Smart TRV

Albermarle

RavingMad said:

We replaced our boiler in Aug and the engineer went round making sure they were all heating as expected.  The lounge radiator was replaced too with a bigger one as it never warmed the room sufficiently.

It's a WB heat only boiler so no flow temps to tinker with. I did think today to crank the one dial on the boiler to max rather than 70/80% that it's on now. That'll heat up the water quicker albeit use more energy?

That dial is for the flow temperature, for some reason some WB boilers do not actually mark temperatures on the dial, but 75% would be around 70 C.
This is already quite high and the boiler will probably not be working at maximum efficiency. If you crank it up higher, you will:
1) Use more gas - so more cost and environmental impact.
2) The rooms will heat up a bit quicker.
3) The radiators could get so hot that you could burn yourself on them, especially an issue if any children or vulnerable people in the house.
4) Probably will be shortening the life of the boiler.

The current flow temperature could be OK if we have a very frosty spell, but currently I would turn it down rather than up .

FreeBear

Albermarle said: The current flow temperature could be OK if we have a very frosty spell, but currently I would turn it down rather than up .

CH heating systems used to be designed & specified using a flow temperature of 80°C. Then condensing boilers became mandatory, and flow temperatures dropped to 70°C. In more recent years, there has been a push to use 60°C or lower. A lower flow temperature (more correctly, the return temperature) pushes the boiler further in to condensing mode which leads to higher efficiency.

On a typical winter day, a system designed to run at 70°C will still keep most houses warm with a 50°C temperature. With a frost outside, going to 60°C may be needed, and the 70°C (or higher) reserved for subzero weather (-10°C). With weather compensation enabled on the boiler (and a WB will be able to do this as long as there is an external sensor), changing the flow temperature would be done automatically.

This graph plots efficiency against return temperature (nominally, 20°C less than flow temperature).

RavingMad

Thanks I'll bear that in mind.  Happy for DHW to take longer to heat up but would have to have a happy medium for length of time it takes to warm rooms up. So might try 50% in the summer and turn the dial to 60 now to see if there's a marked difference in heating times. I'm all for efficiency but not if the rest of the family nag at me lol

Correct about not having any markings on the dial, though.  

ThisIsWeird

RavingMad said:

Thanks I'll bear that in mind.  Happy for DHW to take longer to heat up but would have to have a happy medium for length of time it takes to warm rooms up. So might try 50% in the summer and turn the dial to 60 now to see if there's a marked difference in heating times. I'm all for efficiency but not if the rest of the family nag at me lol

Correct about not having any markings on the dial, though.  

Ah, only a single flow temp for both CH and DHW? In which case, yup - you'll want to keep that as high as you currently have, or else the DHW could take an age to heat up.

If you turn the flow temp down towards, say, 60oC, then you can see that the heat transfer to the DHW cylinder as the stored water approaches that temp will be minimal = slow = unhappy families.

Your boiler should still be largely condensing at your current ~70oC flow temp (much cooler return), and any further efficiency savings by tweaking down the flow temp are unlikely to be worth the drawbacks, imo.

Albermarle

ThisIsWeird said:

RavingMad said:

Thanks I'll bear that in mind.  Happy for DHW to take longer to heat up but would have to have a happy medium for length of time it takes to warm rooms up. So might try 50% in the summer and turn the dial to 60 now to see if there's a marked difference in heating times. I'm all for efficiency but not if the rest of the family nag at me lol

Correct about not having any markings on the dial, though.  

Ah, only a single flow temp for both CH and DHW? In which case, yup - you'll want to keep that as high as you currently have, or else the DHW could take an age to heat up.

If you turn the flow temp down towards, say, 60oC, then you can see that the heat transfer to the DHW cylinder as the stored water approaches that temp will be minimal = slow = unhappy families.

Your boiler should still be largely condensing at your current ~70oC flow temp (much cooler return), and any further efficiency savings by tweaking down the flow temp are unlikely to be worth the drawbacks, imo.

I have a heat only WB boiler. Currently it is set to around 60C ( as no temp markings on the dial this is an estimate) and the thermostat on the hot water tank is set about the same.
The hot water is on for maximum one hour a day, sometimes less,  and it supplies enough for 3 or 4 showers.
The water feels hot enough out of the tap, but not scalding.
The radiators are also plenty hot enough, for this time of year at least.
One point is though that normally the hot water is not on at the same time as the heating, so maybe that helps the water heat up quicker/ need to be on for less time.

Correct about not having any markings on the dial, though.  

OP - I assume you have a similar model to me ( Greenstar RI) The range on the dial is from 35 to 82 degrees ( from the manual)  Centigrade. So if you have it at least half way around it will be around 60 degrees. If you have it 75% the way around it will be around 70 degrees, and two thirds the way around something inbetween. 
By the way neither my better half or my daughter ever complain about the heating or hot water, although they complain about many other things 

RavingMad

Yes, Greenstar Ri 21  I've turned it down a notch to two thirds I'm guessing, so I'll monitor timings.  Approx an hour this morning to go from 17⁰ to 19⁰ according to Hive app.

Albermarle

RavingMad said:

Yes, Greenstar Ri 21  I've turned it down a notch to two thirds I'm guessing, so I'll monitor timings.  Approx an hour this morning to go from 17⁰ to 19⁰ according to Hive app.

A '21' should be easily powerful enough to heat a relatively large house and the hot water.
A lot though depends on the layout of the house, how old it is, is it well insulated, draughty  etc 

FreeBear

RavingMad said: Yes, Greenstar Ri 21

Just skimmed the Ri installation manual - No mention of PDHW, which is a disappointment. If you have an S or Y plan system, it might still be possible to fake it with the right control (Wiser 2-channel perhaps).