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# Worcester Bosch greenstar 28i junior flow rate/temperature controls

edited 7 January at 11:07AM in Energy
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edited 7 January at 11:07AM in Energy
Hi, I have a 12 year greenstar 28i junior. The control panel looks like this:

Can someone explain please what the 'flow rate' is, if it's different to the temperature and how I would adjust the flow rate on this? Also, does anyone know please what the numbered settings on the dial equate to?

Thank you!

* edit - am I getting flow rate mixed up with 'flow temperature'? I

## Replies

• edited 7 January at 11:35AM
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edited 7 January at 11:35AM
Think you're meaning flow temperature.
I have the same boiler, and the dial on the left equates to the following temperatures...
1 = 47
2 = 53
3 = 61
4 = 68
5 = 74
6 = 80
Your hot water temperature (from your taps) is set to 55 degrees, and isn't affected by changing the flow temperature.
Edited to add, nor can your hot water temperature cannot be changed on this boiler.
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vic_sf49 said:
Think you're meaning flow temperature.
I have the same boiler, and the dial on the left equates to the following temperatures...
1 = 47
2 = 53
3 = 61
4 = 68
5 = 74
6 = 80
Your hot water temperature (from your taps) is set to 55 degrees, and isn't affected by changing the flow temperature.
Edited to add, nor can your hot water temperature cannot be changed on this boiler.
Thanks for this. I had it set at 5. Turned it down to 4 this morning to see what it would be like and felt a noticeable difference in the temp of the rads with not that much difference in respect of gas usage.

Ah okay, now I think I remember reading that the water temp is fixed.

What temp do you have yours set at? Do you by any chance have any figures for gas usage tracked over the day each hour or the time period you have it on?
• edited 7 January at 1:14PM
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edited 7 January at 1:14PM
I'm a bit late to the "checking your boiler flow temperature" too @spudwood. I had those figures to hand, as I'd looked them up this week.
I have tried changing the setting years ago, turning it down from 5 to something lower (no clue what), but my system took forever to heat my bungalow, so it got turned back to 5.
I'm just trying it again, with it currently set to 3.5, and it's doing OK enough, but that's during this pretty mild weather. I only changed it on the 4th Jan, so usage figures are a bit thin on the ground, although my first hour of heat a day, does seem a couple/few kWh lower (looking on the Bright App).
I can only think that when I tried it previously, the weather was far more wintry, and I may need to turn it up again should the temps drop.
It may be hard to judge savings though, as my 2022 gas usage was 8600(ish*)kWh, whereas previous years have been 11500-13500. 2022 was warmer, and I had a Hive fitted towards the latter end of 2021, but will 8600kWh be my new norm, or just an incredibly low consumption for me.
* I have my exact usage figures, but cba standing up to get them.
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I should add, my rads still feel very hot with it turned down to 3.5, but they must be cooler than previously, as the place does take longer to get to my desired temp.
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If you're going to turn the heat setting down, you need to accept that the heating will have to be on for longer to heat the house up.  But the boiler should be working more efficiently and using less gas.

The flow rate is set on the pump.  That looks like a combi boiler, so the pump is probably hidden inside the boiler somewhere.  It may or may not have a flow rate switch on it, depending on the model.
If it sticks, force it.
If it breaks, well it wasn't working right anyway.
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Hi thanks Ectophile. Please can you explain what you mean by flow rate and how changes to this can affect gas usage? I've only just started researching this so a bit clueless at the mo
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Vic_sf49. I live in a bungalow too (semi, 1960s) so sounds like we are in a similar position. If you do stand up sometime, and you get your hands on some figures, I would really appreciate seeing them. Also, could you let me know, if you don't mind, how you run the boiler over the day? Does it come on in the morning, reach a set temp and then maintain that all day or do you have periods when it's off completely? I dread to think what my bills would be if I used it like I used to a few years ago ie I'd still be manually turning it on and up at temps of 21+ degrees. I tend to use it in short blasts now, which after posting about this on another thread, I've learned is probably not the most efficient way to use it, as its always heating from cold and doesn't get into the cycling? thing. My usage for the year is estimated at around 11000kwh. I haven't checked back on previous years but could do as I have bills going back years!

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You need a way to measure the return pipe temp, To condense and save gas it needs to be under 54c.

So number 3 or just a few mm over should be perfect, And yes it will take far longer to heat but use less gas.

• edited 7 January at 2:46PM
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edited 7 January at 2:46PM
Plenty of U-Tube video's on this. link to this one as from manufacture

We have a Greenstar 30si which is set to E on the dial. Our heating is set via hive stat to
07:00 to 21:45 @ 19C - might boost (30 min) to 20C if a bit cold
21:45 to 07:00 @ 17C
2 bed bungalow with someone in 24/7

Bonus of only 2 settings, is you do not notice longer heating up times. Takes about 30 mins to get from 17 to 19C

Gas Usage this Dec is down on last year, despite the cold snap. Last year flow was on Max & timer has 4 settings, which I found was being boosted more often in afternoon & evenings.
Yesterday highest temp 19.98C @ 18:00
Lowest  temp 16.96C @ 04:00
Of course every property is different. Just I have found this set up seems to be saving us gas usage.
Life in the slow lane
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@spudwood... Just start to type a username after an "@" symbol, and it pops up a list of users to choose from... eventually (on my tablet).

Before my Hive was fitted in Sep 2021, I had an old style Danfoss thermostat, where you twist the dial and guess at what temperature it is, as it was only marked every 5 degrees on the dial.
Timings were set on the boiler itself (see photos at the end), so I used to have the heating on far more than was necessary, as changing the settings was a faff.
Hive has made it far easier to control, copy heating schedules from one day to the next, and switch it off when I get too warm.
Current timings:
0800 - 1600 = 18 degrees.
1600 - 1915 = 20 degrees.
1915 - 0800 = 16 degrees.
I will hit boost if I'm particularly chilly, or turn the stat down if I'm doing a lot about the bungalow. Obvs timings get shifted depending on my plans, but those are about my core hours.
As I have solar panels too, if there's a decent amount of sun/generation, I'll be getting a fan heater running instead.
Usage from previous years, where the flow temperature has been set to 5..