What are the advantages of an outside temp sensor on boiler?

[Doctor Drivel]

Anyone know the cheapest boiler available with weather compensation? Combi or system.

 

[NGBod]

In operation does it reduce boiler cycling? The exhaust must be pluming constantly .

Weather compensation is ideal for the UK with its changeable climate - warm one day cool the next.

It has reduced boiler cycling on my system, but fine tuning of which compensation curve is used should reduce it even more. IMO a well matched compensation curve should almost eliminate boiler cycling ie. when the CH flow temp is just sufficient to keep the room temp in the middle of the on- off room stats chosen modulation range.

Dave

An on-off stat modulates the burner?
Once the compensator dictates that the input is lower the what the burner can deliver, cycling is inevitable. I think it is around 9kW minimum delivery by this boiler.

No, modulation range was the wrong choice of words for the on- off room stat. I was referring to the proportional bandwidth of the stat or the hysteresis between the on and off temps.
I have the boiler range rated to 13KW max useful output on the CH circuit.
I'm not sure what the minimum is as the tech spec gives 10.6KW as the minimum useful output yet the boiler can be range rated to give 10.6 KW max useful CH output according to the manual. Maybe this means the CH is disabled? I don't think so, but I'm not an expert so would like to know for sure if anyone knows.

 

[Doctor Drivel]

In operation does it reduce boiler cycling? The exhaust must be pluming constantly .

Weather compensation is ideal for the UK with its changeable climate - warm one day cool the next.

It has reduced boiler cycling on my system, but fine tuning of which compensation curve is used should reduce it even more. IMO a well matched compensation curve should almost eliminate boiler cycling ie. when the CH flow temp is just sufficient to keep the room temp in the middle of the on- off room stats chosen modulation range.

Dave

An on-off stat modulates the burner?
Once the compensator dictates that the input is lower the what the burner can deliver, cycling is inevitable. I think it is around 9kW minimum delivery by this boiler.

No, modulation range was the wrong choice of words for the on- off room stat. I was referring to the proportional bandwidth of the stat or the hysteresis between the on and off temps.
I have the boiler range rated to 13KW max useful output on the CH circuit.
I'm not sure what the minimum is as the tech spec gives 10.6KW as the minimum useful output yet the boiler can be range rated to give 10.6 KW max useful CH output according to the manual. Maybe this means the CH is disabled? I don't think so, but I'm not an expert so would like to know for sure if anyone knows.

Sounds like it would be a fixed rate.

 

[blondini]

I'm thinking of experimenting with simple combination of indoor and outdoor sensors.

Does anyone know the resistance values for the Biasi sensor? Multimeter bust.

 

[Doctor Drivel]

I'm thinking of experimenting with simple combination of indoor and outdoor sensors.

The BIASI does not have the capability to have an inside sensor. An outside sensor can be fitted inside, however the correct control slope needs to be selected - and the BIASI may not be sophisticated enough to select a control slope for indoor use.

 

[blondini]

I'm thinking of experimenting with simple combination of indoor and outdoor sensors.

The BIASI does not have the capability to have an inside sensor. An outside sensor can be fitted inside, however the correct control slope needs to be selected - and the BIASI may not be sophisticated enough to select a control slope for indoor use.

I was thinking of two sensors wired together to the same input on the boiler so that indoor temp will also influence boiler output. The trouble is that wiring two standard sensors in series will increase the overall resistance presented compared to a single sensor, and wiring in parallel will reduce it. I just need to know some approximate resistance values for the standard sensor so that I can select some alternative values of cheap component thermistors to experiment with.

 

[Doctor Drivel]

I'm thinking of experimenting with simple combination of indoor and outdoor sensors.

The BIASI does not have the capability to have an inside sensor. An outside sensor can be fitted inside, however the correct control slope needs to be selected - and the BIASI may not be sophisticated enough to select a control slope for indoor use.

I was thinking of two sensors wired together to the same input on the boiler so that indoor temp will also influence boiler output. The trouble is that wiring two standard sensors in series will increase the overall resistance presented compared to a single sensor, and wiring in parallel will reduce it. I just need to know some approximate resistance values for the standard sensor so that I can select some alternative values of cheap component thermistors to experiment with.

Wiring two in is not a good idea at all. You can have 4 inside sensors and average them by wiring them up i series parallel.

You could switch one out and one in via a relay, however the compensator slopes would be very different for each.

A normal on-off stat could switch out the outside sensor and switch in a resistance that kids the weather compensator that it is 25C outside so it
switches off the burner. Which give you no more than what the BIASI already has as standard.

 

[Rog200455]

After various experiements with series / parallel arrangements of thermistors and a potentiomer, I thought i had a set-up which tracked reasonably well on the Glow Worm Ultracom. When I go into the diagnostic menu on the boiler, I get a direct outdoor reading in degrees C. By adjusting the pot I am able to set the outdoor temp against a thermometer. I have checked this at 20 degrees (with the sensor indoors), 11 degrees (sensor outside) and 0 degress (flask of ice/water). It seemed to track within a degree, however the next morning, when the outside temp was a true 8 degrees, the boiler was showing 4 deg. At the moment I just have the thermistor poked outside from the loft, so perhaps condesation is affecting it? I'll have to put it in a sealed box. But is it all worth it? For reasons of condensing efficiency, I don't want to let the return temp get above 55, which means having the flow no higher than 60. The rads are not efficient if the flow temp is any lower, so perhaps the answer is just to leave the flow temp at 60?