How to optimise your combi boiler

jpaul said:
you live in the UK and your house is holding 20C at the moment .. I'm in a <10 year old place, yes - windows have been open during the day, and kitchen whilst cooking, but it's 17C in the hall.
e: trickle vents aren't closed otherwise it'll be stuffy, equally bedroom windows open a jar at night time.
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Not quite. The boiler output is always warmer than the house. The boiler return is more indicative of the house temperature.

As I type this, outside temp is 7'C, boiler output is 19.3 'C (still cooling from the heating last night / never drops too low due to also getting warmed slightly when hot water demand comes on), boiler return is 13.8'C (probably reflecting the temperature on the inside of the wall to which it's attached) and the room temp downstairs is 16 'C according to both the thermostat and another temperature logger sat next to it.

EDIT - I think the thermal probes are off slightly. I reckon they are both actually 16 'C, having just measured them with another device.

House is shut up tight as I can make it it winter to preserve heat. Old double glazing (assume original from when house built ~1985) gets condensation on overnight, but I vacuum it off in the morning and we don't have any damp problems.
 
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You folks have me interested in using some thermocouples to measure the temps in each room vs the flow delta.

I have a multimeter that can measure to thermocouples and delta but a small ardunio with wifi would be useful to connect to the CH pipes fom the boiler too. Any suggestions what people have been using?

We will typically close the living room doors (sealing off from kitchen and stars) which means in the evening the house cools upstairs but remains warm in the living room (single thermostat in living room).
We have TRVs on all except the living room radiator. So initially i’m interested in optimising each radiator delta.
 
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I see Drayton valves now have the auto-balancing.
If and when I change my radiators I'll be fitting these, they might work with a fully smart system.
 
robj20 said:
I see Drayton valves now have the auto-balancing.
If and when I change my radiators I'll be fitting these, they might work with a fully smart system.
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I used Drayton TRVs but never again, the plastic cannot handle the thermal cycling of normal use and breaks resulting in the rad fully open - we had this on all but the coolest of radiators. Not fit for purpose!
 
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After having realised my boiler is actually condensing earlier in the year, i've dug out the instruction manual online and turned off the auto heat for water thing and changed the rad temp down from something like 68 to 52. Also upsized 3 of my radiators with a further 2 to be installed following my internal insulation upgrades earlier in the year. Temp is increased and house feels much more comfortable!
 
Actually it's not true that it doesn't help with standard boilers.

If you reduce the flow temperature it reduces the maximum temperature that your hot water tank reaches. But this is actually a good thing. The cooler the hot water tank the slower it loses heat, so it's ideal to keep it hot but not too hot. Lowering the boiler temperature down keeps the tank cooler, which is good. The temperature setting on the tank itself is more to do with quantity of hot water than temperature and usually doesn't need to be adjusted. However, if the boiler is lowered a lot then the tank thermostat may need a tweak downwards too.
 
NickK said:
I used Drayton TRVs but never again, the plastic cannot handle the thermal cycling of normal use and breaks resulting in the rad fully open - we had this on all but the coolest of radiators. Not fit for purpose!
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I don't have any of their TRVS just the valves.
 
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robj20 said:
Those valves look odd, would they allow a standard head to fit, ie a Honeywell TRV.

Just after self balancing valves as manually balancing isn't an option.
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You're absolutely right. You have to use the Danfoss heads. Agreed, manual balancing doesn't work. I'm having the Danfoss valves put it next week and I'm very excited.

Altecnic, as much as I hate to mention them, also do some https://www.altecnic.co.uk/wp/wp-content/uploads/resource-files/230_231_Dynamical_TRV_Leaflet.pdf
 
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SpellowHouse said:
Actually it's not true that it doesn't help with standard boilers.

If you reduce the flow temperature it reduces the maximum temperature that your hot water tank reaches. But this is actually a good thing. The cooler the hot water tank the slower it loses heat, so it's ideal to keep it hot but not too hot. Lowering the boiler temperature down keeps the tank cooler, which is good. The temperature setting on the tank itself is more to do with quantity of hot water than temperature and usually doesn't need to be adjusted. However, if the boiler is lowered a lot then the tank thermostat may need a tweak downwards too.
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I presume this is aimed at me, think you've misread as I have a combi boiler and no tank, and the temp reduction is on the rads, with the autoheat function turned off for my instant hot water supply.
 
Just for a bit of context, before we install pressure independent TRVs in my house we've done a manual balancing. This was three engineers...we've achieved a 10C dT once everything had warmed up a bit (more like 15C when the rads were completely cold).

