Thanks for picking up on my queries BigW. I am an OK DIY'er, but I've never
payed any attention to CH/HW before. I got recently mugged by a plumber for
£150 ( the wife called them in out of blind panic ) to put a new pump in, so
now I've decided I need to get more genned up on the subject before winter
sets in.
I suspect you are right about the thermostat in the HW tank ( I'll check
tonight ). However, if my boiler has a stat on it with a 140-180°F setting,
I can't see the purpose of the stat on the HW tank i.e what will it
activate/de-activate. If going from my sketch there is a permanent unvalved
supply to my HW coil, then all that I can see could happen is that when the
HW-tank thinks its hot enough, it stops the boiler GCV, but this would then
stop the hot feed to the radiators wouldn't it when perhaps there was a
demand ? I could understand the concept of a HW stat triggering a HW zone
valve to close if one was installed...
I think there is also a immersion heater in the tank but its knacked with
the wiring ripped out of the wall socket. I think I need to verify what
wiring exists & replace the heater. ( I thought that you didn't need an
immersion heater if you had a boiler, but it now seems obvious that I should
have one there as back-up in case the boiler goes down )
Re the zone valve, I assume 'activated' means opened and when no power is
supplied the the valve it springs shut. Therefore there should only be a
power supply to the valve when the 'water+heat' switch is toggled. Please
confirm I've got my head round that one......
....and how have you concluded the valve is three port ? Although my system
may be better suited to a three port arrangement, I can definately assure
you that the valve on my garage wall is a tower 672B 22m 2port valve with an
earthwire, plus four other wires connected. Do you think I should replace
the current 2 port with a 3-port , or just install a 2nd 2-port valve (
15mm if available )on the HW line.
Re the frost guard stat, you reckon this stat will 'only allow heating the
be called for by the rads', but as I've stated above, the HW circuit has
nothing to isolate it , so I can't visualise how this can happen when I have
no stat in the house other than the rad-stat-valves. I can understand the
concept of the frost stat just being a by-pass( short circuit ) to all the
other controls such that it fires up the boiler ahead of the timer eg if I
set it to zero°C... Does that make sense ?
Finally the pump. Although it is clear that the HW is fed from a tee
junction after the pump discharge, does this mean that it absolutely cannot
be a gravity based HW circuit. If the boiler is in the garage and the HW
tank is 3-4m above on the upstairs landing of the house, does it need the
pump to get it round or will just the heat energy/pressure entered into the
water force it round ?
( A am not 100% sure on how a gravity system should/could work. )
I'm sure if I checked my gas bills with other people I'll find out I've been
wasting lots of cash running my system wrong. When I've got better informed,
I want to mod my system so that the HW just gets hot & isolates itself until
its needed and the CH does the same & perhaps stops the pump. I wan't to
learn whether there should be more control over the pump, for instance when
'HW only' selected, can't the pump be tripped.
Pls continue to help
Cheers
"BigWallop" wrote in message
...
From your sketches the system has a constant hot water circulation through
the pump any time the boiler fires up. This means that there is a
thermostat on the hot water cylinder. Correct ?
The motorised valve is only activated when you call for heat to the
radiators.
The wiring sketch shows a "?" on a pair of wires and is most likely the
connection to the hot water cylinder thermostat.
The frost guard 'stat will control the system by over riding the hot water
circulation and only allow the heating to be called for by the radiators.
Everything on the wiring will live mains voltage and should run at no more
than 5 amps at total load. It may even be 3 amps depending on the pump
size
and switching loads of the 'stat and things.
The motorised valve will only open when the programmer calls for heating
to
the radiator circuit. Unless you've seen things in the wrong places and
the
valve is actually a three port, two way valve, which is connected to the
flow pipe after the pump and will swing an arm inside it between the hot
water and heating circuits, or can be set by the system to stop in a mid
point between the two circuits to allow heated water to flow through both
circuits.
A three port valve has three pipes going to in to it. One is the flow
from
the boiler, one is the flow to the hot water circuit and one is flow to
the
radiator circuit.
From your sketch the system relize on the pump to circulate the heated
water
around the two circuits and is fed from a header tank. It looks to be a
very basic, and very easily maintained, system.
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