The heater won't be used as the main heat source, only to get some instant heat into the boat while the stove starts, or if I get home late and can't be bothered with making a fire before going to bed. It won't be on the whole day so I don't envisage it using a lot of fuel.

 

...and yep, I've got a jerry can of diesel stored on the front deck just in case!