Short Cycling, any advice?

[JohnMo]

5 minutes ago, Super_Paulie said:

So no matter what i do to this my efficiency is going to be the same, its about finding the point where im condensing for longer i suppose to try and win back a few pennies and not ruin the boiler through super-low cycles

No not correct.

 

You can get long cycle times, but you have to run it differently. Long runs will decrease gas consumption considerably.

 

You need to think of using your floor more as storage heater. You fill it with energy then switch off the heat source, allow energy to deplete then recharge. That is what a simple thermostat does. Your smart stat may do that for you, but suspect it won't as it will want to run in TPI mode, not in hysterisis mode.

 

This is what my heat pump did last night (boiler does the same but cannot give a pretty image). It was supplying around 6kW against about 1.2kW heat demand. It ran for a long period, because I had allowed the floor to deplete it's energy. All controlled by a simple thermostat.

 

The yellow bit is kW, the red line is flow, green line return. Purple is outside temp. The long green line after the yellow is the combined flow and return (pump stays on). The spike is DHW at about 6.30am. The gap in data was the modem rebooting.

Previous night for reference 

[Super_Paulie]

30 minutes ago, JohnMo said:

No not correct.

 

You can get long cycle times, but you have to run it differently. Long runs will decrease gas consumption considerably.

 

You need to think of using your floor more as storage heater. You fill it with energy then switch off the heat source, allow energy to deplete then recharge. That is what a simple thermostat does. Your smart stat may do that for you, but suspect it won't as it will want to run in TPI mode, not in hysterisis mode.

 

This is what my heat pump did last night (boiler does the same but cannot give a pretty image). It was supplying around 6kW against about 1.2kW heat demand. It ran for a long period, because I had allowed the floor to deplete it's energy. All controlled by a simple thermostat.

 

The yellow bit is kW, the red line is flow, green line return. Purple is outside temp. The long green line after the yellow is the combined flow and return (pump stays on). The spike is DHW at about 6.30am. The gap in data was the modem rebooting.

Previous night for reference 

 

 

Thanks for that that. That is how i would like to go really due to my boiler modulation being shitty, heat that thing up, let it radiate for long periods, thats what i did all winter really.

 

Do you have any suggestions for me John based on the above? I havent had any heating requirement for 17hrs now but its within a degree of the stat calling as we speak.

 

My flow of 57, mixer of 45, bypass rad open 1/4 keeps my return within the range for condensing but with a decaying cycle time ultimately ending the evening on a 8minute cycle.

 

[Super_Paulie]

5 hours ago, JohnMo said:

My approach is set thermostat at 21 to force start boiler. Let it run chasing 21 for about 4 hrs, then reduce thermostat to 20.5, for an hour or 2. Most the time the boiler switches off when the thermostat is moved to 20.5. Then set to 20, boiler switches off. Once set to 20 the floor stabilises and you get some overshoot as the floor releases it's energy. Our heating stopped at 7.30 this morning and by 11 the house was sitting at 20.7.

 

I've had to pop out this evening but I like what you've got there, I'll set up a schedule on my stat and try that out. I've also increased my mixer to 50 as I've still got room to play with on floor temp and I've got a boiler flow temp of 57. This is all higher than I had hoped but needs must if that's what I've got to do.