I believe this is in reference to what they originally designed which was as an example:

A Stelrad Concord Lo-line 296x1600

v

A Eskimo 200x1694

I believe they're referring to the actual water capacity (builder said it's like 1/4 but taking that with a pinch of salt).

Found the 1/4 reference - this is by Eskimo themselves stating it uses 1/4 water volume compared to a steel rad.

Something I'll try to monitor is when the ASHP runs, the temp it's actually running at.
I just checked now and it's on.

It's 10C outside, and it's running according to the panel at 33C.  I'd expect with the W/C it to be at 37.5C atm (I've upped the minimum water temp 32C and with the max at 45C to see if that pulls temps up on milder days).

Don't suppose another Grant user knows of any settings that may be affecting this.  I'm using the ASHP WC Reckoner sheet as reference.

Settings:
2102 - 45

2103 - 32

2104 -3

2105 - 20

Can ignore that, I must have gone down to check at wrong time.  It's 38C which is about right now, return is 36C, so it's close already.  No doubt will turn itself off shortly giving no time for anything to heat up.

@crimson Sounds like the emitter is not emitting enough before the water exits to the return pipe to me. If the emitter is not ‘sucking’ enough energy from the water between entering and exiting the radiator then the DT will show up as less than ideal. My radiators show between 3 and 4 degrees delta. Could you measure the difference on the radiators in the coldest room and see if this is the cause of your grief perhaps? Regards, Toodles.

I should stick to ‘radiator’ rather than muddy the waters calling them emitters the rest of the time! Apologetically, Toodles.

Thanks @toodles , I've put 2 probes either side of a rad in the coldest downstairs room.  Will give it time and report back.  Unfortunately the ASHP is off again, so can't tell straight away.  Reckon it ran for all of 30-45 mins before turning off.

@crimson Is that an Eskimo rad? I have it in mind that the upstairs ones in cold rooms are and that is what I was thinking about. Regards, Toodles

Posted by: @crimson

↑

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.

How many zones do you have and are they in operation at the same time?

The heat pump DT reduces when the thermal energy output becomes greater than that being emitted by the heat emitters. This would normally cause the heat pump to modulate down until it reaches its lower operating limit, which of course would then lead to heat pump cycling.

If the above occurs before the room reaches the desired temperature then I suspect the required LWT is too low and/or the heat emitter capacity is too small.

I would suggest that you measure the temperature of the flow and return pipework at each radiator and see if there are any differences.

Posted by: @toodles

↑

@crimson Is that an Eskimo rad? I have it in mind that the upstairs ones in cold rooms are and that is what I was thinking about. Regards, Toodles

Ahh no sorry I probably wasn't clear.  Zone setup and rads below - rad with probes now attached in bold (width x height in mm).

Apologies if too much info:

Zone 1 (0.5C set back)

Underfloor (sits at 20.5C floor temp according to panel, probe shows around 19C-19.5C - which in that zone is comfortable)

• Kitchen/dining area
• Utility 

Zone 2 (no setback, never hits desired temp of 21-21.5C)

Downstairs (problem zone - sitting around 19.5-20c according to panel, probe in living room 2 shows 18.5C)

• Living room 1 - 2 Eskimo rads (2x 1451x200)
• Living room 2 - 2 Eskimo rads (1x 1694x200, 1x 963x200)
• Hall way - 1 Eskimo rad (233x1500)
• W/C - 1 Reina Florina towel rad (500x800)

Zone 3 (manually left on for heat dump from towel rads/landing rad)

Upstairs

(this zone is manually on)

Heat dump created by heat specialist by having:
TRVs set to Max for - landing rad, bed 3/office max, en-suite towel rad main bathroom towel and tall rad

Rest of the room TRVs set at 1-2

Sits around 19-19.5C on panel on landing, bed rooms - 18.5C, office 21-21.5C

• Bed 1 - 2 Stelrad compact with style (2x 1000x500 K1)
• En-suite - 1 Reina Florina towel rad (1235x500)
• Bed 2 - 2 Stelrad compact with style (2x 1000x500 K1)
• Bed 3 (Office) - 2 Stelrad compact with style (2x 1000x500 K1)
• Bed 4 - 2 Stelrad compact with style (2x 1000x500 K1)
• Landing - 1 Stelrad compact with style (1000x600 K1)
• Main bathroom - 1 Reina Florina towel rad (500x1235) + 1 Corex vertical rad (500x1800)

@crimson The  temperature readings from the flow and return on the problem rads might throw some light on the situation! Regards, Toodles.

Posted by: @toodles

↑

@crimson The  temperature readings from the flow and return on the problem rads might throw some light on the situation! Regards, Toodles.

thanks, currently 29c TRV side, 28.5C lock shield side. ASHP off, showing 34C Just before heating zone (5C Drop to that rad it seems)

Posted by: @crimson

↑

I believe this is in reference to what they originally designed which was as an example:

A Stelrad Concord Lo-line 296x1600

v

A Eskimo 200x1694

 

I believe they're referring to the actual water capacity (builder said it's like 1/4 but taking that with a pinch of salt).

 

Found the 1/4 reference - this is by Eskimo themselves stating it uses 1/4 water volume compared to a steel rad.

According to the manufacturer's websites, the Stelrad is rated at 1784 Watts and the Eskimo at 1540 Watts, I assume at DT50.

What is the calculated heat loss for the rooms in question and the design flow temperature?