Asking for advice, before I speak (again) to our installers (!)
We have Mitsubishi Ecodan 8.5 air source heat pump - currently not really performing well (they fixed a hardware issue a few days ago). My current worries are
a) we can't seem to get to temperature above 19.8, with underfloor heating on all the time, and upstairs radiators set at 18C (they are fine, the upstairs temp is above 18)
b) we are seeing flow temperature and return temperature tracking nearly exactly - most of the time - no more than 2 degrees difference and most of the time less - I thought the differential should be more?
c) significant fluctuations for flow (and of course return) temperatures for a 24 hour period e.g. 19:00 last night %£c, 20:00 43, 21:00 50C, 22:00 54.4, 23:00 54.8, 24:00 50C, Same at 01:00, 03:00 down to 43C, 04:00 back up to 54C and so on! The hot water comes on at 01:00 to 03:00 so that makes sense, but we are seeing jumps 4:00 at 53.4, 5:00 at 48, 06:00 back to 54, 07:00 down to 48, 08:00 back up to 53, and so it continues. Is this "wrong"? Any ideas what it might be?
Any thoughts much appreciated - I'll be calling the installers out, but would really like to know more of what I should be seeing as performance!
Asking for advice, before I speak (again) to our installers (!)
We have Mitsubishi Ecodan 8.5 air source heat pump - currently not really performing well (they fixed a hardware issue a few days ago). My current worries are
a) we can't seem to get to temperature above 19.8, with underfloor heating on all the time, and upstairs radiators set at 18C (they are fine, the upstairs temp is above 18)
b) we are seeing flow temperature and return temperature tracking nearly exactly - most of the time - no more than 2 degrees difference and most of the time less - I thought the differential should be more?
c) significant fluctuations for flow (and of course return) temperatures for a 24 hour period e.g. 19:00 last night %£c, 20:00 43, 21:00 50C, 22:00 54.4, 23:00 54.8, 24:00 50C, Same at 01:00, 03:00 down to 43C, 04:00 back up to 54C and so on! The hot water comes on at 01:00 to 03:00 so that makes sense, but we are seeing jumps 4:00 at 53.4, 5:00 at 48, 06:00 back to 54, 07:00 down to 48, 08:00 back up to 53, and so it continues. Is this "wrong"? Any ideas what it might be?
Any thoughts much appreciated - I'll be calling the installers out, but would really like to know more of what I should be seeing as performance!
thanks lots Sali
Hi Sali and welcome. Sorry to hear of your woes.
A few quick questions to get started:
Can you explain how you are running the system - fixed flow, weather compensation or room temperature?
Are you using any 3rd party thermostats or controls?
Is your house split into zones?
These flow temperatures are very high for ufh - is this intentional?
Are you trying to run the system on Mitsubishi's Auto Adaptation? That's quite tricky to set up for more than one zone and it won't work well (or at all) with ufh.
If your flow temps and/or flow rate are too high the emitters won't be able to emit enough and the flow and return can end up close.
@kev-m Thanks for commenting! and appreciate knowing what I need to share!
a) we are running on curve (weather compensation) - standard setting for the Ecodan i.e. 50C up to close to 0C outside, and 30C from about 15C outside
b) upstairs we have a thermostat but that is linked to the system - we run it at 18C and usually the temperature is above that (open plan) but it does run a bit in the night
c) yes 2 zones - downstairs for the underfloor (Zone 1) and upstairs for the radiators (Zone 2)
d) flow temps - don't think we set these - the engineer did say we needed to watch the dial on the underfloor control which is running between 40 and 50 (either one or the other, not in the middle). We are running at +7C over curve though, in an attempt to get the house a bit warmer (recommended by the engineer - though I don't think he meant to run at +7 for a long time!)
e) don't know if we are using auto adaptation - unless the installers set this - how would I check?
f) flow rate is around 24 I think, it was a lot higher when installed, but the last engineer put it down to 24, which is near the top of the range for what is OK
The frequent fluctuation of flow temp has calmed down a bit (perhaps because it is warmer outside) - I've attached a few images of what we have had two days ago, yesterday and today (hope the date is visible, but named the files with dates)
I'm still trying to learn this, and to an extent rely on the engineers to explain, however we are not getting still above about 20C, but we did have this last year in e.g. Nov (though the flow rate was apparently a lot higher, too high)
PS the "surveyor" is coming out tomorrow to check out - so if anyone is reading, I'd appreciate any questions I should be asking!
