engine block heater question

I just had a block heater installed in my car in preparation for a long, cold, dark winter on the prairies. I’d like to run it through a timer to turn it on some time during the night so that it’s warm by the time I’m ready to leave for work, rather than leaving it on all night long, which I suspect isn’t necessary. What I’d like to know is how long prior to starting the car should the block heater run to gain the benefit of having it without running it longer than necessary and wasting electricity?

Your best bet is to find out be experiment. On a cold night some weekend when you can stay up late turn it on and see how long it takes to warm up to a reasonable temperature. If some night in the future looks colder than your test night give it an extra half-hour or hour of warming.

Don’t know about how long, but make sure you get a good, heavy-duty timer - block heaters can draw a lot of electricity and you don’t want to short out the time.

Of course it depends on where it was installed and the watt output. Is the car
garaged, in a carport, or out in the open? What is the average ambient temp.? I
would agree that experimentation is your best bet w/ so many variables to consider.
It really doesn’t take much temp. rise to make a noticeable difference. I’d start w/ 2-3
hours and go from there. Make sure you have a strong battery, just in case your
estimate is way off, and remember the heater probably pulls around 1500W, so size
the timer and extension cord appropriately. Another accessory you might consider is
one of those trickle chargers for your battery, just don’t forget to unplug the cord
before driving off.

When I was living in Alaska, I had a block heater for my car. I left it on all night and when I went to work, I plugged it in there to a connection in front of where I parked. I also kept an oil pan heater under the engine at night which kept the oil warm. It gets real cold in Alaska. You probably don’t need to run your heater all night, but I suspect a few hours early in the morning would be enough.

You’re heating a considerable amount of coolant and metal in a cold environment, and you’re using a fairly small heater. We’re talking 300-500 watts, right? An hour or two of that is not much on a ten degree night.

On the other hand, if you do go for a timer, you’ll have to use a relay. A typical turn-on-the-lights-to-fool-the-burglars timer will burn out under a 500 watt load, so you need to use the timer to trip the relay. Consult the plastic-pocket geek at Radio Snack.

It’s a 1250 W heater, and the timer I picked up says “1800 W resistive/600 W tungsten” on it, so it should be okay since the heater is a resistive load, right? (It’s also rated to 15 A, and the heater draws 10 A.)

Yes, you’ll be OK.
Is it a water jacket heater or an engine oil heater?

If it’s below 20 degrees all night, leave it plugged it. It probably has a thermostat that will shut it off and on. A warm engine means fewer emissions.

Years ago I did get a programmable outdoor timer from Crappy Tire that was rated for use with block heaters.

Most block heaters I have seen are very simple; an element, a plug that it is mounted in and a cord. I 've never had the impression that there was some sort of thermostat.

I usually plug mine in when I get up in the morning. After an hour the car starts easily and is warm in a couple blocks. Its been -20 the past week, but mind you I do park in an (unheated) garage.

I would think that even parked outside a couple of hours would be plenty to warm the engine enough. I do not know how long it would take to reach equilibrium but the goal is to get the engine to a point where the oil is not viscous and the engine can defrost the window after a short warm up.

The warmer the engine the more efficient certainly, but remember you are heating an uninsulated chunk of steal with electricity pumped a long ways with considerable energy losses and almost certainly generated from methods with considerable environmental impacts. A few minutes of poorer than normal efficiency while the engine warms up isn’t necessarilly a worse environmental impact.

Back when I was a serious gardener, I had a 4-layer seedling table with 16 fluorescent tubes in it. I could get only about two or three weeks out of a cheapo Scars Rowboat timer before it fried the switch. Then I put a relay between the timer and the lamps, and everything worked fine. At the time, I couldn’t find a heavy duty timer that was cheaper than the relay.

Yes, a warm engine runs cleaner, but when I had an engine heater (in the lower radiator hose) my purpose was not having to stop every two blocks on the way to work to rescrape the windshield.

Running a 1250W device for two hours more than necessary will burn 2.5kWh. If electricity is pretty pricey in your area, say 10 cents/kWh, that works out to an extra quarter a day. The additional expense is pretty minor, especially if you find a too-cool car requires more gasoline warming up and more windshield washer fluid to keep the windows clear.

2-3 hours should be fine, even in a wind chill.