Boiler Reported Return Temperature

[webbm000]

There is a very marked difference in the two trends, the one immediately below is exactly as I would expect on recycle, ie the flow&return temps merge shortly after the recycle starts but the bottom trend (from post #26) is different with the flow&return temperatures falling in steps over time?
The parameters difference is I think that the bottom trend is with d.2, the recycle set time set to 60 minutes and the top trend additionally has d.1, the pump overrun time extended from10 minutes to 20 minutes, is this correct??

My understanding is that the pump runs continuously during the recycle period (with pump overrun having no effect) and the pump runs for the overrun time and then stops when all zones programmed off or all stats satisfied.

You might try it with d.1 returned to its original setting and see does the trend then revert to looking like the lower one.







View attachment 338029


View attachment 338028

I think your seeing a data capture timing issue in the bottom one as the capture of flow and return were at different times. I've sorted the issue out in the top one so there should be only a couple of seconds between the measurements.

The lines at the bottom of the chart give radiator, UFH and HW cylinder demand (from thermostats) plus the power going to the internal pump. I've also been able to capture the pump speed (grey line) which looks like it is 100% on ignition for 30sec then 45% the rest of the time

Still trying to find the right EBUS parameters to capture the rest of the boiler information. The pump on/off on the chart isn't correct as it comes on after the power is switch on to the pump and goes off when the burner goes off. It would be good if I could find the status message parameter to see which mode the boiler is in

 

[webbm000]

This may show the difference better. 1 cycling still has demand so boiler flow and return track down towards pipe return temp. Third cycle where the demand is removed and zone valve closes the boiler flow and return reduce slowly as the water is recycled through just the bypass

 

[webbm000]

Well I didn't expect that.

Removed the external ABV and the effect this morning was that the boiler flow / return delta went from 8/9 degC to 10/11 degC but the return away from the boiler delta to the boiler return went from 13/14 degC to 6/7 degC

My assumption is that the external ABV was faulty so more of the flow is now going around the rads so the return is hotter? There is still a significant amount of internal bypass 37.5% (50-44)/(60-44) but a lot less than the 62% before (50-37)/(58-37). This assumes same volume of water coming through bypass and into return which I'm not sure is correct

 

[Johntheo5]

Have you now a closed manual by pass (valve) now or have you just blanked off the by pass completely?
You said previously the pump speed looked like 100% at ignition and 45% for the remainder, if its still 45% and and assuming a "8.0M" head pump then its max head at 45% is 8.0*sq(45/100), 1.62M or 162mb so the internal bypass now wound fully down clockwise to 350mb should be still fully shut??. the pump speed would have to be ~ 66% to give 3.5M head.

How do you determine the pump speed from the trend above?.

 

[webbm000]

Have you now a closed manual by pass (valve) now or have you just blanked off the by pass completely?
You said previously the pump speed looked like 100% at ignition and 45% for the remainder, if its still 45% and and assuming a "8.0M" head pump then its max head at 45% is 8.0*sq(45/100), 1.62M or 162mb so the internal bypass now wound fully down clockwise to 350mb should be still fully shut??. the pump speed would have to be ~ 66% to give 3.5M head.

How do you determine the pump speed from the trend above?.

I removed the ABV and blanked off the pipework

That little grey line at 10 is d.15 Output of PWM pump in %. It's not totally reliably captured and it only has three values that I can see 0%, 45% and 100%. I think the pump only has two speeds so this would make sense and I'm still yet to test turning d.19 to 3 to force it into high speed mode.

r1,,WPPWMPower,d.15 WP_PWMPower_DK,,,,"7300",,,percent0,,,Output of pwm pump

 

[Johntheo5]

Well. either the boiler return pipe temperature measurement is incorrect or the pump speed is = to or > than 66% or the internal bypass is defective or has been incorrectly set to 170mb.
You can't read d.15, pump speed, off the menu?.

 

[webbm000]

Well. either the boiler return pipe temperature measurement is incorrect or the pump speed is = to or > than 66% or the internal bypass is defective or has been incorrectly set to 170mb.
You can't read d.15, pump speed, off the menu?.

Good spot on the pipe temp measurement. When I put the thermocouples in the boiler on the return next to the sensor they are low by ~5 degC. Going to have to first measure the return in the boiler manually to make sure it's the thermocouples that are wrong and then redo the calibration as some how it's drifted which is probably due to me constantly moving them about

Be back again once I've got something more robust

Also d.14 and d.15 don't appear in my manual or on the boiler. However I can read d.15 over the EBUS but not d.14