Boilers: Check My Understanding Please

[charliegolf]

For my diy knowledge...

2 scenarios: (Combi boiler btw)

1 The timer is approaching the start of an 'on' period, when the room temp is, say 19 degees, but the schedule calls for 20.

2 I come home from hols, house is freezing at 10 degrees, I want 20, so I crank the thermo up to full- hot as you can ask for.

I think... that the boiler will act in exactly the same way in each case: ie, it will ignite to 'full' until the requested temp is reached. Am I right? My point is, that I think the boiler is simply on or off, regardless of the temp gradient. Not, 'on low' for scenario 1, cos it's only one degree?

Educate with kindness please!

Ta.

CG

 

[Lower]

If the heating hasn't been on for a while and the water is cold, when the thermostat calls for heat the boiler will light on full fire.

As the circulating water is circulated, warms up and starts to approach the target boiler water temperature, the boiler will start to modulate down.

At whatever point in this cycle the house gets up to temp and the thermostat stops calling for heat the boiler will shut down.

Same will happen in both scenarios.

 

[Mottie]

For my diy knowledge...

2 scenarios: (Combi boiler btw)

1 The timer is approaching the start of an 'on' period, when the room temp is, say 19 degees, but the schedule calls for 20.

2 I come home from hols, house is freezing at 10 degrees, I want 20, so I crank the thermo up to full- hot as you can ask for.

I think... that the boiler will act in exactly the same way in each case: ie, it will ignite to 'full' until the requested temp is reached. Am I right? My point is, that I think the boiler is simply on or off, regardless of the temp gradient. Not, 'on low' for scenario 1, cos it's only one degree?

Educate with kindness please!

Ta.

CG

Funnily enough, I just posted this on another post. Mine won't act in the same way for both scenario's.

"Not always. On my system, with a Honeywell DT90E room stat, as my room temperature starts to get within 1 degree of the target temperature, it will shut the boiler down but the pump keeps running for a few minutes, it then fires up and repeats that boiler shutdown and pump overrun at 0.5 degrees before target temperature and then finally shutting down and doing a final pump overrun when it hits the target temperature. I thought that was wrong and contacted Honeywell and they told me that was a design feature to prevent the room reaching target temperature, shutting the boiler down with heat still coming from the radiator and then overshooting the target by a couple of degrees. It then fires the boiler every 10 mins or so for a couple of minutes to keep the room temperature stable. My stat rarely goes above .5 of a degree above the set temperature. Takes a little while longer for the room to reach target temperature from a cold start but much better than my old analogue room stat that would overshoot by a couple of degrees then had to get a couple of degrees below target temperature before switching the boiler back on."

If my heating has gone off at say, 11.00pm and I want to have a shower after that time, to warm the upstairs and bathroom it's no good just switching it back on with the override as it will take ages to go up a few degrees in 10 mins so I turn it on, whack the temp up to say 28 degrees (from 23 degrees) and it will fire up on full power and not start the half a degree malarkey until it gets to say, 27 degrees.

 

[muggles]

As above, it depends on both your boiler and your thermostat, as different combinations of the two will react differently to different demands