Have to chime in,Bruce, you are correct about the expansion,but the
air gap or accumulator tank doesn,t slow down the pressure rise,it
prevents it,well most of it anyway.It just simply gives a place for
the expansion to go, Ron-- In Diesel-RVs@yahoogroups.com, Bruce
Sherman <bruce@...> wrote:
>
> Gary,
>
> When water or another liquid is heated in a confined space, the
pressure can
> rise very quickly because the liquid wants to expand, and there is
no place
> to go. The pressure rises much more slowly if there is a gas space
in the
> system. The fluid expands into the available space and the gas
compresses.
> System pressure rises much more slowly. Both the gas and the liquid
will be
> at the same pressure by definition. That¹s why accumulator tanks
are used on
> liquid systems.
>
> Bruce
>
> On 1/24/08 8:24 AM, "Chuck & Mary Boros" <elmerfletcher@...>
cleverly
> wrote:
>
> >
> >
> >
> >
> > Gary,
> > The information was given to me by the head engineer at
Shurflo. Don't think
> > that Shurflo would spend all that money and time redesigning
their high end
> > pump heads plus the cost of changing out all the existing new
inventory in the
> > market place. Chuck B
> >
> > Gary Brinck <gbrinck@... <mailto:gbrinck%40cfl.rr.com> > wrote:
> > Chuck,
> > Unless I flunked my physics courses, the pressure in the hot
water tank will
> > be the same whether there is an air head or not. Like everything
else, water
> > expands when heated. For that matter, so does the air head - it
reaches the
> > same temperature as the water in the tank. The air gets
compressed, increasing
> > the pressure throughout the tank and back along the cold water
inlet.
> >
> > This does not dispute the notion that back pressure could cause
pump failures.
> > However, maintaining a good air head won't alleviate that
problem. What it
> > will do is prevent water leakage at the pressure/temperature
relief valve.
> >
> >> > Many water pumps that fail has to do with high back flow
pressure from the
> >> > hot water heaters. Hot water heaters need to have the top of
the tank head
> >> > space of air. If not, the heated water expands from heating
and puts high
> >> > pressure back on the cold water input to the tank. That higher
pressure
> >> goes
> >> > back to the output side of the water pump causing internal
failure to the
> >> > water pump parts. A accumulator tank on the output side of the
water pump
> >> > will compensate for the back flow pressure. Some folks have
recommended a
> >> > back flow valve attached to the input cold water line at the
water heater.
> >> > Most water heater manufacturers advise against that. Shurflo's
high end
> >> pump
> >> > line had high pressure back flow failure problems and the
water pumps had
> >> to
> >> > be redesigned so that the pump can withstand the higher
pressure. All known
> >> > vendor stock was to be replaced as of last August. Camping
World now has
> >> the
> >> > new designed pumps in stock. You can tell the new design by
the pump
> >> > housing. Shurflo warrentee's their high end line for 3 years.
Aquahot
> >> > equipped coaches do not have that problem. Chuck B
> >
> > Gary
>
>
>
>
> [Non-text portions of this message have been removed]
>
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