REFLECTOR: Cabin Heating

[Dave Black]

Chuck,

> Your point of locating it in the cabin is certainly appealing as it's quite
> simple and effective and only needs to heat already heated air.  I can
> assure you I'm not concerned about fresh air turn over in the cabin.  I've
> worked at plugging everything up but I can feel the cold air pour into the
> cabin from the nose gear/keel area.

Exactly. And I'm sure you have plenty of fresh air vents anyway.
 
> My plan (my planning is always good, it's just the execution that comes up
> short) was to install the second cooler in series (up stream of the primary
> cooler).  During the summer months, I'd just take it out of service by
> jumpering around it.  I suppose a three-way valve could be put in line to
> by-pass the cooler but that would require an extra tee in the return line
> from the cabin cooler to the primary cooler.  More hardware but less mess
> than hooking/unhooking oil lines.

I do like the valve method, because temperatures can vary considerably at
opposite ends of a flight. Consider what you'd get this time of year if you
flew from Sebastian to Boston. It would be nice to change oil routing when
desired AND without a mess of oil in the cabin. However, the
Series-With-Bypass method has the drawback of greater resistance to oil flow
than the parallel method. Depending on where you locate your coolers, it may
offer no improvement in oil flow over the original nose cooler -- which often
cannot provide sufficient engine cooling in summer. 
 
> In a parallel installation, what would you think is the best way of
> controlling relative flow between the two coolers?  A single three way valve
> on the feed line that directs the flow to either cooler or a fractional flow
> to one or the other, depending on valve position? 

I favor a proportional 3-way valve, so you could choose the percentage of oil
going to each cooler. It's simple, gives all the control you'll need, and you
can't inadvertently turn both off. In order to keep oil lines short, I'd
locate the actual valve in the vicinity of the firewall.

One builder (sorry I cannot remember his name) came up with what is probably
the ideal method: Mount the first oil cooler in the engine compartment and
plumb it to the Vernatherm exactly as the engine manufacturer intended. This
keeps its oil lines Very short. Install a separate oil-pickup in the engine
sump. This pickup should be up a couple quarts from the bottom so as to
prevent a leak in the cabin heater from stealing your last quarts of oil.
Connect it to an electric oil pump and then on to an oil cooler installed in
the cabin. Whenever you want cabin heat, you turn on the electric oil pump and
the electric blower in the cabin. Temperature could be regulated by cycling
the pump on and off via a thermostat in the cabin.  

> The more I think about your parallel installation idea, the better it looks!

I believe more and more builders are going this route. While the nose cooler
system is a marvel of simplicity, it simply cannot heat the cabin sufficiently
in temperatures below freezing. Not only that, in many cases it cannot cool
the engine sufficiently during summer. This problem has been around since
before I bought my kit 10 years ago. It ain't going away.


Best,
Dave Black
Shortwing RG