Wattage for a Gas Water Heater

[Paintedcow]

According to:

A GAS water heater uses 500 running watts, and 1500 watts to start it.

What the f*ck? Gas water heaters dont use ANY electricity......

[Stormin Mormon]

Some models of gas WH are what's called power vented. They discharge flue gassed through white PVC pipe like newer furnace. In that case, there is an inducer fan motor to feed with power.

[trader_4]

Plus those models typically use electric power for the controls and ignition, which is probably why it's higher to start it, eg hot surface ignitor, etc.

[philo]

"Watt" is simply the term for the rate of energy transfer, It does not have to be measured in terms of volts x amps.

Interestingly , I just read the autobiography of Lee deForest and at one point in the book referred to the "horsepower" of a radio transmitter.

[trader_4]

But here they are talking about the electric power.

[philo]

Oh, I did not read that. Obviously it's wrong then

[trader_4]

No, obviously it's right, if it's a power vent water heater, which are common today.

[Joe (not really)]

Looks pretty accurate to me.

My Lochinvar LVN041G Power Vent Water Heater

40,000 BTU Natural Gas uses 2.7 Amps (~325 Watts)

(measured with a Fluke 902 HVAC Clamp Meter)

and if those facts don't put you to sleep, consider this:

An 8 minute shower causes the heater to run for 26 minutes.

If knew the price per MCF of gas, I could calculate the cost of a shower...but I'm too lazy to go look it up.

[clare]

Power vent water heaters with no standing pilot use some power to operate - but 500 and 1500 sounds a bit high to me.

[trader_4]

It came from a generator sizing chart, which are dubious at best. I agree, it looked high to me too. They also have 800W for a fridge and 400W for a TV. Fridges of the last decade or so use about half that. My new 55" TV uses ~75W. Who knows where their numbers really came from, how old they are, etc. They probably use high end of possible usage for everything. The real issue he had was that he apparently didn't think a gas water heater would use electric, but the power vent type do.

[philo]

If it has an exhaust motor that draws 500 watts when running then it would be about a 2/3 HP motor...I'd think a 1/10th HP motor should be able to move those exhaust gases OK for sure a 1/4 HP motor I'd think.

I was thinking of eventually getting such a water heater but may just go with electric.

[Mark Lloyd]

[snip]

I was monitoring the current from my generator that I used after the tornado last May. The first load I connected was the fridge (new side-by-side from late 2008). It was using a little more than 1A (about

150W). I checked it several times,and it never exceeded that. I think my TV (37-inch LCD with fluorescent backlight) is about that too. [snip]

[trader_4]

See my other post. I agree, I think those numbers are high, probably half that or less is more like it.

[trader_4]

Couple years ago during hurricane Sandy, I had a KillaWatt meter hooked up with a generator too. Monitored a fridge and a freezer, both made within the last 7 years. They kicked up to about 350W when started, then immediately started dropping, down to like ~100W, consistent with what you saw. I also had it on my 5 year old side by side KitchenAid fridge, it pulls ~90W.

[Micky]

That's true, but higher up the page it says "The chart below shows how many watts of **electricity** it takes to run various household appliances". It's about buying a generator and transfer switch.

And how could it use 1000 more watts of gas power for starting than for running? The gas burnt is going to be the same, or close.

[Micky]

It's a hybrid water heater. When there is gas, it heats the water which powers a dynamo which charges storage batteries. When the gas is interrupted, the batteries heat the water.

When you've got money, it's worth spending money to protect oneself from problems, even less common ones.

[clare]

Channelling Stormy now, are we Mikey??

[Tony944]

According to:

A GAS water heater uses 500 running watts, and 1500 watts to start it.

What the f*ck? Gas water heaters dont use ANY electricity......

[trader_4]

Of course the power can change and typically will change. For example, a hot surface ignitor is only on for 30 secs or so for lighting the burner of a water heater. And even those change resisance significantly as they heat up.

Except that it doesn't. The resistance of a light bulb increases dramatically as it goes from cold to hot. I happens quickly, but the effect is still there.

On the part of what writer?

Bingo. And power vent water heaters have a blower motor, which is why they need that AC to power to begin with.

So, what exactly was your point again?

[Scott Lurndal]

No inducer motor will pull 500 watts.

OTOH, 500 watts is about 1700 BTU/hr.