My Viessman boiler journey

[marshian]

Well it was a good plan - but speed one doesn't want to play not sure why - probably a result of building one pump out of two.

 

Running on the grundfos on speed 2 for the next couple of days to see if it reduces the number of cycles per day compared to the DAB pump

[John Carroll]

What is the exact model of your old Grundfos??. If it is a A rated pump (or not) we can then compare the various modes/settings with the DAB.

What model/setting was/is the Dab Evosta3? on to give you 14W, 3.0M, 0.5ms/hr

According to its pump curves, the  Evosta3 in CP2 (constant pressure) mode will give a flow rate of 0.5m3/h at @ 3.0M head but requires 16W, in CC2 (fixed speed) mode it will only flow 0.2m3/hr @ 14W and also 3.0M, a bit strange.

Edited Tuesday at 23:44 by John Carroll

[marshian]

Model info

 

It’s currently running at 58w on speed 2

 

Dab Evosta

 

speed 2 - 15w at 3.0 m head and 0.5 m3/hr (system was noisy but stable from a cycling perspective - boiler flow 32 return 25)

 

speed 1 - 8w at 1.8 m head and 0.3 m3/hr (system was quieter but cycled more and rad deltas not really any better - if anything mean water temps in the rads were lower - maybe 1 deg better diff between flow and return)

 

 

 

[John Carroll]

When you say (Evosta3?) speeds 1&2, which mode are you in, both CP2 & PP2 will have similar outputs at both settings but FS (fixed speed)  2 will draw ~ 21W at a flowrate of 0.5m3/hr and will draw 9W  closed valve power.

 

The Selectric, if I have the correct pump curves will

circulate 0.48m3/hr @ 2.76M speed1, 0.55m3/hr @ 3.63M speed2 and 0.59m3/hr @ 4.18m speed 3, all close if using a evosta benchmark of 0.5m3/hr @ 3.0M.

 

 

Selectric 5M

 

 

Edited Wednesday at 10:52 by John Carroll

[John Carroll]

A rad(s) flow of 0.5m3/hr, 8.33LPM,  with flow/returns of 32C/25C will result in a boiler demand of, 8.33*60*(32-25)/860, 4.06kW, say 4.1kW, if the boiler's minimum output is > this then no cycling, if less, then to increase the rads demand/boiler output means either a greater flow, more noise as higher head required or increasing the flow temperature.

[marshian]

1 hour ago, John Carroll said:

A rad(s) flow of 0.5m3/hr, 8.33LPM,  with flow/returns of 32C/25C will result in a boiler demand of, 8.33*60*(32-25)/860, 4.06kW, say 4.1kW, if the boiler's minimum output is > this then no cycling, if less, then to increase the rads demand/boiler output means either a greater flow, more noise as higher head required or increasing the flow temperature.

 

Boiler min output is quoted as

 

3.2 kWh (at 50/30 flow / return)

2.9 kWh (at 80/60 flow / return)

 

However couple of points 

 

Viessmann technical have not been able to confirm min output kWh at 32/25 (I am assuming that it is more than the 3.2 kWh quoted at 50/30)

 

At min modulation the best I have seen is 4.0 kWh over a period of 1 hour (initial ramp up and period where it modulated down to min was not included) During this period I did not see any increases in modulation as it was 0 Deg C OAT

 

Data if you wish to check the calcs

 

Meter Reading at Start 633.766 m3 09:00

Meter Reading at end 634.130 m3 10:00

Time 60 Mins

Usage 0.364 m3

Calorific Value 39.1

kWh 4.04 kWh

 

I am also waiting for the Viessmann engineer to replace main board and WC sensor because despite having range rated the boiler to min I occasionally see the boiler ramp up to 15 to 20% modulation with no assignable cause - problem is more frequent at warmer air temps (5 deg to 10 deg range)

 

[marshian]

2 hours ago, John Carroll said:

When you say (Evosta3?) speeds 1&2, which mode are you in, both CP2 & PP2 will have similar outputs at both settings but FS (fixed speed)  2 will draw ~ 21W at a flowrate of 0.5m3/hr and will draw 9W  closed valve power.

 

I'm running the Evosta 3 pump on Constant Differential Pressure - data from pump display on speeds 1 & 2 posted earlier

 

2 hours ago, John Carroll said:

The Selectric, if I have the correct pump curves will

circulate 0.48m3/hr @ 2.76M speed1, 0.55m3/hr @ 3.63M speed2 and 0.59m3/hr @ 4.18m speed 3, all close if using a evosta benchmark of 0.5m3/hr @ 3.0M.

