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Really weird behaviour, random heat spikes with Heatmiser!

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(@andehh)
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We have a large bungalow with high ceilings (all 3-4m), lots of big windows but good insulation. Ait tightness of 2.4, 160mm PIR in floor & ceiling, 125mm dri therm 32 full fill cavities. Every bit of insulation double checked during installation by myself. 

 

We then have a Samsung Gen6 12kw ASHP, supplying Joules spec UFH throughout with Heatmiser controls. No buffer tank, no blending valve. We have c20 zones of UFH (as 6 bedrooms, 3 bathrooms, large kitchen & lounge with multiple loops etc). It is over zoned but it is all controlled together, original design intent was controlled as 'all on' & 'all off' during cheap energy periods, with each zone turning off as it hits 21 degrees. General running pattern is a set back at night/during peak price periods to force system off, then run it hard during several hours of day/night for cheap rates. (so 21 degrees to turn system on, then 16 degree when we turn system off) 

 

With the cold spell we are going through right, we are seeing some really odd behaviour from the system though - random weird spikes/temperature fluctuations. This does not seem to be linked to heating itself (because it also happens when there is no demand for heat) and seems to ''start'' around 1.30am. This only started a couple of days ago - potentially linked to the coldest temps this system has seen since installation in July?

 

We have 2 x MVHR systems, but this is occurring in both MVHR zones of coverage. 

 

We have no other heating sources, and this behaviour is seen in ALL rooms - from kitchen, to bedrooms, to study in all corners of the bungalow. Some is MUCH more pronounced but all show similar behaviour. 

 

Pics attached are from one example room on Wednesday (when it was fine) then Thursday and so far today when it had started.

Can anyone please help shed any logic on what could be happening here??

Screenshot 20231201 093446 Heatmiser Neo
Screenshot 20231201 093440 Heatmiser Neo
Screenshot 20231201 093432 Heatmiser Neo

 

This topic was modified 3 months ago 2 times by Andehh

   
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Mars
 Mars
(@editor)
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Posted by: @andehh

With the cold spell we are going through right, we are seeing some really odd behaviour from the system though - random weird spikes/temperature fluctuations. This does not seem to be linked to heating itself (because it also happens when there is no demand for heat) and seems to ''start'' around 1.30am. This only started a couple of days ago - potentially linked to the coldest temps this system has seen since installation in July?

My original thought is that this could be related to defrost cycles. Defrost cycles are usually accompanied by spikes in consumption because the heat pump uses a built-immersion to defrost. The timing also makes sense. When temperatures drop below 3C and there's a lot of moisture in the air, this is when defrost cycles start. 

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ghayne
(@ghayne)
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I think it's defrosting too.


   
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(@derek-m)
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Posted by: @andehh

We have a large bungalow with high ceilings (all 3-4m), lots of big windows but good insulation. Ait tightness of 2.4, 160mm PIR in floor & ceiling, 125mm dri therm 32 full fill cavities. Every bit of insulation double checked during installation by myself. 

 

We then have a Samsung Gen6 12kw ASHP, supplying Joules spec UFH throughout with Heatmiser controls. No buffer tank, no blending valve. We have c20 zones of UFH (as 6 bedrooms, 3 bathrooms, large kitchen & lounge with multiple loops etc). It is over zoned but it is all controlled together, original design intent was controlled as 'all on' & 'all off' during cheap energy periods, with each zone turning off as it hits 21 degrees. General running pattern is a set back at night/during peak price periods to force system off, then run it hard during several hours of day/night for cheap rates. (so 21 degrees to turn system on, then 16 degree when we turn system off) 

 

With the cold spell we are going through right, we are seeing some really odd behaviour from the system though - random weird spikes/temperature fluctuations. This does not seem to be linked to heating itself (because it also happens when there is no demand for heat) and seems to ''start'' around 1.30am. This only started a couple of days ago - potentially linked to the coldest temps this system has seen since installation in July?

 

We have 2 x MVHR systems, but this is occurring in both MVHR zones of coverage. 

 

We have no other heating sources, and this behaviour is seen in ALL rooms - from kitchen, to bedrooms, to study in all corners of the bungalow. Some is MUCH more pronounced but all show similar behaviour. 

