Can I (should I) tap into generator fuel line for diesel heater?

belfert · August 03, 2010, 10:46:00 AM

Would it be advisable to tap into the generator fuel line to provide fuel for my Proheat diesel heater? The Proheat has no return line. I think the fuel line to the generator is 3/8" and the Proheat requires a 3/16" fuel line. I would like to avoid adding another pickup to the tank if possible. (I would never do this with the main engine fuel lines.)

JohnEd · August 03, 2010, 11:04:34 AM

Brian,

I think you have no choice other than installing a separate tank for them. I think the gen pickup is higher in the tank to allow for running the gen dry and still keeping a reserve to get you "out of there". I like your idea of NOT using the main, engine, pickup.

Soooo. here is the problem as I see it: is the 3/8 line enuf to feed both devices while both are "floored"? Do the math only to sat your curiosity. If both call for a min 3/16 line then I think the 3/8 will do just fine. If the gen requires a 3/8 line for it's use alone I would still keep the 3/8 line BUT I would install one of those little in-line fuel pumps, $30, at the tank end They make them in a whole host of different pressures and flow rates. The pump could be switched on when either load device was in use.

Either way you go I would pay attention to the fuel filters.

HTH,

John......ever with at least 2 cents

belfert · August 03, 2010, 11:07:39 AM

My generator pickup is at least as low as the main engine pickup. The generator pickup is the original Webasto pickup from when the bus was a passenger coach. (Original Webasto long gone.)

I don't think I would want the diesel heater running the fuel tank dry any more than the generator runnng it dry.

eddiepotts · August 03, 2010, 11:15:13 AM

You may try running the heater line off of the 3/8 return to the tank. I really don't see what it would hurt if it came from gen or engine on the return line. It is just giving what is not needed back to the tank. The drop from the 3/8 down to 3/16 should give enough volume to run the heater.

Len Silva · August 03, 2010, 11:23:06 AM

I think it will work OK if you keep the tee close to the tank. What's the worst that can happen? One or the other won't perform as they should and you then go to the trouble of adding another pickup.

So, even though I understand why it's not recommended, I would try it anyway.

I don't think you can use the return line because it doesn't generally drop into the tank, just flows to the top.

Nusa · August 03, 2010, 12:27:32 PM

There's likely no flow in the return line if the generator isn't running, and that shouldn't be a requirement to run the heater. Tapping the feed line as close to the tank as practical sounds like the easiest thing to try to me too.

Nick Badame Refrig/ACC · August 03, 2010, 12:29:57 PM

Hi Brian,

I have a custom made fuel pick-up for both my generator & my Proheat that is 4" above my engine pick-up.

They both work off the same fuel line and work well however, there is an issue with the Proheat at start up

just after the generator has been running. The Proheat will sputter for 1 to 2 mins until the the line has

refilled with fuel. It so happens that the generator will suck fuel from the Proheat line when the proheat

is off. Allthough it's not any problem for me or anyone else, it's still and "issue" that's not a problem! LOL...

Good Luck
Nick-

Don4107 · August 03, 2010, 12:40:18 PM

First bus we bought had genny hooked to engine fuel line. Every now and then it would act up. Finally found to be the one running could suck air from the one not running. Solved by putting a low pressure boost pump between the tank and the tap for the genny.

This may only have been because they where both gasoline engines with float carbs. If I remember the engine fuel pump went south not long after that and may have been the cause for the genny sucking air. Just be aware that fuel volume is not the only concern.

Good luck
Don 4107

JohnEd · August 03, 2010, 12:42:51 PM

Nick,

Your Proheat should not admit air into the fuel line to allow it to draw down. This will become a problem as the air bleed worsens and you start to get bubbles in the fuel feed to the gen. I guess a quick fix would be to install a check valve in the line that feeds the Pro heat. A small pump would also solve the problem by preventing a negative pressure at the devices but that isn't better than solving the "problem" you don't yet have. Sounds muddled to me and I said it.

John

belfert · August 03, 2010, 01:28:35 PM

Based on what I am reading it might be best to just buy or build another fuel pickup so it is one less thing to fool with. I can add check valves and so on, but that starts costing money and time.

Any suggestions for building a fuel pickup? I have a plate I can remove to install the pickup in. The Proheat manual is adamant about using 3/16" line. I'll check Craig Shephard's site to see how he did it. Proheat makes a fuel pickup, but it costs $71 (Too rich for me right now).

JohnEd · August 03, 2010, 02:21:10 PM

Brian,

Please do this. Find the area in square inches for a 3/16 inch line. Value X. Find the area of a 3/8 line and let that be value Y. Pie R squared for 3/16 is .11 sq inches and for 3/8 I get .44 square inches. so doubling the diameter (3/16 t0 3/8) gives 4 times the area/size of pipe. I still don't know what the requirement of the heater might be.

Most of this size requirement is based on the length of the run and the resistance of that run to the "flow". Shorten the run and you can get by with smaller size tubing. Pressurize the run and you can get by with whatever size you wish by simply upping the pressure. As an example only. The size is spec-ed on a gravity flow from some small height or head pressure. A small pump would resolve all these size issues. If you stop and think of how much fuel will run out of a gallon jug with a 3/8 hole I think you will agree that no generator we could transport would use that much fuel as a flow. Like wise a heater.

If you have a plate on the top of your tank that you could remove then you can install a pickup that stands off the bottom as far as you like. If you use copper tubing be advised that BioD will react with copper and make a nightmare. Copper or steel tube will silver solder just fine and be stronger than all heck and you only need MAPP gas instead of propane. Be very careful that the tube you install does not interfere with the fuel gauge sender float arm.

Hope my numbers are OK.

John

John

Busted Knuckle · August 03, 2010, 03:29:27 PM

Nick,
Would a small pump in the line as it comes out of the tank prevent this?

BK

steve wardwell · August 03, 2010, 04:49:02 PM

Our everhot is plumbed off the feed line teed in near the genny to a filter to the heater.....5 years never a burp nor fart from ether one..don't remember the line sizes but can run both.......Why on earth would you folks run your tank so low? 1 you don't want whats on the bottom of your tank, and 2. less than 1/2 a tank the mains return line makes all the fuel hot.

JackConrad · August 03, 2010, 05:05:35 PM

We have a separate fuel tank for our generator/ProHeat. A fuel line to a small Racor filter that has 2 outlets. One to the Generator and one to the ProHeat. No problems so far (about 3 years). Jack

Greg Roberts · August 03, 2010, 06:31:13 PM

I installed a proheat unit on one of my motor yachts in the 90's and I actually tee'd into the genset line and installed a low resistance check valve in each fuel line to avoid drawing air from either unit. The check valves were the tubing fitting type and with lapped metal disc and seat. Three trips to Alaska and all around the west end with no issues at all. I have a proheat unit that I will one day install in my Eagle and this is exactly how I will install it again.