[TowerTalk] HN-31 Heathkit Dummy Load

[Jim Lux]

At 10:22 AM 4/4/2006, Jack - K4WSB wrote:
>According to the manual the HN-31 is rated at 1kw.
>Duty cycle is 10 minutes using transformer oil & about 2 minutes using
>mineral oil

The difference is due to the lower viscosity of transformer oil vs mineral 
oil. As the resistor heats up the oil, it rises in the can and moves to the 
outside walls where it cools.  Lower viscosity oil circulates faster, 
cooling the resistor more effectively.


>Check with your local power company.  If you go to the facility that
>handles the transformers you can usually get a fill up at no charge.

Depends on the area and the utility. In big city utilities like those in 
Los Angeles, this would be a big challenge: You'd have to have a friend who 
knows someone in the transformer shop.. there's no way to just walk in.  On 
the other hand, in the LA area, it's easy to just buy transformer oil (I 
get mine at L.T. "Lee" Sawyer in Van Nuys, they're a Shell distributor/jobber)