Heater Maintenance: Little Giant Heaters

Little Giant Heaters are the simplest propane heater used in our industry. They're not known for high heat / high flow, like our flow- fired heaters, but their simplicity makes them a favorite among many users and especially multi- truck companies who want simplicity with regard tooperations and training new people.  But even with that simplicity, there are 3 things from a maintenance and durability standpoint that anyone who owns one should be aware of.  In this section, I’ll describe those 3 things and go into detail about what they are and how to address them.

 

 

Push Button Striker not Working

“Everyone” knows that Little Giant strikers don’t work.  Typically, within  a month of ownership, the striker stops working.  So, virtually all owners of Little Giants resort to using a cigarette or charcoal grill lighter, to provide the ignition to light the pilot. But this isn’t really necessary, because it’s not the striker that isn’t working. (Pull the wire off of the striker and push the striker button, and you’ll see a spark jump across to the bracket that holds the striker.) The problem actually lies elsewhere, in a hidden location.

If you look closely at the wire that leads from the bottom of the striker to the electrode located at the pilot light, you’ll notice that the wire’s insulation is very thin. It’s so thin, that it doesn’t insulate as well as it should and doesn’t hold the current that travels through it securely.  And as a result, it develops a “leak”.  So, I’ve named it a “spark leak”.

What happens is that as the current travels down the wire, at some point along the way, it exits to a ground (metal) location and stops traveling the rest of the way to the pilot location.  And if you look, you’ll see that the wire is wrapped 50 times or more around the pilot tube, all the way down to the pilot.

If you unwrap the striker wire, and connect it back to the striker, it will once again, work.  This is because the distance the spark would have to travel to a ground source is too great for the spark to be able to jump the gap- so it continues on the the next gap it can jump- the pilot.  But leaving the wire loose like that isn’t practical, because it will become tangled and eventually damaged as a result.

So how do you remedy the situation?  Simple:  Insulate the wire better. (It’s not practical to replace it.)

One way is to use “wire loom”, which is a plastic tube that is split down the length of it, so that you can insert the wire.  Loom is designed to protect the wire from being damaged from abrasion, but in this case, it can also be used  as a kind of insulation.

Another way (the one I prefer) is to feed the wire through a clear plastic hose (basically the same as the chemical pick- up hose used on truck mounts).  It’s a bit more complicated to feed it through a ¼” clear hose, but the hose has a thicker wall and no gaps (or splits) in it.

Once you’ve isolated the wire from a premature ground, wire tie it back to the pilot tube, to keep it out of the way.

 

 

Temperature Control Becoming Less Accurate

The temperature control for a Little Giant heater is included in the “Unitrol”.  (Unitrol is a short name for “unified control”.)  Also included in the Unitrol is the thermocouple solenoid and the gas control valve.

Over time, the temperature control loses it’s accuracy.  And this creates two problems, actually.

1.) The delay in time before the temperature drops and the sensor “sees” it is longer.  As a result, the temperature continues to drop more than it should.

     2.)The delay in time between when the temperature rises to the point the      control is set at and the sensor "sees" it is longer.  As a result, the      temperature rises more than it should.

These two events share one common cause: 

The temperature sensor is losing sensitivity.

When the Unitrol loses it's sensitivity, most people try to turn the temperature up to compensate.  But this only makes things worse and doesn't address the underlying issue.  And in fact, it only causes the temperature of the heater to spike upward more, which can result in that heat backing up through the pressure hose that leads to the pump, into the pump, where it can then damage cups, seals and check valves, thereby necessitating the need for pump repair.

Some people try to "adjust the dial" of the Unitrol, by removing it and loosening the nut underneath, turning the "pointer", tightening the nut back and reinstalling the dial.  All this does is change where the knob points.  Nothing more.

So, what is the cause of this and can it be remedied without having to replace the Unitrol?

The temperature sensor or "probe" of a Unitrol is the long, copper, torpedo- shaped piece that extends from the Unitrol and into the heater coil.  New ones look clean and shiny, but over time, they lose that appearance and become to look more "anodized" like anodized aluminum cookware.  In some cases, they actually look white, due to the "scale" (build- up of chemical residues and mineral deposits) that happens over time.

