|
Pump connected after boiler thermostat ?
QUESTION:I recently moved into a house and I've successfully upgraded the CH/HW
controls to an 'S-Plan' type system (see previous posts). My
modifications only required me to replace a mechanical timeswitch with
a programmer, thermostats and 2-port zone valves. In other words, I
pretty much ignored what was in the external boiler housing and
replaced the single mech timer with some more elaborate switching
gubbins.
Over the weekend, I noticed something that I think is a bit odd. The
external boiler housing contains the oil-fired boiler (warmflow, no
pump overrun required) and a circulating pump on the feed. However, the
pump seems to be wired _after_ the boiler thermostat (a small gray box
with a knob from 1..5 that supplies mains power to the burnber unit).
It strikes me that this is odd and potentially damaging. Surely the
circulating pump should be circulating water when either the CH or HW
zones require heat, not just when the boiler is in the part of its
cycle that fires the burner.
Does what I've described sound normal? Or should I rewire the
circulating pump?
ANSWER: The pump should be running whenever the *external* controls are telling the
boiler to fire - even when it's own internal thermostat is telling it not
to.
It you wire it up according to the S-Plan diagram in
http://content.honeywell.com/uk/homes/systems.htm it will be fine!
In brief, the timer and room stat control the CH zone valve. The timer and
cylinder stat control the HW zone valve. Whenever either or both zone valves
are open, power is supplied to the boiler and pump, in *parallel*.
|
|
|
|
