Central Heating Control Loop Basics

[rjhzxc]

Is it the case that a simple programmer (eg Ikon) does not give direct temperature control to the central heating system? Instead, this thermal control only comes from within the boiler (eg Baxi Solo 3 PFL 50) and the water therein?

If this is the case is it possible for a room thermostat (with suitably rated contacts) to directly switch the circulation pump so that regulation is acheived by the boiler switching off due to the restricted water flow?

Or am I really off track here and thinking about a dangerous scenario?

TIA
Rob

 

[spudkey]

many boilers require pump overun to remove excess heat the pump is then controlled by the boiler. The room stat will shut off boiler but pump will keep tuning for a few mind

 

[D_Hailsham]

Is it the case that a simple programmer (eg Ikon) does not give direct temperature control to the central heating system?

A simple programmer or timer only controls the times when the boiler can be used. Temperature control is provided elsewhere

Instead, this thermal control only comes from within the boiler (eg Baxi Solo 3 PFL 50) and the water therein?

All boilers have a temperature control to prevent them overheating (boiling). Some have user-adjustable thermostats.

If this is the case is it possible for a room thermostat (with suitably rated contacts) to directly switch the circulation pump so that regulation is acheived by the boiler switching off due to the restricted water flow?

Any CH thermostat is rated to carry the current required by pumps, motorized valves etc. The usual control method is to have the thermostat turn the boiler and the pump on and off (via a motorised valve if necessary) in accordance with the heating requirements.

Or am I really off track here and thinking about a dangerous scenario?

No! Just reinventing the wheel

 

[Agile]

Or am I really off track here and thinking about a dangerous scenario?

TIA
Rob

I would say that that line of thinking could be dangerous!

Older boilers just switch the gas on/off to control the heat output.

Later boilers modulate the heat down to proportionally control the heat output.

Those later boilers sense the flow temperature by an NTC resistor. Its only on those boilers that a competent electronics enthusiast could make up a circuit to externally control the flow temperature.

The simplest solution would be to use an ORP12 photoresistor and an LED to illuminate it thus isolating the temperature control from the boiler circuit.

Tony

 

[rjhzxc]

Thank you for your responses. This line of thinking came about because it's going to be difficult to route thermostat wiring to the boiler. Getting to the pump is a bit easier.

Don't know if there is a simple wireless solution to this problem. !! ??

Or am I really off track here and thinking about a dangerous scenario?

TIA
Rob

I would say that that line of thinking could be dangerous!

Older boilers just switch the gas on/off to control the heat output.

Later boilers modulate the heat down to proportionally control the heat output.

Those later boilers sense the flow temperature by an NTC resistor. Its only on those boilers that a competent electronics enthusiast could make up a circuit to externally control the flow temperature.

The simplest solution would be to use an ORP12 photoresistor and an LED to illuminate it thus isolating the temperature control from the boiler circuit.

Tony