Diesel heater: want to tie it into my diesel tanks

[GrandWood]

Here is a pic of what I assume is the fuel manifold, I’ve seen pics of other GBs and this is what they all looked like, pretty much original. I could buy what I would need to flange all the copper and tie in somewhere in the manifold. Getting the copper far enough away from the the mounting board to cut it nice would be a pain.

On the starboard side, the main fuel line from the manifold to the engine is rubber fuel line, would like to tap in right after the racors, and I would also have a small filter after that. Thinking this would be the easiest install.

Lmk what ya think, thank you
Joe

 

[Jeff F]

One de can't suck air back through the diesel heater or the little fuel pump. If fuel pumps leaked down, you would have to crank your car engine for 15 seconds every start. It has its own one way valve. I think even when they fail (electrically), they still don't leak down.

And I happen to know that they can even withstand a lot of suction from the downstream side. A couple years ago, I did an ER check before heading out into Queen Charlotte Straight. I had bumped the fuel tank valve lever shut. Just as I got out beyond anchor depth, I lost rpms and the engine died. Running through the possibilities (while the wife kept me updated on the approaching shoreline), I opened the tank valve, which wasn't enough. Air had entered the line and it needed to be bled. But it didn't enter through the diesel heater and pump. It came in somewhere else. Maybe the top seal on the Racors? Maybe the fittings on the manifold? All I really know is that it was far enough back from the secWhat that tells me is that, although my fuel lines don't leak, my engine can "suck" hard enough to draw air in somewhere. Okay. But that somewhere isn't the diesel heater and pump. That line remained primed. I wish I had looked at the vacuum gauge that tells me if my Racor filters need changing. Was the vacuum at 20 In/Hg? 30? Pegged? I've never seen it above 5. But whatever the concerns are about "air" entering through the diesel heater and pump, every other connection in the fuel system is a more likely leak under a powerful vacuum.

I'll offer a counter to this.

The filters and fuel line to the engine are specifically designed and installed so as to withstand some level of vacuum without allowing air to be sucked into the system. Air in any volume may cause the engine to fail.

Every open branch on a fuel line is an opportunity for air to enter the line under vacuum. The more lines and fittings there are in the system, the greater the opportunity for drawing in air.

If you tie into the fuel line a failure anywhere on the furnace line or in the furnace can allow air to be drawn in and stop the main engine. I think that's the vulnerability that should make people nervous. Maybe it's not high probability, but relying on the check valve on the heater to prevent the main engine from failing is a risk that is unnecessary. The heater manufacturer may warn against this. I'm not sure your confidence in this is well founded.

 

[SteveK]

Here is a pic of what I assume is the fuel manifold, I’ve seen pics of other GBs and this is what they all looked like, pretty much original. I could buy what I would need to flange all the copper and tie in somewhere in the manifold. Getting the copper far enough away from the the mounting board to cut it nice would be a pain.

On the starboard side, the main fuel line from the manifold to the engine is rubber fuel line, would like to tap in right after the racors, and I would also have a small filter after that. Thinking this would be the easiest install.

Lmk what ya think, thank you
Joe

I see a regular hose/line already Teed to copper. Where does that go? I would tee into the hose with the small tube that comes with heater. Much simpler than flaring copper.

 

[Dockmaster]

This is exactly how mine is set up with no issues.

These heaters use very little fuel so I have no concern having tapped one of my primary fuel tanks. I would estimate a gallon a day is the most I have ever used. It would take a long time to empty even on of my tanks.

Seems to me like folks are way overthinking this. My heater is a larger unit, 51k btu if memory serves. So I use more than 1 gal/day if it’s cold. But still, just teeing off the gen fuel line works great and is super simple.
My set-up is a little more complicated because the only place I had room for the heater, circ pump and expansion tank was up on the flybridge. I installed a remote fuel tank up there and then a little pump in the engine room. It’s on a float switch that activates the fuel pump when my remote tank drops to 1/4 tank then shuts off just above 3/4 tank. It’s a pretty fast pump so when it is running it’s drawing way more than the heater itself, about 2/gal/minute I believe. Even with the larger draw there has been zero fuel issues with gens, mains or the heater and it’s been in use about 5 years now.

