Worcester Bosch System Boiler - Best pump settings?

[GeddyMortgage]

Time for action!, remember the cold rads problem and the thread title.
The best pump setting is stage 6, 4.5M head, even if the residual head is 4.5M it shouldn't cause the slightest problem when circulating through 15 rads or whatever, monitor 1-A5 flow temp, 1-b8 burner modulation & 1-C2, pump speed. I'm surprised that I didn't see somewhere to monitor the boiler return temp?, that would really help.

Yep, im shocked none of the Bosch range I looked at show return temp. Esp considering how many bloody options this thing has.

I have however bought a fish tank thermometer to measure the return.

Thanks for the insights all: I will report back with findings. And hopefully don’t get too down the rabbit hole of re,re,re, re balancing

 

[GeddyMortgage]

Alriiiight, so revisiting this one as back in the property now and have had time to test it.

So I decided to take the methodical approach and just up the setting by one. 3 was default, (constant pressure 250mbar). I set it to option 4, (constant pressure 300mbar). Results below.

:- Radiators weren't on whole warmer, some felt the same, 1 of them (furthest from the boiler) was actually really cold. Never had the issue with that one when the setting was on default, any idea whats going on there?

:- Remember earlier in this thread I said the boiler takes ages getting to full %output but climbs very slowly, well on option 4 it didnt do that, it went to max output much quicker...not instantly but in maybe half the time of default....I guess is that expected?

:- I also mentioned in this thread the boiler would get to exceed target flow temp, cut out for 1min, drop 20c on the flow temp, then gradually work its way back up at a modulated output. This didn't happen on this setting either, it did still modulate down when it got to target temp, but did not cut out the burner at all. Just gradually modulated its way down over time.


Any thoughts on the above folks? and what other question :- given the above do you think its most wise to balance the rads on this setting? or turn the setting up again (option 5) and see how that goes?

 

[GeddyMortgage]

Oh and I totally forgot, to add a bit of context, i've done a little map of how the rads are piped up (birds eye view)

starts at 28mm for the first meter or so, then splits into 2 x parallel runs of 22mm, then down to 15mm to each radiator, for the last meter or so.


On setting 4, it was rad 14 that was not warm at all.

 

[Johntheo5]

I would go straight to setting 6, 400mb.

 

[GeddyMortgage]

I would go straight to setting 6, 400mb.

Thanks John, was a cold night last night so had chance to try it again, tried both setting 6 and setting 5, both verrry similar outcome.

:- All the radiators except rad 14 got hot, that one stayed cold for about 30-45 mins. It did get hot after about an hour or so though, long after all the others were fine. Does this suggest a problem or could just balance now?

:- I noticed (probably the same on all settings to be fair) the bottoms of the radiators are colder than the tops, still warm, but not piping, tops are piping hot. Is that weird?

:- I noticed on radiator #2 an odd noise i hadn't heard before. I've linked a video to it below, any idea what this is and whether i should be concerned? Does this indicate there's crap in the pipes? (there's a mag filter fitted and the pipes cant be older than a few months)

Video - Rad Weirdness Noise


I'm yet to try it on setting 1 (the relative pump to heat setting).

 

[Johntheo5]

Thanks John, was a cold night last night so had chance to try it again, tried both setting 6 and setting 5, both verrry similar outcome.

:- All the radiators except rad 14 got hot, that one stayed cold for about 30-45 mins. It did get hot after about an hour or so though, long after all the others were fine. Does this suggest a problem or could just balance now?

A bit of balancing mightnt go amiss now, at pump setting 6.

:- I noticed (probably the same on all settings to be fair) the bottoms of the radiators are colder than the tops, still warm, but not piping, tops are piping hot. Is that weird?

This is normal, will post a photo of temps from one of mine in a day or two when at home.

:- I noticed on radiator #2 an odd noise i hadn't heard before. I've linked a video to it below, any idea what this is and whether i should be concerned? Does this indicate there's crap in the pipes? (there's a mag filter fitted and the pipes cant be older than a few months)

Video - Rad Weirdness Noise

Cant hear anything.

I'm yet to try it on setting 1 (the relative pump to heat setting).

Suggest first balancing on pump setting 6 and then maybe try it.

 

[GeddyMortgage]

Cant hear anything.

Listen about 10-15 secs in, there's a distinct knocking / dripping noise and im not sure what that is. May need the volume up a bit.

 

[Johntheo5]

That (rushing) sounds like a lot of air still in the system, is it only occuring in this rad?.

Below is a screenshot of one of my rads, the flow is from left to right, as you can see, the hotter water moves vertically upwards in the first 120mm or so, then falls pretty uniformly downwards through the remainder of the rad to give those indicated temperatures and a rads output of 1.16Kw, that rad has a TRV so once room temperature up to its SP of 20C will throttle right down to give the required rad output.