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Old 05-11-2019, 10:36 AM   #1
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Sharing a fuel filter

I'm installing an ITR hydronic heater, recommended install is a dedicated small spin on type filter from a dedicated supply line. I am pressed for room to install this. I'm thinking of teeing off the Racor 500 which feeds the genset. While perhaps less than ideal, why is this a bad idea?

The Racor 500 will supply 60 gph at 0.25 psi pressure drop, and 17 gph with 0.1 psi drop. The genset consumes something like 0.5 gal/hr at full load (and is rarely run), the heater about 0.25 gal/hr. Even considering the spill fuel for both, I am way below any capacity problem on the filter. This would save me the room, and the maintenance of another filter.

Anything I haven't thought of here?
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Old 05-11-2019, 11:43 AM   #2
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It might work, but even ignoring the filter, I'd be concerned about the genset starving your hydronic heater. The hydronic heater fuel pump most likely cannot compete with the genset fuel pump.
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Old 05-11-2019, 11:56 AM   #3
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It might work, but even ignoring the filter, I'd be concerned about the genset starving your hydronic heater. The hydronic heater fuel pump most likely cannot compete with the genset fuel pump.
I agree
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Old 05-11-2019, 12:01 PM   #4
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It might work but I'd be concerned about the genset starving your hydronic heater. The hydronic heater fuel pump most likely cannot compete with the genset fuel pump.
Or it could be the other way around. We had a Webasto DBW2010. The gear pump on the unit, delivers fuel from the tank to the heater at ~140 psi if I remember right. We were recommissioning the heater after a layup and the return line didn’t get opened. What a mess after it blew a hose off a double clamped fitting.

Regardless, when we installed the Webasto, we were told to keep all the systems separate.
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Old 05-11-2019, 12:05 PM   #5
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I do that, and my fuel flow to the engine is under one gallon per hour and usually about half of that when underway. I have never had any issues from operating the heater while underway at any rpm, but put a valve in the line between the heater and fuel filter just in case.

You very probably won't have any issues, that is the way my Webasto is set up and it's fuel demand is similar to your genset. My heater also requested a dedicated line from the fuel source, but limited access to the top of the fuel tank made it impractical.
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Old 05-11-2019, 12:27 PM   #6
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Would a check valve work after the filter for each feed?
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Old 05-11-2019, 12:36 PM   #7
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The negative pressure on the lines from the opposing fuel demands would be the issue, so check valves wouldn't solve the problem IF there was a problem. With a fuel filter of this size and the low total demand from both units I can't see there being any issues.

A valve to isolate one demand from the other was my choice, just in case there was a conflict between the two, or if there was a fuel leak between filter and heater with it's multiple connections with filter-pump-heater in small diameter lines.
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Old 05-11-2019, 01:23 PM   #8
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My Racor 900 primaries serve a valve manifold that serves 2 Detroits, 2 generators, a boiler and a diesel stove without fuel starvation issues. Each diesel engine has a secondary filter and the appliances have a small inline filter. The Racors have 2 micron elements that, you would think, should increase the chance of fuel starvation but doesn't. Because I keep my tanks clean, the 2 micron primary elements go 500+ hours.
Shared primary filters and individual engine secondaries is the usual setup on ships and big boats.





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Old 05-11-2019, 01:26 PM   #9
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Just have to be careful that air can't be drawn backwards through the fuel system of a machine that is not running. Some fuel pumps are effective check valves to prevent this, some not so effective.
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Old 05-12-2019, 11:02 AM   #10
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Just have to be careful that air can't be drawn backwards through the fuel system of a machine that is not running. Some fuel pumps are effective check valves to prevent this, some not so effective.
That is something to consider. The ITR heater has a common Facet electric pump, probably 5 psi. I think to starve it the genset would need to pull a bit of pressure drop in the filter, this is quite unlikely with 0.5 g/h genset consumption through a 60 g/h filter. But the genset could suck air from the heater, maybe. Check valves might be a good idea, though they involve a small pressure drop.

The fuel system is set up with a manifold from the tanks feeding the main engine, genset, and now heater. The QSB Cummins can draw 50 g/h through its Racor 900, but also through the manifold. If there's pressure drop problems, that's probably where they will be - but the factory sets them up that way so I assume experience says it's OK.
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Old 05-12-2019, 11:34 AM   #11
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If your fuel tank level is above the Racor, it may well be OK. If the Racor is above the fuel tank level it may be problematic.
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Old 05-12-2019, 11:51 AM   #12
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I attempted this setup, using a tee with check valves from one fuel tank, one leg going to a Espar hydronic and the other to my genset. It worked, sort of. I found, however, that the check valves would sometimes stick and the Espar would periodically starve for fuel, it's lift pump being about the size of a peanut. The fuel tank was slightly below and about 8 ft away, which didn't help. All problems went away when I installed a dedicated day tank for the Espar, slightly elevated, eliminating the tee and check valve arrangement. The genset's lift pump is fine with this revised setup.
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Old 05-13-2019, 09:54 AM   #13
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DDW,
On my boat (it came this way when I bought her and I think from the factory as well) my Espar heater and generator share one small Racor spin on filter (R12). The Espar fuel line has a separate shutoff valve after the Racor. I have not noticed any issues with this system. I leave the Espar fuel line shut off when not in use. My generator is powered by a Kubota 3 cylinder engine (Onan 9Kw).

My fuel tanks feed from the bottom and this Racor is slightly above that level. Not saying anything more than giving my experience with this setup. Maybe I am lucky??
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Old 05-13-2019, 09:59 AM   #14
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My fuel tanks feed from the bottom and this Racor is slightly above that level.
OK, What am I missing here? Why do you consider it a plus to have your Racor above the bottom level of your fuel tanks? blush:
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Old 05-13-2019, 10:26 AM   #15
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Codger,
Didn't say that there was any advantage (or plus as you put it), just relaying what I remember (or think) is the actual setup in my boat and the fact that it has worked well for me (so far). My fuel tanks are behind a bulkhead (aft of the ER) and the fuel lines enter the ER below the height of the Racors. If I had to guess (I have not actually measured), the height of the Racors would be at about the 1/4 to 1/8 full mark of the tank. I have never let the fuel level get that low (yet). Never experienced any fuel problems.
My intent was (is) just to inform the OP of what my setup looks like (to me) and how (well) it has functioned in actual use. I am not advocating that this is the best setup.
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Old 05-13-2019, 10:29 AM   #16
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I think the level of the fuel in the tank relative to the filter is relevant. If higher, you need to shut off the feed to the filter when you change it, or fuel will flood out. But also gravity self feeds the filter so the pump doesn't need to be strong.

On my boat they are about the same level, I think with tanks full fuel would be near the level of the filters, tanks empty a bit below.

I think I will try it, can always change it it doesn't work. I'm not too worried about the genset starving the heater, it uses so little through so large a filter. Ski's point is a good one though, I'll need to watch that. It would be insidious too, as you'd not see bubbles in the filter.
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Old 05-13-2019, 10:52 AM   #17
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I think the level of the fuel in the tank relative to the filter is relevant. If higher, you need to shut off the feed to the filter when you change it, or fuel will flood out.I consider that a plus as it is so easy to crack the shutoff and refill the Racor.
Thanks for your explanation!
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