For what it’s worth, I don’t recommend installing the way I did. With the heater up high it gives me trouble trying to push the heated fluid down to the zones. I occasionally have an issue with the heater tripping the high temp switch.

 

[GrandWood]

I see a regular hose/line already Teed to copper. Where does that go? I would tee into the hose with the small tube that comes with heater. Much simpler than flaring copper.

This pic? It’s goes to the racors, then there’s more rubber line between racors and lift pump. I’d prefer right here because the fuel lines to pulse pump would be outta the way and heater is about 2 ft away on other side of bulkhead

 

[Jeff F]

Personally my concerns with tee-ing off a main engine fuel line for a heater are centered around the fuel lines typically used. Light weight plastic. Especially the fuel lines used on the Chinese diesel heaters. If it fails you may get enough air in the main engine fuel to cause problems. Maybe the inexpensive pulse pump doesn't seal well and the main engine sucks air. Maybe a failed heater line will dump a tank full in the bilge.

Fully agree. These heaters are designed for use with a day tank. I wouldn't integrate one into my main fuel system.

Filling the existing furnace tank as needed from the main tank(s) may satisfy the OP's needs and is easily accomplished without compromising existing systems.

 

[Jeff F]

Why not tee into a fuel line? If the concern is the engine would suck air from the heater, that really depends on engine size and consumption and main fuel line size (I have 1" crossover lines from my tanks and my engine consumes 1.5 gph). Worst case, shutoff valve to heater and keep it closed unless at rest.

Am I missing something?

Peter

I don't think small engine/big lines is relevant in discussing worst case scenarios.

I understand that you're describing a case where vacuum is going to be extremely unlikely through design.

But take the generic case, which also conceivably applies to you. For some undetermined reason - maybe a clogged pickup - the vacuum level on the fuel system starts increasing.

What's your protection/warning/impact look like for that rare event?

Step 1 I think is ensuring that your fuel system will support a certain level of vacuum pressure before allowing air to enter.

I can't point to any specific numbers, but I'm sure they're out there somewhere. I'm sure ABYC goes into this. I'm also guessing it's in Racor specs.

I'm quite certain that no furnace offers any guarantee of performance under vacuum. Mine comes with explicit warnings against sharing a fuel line with propulsion engines.

So you could have a valve system to satisfy this requirement, but it's far from optimal.

The requirement for a dedicated pickup tube is mostly about maintaining the integrity of the fuel feed to the propulsion engine IMO. Taken in that light the tube itself is a side issue. Tapping a fitting anywhere on the side of the tank would be functionally equivalent.

 

[SteveK]

This pic? It’s goes to the racors, then there’s more rubber line between racors and lift pump. I’d prefer right here because the fuel lines to pulse pump would be outta the way and heater is about 2 ft away on other side of bulkhead

I would agree, but install a small inline filter, inexpensive, does not need to be a racor.
My GB had it connected the same and with two running 120's there was never a problem. Perhaps in higher volume draw and flow cannot be maintained from the tank there could be backflow, but I suspect the injection pump for the heater (on/off) already causes a blockage for backflow.

 

[SteveK]

Fully agree. These heaters are designed for use with a day tank. I wouldn't integrate one into my main fuel system.

Filling the existing furnace tank as needed from the main tank(s) may satisfy the OP's needs and is easily accomplished without compromising existing systems.

where did you get that information. A day tank is for convenience if you choose not to integrate to main tank.

 

[Jeff F]

where did you get that information. A day tank is for convenience if you choose not to integrate to main tank.

Integration to main tank has very specific requirements and is not risk free

I have hands-on experience installing and using Espar/Webasto small heaters, and recently helped my son with installing and troubleshooting a Chinese knockoff in his camper van.

In general, I was quite impressed with the unit, given that he paid a *lot* less than the cost of the European units. His came in a frame with a built-in tank.

One pretty immediate observation is that his pulse pump is ****. The unit stops working when the tank is low but not empty. The fuel lines wouldn't pass any minimal standard for marine use.

I'm not suggesting they shouldn't be used, but they're not really up for full integration into a marine system. Opinion only.

 

[mvweebles]

I don't think small engine/big lines is relevant in discussing worst case scenarios.

I understand that you're describing a case where vacuum is going to be extremely unlikely through design.

