Using inverter for fan on a gas power vent water heater

[5Circles]

I've just installed (had installed to be precise) a gas water heater to replace the old electric heater. One of the benefits I thought I'd get from this and the gas furnace was to eliminate problems with power outages - especially worrying with all the storms at the moment. But I didn't realize until the install was underway that the heater needed electric power. (I was earlier thinking about a tankless water heater, but it didn't pencil out, and I guess I didn't connect all the dots.)

I don't have a generator, but when I saw an ad for a Kawasaki 800w inverter for $40 I thought it was worth a shot. Hopefully it would be able to power the fan (2.8 amp on the plate), and maybe run a TV as well. But experiences so far haven't been positive.

I connected the inverter to the car battery using the supplied leads. I used a jumper cable to add the ground lead (why didn't Kawasaki supply one?). Then connected to the gas heater.

Unfortunately the heater doesn't work. Moreover the status lights identify the problem as 'wiring error or high resistance to earth ground'.

I wonder if the car chassis needs to be connected to the house ground. I don't see a ground wire from the gas heater (and the power just comes from a 3 pin grounded cable), but maybe I'm missing something. Would connecting the vehicle ground to the house ground cause any problems? Or perhaps I just need to ground the water heater to the house?

Ideas appreciated.

Thanks

[zxcvbob]

This is a guess -- the heater electronics is sensing a high resistance between neutral and ground. The inverter probably has a floating neutral.

Bob

[Erma1ina]

I think Bob is right.

The same problem arises with some generators (like my Honda EU2000i which has a floating neutral) and the flame sensors of some newer furnaces. Here's a link to a couple of messages posted on alt.energy.homepower about the problem and solution regarding bonding neutral and ground:

Here's an excerpt:

"The flame sensor works based on the fact that the flame consists of ionized gas and ionized gas conducts electricity. When the burner is operating the flame allows about 5-7 microamps of current to flow from the flame sensor rod to the grounded burners. The control board measures this current to know when flame is present. In order for a microamp flame sensor to work neutral and ground must be tied together . . ."

Here are the 2 solutions described (the 2nd a wee bit more "professional" than the first:

". . .just ran line/neutral from the Honda eu2000i, and let the ground float, and it all works fine. I have a cheater cord which is an old

2-prong cloths iron coard, with aligator clips on the other end. Plug that into the generator, and aligator clip to just line and neutral of the 3-prong plug on the furnace, and it works. Whats the dealy-O ? I don't imagine that I can tie neutral and ground together at the generator since its an inverter." . . . "No, don't try to ground the portable generator at the generator that is totally unnecessary effort. Instead install a double pole double throw center off switch in place of the furnace disconect switch. One end of the switch connects the furnace to the neutral and hot of the furnace branch circuit of the homes wiring. The other end of the switch connects the furnace to the neutral and hot of a flanged inlet to which the female cord cap of an extension cord from the generator will connect. since the switch is two pole the Equipment Grounding Conductor (EGC) of the generator and the home are now interconnected. That will clear up the furnaces floating neutral problem when on generator power."

[ransley]

Another issue you didnt check is furnace draw and surge load, Any AC furnace blower is more than 2.8a, a total furnace load might be as low as near 375-400 watts unless its Vsdc and surge maybe a minimum of

6-800, what does the Kawasaki take, it might not even handle the water heater to start it. Is it outputting 120v 60hz under load of startup, you have to check it yourself. at alt.energy.homepower are people that use this stuff everyday

[trader4]

Hmmm? Connected the supplied Kawasaki LEADS (plural) and then used a jumper to add the ground to the car? The car battery only needs two leads to connect to the battery, so if they supplied and you connected LEADS, why would you need anything else?

It's a water heater, not a furnace. But with an 800Watt inverter how much sense does it makes to screw around with a water heater? If power goes out, unless it comes right after a huge draw that depletes the tank, you should have plenty of hot water, which used appropriately, will last a couple days. And if power outages are that big of an issue where you live, then most people would want a solution more substantial than an inverter.

Any AC

[makolber]

yes I found this to be the case with my inverters also...both the hot an neutral are floating relative to ground and you cannot just tie the neutral to ground. The common inverter works by generating something like +165 Volts DC and then commutating that DC voltage to the hot and neutral. So you CANNOT tie the neutral and ground together. This is fine for almost every apliance but as someone pointed out some HVAC controllers flame sensors need the netrual and ground tied. So I don't see a solution for you here..... unless you use a big isolation transformer and then you can feed the primary with the inverter and tie the secondard neutral to ground. But again why bother ... the hot water in the tank will last a good day without power.

Mark

[Steve Barker]

i wonder if you used a UPS that was plugged into an inverter, then everything would straighten out?

s

yes I found this to be the case with my inverters also...both the hot an neutral are floating relative to ground and you cannot just tie the neutral to ground. The common inverter works by generating something like +165 Volts DC and then commutating that DC voltage to the hot and neutral. So you CANNOT tie the neutral and ground together. This is fine for almost every apliance but as someone pointed out some HVAC controllers flame sensors need the netrual and ground tied. So I don't see a solution for you here..... unless you use a big isolation transformer and then you can feed the primary with the inverter and tie the secondard neutral to ground. But again why bother ... the hot water in the tank will last a good day without power.

Mark

[zxcvbob]

Maybe you *can* tie the neutral to ground. You could certainly do so at the water heater and leave the ground disconnected at the inverter -- it would never know. I'm not saying it's a good (or safe) idea, there's not enough info.

It may only need a 47k ohm resistor connected between neutral and ground to keep the flame circuit happy.

Bob

[5Circles]

Thanks to all for great ideas to try, leads for more information etc.

All much more helpful than the response from the manufacturer - "we tend to see problems with the water heater not operating very well with a generator"

Mike

[Mark Lloyd]

When I took a trip recently, I was using a heating pad on an inverter. I found that some would not work (often a power LED would flash, and no heat).

[makolber]

t the water heater

this will elevate the chassis ground of the inverter which includes the body of the car it may be connected to ...to a high voltage...not a good idea at all.

Using a UPS instead..., the kind with a real transformer inside,,, may wrok better. Mark