That build- up of deposits is the cause of the temperature becoming more and more erratic over time, because that build up acts like an insulator between the probe and the water it's monitoring.

So, how can this be remedied?  It's pretty simple, really.  Remove the scale. But removing the scale can be more difficult than expected.  Sandpaper works, but it's very slow.  Drywall screen produces similar results.  But the wire wheel of a bench grinder and does the job easily and quickly.  And once the scale is removed and the copper probe looks "new", the Unitrol is ready for reinstallation.

Copper Coil Scale: The Rest of the Story

So... An obvious question arises:  If the copper probe of the Unitrol has scale that affects temperature transfer to the probe, what about the heater coil, which is also made of copper?

If there is scale on the probe, there is scale on the coil.  Cleaning the probe will restore the heater's ability to control temperature to "like new".  But scale on the coil also acts as a thermal insulator.  And in the case of the coil, the result is that the heat source (the burner flame) is being interfered with in terms of the heat it generates being able to transfer into the coil.

In other words, the coil is insulated from the heat, so it takes more heat to raise the temperature to the desired level.  Put more simply, the heater loses efficiency and requires more propane to do the same thing that less propane did when it was new.

De-scaling the heater core of a Little Giant can only be done with a suitable acid being used to flood the coil, stay in contact with the inner coil long enough (over night) and subsequently flushing the contents out of the coil.

Flushing the coil is rarely called for, however, because the loss in efficiency is rarely to such a degree (pardon the pun) that it's hugely noticeable.

 

 

Freezing a Little Giant Heater

Put simply, DON'T LET THIS HAPPEN!  The copper coil of a Little Giant is a great conductor of temperature.  (Copper is almost twice as efficient as aluminum at heat transfer and aluminum is more than 10 times more efficient as stainless steel.)  It's very good at heat transfer- to and from the coil.

Heat travels from the location of highest temperature, to the point of lowest temperature.  So, when the heat is greater outside the coil- like when it's in the process of heating- the direction is into the coil.  But when the outside temperature is lower than the temperature inside the coil, the heat travels out of the coil. 

As a result of the heat traveling out of the coil, the temperature in the coil drops until it reaches a point that it's the same temperature in the coil as it is outside.  And if that temperature is below freezing, then the water inside the coil will freeze.

The amount of pressure that water can generate when it freezes is always more than a Little Giant coil can handle. (It's a complicated subject that is affected by things such as the precise content of the water, the precise temperature and even the pressure of the water before freezing occurs.)  But the bottom line is that you must prevent your Little Giant from freezing.

Here is what we recommend, in order of recommendation:

1.) Park your system inside a heated garage.

If a heated garage isn't available, then:

2.) Put a heater in the van, truck, trailer, etc., to keep the temperature above freezing.  And leave the pilot flame of the heater "ON", but keep the heater set to "Pilot"- not "On".

We recommend propane heaters for this.  They are about $50 from Home depot and they look a lot like satellite antennas.  When installed on a small barbeque grill bottle (the kind that you can exchange for pre- filled ones at convenience stores), and set on "Low", they'll heat for 32 hours, which is basically 4 eight- hour nights.  Larger bottles will heat much longer.

A propane heater like the one described above, set on Low, will keep your van well above freezing in temperatures down to single- digit weather.  But there are cautions:

1.) Crack a window so that the heater can "breathe",  Propane heaters consume oxygen.  If they consume enough, they simply go out.  So leave a window cracked in order to prevent that from happening.

2.) These heaters "point the heat".  In other words, they are very directional.  Behind them, there is no heat.  But in front, there is a lot.  Point them toward the system and heater, but make sure to locate them 3 feet or more from the nearest surface that they are pointing to.

 

Why We Do NOT Recommend Electric Heaters

Electric heaters simply don't generate the levels of heat that propane ones do.

In the worst weather, power goes out more frequently.  And if it does, you have no heat.