But take the generic case, which also conceivably applies to you. For some undetermined reason - maybe a clogged pickup - the vacuum level on the fuel system starts increasing.

What's your protection/warning/impact look like for that rare event?

Step 1 I think is ensuring that your fuel system will support a certain level of vacuum pressure before allowing air to enter.

I can't point to any specific numbers, but I'm sure they're out there somewhere. I'm sure ABYC goes into this. I'm also guessing it's in Racor specs.

I'm quite certain that no furnace offers any guarantee of performance under vacuum. Mine comes with explicit warnings against sharing a fuel line with propulsion engines.

So you could have a valve system to satisfy this requirement, but it's far from optimal.

The requirement for a dedicated pickup tube is mostly about maintaining the integrity of the fuel feed to the propulsion engine IMO. Taken in that light the tube itself is a side issue. Tapping a fitting anywhere on the side of the tank would be functionally equivalent.

There absolutely should be a valve on the tee'd off supply to the heater. Vast majority will use the heater for occasional use while at the dock so they'd have to remember and if there is an ABYC standard, probably not compliant. The added expense and hassle of doing anything other than tee-ing is a personal choice.

I have a lot of respect for ABYC standards. But I cannot afford a fully compliant boat. I can afford a very safe and serviceable boat and pay attention to electrical requirements, but a lot of the requirements are difficult and expensive to comply with and the risk reduction is out of whack with the cost. Fine if you're having a 7-8 figure boat built by a builder who claims ABYC compliance. But for folks on the $100k-$400k used boat market, difficult.

Peter

 

[GrandWood]

There absolutely should be a valve on the tee'd off supply to the heater. Vast majority will use the heater for occasional use while at the dock so they'd have to remember and if there is an ABYC standard, probably not compliant. The added expense and hassle of doing anything other than tee-ing is a personal choice.

I have a lot of respect for ABYC standards. But I cannot afford a fully compliant boat. I can afford a very safe and serviceable boat and pay attention to electrical requirements, but a lot of the requirements are difficult and expensive to comply with and the risk reduction is out of whack with the cost. Fine if you're having a 7-8 figure boat built by a builder who claims ABYC compliance. But for folks on the $100k-$400k used boat market, difficult.

Peter

Have a fuel on off valve on my current day tanks nd it will get used when I reroute off fuel tank. All the hard lines off the fuel tanks go down into the bilge area under the battery bank, which all the batts are in there own plastic tray with lid. So I think I’m just going to go off the rubber fuel line at the manifold, furthest from engines and call it good, will be a simple install.

I will keep a good eye on it

 

[GrandWood]

Main reason I’m doing this is I don’t want a bunch of fuel cans all over my deck, and here in the PNW it can rain for days and I don’t want to be filling day tanks in lazzerette in the pouring rain, or taking the dink to shore for fuel. Bad enough i have to take my dog to shore 3 times a day in it, dont want any water getting into my fuel either

 

[GrandWood]

Also I have brass tees in place of the cheap plastic ones supplied with the heater were needed, I won’t use any type of plastic fitting in a fuel line

 

[Jeff F]

I have a lot of respect for ABYC standards. But I cannot afford a fully compliant boat. I can afford a very safe and serviceable boat and pay attention to electrical requirements, but a lot of the requirements are difficult and expensive to comply with and the risk reduction is out of whack with the cost. Fine if you're having a 7-8 figure boat built by a builder who claims ABYC compliance. But for folks on the $100k-$400k used boat market, difficult.

You're talking about living with reasonable compromise and risk.

I have a valved feed to my furnace. But I recognize it as a less-than-ideal arrangement, and wouldn't recommend it to others as a universally acceptable practice.

You asked why not, and I was trying to provide an answer. We discuss ABYC often when talking about retrofitting old boats. Why would we completely ignore their guidance if it exists for this sort of system?

 

[mvweebles]

You're talking about living with reasonable compromise and risk.

I have a valved feed to my furnace. But I recognize it as a less-than-ideal arrangement, and wouldn't recommend it to others as a universally acceptable practice.

You asked why not, and I was trying to provide an answer. We discuss ABYC often when talking about retrofitting old boats. Why would we completely ignore their guidance if it exists for this sort of system?

