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New and confused ASHP owner

 
Air Source Heat Pumps (ASHPs)
Last Post by Spud 3 years ago
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 Spud
(@spud)
New Member Member
Joined: 4 years ago
Posts: 5
Topic starter 06/04/2023 2:45 pm   [#917]

We moved into our house in December. It is roughly 5 years old, A rated wit a Mechanical Heat Recovery System and an 11Kw Ecodan with UFH upstairs and down.

The control system, is really odd. We have Uponor manifolds for the UFH. They are fitted with Uponor 24V actuators and T148 thermostats in the various rooms. Some odd things with the Uponor system is that it seems like a bus wired system for the thermostats so they are all wired together and back to the control unit. They have a night time set back which was at 4 degrees, we changed this to 2 degrees because the house was taking too long to get back to comfort levels in the morning and it seemed to be unnecessary cycling. Another weirdo with the Uponor is that the manifolds have a timer control, this manages things like the set back, but there is no battery backup so both timers need to be reset after a power cut. If I could I would junk the Uponor system and replace it with Heatmiser, but the thermostats are bus wired.

I have been trying to optimise the system in various ways as the COP seems to be about 2.2. The system design seems to be fairly poor as well. There are towel rails in the upstairs bathroom and these are T'd off the heating flow and return with no control valves and therefore rely on TRV's. Even odder is that when the UFH manifolds are off, the towel rails still run suggesting the heating is permanently on and not wired to the UFH manifold controllers. I suppose this could be so that the heating runs all the time and the room stats shut off the various rooms when they reach the thermostats settings. Then I guess we rely on flow vs return temps? There also seems to be two zones, but no idea if this is upstairs or down or just a config error.

When I look at the melcloud App, both zones typically show a room temperature of 26 with a set temperature of 21.

Any advice welcomed!

 

Thanks

Bob



   
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 redbuzzard
(@redbuzzard)
Active Member Member
Joined: 3 years ago
Posts: 18
06/04/2023 4:03 pm  

Posted by: @spud
↑

the COP seems to be about 2.2.

Bob

 

Where are you getting the numbers from?  I have about the same, based on the "Energy Delivered" reported by the FTC6 controller. 

However the total energy consumed in 12 months by the heat pump according to the separate meter is about 3850kWh.  The 'contract of performance' states 2623kWh input  for space heating and 1586kWh input for hot water, total 4209 kWh so we are coming in under that.  This suggests that the FTC6 isn't a reliable source for the energy delivered.  (the FTC6 reports about 10% more kWh consumed than the actual heat pump meter).

We probably save a bit on hot water as there are only 2 of us in a 5 bedroom house, but most of the house is heated to c. 21C. The running cost of the MVHR and the pumps do not go through the heat pump meter so I suppose total heating cost should include that.

Quite early on, I tackled the supplier about the poor COP.  TBH I got a bit of a brush off - they said the FTC6 implied COP is just an "estimate" and should be ignored.  Apparently I would need a heat meter to get a proper measurement of COP (I do not have one fitted).

In a nutshell, the COP as measured by the FTC6  is pathetically low, but the actual electricity consumption is more or less what it should be.

Is this the case for you?

 


This post was modified 3 years ago by redbuzzard

2021 built 2 storey detached house, 212 sq.m. / 2300 sq.ft. heated area. EPC 87B. Mitsubishi Ecodan 11.2Kw ASHP, weather compensated flow temp, UFH, MVHR.


   
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 redbuzzard
(@redbuzzard)
Active Member Member
Joined: 3 years ago
Posts: 18
06/04/2023 4:10 pm  

Incidentally, it seems odd to have the towel rails tee'd off the heating flow.  Our flow temp (UFH) is never higher than 40C and often not even at blood temperature.  It would make more sense to be on the DHW flow (except insofar as it isn't heating water most of the time).  

Maybe it's taking heat from the hot water tank? That would seem a bit silly especially if it were 24/7.

I put electric towel rails in our bathrooms.  I have some controllers fitted whereby a push of a button puts them on for 2 hours.


2021 built 2 storey detached house, 212 sq.m. / 2300 sq.ft. heated area. EPC 87B. Mitsubishi Ecodan 11.2Kw ASHP, weather compensated flow temp, UFH, MVHR.


   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
06/04/2023 4:15 pm  

Posted by: @spud
↑

We moved into our house in December. It is roughly 5 years old, A rated wit a Mechanical Heat Recovery System and an 11Kw Ecodan with UFH upstairs and down.

The control system, is really odd. We have Uponor manifolds for the UFH. They are fitted with Uponor 24V actuators and T148 thermostats in the various rooms. Some odd things with the Uponor system is that it seems like a bus wired system for the thermostats so they are all wired together and back to the control unit. They have a night time set back which was at 4 degrees, we changed this to 2 degrees because the house was taking too long to get back to comfort levels in the morning and it seemed to be unnecessary cycling. Another weirdo with the Uponor is that the manifolds have a timer control, this manages things like the set back, but there is no battery backup so both timers need to be reset after a power cut. If I could I would junk the Uponor system and replace it with Heatmiser, but the thermostats are bus wired.

I have been trying to optimise the system in various ways as the COP seems to be about 2.2. The system design seems to be fairly poor as well. There are towel rails in the upstairs bathroom and these are T'd off the heating flow and return with no control valves and therefore rely on TRV's. Even odder is that when the UFH manifolds are off, the towel rails still run suggesting the heating is permanently on and not wired to the UFH manifold controllers. I suppose this could be so that the heating runs all the time and the room stats shut off the various rooms when they reach the thermostats settings. Then I guess we rely on flow vs return temps? There also seems to be two zones, but no idea if this is upstairs or down or just a config error.

When I look at the melcloud App, both zones typically show a room temperature of 26 with a set temperature of 21.

Any advice welcomed!

 

Thanks

Bob

Please provide more details of your system.

How are operating the system, fixed LWT or weather compensation mode?

What value is the LWT and RWT?

 



   
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 redbuzzard
(@redbuzzard)
Active Member Member
Joined: 3 years ago
Posts: 18
06/04/2023 4:39 pm  

Posted by: @spud
↑

 

When I look at the melcloud App, both zones typically show a room temperature of 26 with a set temperature of 21.

Bob

I'm guessing that is the temp at the location of the FTC controller.  Mine is in an "airing cupboard" with the pre-plumbed tank etc and when the door is shut the temperature in there can reach mid-30s, which Melcloud gives as Room Temp.  I'm going to insulate all the warm pipes I can find in there.

 


2021 built 2 storey detached house, 212 sq.m. / 2300 sq.ft. heated area. EPC 87B. Mitsubishi Ecodan 11.2Kw ASHP, weather compensated flow temp, UFH, MVHR.


   
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 Spud
(@spud)
New Member Member
Joined: 4 years ago
Posts: 5
Topic starter 06/04/2023 9:20 pm  

@redbuzzard 

Thanks, yes I am using the data from the FTC. I'll see what I can get monitoring the actual power consumed.



   
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 Spud
(@spud)
New Member Member
Joined: 4 years ago
Posts: 5
Topic starter 06/04/2023 9:23 pm  

@redbuzzard 

Hadn't realised that the Ecodan measured the temp in the airing cupboard, but yes that is where it is located and it does get warm in there. Again, when I get to it I will check if that is where the temp is being measured.



   
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 Spud
(@spud)
New Member Member
Joined: 4 years ago
Posts: 5
Topic starter 07/04/2023 12:11 pm  

@derek-m 

Weather compensation, 45 degrees at -5 going to 30 when outside is 15



   
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