 

 

Selectric 5M

 

 

 

That's really interesting and if I can summarise "for the cheap seats" (Me) 

 

Effectively order in terms of flow is

 

Evosta3 Speed 1 - 0.3 m3/hr

Grundfos Speed 1 - 0.48 m3/hr

Evosta3 Speed 2 - 0.5 m3/hr

Grundfos Speed 2 - 0.55 m3/hr

 

Does explain why system doesn't like Evosta3 speed 1 and why I feel Evosta3 Speed 2 is a little noisier (system noise) than my old Grundfos was and sort of validates my want /need for the old pump from a noise perspective

 

Please note - the noise aspect is me being really (expletive deleted)ing picky and to be honest from an energy usage perspective I should probably go back to the Evosta3 on speed 2 as I could run that pump for 4 hours (15 w) for the same consumption as the Grundfos chews thro (58 w)

 

I'm pretty sure the consumption would be ~40w on speed 1 if it worked but as it doesn't and I don't know why

 

My gut tells me I need a setting between speed 1 and speed 2 on the Evosta3

 

Thanks for you input @John Carroll

 

[marshian]

Pump Mode selection was covered here

 

 

[John Carroll]

5 hours ago, marshian said:

 

I'm running the Evosta 3 pump on Constant Differential Pressure - data from pump display on speeds 1 & 2 posted earlier

 

 

That's really interesting and if I can summarise "for the cheap seats" (Me) 

 

Effectively order in terms of flow is

 

Evosta3 Speed 1 - 0.3 m3/hr

Grundfos Speed 1 - 0.48 m3/hr

Evosta3 Speed 2 - 0.5 m3/hr

Grundfos Speed 2 - 0.55 m3/hr

 

Does explain why system doesn't like Evosta3 speed 1 and why I feel Evosta3 Speed 2 is a little noisier (system noise) than my old Grundfos was and sort of validates my want /need for the old pump from a noise perspective

 

Please note - the noise aspect is me being really (expletive deleted)ing picky and to be honest from an energy usage perspective I should probably go back to the Evosta3 on speed 2 as I could run that pump for 4 hours (15 w) for the same consumption as the Grundfos chews thro (58 w)

 

I'm pretty sure the consumption would be ~40w on speed 1 if it worked but as it doesn't and I don't know why

 

My gut tells me I need a setting between speed 1 and speed 2 on the Evosta3

 

Thanks for you input @John Carroll

 

Try PP2 which may by my calcs may give a flowrate of just less than 0.4m3/hr at 1.9M.

Edited Wednesday at 19:06 by John Carroll

[marshian]

9 minutes ago, John Carroll said:

Try PP2 which may by my calcs may give a flowrate of just less than 0.4m3/hr at 1.9M.

Hmm - I’ll need to check the destuctions but from memory that mode has 6 settings not 3 - accessed by a long 20 sec press - I was going to try that if the grundfos pump turned out to be a bust (which it did) but at least I now know why I favoured the old pump on speed 1 and why I have to run the new pump on 2 rather than 1

 

thank you @John Carroll

[marshian]

50 minutes ago, marshian said:

Hmm - I’ll need to check the destuctions but from memory that mode has 6 settings not 3 - accessed by a long 20 sec press - I was going to try that if the grundfos pump turned out to be a bust (which it did) but at least I now know why I favoured the old pump on speed 1 and why I have to run the new pump on 2 rather than 1

 

thank you @John Carroll

 

Yep I think I was right

 

 

Couldn't find pump curves for these settings but I'm going to assume that it gives a finer level of step than the std 3 positions

[John Carroll]

2 hours ago, marshian said:

 

Yep I think I was right

 

 

Couldn't find pump curves for these settings but I'm going to assume that it gives a finer level of step than the std 3 positions

DAB Evosta-2-3-Installation-and-Operation-Manual_UK.pdfDAB Evosta-2-3-Installation-and-Operation-Manual_UK.pdf

 

The standard (3) PP settings are the ones I'm looking at, you have to press the setting button for 20 secs or so i think to get the advanced (6) PP settings.

You can see by my trusty spreadsheet that it looks like PP2 will give a flowrate of 0.4m3/hr ish @ 1.95M

 

Dab Evosta3 PP2.xlsx

[marshian]

4 minutes ago, John Carroll said:

DAB Evosta-2-3-Installation-and-Operation-Manual_UK.pdfDAB Evosta-2-3-Installation-and-Operation-Manual_UK.pdf 3.42 MB · 4 downloads

 

The standard (3) PP settings are the ones I'm looking at, you have to press the setting button for 20 secs or so i think to get the advanced (6) PP settings.

You can see by my trusty spreadsheet that it looks like PP2 will give a flowrate of 0.4m3/hr ish @ 1.95M

 

Dab Evosta3 PP2.xlsx 18.13 kB · 0 downloads

 

Yep I get that you are using the std 3 settings

 

I'm just musing that 0.4m3/hr might be a smidge lower than the old grundfos - now that might be perfect but and on the basis that the six settings might give a finer control

 

1 of 3 = 1 of 6

2 of 3 = 3 of 6

3 of 3 = 6 of 6

 

Then maybe 4 of 6 closer to the 0.48 of the old grundfos pump

[John Carroll]

Where can/do you see the max/min settings for all the 6 PP settings?, the manual only shows the 3 standard PP settings data?. Anyway if you can see it somewhere just change the settings in the spreadsheet.

