I'm replacing an old boiler with a new high efficiency
condensing boiler.
The old system had 1 circulator pump, the new boiler
installation manual shows 2 circulator pumps.
One for the boiler loop and 1 for the zones. What is the
reason for 2 pumps?
A neighbor had a new high efficency boiler installed last
year by a licensed contractor
and they only put in 1 pump.

ppp wrote:
I'm replacing an old boiler with a new high efficiency
condensing boiler.
The old system had 1 circulator pump, the new boiler
installation manual shows 2 circulator pumps.
One for the boiler loop and 1 for the zones. What is the
reason for 2 pumps?
A neighbor had a new high efficency boiler installed last
year by a licensed contractor
and they only put in 1 pump.




Must be for a hot water tank.

--
LSMFT

I look outside this morning and everything was in 3D!

LSMFT wrote:

ppp wrote:
I'm replacing an old boiler with a new high efficiency
condensing boiler.
The old system had 1 circulator pump, the new boiler
installation manual shows 2 circulator pumps.
One for the boiler loop and 1 for the zones. What is the
reason for 2 pumps?
A neighbor had a new high efficency boiler installed last
year by a licensed contractor
and they only put in 1 pump.




Must be for a hot water tank.

"Indirect fired domestic hot water"

On Mon, 23 Aug 2010 11:24:08 -0700 (PDT), harry wrote:

On Aug 23, 5:46*pm, "ppp" wrote:
I'm replacing an old boiler with a new high efficiency
condensing boiler.
The old system had 1 circulator pump, the new boiler
installation manual shows 2 circulator pumps.
One for the boiler loop and 1 for the zones. What is the
reason for 2 pumps?
A neighbor had a new high efficency boiler installed last
year by a licensed contractor
and they only put in 1 pump.

The reason is that high efficiency boilers need a fixed (and
optimum)amount of water circulating through them at all times.
One pump circulates a fixed amount of water through the boiler. The
other takes water out of this loop and circulates it round your
radiators.

Nonsense. That would waste a terrific amount of energy. The boiler cycles to
maintain its temperature. A domestic coil can be used for hot water but there
is no bypass to guaranty a fixed amount of water through the boiler.

If you think about it, as your radiators are shut down in an old
fashioned system, the water circulating round the system is reduced.
No good for your new boiler.

Nonsense again. The boiler will just cycle off when its temperature limit is
reached.

If you have thermostatic radiator valves, you should also have a
balancing valve in the system. This prevents the rise in system
pressure as thermostatic valves close from the tendency to defeat
them.

More crap.

I don't believe condensing bolers are in wide use in America, that's
probably why your neighbours boiler has been incorrectly installed.
We have had them in Europe for more than 20 years & plumbers all know
about these things.

You're batting zero.