Completely fair statement. Nothing wrong with knowing what is best practice, (ABYC in many instances), then making a decision based on circumstances.

To be fair, many diesel heaters aren't that safe to begin with. How they're connected to diesel supply isn't the most important safety measure. That said, I'd probably go with a 3-gal day tank that gravity feeds the heater is probably a good option. The day tank can be filled from the main tanks (via pump) every few days.

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Peter

 

[Jeff F]

The added expense and hassle of doing anything other than tee-ing is a personal choice.

It's a personal choice like most other things.
The best personal choices on system choices are made with a clear view of risks, expense, and future hassle.

I don't see how tee-ing becomes the champion here. It's not. I view it as a lazy compromise that potentially endangers the boat.

 

[SteveK]

You're talking about living with reasonable compromise and risk.

I have a valved feed to my furnace. But I recognize it as a less-than-ideal arrangement, and wouldn't recommend it to others as a universally acceptable practice.

You asked why not, and I was trying to provide an answer. We discuss ABYC often when talking about retrofitting old boats. Why would we completely ignore their guidance if it exists for this sort of system?

Jeff, be safe.
Do you run the diesel heater while you sleep or are away from the boat?
The fuel pickup installation is the least concern. A shut off valve is nice to have, I suppose, however not needed IMO as the diesel heater fuel pump is like a shut off valve when not in service and momentary while in use.

 

[Jeff F]

Jeff, be safe.
Do you run the diesel heater while you sleep or are away from the boat?
The fuel pickup installation is the least concern. A shut off valve is nice to have, I suppose, however not needed IMO as the diesel heater fuel pump is like a shut off valve when not in service and momentary while in use.

I run my diesel heater pretty much all the time this time of year . If underway I turn it off and use engine waste heat. I have a 50k btu ITR system, quite different from the OP's.

See my earlier point. The fuel lift pump is not specifically designed to resist suction, and with the Chinese units I'd have minimal expectations on anything.

My rationalization is that as soon as i encounter symptoms of fuel starvation or air infiltration I can shut off the furnace supply. That works for me, but might not be foolproof with a less hands-on captain. No way would I have a tee without a shutoff. I leave mine open.

 

[Jeff F]

That said, I'd probably go with a 3-gal day tank that gravity feeds the heater is probably a good option. The day tank can be filled from the main tanks (via pump) every few days.

OP has a day tank now, and the system works fine. I think we agree

 

[heysteve]

When I installed my Wallas heater, I used the dip tube assembly they sell as an option (here). I found a place in the back of a cabinet over the tank and cut a large hole in the floor. This gave me access to the top of the tank and so was able to cut the small hole in the tank and install the tube. I cut the tube to about 3 or 4 inches above the bottom of the tank.

I like the idea that the heater fuel feed is completely independent of the main engine supply.

 

[Jeff F]

OP has a day tank now, and the system works fine. I think we agree

All they need is a cheap transfer pump and line behind a valve. This is completely benign because the valve is off in normal use, so the valve can tee into the fuel system wherever convenient.

Downside is they have to use the pump when furnace tank runs dry. Not a bad compromise I'm guessing.

 

[Jeff F]

The fuel lift pump is not specifically designed to resist suction, and with the Chinese units I'd have minimal expectations on anything.

Now that I reflect a bit more on recent experience with my son's unit, I came to the conclusion that the pulse unit wasn't a pump, but a metering device. It was designed around gravity feed.

Documentation describing this is pretty much non existent. They look and feel like the originals, but there are some differences under the hood.

 

[SteveK]

Jeff, my pump is at the top of the tank level, I do have a tube inserted btw, so no gravity feeding. On my previous boat the heater was above tank and the injection pump pumped uphill. Real life, not guesses.

 

[Jeff F]

Jeff, my pump is at the top of the tank level, I do have a tube inserted btw, so no gravity feeding. On my previous boat the heater was above tank and the injection pump pumped uphill. Real life, not guesses.

Right. That's been my experience with Webasto/Espar. I guess my recent experience showed me that generalizing these things to the Chinese clones can be problematic.

 

[GrandWood]

All they need is a cheap transfer pump and line behind a valve. This is completely benign because the valve is off in normal use, so the valve can tee into the fuel system wherever convenient.

Downside is they have to use the pump when furnace tank runs dry. Not a bad compromise I'm guessing.