Hoping the PITRVs will be installed next week and that dT will jump up!
 
dirtychinchilla said:
I'm having the Danfoss valves put it next week and I'm very excited.
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Looking at the RAS-B2 dynamic radiator pack would I be right in thinking that a lockshield valve is no longer fitted to the outlet? How much are you getting them for?

Do let us know how you get on with them, I'm keen to replace almost all my valves with the dynamics as part of system optimisation. It's a shame you can only use the Danfoss thermostatic heads on them as I did consider putting the Hive smart TRVs on.
 
Mysterae_ said:
Looking at the RAS-B2 dynamic radiator pack would I be right in thinking that a lockshield valve is no longer fitted to the outlet? How much are you getting them for?

Do let us know how you get on with them, I'm keen to replace almost all my valves with the dynamics as part of system optimisation. It's a shame you can only use the Danfoss thermostatic heads on them as I did consider putting the Hive smart TRVs on.
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I think it’s them, but we sell them under a different brand so I’m not 100% sure. Free of charge as I work there :) they aren’t cheap I’m afraid.

Yeah so you can replace both the Lockshield and the TRV but only if you want the finish to be identical. I’m actually just replacing the TRV because the Lockshield already looks very similar.

I’m told they do a Bluetooth smart home head for the TRVs, but I’ll not be using them. I guess they integrate with Home Assistant.
 
At around £26 for the dynamic valve, the TRV, a replacement non-lockshield replacement and even a painter's cap I think is pretty good value.

https://www.wolseley.co.uk/product/danfoss-ras-b2-dynamic-radiator-pack-15mm/

If you are fitting a lot of them then the cost does mount up. I think I'll aim to fit them to the upstairs zone first as that's where I have the particular balancing issue.
 
Mysterae_ said:
At around £26 for the dynamic valve, the TRV, a replacement non-lockshield replacement and even a painter's cap I think is pretty good value.

https://www.wolseley.co.uk/product/danfoss-ras-b2-dynamic-radiator-pack-15mm/

If you are fitting a lot of them then the cost does mount up. I think I'll aim to fit them to the upstairs zone first as that's where I have the particular balancing issue.
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Awesome. With prices increasing as they are, they should be helpful. We haven’t tested with a combi boiler until now, but we’re expecting to increase efficiency by upping reducing the flow temperature and upping the dT (reducing return temp as well). I’ve been struggling to get as much heat out of the rads as I think they can achieve.

Let me know how you get on!
 
I noticed my combi was starting to struggle to heat the house with the temperature drop, I recently dropped the rad temp to 60c and the boiler was struggling to hit the target temp on the thermostat, everything I was reading on the internet was stating to achieve condensing mode and have your boiler run as economical as possible the rad temp must be as low as possible and return at 55

I've been monitoring mine with 60, 65 and 70 over a few days and the boiler is able to achieve the target temp and the house feels much more comfortable at 70c, seems to be using less gas running at a higher temp and shutting off rather than constantly running at a lower temp as it's able to hit the target thermostat temperature much easier

I think it's all to do with the age and type of house, mines a 1960's semi with cavity walls so no where near as efficient as a modern build which would likely be able to get away with the lower flow temps
 
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Relentless81 said:
I noticed my combi was starting to struggle to heat the house with the temperature drop, I recently dropped the rad temp to 60c and the boiler was struggling to hit the target temp on the thermostat, everything I was reading on the internet was stating to achieve condensing mode and have your boiler run as economical as possible the rad temp must be as low as possible and return at 55

I've been monitoring mine with 60, 65 and 70 over a few days and the boiler is able to achieve the target temp and the house feels much more comfortable at 70c, seems to be using less gas running at a higher temp and shutting off rather than constantly running at a lower temp as it's able to hit the target thermostat temperature much easier

I think it's all to do with the age and type of house, mines a 1960's semi with cavity walls so no where near as efficient as a modern build which would likely be able to get away with the lower flow temps
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Assuming you're using TRVs, you could try keeping the flow temp at 60C but setting TRVs on your rads a little higher and seeing how you get on.
Aim is to get the same amount of kw into the rooms as you were getting at 70C flow that you found comfortable but achieve it at 60C, means you've got to let more in at the lower flow temp.
 
eddyr said:
Assuming you're using TRVs, you could try keeping the flow temp at 60C but setting TRVs on your rads a little higher and seeing how you get on.
Aim is to get the same amount of kw into the rooms as you were getting at 70C flow that you found comfortable but achieve it at 60C, means you've got to let more in at the lower flow temp.
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but what if your TRVs are already opened to the max and temps are still shoot at 60C flow??? mine works way better at 70C and thats where its staying
 
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