Diesel heater fuel float valve.

[Graham_Wright]

One of the sages on here suggested that supplying a diesel heater dosing pump with pressurised fuel (albeit low ~3-4 psi) as opposed to a zero pressure feed would possibly cause an over supply to the heater resulting in coking and malfunction.
To counter that, I intend to instal a buffer tank, ventilated and supplied with pressurised fuel regulated by a float valve rather like that used in a carburetor float chamber.
The only references I can find to float valves refer to sanitary cistern valves.
Any steers please?

 

[Graham376]

Why so complicated, are you not able to fit the normal standpipe into main tank? On one boat we had, I just teed into the fuel line after the primary filter, worked fine whether engine running or not.

 

[Graham_Wright]

Why so complicated, are you not able to fit the normal standpipe into main tank? On one boat we had, I just teed into the fuel line after the primary filter, worked fine whether engine running or not.

The tanks are in the keel and the dosing pump won't lift high enough.
I have the same problem with the engine so both tanks are fitted with low pressure pumps (automotive variety).

I think I can modify a non-return valve with a float to close it.

 

[penfold]

I'd say unnecessarily complicated; install a loop of pipe that returns to the keel tank and tee off for the heater from near the top of the supply side. No need for a tank. Probably a good idea to have the pump supplied by the same breaker as the heater so it's on and pumping before you press 'heat'.

 

[Graham_Wright]

I'd say unnecessarily complicated; install a loop of pipe that returns to the keel tank and tee off for the heater from near the top of the supply side. No need for a tank. Probably a good idea to have the pump supplied by the same breaker as the heater so it's on and pumping before you press 'heat'.View attachment 146715

Unfortunately the pump(s) supply the engine and the arrangement as shown would reduce the pressure to the engine. The pumps can. be selected and then feed an air trap and primary filter. I need to retain the filter or introduce another one for the heater.
I'm inclined towards a non return valve with the spring replaced with a float.

 

[penfold]

If you need to retain pressure for the engine fit an orifice plate, although I'd be surprised if a diesel would notice the reduction in pressure.

 

[NormanS]

I simply installed a separate 20 litre tank for my heater, at a height that the heater could cope with. Having a separate tank also means that I can run the heater on kerosene.

 

[Rappey]

My tank is in my keel but I have no problems getting fuel to the pump which is a good 4 metres away.
You do need to use the tiny bore pipe that comes with the heater. Oversize it and the pump cant pull the fuel through

 

[Graham_Wright]

My tank is in my keel but I have no problems getting fuel to the pump which is a good 4 metres away.
You do need to use the tiny bore pipe that comes with the heater. Oversize it and the pump cant pull the fuel through

Not my experience. The problem seemed to be excessive fuel to the heater causing it to coke up and shut down. A local supply seems to have fixed this hence the search as described. The heater is around two metres above the bottom of the keel tank.

 

[Graham_Wright]

I have finally found a solution! (Not been looking continuously since my last post!).

I have a reservoir - actually a large diameter sight glass that was to hand. There is a tee connection at the bottom that is connected to the pumped fuel from the filters and the dosing pump. The supply is valved with a solenoid valve (normally shut). There is a connection from the top of the reservoir to a washing machine electric pressure sensor. (These are very sensitive).
When the pressure inside the reservoir drops, the sensor opens the valve and the reservoir pressure is topped up.
Out of curiosity, I connected an led across the valve. It opens for around half a second every minuted when the heater is on full setting. The contents level moves almost imperceptively. I think there is an adjustment on the sensor for hystresis as well as pressure if needed.

 

[Freebee]

you could use a float with solenoid valve

 

[Boater Sam]

Something like this 0-220V Stainless Steel Tank Pool Liquid Water Level Sensor Vertical Float Switch | eBay

or Liquid Level Float Switch Stainless Steel 0-220V Liquid Water Level Sensor For❀ | eBay Feed the pump via a relay, these switches are only reed switches, low current.

 

[dgadee]

I have a gravity day tank on my Sigmar 100. An old fuel pump is connected to the boat fuel tank and I pump when needed. You can also see what is in the day tank. It means that you can leave it running knowing that at some point the heater will run out of fuel (e.g. in your bunk). eBay.

 

[penfold]

What an unfeasibly complicated way of doing it.

 

[dgadee]

What an unfeasibly complicated way of doing it.

What? My approach? Seems very simple to me.

 

[penfold]

No, the OP's; it clearly works but he has overcomplicated it rather. Yours and his are both header tanks.

 

[NormanS]

I have a gravity day tank on my Sigmar 100. An old fuel pump is connected to the boat fuel tank and I pump when needed. You can also see what is in the day tank. It means that you can leave it running knowing that at some point the heater will run out of fuel (e.g. in your bunk). eBay.

View attachment 164592

22mm?

 

[dgadee]

22mm?

?? Not sure I understand.

I have a y piece onto the engine fuel pipe then a one way valve to the day tank to stop the engine taking the fuel from that pipe. All just rubber 8mm fuel hose. The pump may be an old mini type - not particularly fast at filling the tank. From the day tank down to the Sigmar it is fuel pipe then 8mm copper pipe.

Edit: Ah, I see. 220mm it will be.

 

[Graham_Wright]

you could use a float with solenoid valve

Too big.

 

[Graham_Wright]

What an unfeasibly complicated way of doing it.

No, it's simple and, with the led, fascinating to watch!