I could live with this set up, i will look into this and try and find a small fuel xfer pump. Then I don’t have to move anything, as you said, everything is working just fine as is.

 

[GrandWood]

Something like this?

 

[Marco Flamingo]

Right. That's been my experience with Webasto/Espar. I guess my recent experience showed me that generalizing these things to the Chinese clones can be problematic.

My experience with Webasto, Espar, and several Chinese heaters is they work exactly the same. The fuel pump is really a metering device as it doesn't pressurize downstream like most fuel pumps. But like a fuel pump, it has an integrated one-way valve (at least the Chinese ones do and I assume that others have copied). The "tick" of the pump sends a tiny amount through the one-way valve and then it reseats because of a pressure spring. Like a regular fuel pump, it could hold pressure, but the meter simply pushes tiny droplets of fuel into the ambient pressure in the fire chamber.

One could add another manual valve shutoff to the fuel line. In fact, one could install several to be really redundant. Then when the heater is turned on, it will detect a fuel starvation issue and shutdown, giving an error code. The error code will remind you that you have to turn on the valve(s). If there are no extra hand-operated valves, then when the heater shuts down the tick pump shuts down and the normally closed one-way spring-loaded valve in the pump stops any backflow (or draining of the system or air entering the system if an internal vacuum develops.) Your choice.

That was my experience when I accidentally shut off the fuel tank and created a strong vacuum throughout my entire fuel system. The common excessive vacuum problem in fuel lines develops after the fuel filters when the fuel filters get clogged. My T into the fuel line is beyond the filters (so that the heater gets clean diesel) and was subjected to a strong vacuum. But Racor filter canisters themselves aren't designed to withstand strong vacuums. That is where air got into my system, not via the diesel heater and metering pump. I doubt that is just a benefit of using the Chinese heaters with a backflow prevention in the metering pump. I would assume Webasto and Espar do the same. Before installation of a Webasto/Espar meter, suck on the downstream side of the meter to check?

If one is concerned that their heater pump may not have this common feature, there are one-way fuel line valves available for about $5. Just install one of those in addition to the pump. No need to have the heater give an error code to remind one to turn on a manual valve.

When using the term "day tank," I tend to think of gravity fed tanks above the heater/stove. Over the years, I have replaced two of those in favor of a T and meter pump in the main fuel line. Mainly for safety reasons but it is nice not to screw around pouring diesel into a little tank on deck. The only downside is the "tick" of the pump can be heard at anchor. It is not too difficult to reduce that (by not using the bulkhead mount that usually comes with the kit).

As to the idea that these heaters are "designed" to use the cheap little tanks that often ship with them, my understanding is that the little tanks allow a heater installation in a vehicle that is gasoline or an offgrid situation where there is no existing fuel tank. No need to use the little plastic tank when there are simpler, safer options on diesel powered boats.

 

[Jeff F]

No need to use the little plastic tank when there are simpler, safer options on diesel powered boats.

Hmm. Let's compare and contrast the two solutions.

Day tank pluses:
- limits fuel spill in case of furnace leak/failure
- does not in any way jeopardize fuel delivery to main engine.

Day tank negatives
- when empty needs to be refilled by opening valve, activating pump and closing valve

Tee into main line pluses:
- no need to manage day tank

Tee into main negatives:
- Furnace leak could drain tank(s) into bilge
- furnace leak could stop main engine
- eliminating these risks involves changing valve each time using furnace

The fact that you've never encountered the negatives does not mean they don't exist. I know which option I'd pick to satisfy the simple and safe criteria.

ETA: the third option is for the furnace to draw directly from the tank. This maintains the integrity of the engine fuel system, so would be the appropriate choice if eliminating the day tank.

 

[tiltrider1]

If you want to talk best practices, a heater should have its own fuel line where the dip tube ends at the tanks minimum reserve level. What’s minimum reserve level? That’s a question with no answer.

This is more important in a sailboat with a 30 gallon tank that is sailing long periods in cold weather or a boat that spends long periods anchored out in cold weather.

Most of us with big tanks or summer cruising plans or tropical destinations are not real concerned with the heater draining our tanks. In which case T’d into the main line will work just fine. While it’s not the best practice it is extremely low risk.