On Nov 4, 12:29*am, "JimT" wrote:
wrote in message

...





On Wed, 3 Nov 2010 16:13:21 -0700 (PDT), wrote:

On Nov 3, 5:38 pm, "JimT" wrote:
wrote in message

...

On Wed, 3 Nov 2010 13:27:42 -0500, "JimT" wrote:

Oh yeah and no doubt. The fact is, a pool heater that is heating
should
not
be just "shut down". Those sensors are for problems like power
interruptions
and pump failures. I don't think the mfg of Raypak want their heaters
to
fry
circuit boards on shut down but you should let your pool heater run
for
awhile anyway, after it's been heating, to let the pool water cool
down
the
heater. I don't have a problem "going manual."

I just officially claimed pool season is over. I can turn the heater
off
and
put my pump "off timers" back on. I'm thinking I'll cycle the pool for
about
4 hours a day.

Jim

The instructions for your pool heater will say you should be using a 2
stage timer that lets the pump run a few minutes after the heater goes
off.

No such instuctions for the Jandy here. *As soon as the pump cuts off,
the heater goes off. * Nor does it have any capability of doing that
even if I wanted to. *The water flowing through it keeps the thing
cool while it's fired up. *The water leaving this 400K BTU heater is
only 7 deg F warmer than it comes in. * Any residual heat that results
when the pump and heater shut off at the same time may warm the water
a bit, but not anywhere near hot enough to be concerned about.

This is from page 20 of the Sta-rite gas heater installation book.

"The filter pump should run continuously when the
heater is on, and for at least 15 minutes after the
heater is off."

The instructions on my Raypak talks about the dual timer:

"To operate the heater with a time clock, connect the
timer to the fireman's switch connection in the heater's
wiring. The time clock should be of the dual switch
type and set to shut off the call for heat to the pool
heater 15 to 20 minutes prior to shutting down the pool
pump."

Jim- Hide quoted text -

- Show quoted text -

OK, I stand corrected on what Jandy has to say.

Here's what Jandy has to say on the subject from the installation
manual for one of their similar heaters:

"If you install a time clock to control the filter pump operation,
it's recommended that the time clock have it's own low voltage
(fireman's) switch to turn off the heater before turning off the
pump. The switch should shut off the heater about 15 minutes before
the filter pump shuts off. This will allow for a more efficient
operation by removing any residual heat contained in the heat
exchanger back to the pool."


I think the important thing here is the REASON for the
recommendation. Jandy is not saying shutting off the pump and heater
at the same time is going to destroy the control panel or destroy the
heater. Only that it allows for more efficient operation by allowing
the remaining heat from the heater to make it to the pool instead of
being wasted. Similar to a forced air heating system where the
blower continues to run after the burner shuts off so as to not waste
the remaining heat. In the grand scheme of pool heating, I'd say
this little bit of heat is insignificant.

The pool here with a Jandy was installed by one of the largest
installers in the area and it has a single switch timer. The pump and
heater turn off at the same time. It's been running for 5 years with
no problems. When it shuts off, there is no evidence of the heater,
pipes, etc getting hotter than they do during normal operation. If
that's all it took to ruin the heater, what would happen when a
breaker tripped or you had a power outage? When it shuts off, the
heater is full of water at 85 deg. IMO, and apparently Jandy's too,
there isn't enough heat left in the heat exchanger metal to raise that
water temp high enough to cause any problems.

If I was doing a new install though, I would agree that I'd use a two
switch timer, as all it requires is a timer with that capability and
it does capture a tiny bit of extra heat.