Re: Gas boiler control

["Neil Fuller" <neil@xxxxxxxxxxxxxxxxx>]

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 your
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 calculates
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 in
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 to
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 £2800. They
saved over £4,000 a year in gas costs directly attributed to our
installation. (in fairness, their total gas bill last year was £600,000)

HTH

Regards

Neil




----- Original Message -----
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 account
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
electrically
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
>
>
>
> UK Home Automation Meet 2004 - BOOK NOW!
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>
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>
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>
>
>
>
>




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