Input needed for a Project for a NOOB for a Heating Control System

Hi guys,

We are doing some renovations at home (Sydney Australia) and as part
of this we are going to implement a Hydronically heated floor.
(basically pump hot water through a slab)
This will be in and running for next winter.

What i need built is essentially a fancy differential temperature
controller - as i can not find anything even remotely similar on the
market that will do everything that i want.

I will have a storage tank of hot water which i will need to monitor
the temperature of - during the day this will be heated by a solar
setup on the roof so i will need to be able to have a settable
temeprature difference between the two that would control a 24v relay.
e.g. Lets say i set that i want the tank to be at a maximum of 40
degreee C. (Set point 1) So this would need one temperature probe that
could be positiioned in/on the tank

I also want to set that if the roof is 5 degrees (or more) warmer than
the tank (and the tank is not at 40 degrees) then turn on the relay
(which will activate a small circulating pump). In the event that the
differential temperature becomes less than 5 degrees turn off the pump

The system would then need to have a 2nd Set point for monitoring the
room temperature (lets say i set that to 22 degrees) ( I would
actually like a couple of these inputs (say 3) for 3 seperate
thermostats) which the system could monitor and have seperate outputs
(relay) for each one. (So i could have 3 different areas that were
being monitored and potentially running at different temperatures)

Each of these outputs would be tied into a "master" so if any were
active the master was also active - this would drive a relay which
would drive a circulating pump and finally the outputs of each of the
3 zones would then drive a solenoid for each zone that would be on or
off

Lastly a time controller that could contol the different temperatures
for potentially differnet times of the day - so for instance the Home
theatre would run at 18 degress during the day but at 5PM would raise
the temperature to 22, whereas the laundry and bathroom area would run
at 22 degrees during the day and then go down to 15 degress overnight
??

All of this would have some form of LCD interface to enable the
monitoring and setting of each of the elements

Any ideas how i would go about this - i am not up on Electronics but
do COmputer systems for a living.

Craig

 

As you are already familiar with computer systems, how about a PC
based solution using something like National Instruments
multi-function card

http://sine.ni.com/apps/we/nioc.vp?cid=14117&lang=US

They also do some software called Labview. which is a visual
programming thingy where you just use drag and drop and a minimum of
coding.

National Instruments aren't the cheapest for this sort of stuf, there
are other manufacturers.

Another option is a PLC, but by the time you have added an LCD
display, it becomes more expensinve than a PC based version.

Kevin R

 

The centre for alternative technology in wales, uk have a pamphlet on how
to build a simple solar heating controller that sounds similar to what you
want. This uses two diodes as temperature sensors, and has a full circuit
diagram and pcb mask included. So you could try emailing them -
www.cat.org.uk

 

Heated floor in Australia???, come on, I thought your country was Phooo!
hot!!

How can you get rid of the latent heat in the floor during the day?

Kind regards, Gordon.

 

IN winter it can be chilly and our houses are never designed for it
(DOuble Glazing etc).

The particular area that i intend to heat has very little area exposed
to sunlight in winter so i do not have many issues with "Solar Bloom"
(what happens when the sun contributes to the heat of the room).
Hopever having said that i intend to run a constant circulation
systsem whihc tend sot be slef balancing when left alone

Craig