Voltage Required to Fire Off Diesel Heater

I have an older model Espar diesel heater (Model D4) in my 44' Tollycraft and it takes about 12.3 to 12.4 volts to fire off. To me, this seems to be a pretty high voltage for your boats heater to have to work with. (Early in the discharge cycle when anchoring out.) Anything lower and it will not ignite. I had an Espar service rep tell me that that 12.3 is about the minimum voltage required to fire off these units. Was curious if anyone else has similar issues with their diesel heaters rather they be Espar's or others brands.

Thanks

Jerry,
I do not have an Espar (I have an ITR). Last winter the heater would run fun on shore power but when running off the batterys it would not ignite every 2nd or 3rd try. I first thought I had a fuel filter issue. I was moving the boat down the ICW and could not get the parts I needed to rig a clean test fuel system. After a few days of intermittent heater use, I woke up realizing the common item of when it would and would not start had to do with the electirical supply.
I changed the igniter to a new unit and it started even when running on battery. You might check to see what the resistance of the igniter is?

The Espar D8LC on my boat fires up fine at 12.1 volts. I don't know if it would fire at lower voltage since I don't let the battery voltage drop any more.

Installed a new igniter with the same results.

I cannot get thru the night at anchor without my batteries falling below 12.3 volts so maybe am due for some new batteries. Specific gravity checks good but voltage seems to fall pretty fast with even just a small load.

I don't know about the D4, but the Espar D9W and Hydronic 10 manuals say the low-voltage shutdown should happen at 10 volts. The big current draw with these is at startup, with the glow plug and igniter and water pump and everything going at once, and if you have a loose or corroded electrical connection, or a long run of undersized cable, it certainly is possible for the heater to see a significantly lower voltage than right at the battery terminals.

Have you put a voltmeter on the Espar unit itself?

jstauffer said:

Installed a new igniter with the same results.

I cannot get thru the night at anchor without my batteries falling below 12.3 volts so maybe am due for some new batteries. Specific gravity checks good but voltage seems to fall pretty fast with even just a small load.

Click to expand...

Sounds like weak batts. Have they been adequately serviced and charged?

Had an older Espar D7 with start up challenges. The basic problem (outside of low battery voltage) is that the harness wiring to the glow plug is relatively small, and if there is any distance to your panel/source, the voltage may not be consistently adequate. As QB says, put a meter on the glow plug.


There are multiple solutions: Higher battery voltage, new/clean glow plugs, and routing 12VDC wiring direct to battery. The best solution I had was to run a #6 wire directly from the 12VDC battery, and then connect directly with the glow plug via a relay that was activated by the existing glow plug wiring. Never failed to start after that.

If the units are chronically sensitive to low voltage, another solution would be a DC/DC converter to create a stabilized power source for the heater. That way you could always keep its voltage around 13V. Just another idea

All these unit are bus or truck units and expect to be operated at 14+ volts.

Bosch glow plugs are rated for 7.5V but will operate at lower voltage , as little as 6.

The Espar folks did not expect multiple (thermostat) starts , just light it and drive.

There is a large coil of nicrome wire on top of the unit that reduces the voltage to the glow plug.

After you wire the unit in the boat system with #6 or #8 wire , measure the voltage at the glow plug during a start sequence.

Cut usually 2 turns off the wire coil if the voltage is below 6.

You want to see about 7+ v during a battery start.

A fuel tank with 50% to 100% kerosene as fuel is a huge help if its a liveaboard and will see extended winter starts.

Truck heaters do work in boats , but have to be set up for the service.

If slow starting has been chronic it is likely that the nozzel and set of washers attached are gunked up.

Replace them with the annual overhaul.

Some folks will tale off the duct work and block the output.

This forces an over temp, no big deal its got protection , and after 3 or 4 overheats much of the carbon is burned off.

Just watch the chunks fly out of the exhaust.

In NY Bosch would charge $75 for a tech to come and simply over temp the unit as a "cure".

The real cure was much heavier wiring as the unit will draw 40A or so during starting .

Good luck, and remember slowing the fuel delivery , "full or half "on the operating plate is a better temp control than off / on.

Purchased this boat about 5 years ago and batteries are probably 8 years old and may be close to being replaced. However, now, even with shore power and charger going with batteries at full charge, unit will not fire off. This fiasco started when I thought I would try to improve starting by cleaning the glow plug. While trying to clean it I broke the wire. So had local shop order me a new glow plug and it came with only one terminal (old one had two terminals one for negative and one for positive battery). Apparently some of the Espars used the unit case are ground (battery return) I went ahead and installed it and using a jumper wire from ground to the case of the glow plug was able to get unit to fire off. But, did not want to rig it to work that way so had them order me the correct glow plug. Installed new glow plug and it fired of a couple of time although it took longer than normal. Now it will not fire off at all. I am loosing more voltage thru the control relay than I would expect, but it was working before changing the glow plug. After unit fails to start I can pull the glow plug and it is very dry so maybe I'm not getting enough fuel to the plug or maybe it is hot enough the fuel is burnt off by the time I get it pulled. I can disconnect the fuel line and get fuel when the pump starts, but maybe it is not enough. I think I will try and put a new fuel filter on it see if that helps.

Thanks guys for the tips so far.

Try putting a start battery in the area and use Quality auto jumper cable to assist the start voltage, and see if it works. Measure the voltage during start at the glow plug.

Once the holes in the delivery spray tower , attached to the fuel pump are gunked , it needs to be replaced.

I talked with a different Espar service rep and he tells me anything over 11 volts should ignite the heater and I have 11.4. My problem now is that when it does ignite it takes about 80 seconds. The service rep says it should ignite in 30 seconds. This probably explains why it smokes pretty bad when it does ignite because of all the excess fuel being pumped into the chamber. After running for 30 minutes or so the amount of smoking reduces but is still more than normal. When I remove the glow plug and look down into the chamber it looks really clean. Talking with someone else they said there is a material, that acts like a wick to absorb the diesel fuel, inside the chamber. If that is true I'm wondering if that needs replaced or can it be replaced. I guess it is about time to remove it and tear it apart.