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MG MG Y Type - YB Heater Amps

I'm just in the painful throws of fitting a Smiths Heater to my YB and wonder if anyone can tell me the value of the fuse I should use. In addition should I connect to the A terminal on the RB106 for the power?
The heater has Code 620/36 and 12V marked on a small plate but the section dealing with Kilowatts is blank.

Ted Gardner

Hi Ted

I am probably going to be shot down in flames on this as it has been a very long time, and I only did General Science at O'Level (when they meant something) and only got a B grade at that, but ...

If I remember Ohms Law correctly it is V=I/R where V = volts, I = current and R = Resistance, hence by measuring the resistivity of the heater, and using 12 Volts and inverting the formula you can calculate the current draw of the heater.

Alternatetively, the fuse fitted to the fuse holder in the regulator I took off the car had a 35 amp fuse in it. I do not know if that was sufficient or not as the car was a non-runner!

So over all, not a lot of use was it!

Hope someone else has a good idea!

Regards

Paul
Paul Barrow

Yep - remembered it now - it is V=IR ie I times R where current is measured in Ampers, and resistance is, of course being Ohms Law, measured in ohms.

Useful stuff education!

Paul
Paul Barrow

OK, Thanks Paul and others, I have completed my heater installation and electrics successfully. Now to wait for a really cold day.
TG
Ted Gardner

Ted: assuming this is a Smiths hot-water heater and not an electric-element heater, and if it's the same model as my car (Y6814) the heater motor only draws about 20W, or less than 2Amps, judging from the ammeter reading. So for a separate fuse to the motor, 5A should cover it. Otherwise the 35A auxiliary fuse will serve.

If your main radiator matrix is good (ie not blocked), and the engine is cooling properly, you may find that on cold days the supply of heat to the interior of the car is less than ideal: I have found that blanking off some of the radiator helps considerably.
Tim Griggs

Fuses! They are rated differently in the USA. A British 35 Amp. would be a US 25 Amp. Buss AGC 25 is the number to use.
Scott Barrow

Hi all, hi Scott.

I'm very interested to know why US fuses would be rated differently to any others, ie Scott said a US 25 amp fuse is the equivalent of a British 35 amp.

Watts (an indication of power or work being done) divided by voltage equals amps. Thus, a 60 watt fan in a 12 volt heater should draw 5 amps, worldwide.

I teach stage 1 auto electrical subjects to apprentices, and have owned numerous cars and bikes from most countries of the world and have not run across this before, but I would like to be able to explain this US rating system to my students.

Any Ideas?

Regards to all, Geoff Meller, YT3477
Geoff Meller

Hi Geoff, et. al.,
It has been a long time since I came across this bit of information on AMP ratings, but I beleive it was in a Buss Fuse Application book. I worked for a large Auto Parts Warehouse Company at the time, and read everything at hand to fend off boredom. There must be some difference in British Amps and U.S. Amps, like there is a difference in inches, pints, quarts, gallons, etc., from one country to the other.
Happy New Year!
Scott Barrow
Scott Barrow

As a matter of interest when I installed the heater electrics I got around to measuring the Amps and they came out at 1.9 Amps with fan on full blast.
I am no expert on electrics but am also at a loss to understand the described difference between US & UK Amps. Wasn't Ampere French anyway?
Happy New Year, by the way the heater is too good,I have to open the window!
Ted Gardner

Hello,
I checked with my buddy Larry, an electrical engineer, who assures me that all Amps are the same: no Imperial Amps to to worry about!
I looked up "Fuses" in my POCKET REF book by Thomas J. Glover, and under "Fuses-Small Tube Type", all the number/letter prefix designations for the various types are defined.
An AGC type(I use AGC-25)is defined as:
"Fast Acting, Glass Tube, 110% Rating, Will blow at 135% load in one hour." 1/4 inch Diamater X 1 and 1/4 inch length.
So, 25 AMPs multiplied by 1.35 = 33.75, very close to a Lucus 35 AMP. The AGC fuse has a flat metal bridge connector inside, and the Lucas 35 has a round wire connector.
The old Buss Fuse Co. Application Selector Guide, as I remember it, reccommended replacing Lucas 35 AMP fuses with their AGC-25.
I don't recall what the replacement for the 50 AMP Lucas (horn Circuit) was.
Scott Barrow
Scott Barrow

Hi Scott

Many thanks for that very informative bit of "gen". I like the bit about Imperial Watts too - very funny!

Happy new year and thanks for putting us all at rest! Hurry up and get a Y!

Paul
Paul Barrow

If your Smiths heater is the round type (I'm not familiar with the Y interior) and it is the same as fitted to a Series 1 Landrover, it is rated at 1.3 Kw. This is a bit of a joke really, as it obviously depends on the water temperature and air flow thru the heater.
Re fuses, it may be the difference between the normal current carrying capacity of a fuse and the current at which is blows. Industrially it can be a minefield, there are "slo-blows", fast, ultra fast, normal etc. The old Lucas fuses are pretty crude by modern standards, I'd say they are rated at current carrying capacity. I'd say they are more to protect the wiring than the device at the end of the wire, so the value isn't critical.
Gordon
Gordon

This thread was discussed between 01/12/2002 and 30/01/2003

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