[marshian]

Just now, John Carroll said:

Where can/do you see the max/min settings for all the 6 PP settings?, the manual only shows the 3 standard PP settings data?. Anyway if you can see it somewhere just change the settings in the spreadsheet.

 

They aren't specified in the manual - I'm taking an educated punt

 

Not difficult to establish the settings - the pump will tell me what they are Just need to start it on the lowest of the 6 and give 5 mins between each change to stabilise the pump

[John Carroll]

6 minutes ago, marshian said:

 

They aren't specified in the manual - I'm taking an educated punt

 

Not difficult to establish the settings - the pump will tell me what they are Just need to start it on the lowest of the 6 and give 5 mins between each change to stabilise the pump

 

Very good, on any PP setting, does the Evosta3 show the actual pump head?. (as well as the flowrate & power). I have the Rolls Royce of PP & CP settings on my Wilo Yonos Pico where the settings can be incrementally changed in 0.1M steps to give almost infinite "control" but the head is only displayed while its being changed, no big deal really but nice to have displayed if available.

[marshian]

4 minutes ago, John Carroll said:

 

Very good, on any PP setting, does the Evosta3 show the actual pump head?. (as well as the flowrate & power). I have the Rolls Royce of PP & CP settings on my Wilo Yonos Pico where the settings can be incrementally changed in 0.1M steps to give almost infinite "control" but the head is only displayed while its being changed, no big deal really but nice to have displayed if available.

 

Yes regardless of the mode selected - all three parameters are displayed

[marshian]

DAB pump swapped back in

 

On PP setting (3 speed selection)

 

CH	Proportional differential pressure regulation
Speed	Watts	Head (m)	m3/Hr
1	6.5	1.3	0.4
2	9.3	1.9	0.5
3	17.0	3.4	0.5

 

On PP setting with the optional 6 speed selection

 

CH	Proportional differential pressure regulation
Speed	Watts	Head (m)	m3/Hr
1	6.5	1.3	0.4
2	8.5	1.7	0.4
3	9.5	1.9	0.5
4	10.0	2.0	0.5
5	11.0	2.2	0.5
6	17.0	3.4	0.5

 

I've set it to PP2 (of 6)

 

Sitting in the living room all I can hear is the wall clock ticking...............

 

[John Carroll]

How many rads in use? and what is/was the boiler flow/return temperature(s).

[marshian]

Just now, John Carroll said:

How many rads in use? and what is/was the boiler flow/return temperature(s).

 

28.9 flow 20.4

 

9 out of 13 rads in circuit

[marshian]

Actually that might not be representative as the boiler was off for an hour while I fugged about swapping the pump and then played with the settings to get the data

[John Carroll]

You can check it again tomorrow or sometime when it settles down.

Based on the above, the rad output(s) is 0.4*16.666*60*(28.9-20.4)/860, 3.95kW

[John Carroll]

 

12 hours ago, marshian said:

Actually that might not be representative as the boiler was off for an hour while I fugged about swapping the pump and then played with the settings to get the data

Yes, doesn't make a lot of sense.

Your flowrate of 0.4m3/hr, say average of 0.044m3/rad would be fairly typical of a T50 rad with a ~ 20C dT, see attachment, to give a 9.0kW output if all T50 rads at 100% output.

Using your dT of 8.5C gives a total output of 0.41kW and even using he same flowrate as at 100% output gives only 0.83kW at @dT of 1.81C, if the average output of each rad is 1.5kW @ 100% output then the numbers become 13.5kW, 0.615kW & 1.245kW, both a long way from the  boiler output of 3.95kW or so.

 

 

 

Rads output mars Rev 0.xlsx

Edited Friday at 12:40 by John Carroll

[marshian]

1 hour ago, John Carroll said:

 

Yes, doesn't make a lot of sense.

Your flowrate of 0.4m3/hr, say average of 0.044m3/rad would be fairly typical of a T50 rad with a ~ 20C dT, see attachment, to give a 9.0kW output if all T50 rads at 100% output.

Using your dT of 8.5C gives a total output of 0.41kW and even using he same flowrate as at 100% output gives only 0.83kW at @dT of 1.81C, if the average output of each rad is 1.5kW @ 100% output then the numbers become 13.5kW, 0.615kW & 1.245kW, both a long way from the  boiler output of 3.95kW or so.

 

 

 

Rads output mars Rev 0.xlsx 13.91 kB · 1 download

Typically my delta at the boiler is 5.5 to 7.0 max

 

Start of burn it's wider, just before the boiler shuts down it's narrower - I tend to quote only the narrow end or give an average

 

Last night it had a much cooler circuit to start from

 

I might have to up the pump speed by one as between midnight and 8am the boiler fired 9 times compared to it's normal 7 or 8 max

[John Carroll]

Wonder was it cycling due to the minimum boiler output being more than the rad demand or due to a roomstat switching it off when room temperature reached its SP.

Edited Friday at 14:54 by John Carroll