Worcester Bosch greenstar 28i junior flow rate/temperature controls

vic_sf49

I should add, the kWh usage in my previous post, are from my own calculations that I built into my excel spreadsheet. Meter reads are m3.

So I may get billed slightly differently due to the changing calorific values of gas, but keeping the same calculation is good enough for my purposes.

BUFF

vic_sf49 said:

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.

At 5 (74C flow temp according to above info) imo it will be marginal whether your boiler is condensing or not. 4/68C (or lower) should be a fairly safe bet for condensing.
The important temp is actually the return temp, it typically needs to be ~55C or lower to allow condensing - the lower the better for efficiency. Usually the return temp will be 15C-20C lower than flow temp. but every system will vary so if you can physically measure the return temp. that is ideal. 

However, your radiator system will have been designed & installed to use higher flow temps. so in order to radiate the same amount of heat into the room you either need to run the system longer (but more efficiently) or replace the rads with higher output ones.

There may be (colder) days when you decide that you need to increase the flow temp. from your new "normal" for comfort (modern controls may well do this automatically using weather compensation - unfortunately your Hive & WB boiler can't communicate at the bus level to do this).

I think that 2022 may prove to be a lower than average year for heating (certainly was for me ~30% down on previous years averages) but only time will tell ...

vic_sf49

Yes, I agree with all of that.

I doubt I'll ever go as far as checking the return temps, so the system will be run at a low(er) flow temperature when possible, but high enough to keep the place warm.

At least now with hive, and the Bright App, I can get down into the weeds of the figures a bit more.

And thanks to the gazillion threads I've read on here, some of the explanations of things (condensing boiler explanations for one), have helped massively.

Ectophile

spudwood said:

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

It's about the speed at which the pump pumps water around the system.  My boiler uses an external pump, that has 3 settings: fast, medium and slow. A slower pump gives more time for the water to cool down as it goes around the radiators.  But if I set it too slow, the heat never really gets to the furthest points in the system.

Flow rate is a separate thing from temperature.  But they interact with each other.

lohr500

vic_sf49 said:

Yes, I agree with all of that.

I doubt I'll ever go as far as checking the return temps, so the system will be run at a low(er) flow temperature when possible, but high enough to keep the place warm.

At least now with hive, and the Bright App, I can get down into the weeds of the figures a bit more.

And thanks to the gazillion threads I've read on here, some of the explanations of things (condensing boiler explanations for one), have helped massively.

A reasonable quality clip on pipe thermometer made by Brannan will only cost you £11 or so and in my opinion is money well spent to check the return temperature. Search Amazon or RS Components for Brannan pipe thermometer. If you can get the return to around 45C, your boiler will be condensing nicely and working efficiently. As mentioned above, it will start condensing below 54C, but the lower the better, so long as your radiators can heat the rooms adequately.

vic_sf49

lohr500 said:

vic_sf49 said:

Yes, I agree with all of that.

I doubt I'll ever go as far as checking the return temps, so the system will be run at a low(er) flow temperature when possible, but high enough to keep the place warm.

At least now with hive, and the Bright App, I can get down into the weeds of the figures a bit more.

And thanks to the gazillion threads I've read on here, some of the explanations of things (condensing boiler explanations for one), have helped massively.

A reasonable quality clip on pipe thermometer made by Brannan will only cost you £11 or so and in my opinion is money well spent to check the return temperature. Search Amazon or RS Components for Brannan pipe thermometer. If you can get the return to around 45C, your boiler will be condensing nicely and working efficiently. As mentioned above, it will start condensing below 54C, but the lower the better, so long as your radiators can heat the rooms

 Oh, thanks for that, I could have sworn I'd seen links to those sorts of things, which were much more expensive. That's a good price.

Must overcome Sunday inertia, and look that up.... but after coffee. 

vic_sf49

And so to the potentially stupid question(s)..

Can the Brannon pipe thermometer attach / get a good enough reading from the radiator valve? Cos, err, well, plastic microbore pipework.

Also, cobwebs help with insulation don't they?

lohr500

I only use my Brannans for the flow and return temperatures on the copper pipes close to the boiler.

For checking individual radiators, I think you might struggle getting a good contact between the central sensor button on the back of the thermometer and the metal on the valve, but it might work if attached to the large nut on the valve.

I don't think they will work well on plastic microbore pipe due to both the diameter and the insulating properties of the pipe. 

vic_sf49

lohr500 said:

I only use my Brannans for the flow and return temperatures on the copper pipes close to the boiler.

For checking individual radiators, I think you might struggle getting a good contact between the central sensor button on the back of the thermometer and the metal on the valve, but it might work if attached to the large nut on the valve.

I don't think they will work well on plastic microbore pipe due to both the diameter and the insulating properties of the pipe.

 Might be worth a try with one eh. Thanks.

Defo won't be putting it on the plastic pipework.

spudwood

markin said:

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.

Hi, thanks for this. Do you mean the return water pipe to the boiler? How can I identify this pipe please?