On Tue, 11 Mar 2008 06:12:34 -0700, jives11 wrote:

Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along with
some towel rails, to warm them in summer even though the main CH system
may be off.

My Question is when the timer has both CH & HW on, how is this conflict
resolved.

Good Q.

Does the controller prioritise HW, or is the switch in a Tee
position where it routes the water from the boiler to both HW & CH ? IS
HW only selected when the CH is OFF i.e in the summer ? I tend to rely
on a timer stat so my CH is always ON and I allow the programmable stat
to determine when the pump gets enabled

Systems can either the one-or-the other using a 3-way diverter valve or
both together if needed using a mid-way capable valve.

Older installations tend to have mid-way valves (Y-plan). More modern
ones ave diverter valves (W-plan) or more likely 2(or more) 2-port valves
(S-plan/extended S-plan).

What happens during both HW+CH demands depends on how the system was
installed. even with a mid-way valve the system may still effectively
prioritize the HW tank. The modern idea is that the HW cylinder can be
reheated very quickly typically (10-15 minutes for a bath full) and so
the house heating can be switched off while the HW cylinder is reheated.


My tank has a moulded foam insulation plus an additional lagging jacket.
Fine.
I'm finding in cold weather the house takes a long time to get up to
desired temperature, if at all. While this may be affected by insulation
etc, I wonder if the conflicting requirements of HW & CH reduce the
responsiveness.
Possibly.
Test 1. does the system heat the house when the HW is switched off?
perhaps I should schedule HW much earlier in the day and
rely on good tank insulation to keep it hit until evening ?

If the tank has a thermostat then it should only take a small proprtion
of the time to do HW.

There are dozens of reason why the heating is not adequate, HW coil short
circuiting the HC probably does not make the top 5.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html