Posted by: @eggchaser

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Hi, I have a simple question, should I balance each Radiator to a DT of 5 or leave the System to manage the flow rate and temperature DT with the lock shields all open?

BTW We do not have any cold rads or rooms when they are all open on the lock shields...

Our system has been sized right, we have the right size radiators in each room + a full re-pipe (28mm backbone), our Daikin system is on weather comp and the highest the flow rate has been 35 degrees this year so far….the system was installed in the summertime so we could not balance the radiators if needed.

thanks Neil

I would suggest that you leave the system as it is for the time being, but monitor the temperature in each room. If any particular room starts getting too warm, then make an adjustment as required.

@derek-m thanks for the reply, I will monitor each room, I have noticed the room with the madoka thermostat heats quickly, it has 3 radiators....have balanced one down and will double check in a few days

@derek-m Similarly, our Daikin system was commissioned in mid-February and thus I could only crudely set the DT for the radiators in that milder weather (a week or two earlier would have been another matter!); having done my best to balance them (found that a DT of 4 to 4.5 across the ten radiators was as close as I could get. My installer told me that with a low-loss header, the DT setting on individual radiators is not as critical by any means, I found a ‘comfortable and quiet running speed for the Wilo variable speed pump seems to allow for a steady performance and although I am now settling in with a Homely smart controller from Evergreen Energy - I found that the MMI did a pretty reasonable job of keeping a constant temperature. I had LWT set to 38 degrees and WC switched on. I have tweaked a few radiators since the cooler weather arrived a few weeks back but have tried to avoid imposing controls from TRV’s on the emitters preferring to balance all the radiators (this is better heat pump practice anyway), I have just one Hive TRV in the bedroom for reducing temperature at night as we have the HP on 24/7 at a constant setting. As I have a secondary pump, using the original Heatmiser stat meant that if I wanted the HP to control things, I had to leave the Wilo pump on 24 hours; this is now controlled by the Homely and does switch off when the HP does. Regards, Toodles.

Thanks for the guidance, we do not have a buffet vessel/low loss header, just the one pump within the monoblock that I can see changing the flow rate on the MMI, I have strapped some sensors on the flow and return, and can see within home assistant a DT between 3 and 5....when its maintaining temp, it's using between 300 and 500 watts, that appears to be good, but I do not have a reference to compare, we have an 8kW system

Posted by: @eggchaser

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@derek-m thanks for the reply, I will monitor each room, I have noticed the room with the madoka thermostat heats quickly, it has 3 radiators....have balanced one down and will double check in a few days

You are obviously already aware that for best overall efficiency, water should flow through the maximum heat emitter capacity.

It is very unlikely that the heat emitter capacity will match the heat loss in each room, also the water flowing from the pump will take the route of least resistance, which is why balancing can be necessary.

I am of the opinion that balancing should be to match the thermal energy supply to the thermal energy loss in each room, rather than trying to achieve a specific Delta T (DT) at each heat emitter. This of course to achieve the desired room temperature.

Correctly balancing your system is not a 5 minute job, and may need to be performed over quite a number of weeks. As they say, patience is a virtue.

Posted by: @eggchaser

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Thanks for the guidance, we do not have a buffet vessel/low loss header, just the one pump within the monoblock that I can see changing the flow rate on the MMI, I have strapped some sensors on the flow and return, and can see within home assistant a DT between 3 and 5....when its maintaining temp, it's using between 300 and 500 watts, that appears to be good, but I do not have a reference to compare, we have an 8kW system

I believe that some heat pump try to maintain a fairly constant DT, by varying the water flow rate, while other keep a fairly constant water flow rate and allow the DT to vary.

A 8kW heat pump drawing 500W of electrical energy, probably at a COP of 4 or higher at the moment, should be producing 2kW or more of thermal energy. The heat pump will try to meet the demand, which in CH mode will be your home's heat loss. Obviously as the Outside Air Temperature (OAT) reduces, the heat loss increases, and the heat pump has to work harder to supply the demand.

Because heat pumps obtain much of this thermal energy from the OAT, as OAT reduces, so does the amount of thermal energy that is available, the heat pumps efficiency (COP) reduces, which disproportionately increases the quantity of electrical energy required to operate the system.

In basic terms, as the weather gets colder, the heat pump becomes less efficient, and uses more electrical energy. Keeping the Leaving Water Temperature (LWT) at the lowest value that meets the heating demand, helps to keep electrical energy consumption to a minimum.

@derek-m Ours is also an 8 kW system; (Daikin EDL08E2V3) in a 4 bedroomed semi with good insulation (EPC of ‘B’) I have spent a few happy hours 😉 tweaking the lockshields. I have 5 of them fully open and the other four* in tweaked positions. We like to keep the bathroom a few degrees warmer and so this radiator is fully unrestricted to water flow. Though I do wonder whether the manufacturer’s ‘fully open’ is indeed fully open and not restricting flow at all. * The tenth radiator has a Hive TRV for reduction at night but during the day it is also fully open. We do not shut any internal doors normally and air flow means temperatures are very consistent but there are no draughts so I think the balance must be pretty close. I have placed 8 Govee thermometers around the house and they indicate within 0.5 degrees of eachother nearly all the time, except the bathroom of course. Regards, Toodles.

@toodles

I think that you may find that even when fully open, the valve internals will have a smaller diameter than the attached pipework. Also radiators, and their associated valves, were probably designed for use with gas or oil boilers, operating at a DT of 20C and correspondingly lower flowrate. When used with a heat pump at a DT of 5C, the flowrate would need to be 4 times greater to transfer the same quantity of thermal energy, which in turn increases the pressure drop across any valves, thereby limiting the possible flowrate.

@derek-m Thank you Derek M, I suspect that we are right to be a little suspicious of ‘fully open’ being very close to totally unrestricted; so direct pipework without a valve body would actually increase flow - but, yes I can see there are snags to that too!. Regards, Toodles.

Thanks for all the great advice, yes, I think it will take a while to figure out the optimal setup, the Daikin controller is rather independent controlling the flow rate and temp to manage the DT.
I have gone with all down-stairs rads are fully open on the lock Shields and TRVs, except one out of three (DT 5 via the lock shield) in the room with the madoka as this room heats up quickly even at a flow temp peaking at 35 (the system has been designed to 45 but have Weather compensation with 10 degree modulation)...upstairs is all open on the lock shields but the TRV set to a room (floor) temp of 18 Degrees. Our heating is on 24/7 with no setback (I work from home), also all doors are also left open except the stairs. take care Neil