liquid vs direct air heaters

["Gary Graunke" <gary@whitecape.org>]

David Roden wrote:

> If you are going to heat the air in the vehicle, the more efficient way is
to
> heat the air directly with a heating element of some kind. IMO, the only
advantage
> to a liquid heater is that it's easier to install because you can leave
the old
> heater core in place. But it heats up more slowly, and (potentially)
wastes
> more energy through losses in the tank and plumbing.

I noted that some of the EV suppliers sell 1500W ceramic heater cores as
well--at least one person has presumably thought about approriateness for an
EV (vs general use).

I also had some notes from an OEVA meeting on heater relays--the note said
to use magnetic blowout relays--the others are a fire hazard. However, I
haven't really found any that have the appropriate DC voltage rating,
especially for a higher voltage (>200V) pack.

Since I in the middle of an insight conversion, the heater is on the list of
things to do. Wayland recommended that, due to the complexity of the insight
climate control, I use a small liquid system rather than the easier
replacement ceramic heater under the dash as he normally does. Currently,
the insight uses a "mix" motor to move a valve to allow varying amounts of
heat in to the system.

My US Electricar S10 truck also has a 1500W liquid system, which works well.
However, it uses 10" by 5" by 8" black box, a 4" x 4" x 7" electrical box,
and a small fluid resevoir. I'll have to take it apart next time I have the
pack apart.

Has anyone else done a liquid system?

Do you need a pump to circulate the water?

Is the electrical isolation more of a problem, given the liquid conductor vs
air?

Gary