Re[2]: Gas boiler control

["Pete Shew" <ukha_d@xxxxxxxxxxxxxxxxxx>]

Thanks for your responses. It seems like what I should consider are -=20

Thermostats (wireless if necessary) in the main room in each zone

OSS - delay start in warmer weather

Dump jacket heat at shutdown - this could be complicated as currently the
b=
oiler is controlled by the zone valves. The boiler continues to pump after
=
shutdown, but it can only circulate through the bypass.

VT - outlet temperature governed by outside ambient temperature - this may
=
require a boiler modification.

Boiler in service and standby cycle automated - would require installation
=
of electric isolation valves. Without isolation the water would short
circu=
it through the inactive boiler (Thought, would a one way valve impose too
m=
uch restriction in normal use?)

Occupancy detection - too difficult, plus we need to keep the fabric
slight=
ly warm throughout. One room in particular has some damp problems that we
h=
aven't resolved. Maybe a manually set profile for absence with a manual,
or=
dtmf or wap reset to "occupied" status.

Temperature and boiler burn time data logging to allow analysis and
experim=
entation.

It probably means a RYO solution, so a project for the summer.

Pete

*********** REPLY SEPARATOR  ***********

On 09/04/2004 at 23:14 Neil Fuller wrote:

>Pete
>
>There's lots of commercial kit available that would reduce your gas
bills.
>
>It usually goes by the name of BMS or BEMS - Building Energy Management
>Systems - A business I have been in for the last 15 years.
>
>There are several techniques and algorithms that would be suitable for
you=
r
>situation.
>
>The first thing you may like to look at is optimisation or OSS -
Optimum
>Stop-Start. This looks at the inside and outside temperature and
calculate=
s
>the latest possible time to switch the system on to ensure that the
space
>temperature is satisfied by the start of occupancy. So, if it is cold
>outside and inside, the system may start 3 hours before the start of
>occupancy OTOH, if it is warmer inside, it may start 1 or 2 hours
before
>start of occupancy. The best systems calculate the system heat losses
and
>self adapt to the current temperatures.
>
>Honeywell do an OSS programmer but it is pretty rudimentary and does
not
>(at
>least the one I looked at did not) have an outside air temperature
sensor.
>
>Having a zoned system is good :-) This enables you to run only the
>currently
>occupied zones - Do you really need the upstairs heated when everyone
is
>downstairs?
>
>It also enables you to extract the most from your boiler when you turn
all
>zones off by "dumping" the excess boiler jacket heat (which
would normally
>be discharged up the flue) in to an appropriate zone.
>
>To realise the greatest return from any system, you need to be
pro-active
>with time zone setting - Getting an OCC signal in to the system is also
>good, although ideally you would want an OCC signal in to each zone.
>
>Boilers are at their most efficient when highly loaded. Running a
boiler i=
n
>a low load scenario will make it dry-cycle, which is extremely
inefficient=
.
>Keeping one of your boilers off is a very good idea but it would be
good t=
o
>automate the sequencing and rotation of the boilers to ensure system
loads
>are met and boiler run hours are even.
>
>Another useful "technique" is VT or Variable Temperature
control. This
>method utilises the Outside Air Temperature (OAT) to calculate a
required
>flow temperature - The colder it is outside, the hotter the flow.
Typical
>setpoints are 80 DegC Flow @ 0Degc OAT and 20 DegC flow @ 20 DegC OAT.
>Utilising an internal or space sensor for room boost or setback can be
>useful.
>
>However, you achieve this you would probably need to have extensive
>mechanical works carried out to the system.
>
>So, to summarise, yes there's lots of kit available to do pretty much
>whatever you want to do BUT, it's aimed at commercial installations and
>that
>is reflected in the price - How deep are your pockets or, how much
capital
>do you want to spend to realise longer term savings?
>
>A final thought - A job we completed last year cost the client =A32800.
Th=
ey
>saved over =A34,000 a year in gas costs directly attributed to our
>installation. (in fairness, their total gas bill last year was
=A3600,000)
>
>HTH
>
>Regards
>
>Neil
>
>
>
>
>----- Original Message -----=20
>From: "Pete Shew" <ukha_d@xxxxxxx>
>To: <ukha_d@xxxxxxx>
>Sent: Thursday, April 08, 2004 10:04 AM
>Subject: [ukha_d] Gas boiler control
>
>
>> I have just received a nice large gas bill. What I am wondering is
are
>there any smart central heating controllers that, for example, take
accoun=
t
>of the temperature drop in the circuit, to reduce boiler on time.
>>
>> I have a fairly large system with two boilers in tandem and three
zones
>plus hot water. All radiators have thermostatic valves, except bathroom
>towel heater type which I shall be fitting soon. The current control is
by
>means of a triple and a single time switch controlling zone valves.
These
>are commoned via a contactor to drive both boilers.
>>
>> However, I don't use both boilers at the same time as one is
electricall=
y
>and liquidly isolated. From time to time I switch the active boiler,
and
>haven't yet felt the need to run both to provide the required heating.
>>
>> If there are no products commecially available, has anyone
experimented
>with microcontroller heating control?
>>
>> Pete
>>
>>
>>
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>>
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>>
>>
>>
>>
>
>
>
>
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