 

Pics attached are from one example room on Wednesday (when it was fine) then Thursday and so far today when it had started.

Can anyone please help shed any logic on what could be happening here??

Screenshot 20231201 093446 Heatmiser Neo
Screenshot 20231201 093440 Heatmiser Neo
Screenshot 20231201 093432 Heatmiser Neo

 

From the range on the charts, I'm assuming this is the IAT that is being shown.

I doubt whether the heat pump would cause spikes to the IAT, so I would suspect that they are being caused by the MVHR system.

 


   
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(@newhouse87)
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Screenshot 20231201 223932 Yuno

   
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(@newhouse87)
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Same as me. heatpump running and mvhr. Derek have to disagee no way was it mvhr causing this. I have meter for heat pump. Must have been defrost. Temps dropped 4 degrees in hour to minus Wednesday evening. My flow temp fixed so was shocked usage doubled in hour. Heatpumps costly in minus territory. 


   
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(@derek-m)
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Posted by: @newhouse87

Same as me. heatpump running and mvhr. Derek have to disagee no way was it mvhr causing this. I have meter for heat pump. Must have been defrost. Temps dropped 4 degrees in hour to minus Wednesday evening. My flow temp fixed so was shocked usage doubled in hour. Heatpumps costly in minus territory. 

If it is not the MVHR causing the spikes then please explain what may the cause and how?

 


   
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(@newhouse87)
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Posted by: @derek-m

Posted by: @newhouse87

Same as me. heatpump running and mvhr. Derek have to disagee no way was it mvhr causing this. I have meter for heat pump. Must have been defrost. Temps dropped 4 degrees in hour to minus Wednesday evening. My flow temp fixed so was shocked usage doubled in hour. Heatpumps costly in minus territory. 

If it is not the MVHR causing the spikes then please explain what may the cause and how?

 

why would mvhr cause my usage to double? See the chart when no heating running before 12pm. My usage less than0.3kw per hour, thats with mvhr running so unless my mvhr increases usage at6pm 10 fold, its not that.  Also myheat pump meter jumped. That doesnt measure mvhr usage. Unfortunately heat pump in minus territory v costly. Went from3-4oat to minus 1 or less and energy doubled in them hours.

To clarify its my doubling of enegy usage im blaming on heat pump. Mis read op. Apologies.


   
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(@derek-m)
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Posted by: @newhouse87

Posted by: @derek-m

Posted by: @newhouse87

Same as me. heatpump running and mvhr. Derek have to disagee no way was it mvhr causing this. I have meter for heat pump. Must have been defrost. Temps dropped 4 degrees in hour to minus Wednesday evening. My flow temp fixed so was shocked usage doubled in hour. Heatpumps costly in minus territory. 

If it is not the MVHR causing the spikes then please explain what may the cause and how?

 

why would mvhr cause my usage to double? See the chart when no heating running before 12pm. My usage less than0.3kw per hour, thats with mvhr running so unless my mvhr increases usage at6pm 10 fold, its not that.  Also myheat pump meter jumped. That doesnt measure mvhr usage. Unfortunately heat pump in minus territory v costly. Went from3-4oat to minus 1 or less and energy doubled in them hours.

To clarify its my doubling of enegy usage im blaming on heat pump.

There appears to be some confusion. My post was a reply to the question set by Andehh, who appears to experiencing spikes in temperature as shown in the charts above.

The reason that I suggested the MVHR may be the cause, is the fact that the spikes are still occurring when the heat pump is not running.

Your high usage, I agree, is probably being caused by defrosting, along with the fact that the weather is cold. I seem to remember all heating systems use more energy during colder weather, our gas boiler is certainly using more at the moment. 🙄 

 


   
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(@newhouse87)
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@derek-m unfortunately  must be defrosting twice an hour. Crazy to go from2.5 to 5kw per hour an hour apart.


   
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(@andehh)
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Topic starter  

Found it.....thank you Derek... it's the MVHR, turned them both off at the mains and all looks to be be resolved after 14 hours.

After several hours of research found someone on Facebook who had similar and discussed it bring an anti frost thing the MVHR was doing.

Having looked at the MVHR manual (vent axia sentinel) it does say below 0 degrees it does activate frost protection.

For now, I'm just happy to have found the culprit.


   
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