I believe it’s all been balanced. Chap said they’re all filling up well once got air out system.

Other half has moaned it’s now too warm so dropping WC at top temp to 43C to see if pulls down a little. Now we’re not using thermostat upstairs that’s a game of adjust down TRVs. We tend to have hall door to kitchen diner (underfloor zone) open so now it’s likely that’s not compensating for hall being bit cooler so brought that down. Going to be a balancing act.

Downstairs zone was 21C this morning, living room probe 19.5C. That’s with WC set at previous post. Will see where it is tomorrow with top temp at 43C.

Seems ASHP still cycles but longer runs.

Seeing as upstairs and underfloor zones basically hit temps no issue and very quickly I think logical thing now is oversize the downstairs rads more. I could live with the hallway rad as is as landing one above seems to help. Living room ones just need to get temp quicker really.

Obviously it’s 11C outside so hard to judge how would be in a proper cold snap.

hear dump approach seemed to have had a good impact and obvious benefit of having towel rads that are warm is always useful.

Having the largest heat emitting capacity will always be useful within a heat pump based heating system, but it should be remembered that the lowest operational LWT will be set by the most difficult room to heat. Heat emitters should therefore be sized to try to match the heat loss of each room at the same operational LWT.

Correct balancing of a heating system is not an easy task, since external effects such as solar gain, human activity, wind chill and rain effect may all cause variations to individual room temperatures.

I suspect that to balance a heating system from scratch it would be necessary to fully open all the valves, TRV's, lockshield and flow regulators, and allow the temperatures in each room to stabilise, while the heat pump is operated in as steady state as possible. This should allow the coldest, most difficult room to heat, to be identified, and also the warmest, easiest room to heat, will become apparent. Ideally this should be carried out on a day when external effects are likely at a minimum.

The valves on the heat emitters in the coldest room should be left fully open, and the temperature in the other rooms should be adjusted to the desired value using the lockshield valves, with any TRV's kept fully open. Starting with the warmest room, gradually reduce the flowrate until the desired room temperature is achieved, then repeat the process in the next warmest room, and so on and so forth. It may be necessary to repeat the process until all the desired room temperatures are achieved.

Once the system is correctly balanced, changing the LWT should have a fairly constant effect in all the rooms within the home.

@derek-m Being in the position of having plenty of time as I am retired (and being a bit of a nerd!), I instructed the installers to carry out the first stage of radiator balancing as I would continue the job as the weather might permit. The 19th. Of February 2023 was a very mild day (commissioning day) and hardly conducive to setting up heating systems! Over succeeding weeks, I performed the tweaking exactly as you describe and must have carried out 5 rounds of adjustments to the lockshield valves before I felt satisfied with my efforts. Our house is effectively, ‘open plan’ as internal doors are usually door-wedged open and we wanted a similar temperature throughout the house. I use one Hive programmable TRV in our bedroom for cooler nights but the rest of the emitters run without any further interventions 7 days a week. Regards, Toodles.

Not posted for a little while as been busy with other things.

I've kept the system on Grant's default WC settings.  It's been mostly quite mild so hard to test.  Downstairs keeps at reported 20C on panel, about 19-19.5C in the room.  It's ok, could use being warmer.

I followed up with builder on what the heat specialist thought could be done with rad sizing.  He reviewed the calcs and found he reckons they are correctly sized output wise.  The issue however seeing as having a heat dump upstairs had an effect is – the amount of water these eskimo rads require is around 1/4 of a standard rad and only 5 rads the zone is proportionally small.  Current thinking is a buffer tank or volumizer may help with that.

Well I'm now currently stuck in a who's liable for installing the buffer tank for this install / myself querying is this 100% going to rectify the issue over just upsizing the rads.

Frustrated to say the least, as wording being used is "to make system more efficient", which I wholly don't agree with as I'm left with a zone that doesn't get to temperature unless the ASHP is throwing 45C constant.

What are thoughts on buffer tanks in these setups?

Have you checked that the valves on both ends of the radiators are correctly adjusted? Any TRV's should be fully open and the lockshield valves should be adjusted to balance the room temperatures.

@derek-m And at the risk of teaching grandmother to suck eggs… Open the lockshield valve fully anticlockwise to start off and unless you have a problem elsewhere, the radiator should start to warm up. Once you have stripped down to your tee shirt, you can start closing the lockshield clockwise in half turn adjustments and allowing time to cool. Regards, Toodles.

Hi both, the rads heat when the ASHP runs, I don't believe there's any issue there, this was something the heat specialist checked (bled, check TRVs on max and checked the lock shield valves etc).  The issue seems to be as the ASHP runs, after not long the flow and return temps get close meaning then the ASHP turns off, not leaving enough time for the rads to get the room to temp.  The heat dump creation by having upstairs landing rad, and towel rads call for temp (zone valve manually left on) constantly reduced the amount of cycles but doesn't seem to have done the trick.

@crimson If “The issue seems to be as the ASHP runs, after not long the flow and return temps get close meaning then the ASHP turns off, not leaving enough time for the rads to get the room to temp.” That suggests that the radiators are not able to emit sufficient heat to allow for the return flow to run cool enough - are you sure the radiators are large enough for the space they should heat? Regards, Toodles.

Thanks Toodles, this is the ongoing back and forth unfortunately with the builder, plumber and now heat specialist.  According to the builder the heat specialist looked at calcs and the Eskimo specs and feels they have the correct output.  However the water volume they hold on this smaller circuit doesn't seem sufficient, hence suggestion of a buffer tank/volumiser.  In my mind it's at the point of just double the height of them to get more from them but they seem to be holding against that (cost I suspect of works to do so).

In the interest of not trusting a soul who's been involved in the project, I've just checked the lock shields.  A slight turn remained on hallway rad anti-clockwise.  Then final rad in a living room, similar.  The other in that room took a good bit of turning anti-clockwise.  Will see if yields anything overnight.  ASHP currently off.

@crimson There is a practice with valves being opened fully then cranked back a fraction to make it easier to free up if at some time in the future, the valve needs to be closed and it has siezed, the valve can be ‘rocked’ in either rotation alternately to free it up. This applies to most if not all valves, not just lockshields, I had this tip from a plumber of some 40+ years of plumbing. It still sounds as though the water is not losing enough energy during the time it is passing through the radiator; you say that the radiator has a much smaller volume of water capacity - any idea why they have been designed that way? Regards, Toodles.

And one more thought: if the radiator contains less water, then it would need to be able to extract more thermal energy from the smaller amount of water passing through it to provide the same heat output - in this case the water entering the return pipe should be much cooler than for ‘conventional’ radiator designs. This suggests the Delta T would be at least 15 degrees! From your details, it doesn’t sound as though this is the case though. Regards, Toodles.