Thanks loads Sali
Sali,
there is something wrong here. The flow and return temps aren't just close; they are almost identical. Is it possible the sensors are installed wrongly, e.g. both on the same pipe? The oscillation in flow temp is consistent with defrosting (which will happen in cold weather) but the extremely close match to return definitely isn't. The defrosting will stop when it gets warmer.
Another point is that these are very high flow temperatures. Your curve is set high anyway but then it's bumped up another 7 degrees to over 55 degrees. That must be costing you a fortune to run.
Do you have heat loss calculations? If so, what is the design flow temp? If it's 50 at 0 degrees you shouldn't have to increase it by 7 degrees to get your house warm. A properly designed ASHP system shouldn't be running at 55 degrees plus. As I said before, 55 is very high for ufh and can damage some floors.
I would show the surveyor these pictures and ask why there isn't the expected 3-5 deg difference between flow and return and why the traces are so close. Also ask why the house isn't warm enough even at 55 degree flow temps.
PS the "surveyor" is coming out tomorrow to check out - so if anyone is reading, I'd appreciate any questions I should be asking!
Thanks loads Sali
As Kev has suggested, the first thing to check would be LWT and RWT indications and sensors to see if they are correctly installed, since they can determine the water flow rate. If you have a suitable thermometer then try to measure the temperature of the pipes coming from (LWT) and going to (RWT) your heat pump. See how they compare with the above readings.
Do you have a buffer tank, low loss header or plate heat exchanger within your system?
As Kev also stated your LWT is very high, particularly for UFH. I would suggest starting by changing the +7 to 0 and see what happens to the various temperature indications and room temperature measurements, then report back your findings.
Some photo's of the different equipment within your system would probably be useful.
Ask the surveyor what the maximum permitted temperature is for UFH. If their answer is more than 40C then it is possibly that they don't know what they are doing.
Quick update after the surveyor came - he found a number of issues.
a) One thing he saw that we didn't realise is that for the UFH, we have 5 "tracks" (what is the right word? zones?) - two for the kitchen/diner, two for the family room, and one for the lounge (smaller). The tracks for the kitchen/dining appeared to be at full flow of around 4l/m (both fully open), the lounge is at 0 so only a trickle of warmth going through, and the family room one was at about 1 l/m and the other at 0. So in effect the kitchen/diner is heating the lounge and family room (open doors / open plan) as well as upstairs. He tried to amend but couldn't - the UFH is around 20 years old - so the company will quote for replacement manifold (which will also remove the pump on UFH given the heat pump is pushing into the system, and remove the 'blender' which he says is no longer required). We'll get another quote as well and see if anyone can manually adjust the flows for the two rooms which are too low. The flow overall for the UFH is therefore reduced.
b) multitude of pumps arguing! There is a pump (well, more than one I think) upstairs pushing out to the UFH and radiators, and a pump on the UFH. The previous engineer had adjusted the flow upstairs down, but we also found there was another pump on the return, which was behind a panel where the old boiler was, which the engineer had not spotted - while the pump(s) upstairs was set lower, the one downstairs on return was set to 3 / full. Upstairs (flow) and downstairs (return) are now both set at 2, and the pump for UFH is off. We will see what happens
He has moved us back down to +2 above curve, though I will reduce this when I can (trying shutting doors to the other downstairs rooms for now). The outside temp is around 3-5 so we should be ok to go back to curve later this morning 😉
So with the reduced flow, and reduced use of curve, he is hoping we will get more towards the differential for flow and return - I will monitor this. He does want us to try to fix the UFH controls for the other 2 rooms so there is at least some flow going through (!) so we may need to find an engineer or plumber to adjust the controls in the short term. Looking at the UFH now, it looks like flow for kitchen/diner is now down to 1 + 1 (since he's gone, and switched off the UFH pump), but the others are still the same. I can't see how to adjust either, and not something I should play with!!
