Posted by: @marzipan71

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Hi all – reading @toodles thread here got me thinking about my own system…we have a 16kW Daikin Altherma HT feeding two zones – UFH and radiators, running on WC, in-room stats functioning as on/ off only. We have 7 radiators mostly quoted at around 1800W (T50) with one large unit quoted at 4400W (T50), all ground floor, 12 or 15mm (legacy) pipework (table below). All the rads have TRV locked fully open, and prior to this week all the lockshields were fully open also. Delta T is set at the ASHP at 8; secondary (auxiliary) pump is set to 3 on the UFH loop, constant pressure (only way to get flow rates above 1 – another story…), and 1 on the rads loop, proportional pressure – I’ve tried this pump on 2 but I get a whooshing noise in the rads and Caleffi tell me that means the pump needs to be dialled down. There is a LLH in the system. When I started up the system this winter I cleaned and flushed with Caleffi C3 cleaner then added Caleffi C1 inhibitor.

I’ve been fiddling with the lockshields this past week to try to get them all to be a similar temperature which has been partially successful – most are set a quarter turn or less open. I have a digital laser thermometer thing to measure the temps. Reading various bits on the internet I see there’s meant to be a delta T across each radiator which I’m just not seeing with my radiators – at most 1 or 2 degrees.

I did some tracing back through the system and below are some temps at various points (photos attached):

Daikin Controller (OAT only) - LWT	39.6
Daikin Controller (OAT only) - RWT	31.1
Pipe gauge on rad loop near to ASHP - LWT	34
Pipe gauge on rad loop near to ASHP - RWT	29

 

The temps on the radiator manifold at points A and B on the photo are 34.9 and 30.5 respectively; then the pipe temps are:

	Upper	Lower
1	26.1	25.0
2	26.3	26.0
3	24.3	23.0
4	24.5	22.9
5	23.4	22.3
6	24.0	23.2
7	24.5	22.5

...which are more or less comparable to the flow and return temps at the radiators (I have no idea which pipes lead to which radiators, alas).

Does the above look right?

• A LWT of 39.6 from the ASHP dropping to 34.9 at the manifold, and then immediately dropping to 22-26 at the pipes on the same manifold (e.g., between 'A' and '1')?
• Negligible temperature difference between the flow and return temps on the pipes? Are the pipe sizes too small?
• Big difference between the RWT measured at the pipe gauge near the ASHP and the actual return temps at the manifold?

Is there anything I should be doing that I’m not? Should I be worrying at all? Thanks for any advice or help as ever.

 

I would suggest that you check the specified accuracy of your laser thermometer and maybe try a more convention type thermometer pushed underneath the pipe insulation.

When carrying out tests, the first thing should be to ascertain the accuracy of the readings obtained.

Hi @derek-m thanks for the pointer. I'm using one of these and one of the use cases they give is for checking heating performance; that said, I checked the manual and they claim an accuracy of +/- 1.8C between 0 and 100, which admittedly isn't great if I'm looking at differences in flow and return temps of ca. 1 to 2C...! Nonetheless, even with that possible error added to the pipe temps at the manifold there's still what looks like a significant drop-off between the Daikin-claimed LWT of 39 and the temp at the pipework at the manifold (e.g., 26.3 +/- 1.8C for the warmest pipe). I was just wondering if that is normal/ to be expected. Of course, the Daikin-claimed RWT is 31 and that doesn't agree at all with the (presumed) return temps at the manifold of 22-26 +/- 1.8C. Maybe the individual thermometer I have is faulty, or the Daikin controller is faulty, or maybe something else is going on between the Daikin controller and the rads that is somebody here can identify and which may help me improve efficiency.

