Unscrew and remove the top cap, inside you will find a 6mm hex grub screw, which is the actual lockshield valve.
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Thanks all for the help,
There was half a turn left before fully open on that rad, the temp differential on it is now down to around 5 degs.
Been walking around the house with my FLIR and keeping a day by day record. Looks like I can restrict all the rads but one on the first floor as an experiment to get all the rads to roughly the same temp, then see if the rooms are in fact then roughly the same temp which is at the end of the day the greater point.
All a learning experience… 
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You can then see if a single radator is unsized compared to the others, if so, replacing it will allow a lower flow temperature.
Am I reading right? Is your heat pump deltaT 2-3 degC but the radiator detaT 10 degC?
If yes… you want to look for a bypass in the system that’s sending the hot water from the heat pump straight back to the return… and eliminate it.
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Hi Marko,
Nope, the range between the coldest to hotest parts in the panel of the radiator was 10 degrees.
I opened up the lockshield valve fully on the radiator and now the differential is 5 degs.
So the issue on that one rad was caused by the flow being too restricted via the lockshield.
Hi Folks,
Firstly thanks so much for all the help everyone, much appreciated.
Think I am ready to get back to my installer. Before this however I thought I would summerise where I am at, then hopefully ask a final couple of questions if you don’t mind.
- We have a detached house in Scotland. Around 30 years old, 95m2 in size and with insulation which tally’s to a house built in that period I would speculate
- We were advised to upgrade our radiators, but decided not to for a year to see where we sit.
- Aerotherm 5+, curve 0.6, daytime temp 17.5, going to 16 overnight.
- All visible pipes to rads not microbore, but can see microbore pipes via a manofold through a hatch in the kitchen. I cannot access this underfloor space to see where they go, might be to the sinks/bath/showers upstairs.
- When in standby, the temp deltaT between the out and return flows is 0.4 deg with the return being wamer than the flow. This must be caused by a poorly calibrated temp sensor.
- When the pump is on, the deltaT between the flow and return temp is 2 deg.
- We are unhappy with our COP versus what should be expected for our heat curve/outside temp/desired indoor temp. However the sensor issue noted above is prob leading to the COP being underestimated by 20% or more.
- Although our COP has been low, our heating bills have also been low.
- Earlier in the year with the milder weather, plus our low desired temp, some of the low COP could be explained by cycling.
- We have experimented with Active versus expanded modes and it doesn’t seem to move the dial COP wise much if at all.
- It has been fairly cold here for the last few days. However even though the house warms slowly, we have been able to reach our desired room temp of 17.5 even at -5 outside.
Taking just heating, ignoring DHW:
Yesterday the outdoor temp has averaged -0.5, indoor 17.2.
We used 17.1 kWh
COP was 2.5 - If we assume that the COP is 20% under-represented, then the COP would be 3
Today at 5pm. Outdoor temp has averaged -3.7, indoor 16.7.
Used 16.4kWh so far
COP so far is 2.2 - If we assume that the COP is 20% under-represented, then the COP would be 2.6
So first question, do the above figures seem bad/reasonable/good to you guys?
Looking at the actual monthly bills cost, we are doing far better than our old gas boiler. But then it was quite old…
Second question relates to the size of the rads. As mentioned above the installer said that as far as the heat loss calcs specified, we should upgrade all our rads.
However he also advised that based on his local knowledge, we should try it out for a year and see where we are.
Once I get back to him, in case he mentions the rads I just want to make sure that the I have something clear in my mind.
Am I right in saying that the size of the rads and it’s affect on the COP purely relates to the fact that with undersized rads a higher heat curve needs to be used, and hence higher flow temps?
Lets say we clone my house in the same geographic locale as a thought experiment. In one house we have the size of rads as they are now in my house, in the other the larger rads as stipulated in the heat loss calcs.
In both houses the heat curves, desired indoors temps and all other settings are identical.
Firstly I would expect that the heat bills in the cloned house would be lower as it would reach the desired temperature quicker. (when in expanded mode so indoor temp used to cut off the heating)
However, because in both houses the flow temps are always identical, would the COP then be the same?
Or can the size of the rads also affect the COP in this scenario, presumably because the cloned house would reach the desired temp quicker than my house, then just cycle?
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