My worry now (but will watch this) is that with a flow of 1 l/m through 3 of the 5 and 0 through 2, the UFH is only drawing 3 l/m on a heat pump flow of 23-24 l/m, which to me sounds a bit weak. I might amend the hot water timer - at present it is set to come on at 3am and that is all, so I might add an afternoon HW for a short while and reduce the 3am HW - but only once everything else is stabilised...
I'm going to read up more on UFH (in particular, google flow rates and controls), and monitor the room temperatures and heat pump performance and temperatures. I've attached pictures of the UFH though not sure how much can be seen
I'll also ask my OH about paperwork for the heat pump to check design temperatures - the curve is the default when it was installed but I get the point that we are running too high!
Will report back later so that there is a thread in case anyone else has a similar issue
Quick update after the surveyor came - he found a number of issues.
a) One thing he saw that we didn't realise is that for the UFH, we have 5 "tracks" (what is the right word? zones?) - two for the kitchen/diner, two for the family room, and one for the lounge (smaller). The tracks for the kitchen/dining appeared to be at full flow of around 4l/m (both fully open), the lounge is at 0 so only a trickle of warmth going through, and the family room one was at about 1 l/m and the other at 0. So in effect the kitchen/diner is heating the lounge and family room (open doors / open plan) as well as upstairs. He tried to amend but couldn't - the UFH is around 20 years old - so the company will quote for replacement manifold (which will also remove the pump on UFH given the heat pump is pushing into the system, and remove the 'blender' which he says is no longer required). We'll get another quote as well and see if anyone can manually adjust the flows for the two rooms which are too low. The flow overall for the UFH is therefore reduced.
b) multitude of pumps arguing! There is a pump (well, more than one I think) upstairs pushing out to the UFH and radiators, and a pump on the UFH. The previous engineer had adjusted the flow upstairs down, but we also found there was another pump on the return, which was behind a panel where the old boiler was, which the engineer had not spotted - while the pump(s) upstairs was set lower, the one downstairs on return was set to 3 / full. Upstairs (flow) and downstairs (return) are now both set at 2, and the pump for UFH is off. We will see what happens
He has moved us back down to +2 above curve, though I will reduce this when I can (trying shutting doors to the other downstairs rooms for now). The outside temp is around 3-5 so we should be ok to go back to curve later this morning 😉
So with the reduced flow, and reduced use of curve, he is hoping we will get more towards the differential for flow and return - I will monitor this. He does want us to try to fix the UFH controls for the other 2 rooms so there is at least some flow going through (!) so we may need to find an engineer or plumber to adjust the controls in the short term. Looking at the UFH now, it looks like flow for kitchen/diner is now down to 1 + 1 (since he's gone, and switched off the UFH pump), but the others are still the same. I can't see how to adjust either, and not something I should play with!!
My worry now (but will watch this) is that with a flow of 1 l/m through 3 of the 5 and 0 through 2, the UFH is only drawing 3 l/m on a heat pump flow of 23-24 l/m, which to me sounds a bit weak. I might amend the hot water timer - at present it is set to come on at 3am and that is all, so I might add an afternoon HW for a short while and reduce the 3am HW - but only once everything else is stabilised...