Posted by: @marzipan71

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Hi @derek-m thanks for the pointer. I'm using one of these and one of the use cases they give is for checking heating performance; that said, I checked the manual and they claim an accuracy of +/- 1.8C between 0 and 100, which admittedly isn't great if I'm looking at differences in flow and return temps of ca. 1 to 2C...! Nonetheless, even with that possible error added to the pipe temps at the manifold there's still what looks like a significant drop-off between the Daikin-claimed LWT of 39 and the temp at the pipework at the manifold (e.g., 26.3 +/- 1.8C for the warmest pipe). I was just wondering if that is normal/ to be expected. Of course, the Daikin-claimed RWT is 31 and that doesn't agree at all with the (presumed) return temps at the manifold of 22-26 +/- 1.8C. Maybe the individual thermometer I have is faulty, or the Daikin controller is faulty, or maybe something else is going on between the Daikin controller and the rads that is somebody here can identify and which may help me improve efficiency.

Do you have a buffer tank or LLH?

Yes I mentioned in the (overlong) intro post that there's an LLH, which I suspect may be important...

Posted by: @marzipan71

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Yes I mentioned in the (overlong) intro post that there's an LLH, which I suspect may be important...

Try measuring the temperatures at the LLH, if there are large differences then the primary and secondary flowrates are not balanced.

How many water pumps do you have and what are their speed settings?

Hi @derek-m thanks for reply, apologies for delay – kids football got in the way of me tinkering with the LLH. So – photo attached of the LLH with apologies in advance for the state of the insulation – its on the to-do list to upgrade. Current LWT and RWT indicated on the Daikin controller are 34.5 and 28.3 respectively. The temps (all temps below +/-1.8C) at the 4 points indicated are:

1 – 34.2

2 – 28.4

3 – 36.4

4 – 28.7

I checked the temps at the radiator manifold and (per photo) the temps are:

A – 33.8

B – 28.3

The temps of the 1-7 radiator pipes are in the range 22-24C, so still seeing that drop at the manifold from the large pipes (A and B) temps as soon as the water enters the smaller copper piping. I don't understand why there is a ca. 10 degree drop in temp between pipes A and B and the pipes labelled 1-7 in the manifold photo - Daikin controller says 34.5 and it seems to be arriving at the manifold at 33.8 or so, but then immediately drops to 22-24 at the piping.

We have two auxiliary Evosta 2 pumps – model is the 4-70/150 SAN. There is one for each zone – UFH and rads. The one in the LLH pic is a recirculation pump for the DHW which is permanently off. The radiator pump is set to speed 1 (lowest) of 3, proportional pressure. I’ve tried this on speed 2 and get a whooshing sound in the radiators, which have all been bled this season, and which Caleffi say (the valves are all Caleffi) ‘A sound or hissing noise during modulation is due to the fact that the valve is subjected to an excessive head’ which I assumed translated to advice to drop the pump speed back to 1.

The pump for the UFH has been at speed 3 (highest), constant pressure, for the past few weeks. My UFH manifolds do not have manifold pumps and do not have actuators. There is one manifold for the UFH zone for the 3 ground floor bedrooms and bathrooms (9 loops), and one manifold for a ‘tower’ bedroom and bathroom upstairs (2 loops). None of the flow meters on the manifold register a flow greater than 1 l/min unless the pump is at speed 3, when they push 2 l/min or so which is a little less than the design flow rates (as far as I can determine).

So much for the observations - not sure what it all means! Are the primary and secondary flow rates unbalanced? Are those different auxiliary pump speeds a problem? Thanks in advance, as ever.

@marzipan71

The first thing that I would suggest is repeating the temperature measurements using an actual thermometer, since even if there is no actual flow through the smaller pipes, there should not be a 10C difference in temperature readings. I suspect that your laser thermometer does not like copper piping.

The DT between 'A' and 'B' would indicate that flow is taking place and thermal energy is being dissipated. Does the 'Caleffi' manifold have a part number, as I am struggling to understand the internal flow arrangement. Each of the pairs of pipes feeding the radiators, should have the flow pipe  connected to manifold 'A', and the return pipe connected to manifold 'B', not as the photo appears to show.

What are the temperatures at the actual radiators?

I have an infrared thermometer gun thing myself, and have found it fairly reliable.  if comparing readings from different places you do need to make sure that the surfaces are both prepared in the same way, so comparing polished versus dusty or slightly corroded copper will give you a different reading.  If you really want accuracy you can also adjust the emissivity factor, although it does just say 3 modes are available, which will presumably be 3 separate emissivity settings.  Mine is much more adjustable but I got it from a measuring instrument company for checking my furnaces.

Recently I have been using it to find cold spots in the ceilings after topping up the attic insulation, turns out it is harder than you think to get insulation into the corner bits.

Hi @derek-m thanks for reply. I did indeed try using a thermometer - a cheap meat thermometer was all I had to hand that could be inserted between the insulation and the pipe. Photo shows the meat thermo showing a temp of 33C and the laser thermo showing 22 on the same pipe... 😆 

So - per your first post looks like the laser thermo is something of a random number generator. I did a google search and it does seem to be a common problem (and thanks @guthrie for input here also) when using these things for shiny surfaces - the suggestion from a few folks was to wrap black insulation tape around a shiny pipe if you want to use them. You're absolutely right though Derek - best avoided and use a more conventional thermo in these scenarios. So - consigned to the draw of useless gadgets...with apologies for perhaps wasting folks time. At least we have something for the record in the forum which people can refer to if they're using these laser thermometers in the future - don't!

Now - the Caleffi manifold is I think a Caleffi 356. I'll confess more assumptions on my part here as I assumed the pipes were in pairs on each side, only because we have 7 radiators and it looked like I had 7 pairs with one pair cut away. This is a legacy manifold from when we had the house renovated. I can't say whether our plumber was competent or not but I have heard from other plumbers who we've had to the house since that he liked to take shortcuts with piping and valves and the like - that said, our ASHP seems to work and we've not had leaks etc. The little logos on the manifold show a left and right arrow which implies as you say that the pipes are in laterally-arranged rather than vertically-arranged pairs; and that makes no sense to me since as I say we have 7 rads. Unless maybe we have 6 pairs of pipes and he put 2 rads on a single 'loop' (i.e., in series, if that's a thing) and we have a cut pair of pipes and two pipes (the sort of orphaned vertical pair) that are not used for anything. Incidentally, we have 11 loops on our UFH manifolds and he helpfully didn't label any of them with which loop corresponds to which room. He also made off with bits of non-essential kit which I know were supplied and paid for but never installed - more an annoyance. I've learned to take deep breaths.

Just to add @derek-m I was able to find a diagram (for a Caleffi competitor, but I assume its the same) which shows the flow arrangement for these 'coplanar manifolds' - I had no idea how they worked, per my last post. Seems Pipe A is the return and Pipe B the flow and the rad piping is arranged in vertical pairs with the upper pipe the flow and the lower the return, which would accord with the temp measurements from my (RNG) thermometer and I have one pair per radiator.

Should I worry if there is a low temp difference between flow and return from these radiators? I've seen articles saying 12 degrees temp difference across an individual radiator in a boiler setup, and others saying a lower temp difference is permissible in ASHP setups. Mine are a couple of degrees at most measure using the meat thermometer and the laser thermometer.

Also apologies for thinking that 'as you say that the pipes are in laterally-arranged' - I realise that is probably not what you were saying, just my ignorance of how the manifolds work.

Posted by: @marzipan71

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Just to add @derek-m I was able to find a diagram (for a Caleffi competitor, but I assume its the same) which shows the flow arrangement for these 'coplanar manifolds' - I had no idea how they worked, per my last post. Seems Pipe A is the return and Pipe B the flow and the rad piping is arranged in vertical pairs with the upper pipe the flow and the lower the return, which would accord with the temp measurements from my (RNG) thermometer and I have one pair per radiator.

Should I worry if there is a low temp difference between flow and return from these radiators? I've seen articles saying 12 degrees temp difference across an individual radiator in a boiler setup, and others saying a lower temp difference is permissible in ASHP setups. Mine are a couple of degrees at most measure using the meat thermometer and the laser thermometer.

Also apologies for thinking that 'as you say that the pipes are in laterally-arranged' - I realise that is probably not what you were saying, just my ignorance of how the manifolds work.

I have once again learned something new.

A low DT across the radiators would indicate that you have a high water flowrate. The quantity of thermal energy being transferred is dependent upon the water flowrate and the DT.

If the flowrate is fixed, then the DT should vary with demand, during milder weather when the heating demand is lower then the DT will likely be lower.