I'm going to read up more on UFH (in particular, google flow rates and controls), and monitor the room temperatures and heat pump performance and temperatures. I've attached pictures of the UFH though not sure how much can be seen
I'll also ask my OH about paperwork for the heat pump to check design temperatures - the curve is the default when it was installed but I get the point that we are running too high!
Will report back later so that there is a thread in case anyone else has a similar issue
thanks again so much for your help!
Sali
What is the make and model of the white (with the blue top section) valve actuators?
They would appear to be temperature controlled valve actuators, the blue section indicating how far open they are. As you can see, three are open and two are virtually closed.
What is the make and model of the white (with the blue top section) valve actuators?
They would appear to be temperature controlled valve actuators, the blue section indicating how far open they are. As you can see, three are open and two are virtually closed.
The closed ones obviously require adjustment.
Hi Derek - they don't have a brand name or any identification on! They are replacements of the smaller ones (the old smaller ones are still there but removed) - the nearest I could find is these: https://www.heatingcontrolsonline.co.uk/clipon-thermal-actuator-p-470.html which look like a generic replacement
While the blue is showing, which suggests (I think) the pin is up, the indicator below them (in the first picture) shows zero and there is no warmth in the pipe.
I've tried adjusting (turning through 360 degrees anticlockwise) but there is no movement showing in the indicators, so I'm guessing either electrical fault or mechanical - I've phoned a local heating chap who hopes to be able to come look in the next day or two...
At least the temperature in the main room is now around 21.6 which is great!! 🙂
What is the make and model of the white (with the blue top section) valve actuators?
They would appear to be temperature controlled valve actuators, the blue section indicating how far open they are. As you can see, three are open and two are virtually closed.
The closed ones obviously require adjustment.
Hi Derek - they don't have a brand name or any identification on! They are replacements of the smaller ones (the old smaller ones are still there but removed) - the nearest I could find is these: https://www.heatingcontrolsonline.co.uk/clipon-thermal-actuator-p-470.html which look like a generic replacement
While the blue is showing, which suggests (I think) the pin is up, the indicator below them (in the first picture) shows zero and there is no warmth in the pipe.
I've tried adjusting (turning through 360 degrees anticlockwise) but there is no movement showing in the indicators, so I'm guessing either electrical fault or mechanical - I've phoned a local heating chap who hopes to be able to come look in the next day or two...
At least the temperature in the main room is now around 21.6 which is great!! 🙂
I would suggest removing (they should just clip on) one of these actuators from one of the loops that is cold and see if the underlying valve opens up.
If the water valve closes rather than opens with the actuator removed, then see if you can push the operating pin down and tape it in the open position.
With a heat pump system you do not actually require these actuators since the heat pump controller should be used to control the water temperature.
a) One thing he saw that we didn't realise is that for the UFH, we have 5 "tracks" (what is the right word? zones?)
I think you could call it a circuit. I would think that the two circuits labelled Lounge would be, collectively, called a zone.
I'm going to read up more on UFH (in particular, google flow rates and controls),
You will probably want to establish
pipe length (may be written on the pipe)
pipe diameter pipe spacing (you may be able to work this out from the pipe length)
base floor material (concrete, screed)
floor covering
I used the following for spacing <-> length
5 meters of pipe per sqm 200cm pipes
6.67 meters of pipe per sqm 150cm pipes
rough flow rate calculator is loop length/40 in lpm (a starting point, but there are more sophisticated formula that you will find on the web).
I worked backwards from the output I needed at the dT, floor temp and room temp, knowing already that the floor and covering supports that output level. in my case I needed about 2.5kW worst case (about 65W/sqm) @dT 3 using l/s = kW/( 4.18 ⋅ ΔT) = 0.2 l/s = 12 l/m / 5 circuits = 2lpm per circuit (all circuits [about] the same length). I need a floor temp of about 26 @ room temp of 20 to get 65W/sqm. [if my calculations are correct].
It is a lot easy to use an online tool, which I did to check I was in the right ball park. (via a trial of the software)
