Posted by: @iraknic

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Is there a way to see the number of on/off cycles?

I am not familiar with the Hitachi monitoring so someone else will need to answer this.  If you can monitor power consumption it will be visible in this though.

More generally, what problem are you trying to solve.  Is consumption high/COP low, or something else?  It does sound like your heat pump may be trying to deliver a lot more energy than your floor is absorbing.

Can you provide a bit more info eg Capacity of heat pump, house loss

33-14 is quite high for UFH, how were these figures determined.

I am presuming from your description that are heating part time, is this by design (if so why) or because thats what it takes

Hey JamesPa thanks for the reply. The reason for my post is my observation of the low dt and my concerns on the stress that the system undergoes. I have no dedicated consumption meter for the heat pump to know exact consumption or COP. The set flow temp is based on my day to day experience. With the current setting, it takes about 6-8 hours for the air temp to go up by 1 degree and the heat pump shutting down by itself. Anyway the thermostat is turned down by one degree at night to prevent heat pump turning on due to my preference for complete silence (is this a bad practice?). I have wood parquet installed so there is a noticeable heat loss/delay in heat delivery there. Capacity of the heat pump is 17,8 kw. Although i haven' exactly measured house loss i would say that any loss is low as there is a loss of 0,5 degrees at room temp in 12 hours. 

i have limited knowledge on the matter hence the questions. Any input from people knowing more, is appreciated

@iraknic Ok

I was hoping 6 was 6kW not 6 tons (an American measure of capacity roughly equal to 3kW).  I suspect it's well oversized.  What do you know about how it was sized or the house construction/age.

House is a construction of 2020 with xps insulation and double glazed windows. No clue on sizing. It was decided by the engineers during construction stage

Posted by: @iraknic

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House is a construction of 2020 with xps insulation and double glazed windows. No clue on sizing. It was decided by the engineers during construction stage

That's disappointing.  It's way oversized almost without any doubt.  6kW is probably nearer the mark, possibly less.

I will re-read your description and see what I can suggest given the assumption that it's way oversized.  Cycling is inevitable even at low outdoor temperatures.  You may want to experiment with forcing longish cycling (as a way of preventing short cycling) by having it on for an hour or two then off for an hour or two.  If you are really lucky you might be able to operate only during the octopus cosy cheap periods, which would make it very low cost to run.  (As I think about this more,  designing the schedule  around electricity tarrifs feels ever more sensible given the likely scale of oversizing)

I've started a new thread on oversized heat pumps as it's unfortunately common.  You may want to follow that also.

I will respond to your specific again later when I have given it some thought.

Are you able to measure the delta t on both primary and secondary (ie the circuit to/from the heat pump and the circuit to/from the emitters)?

@iraknic have you established that you can hear your system? Ours is very much quieter than the old gas fired boiler, no radiator creaking for example. So it wouldn’t be a problem to be on all night.

If your temperature only drops by 0.5C in 12 hours then you could easily choose to heat in just smaller set periods.(as James suggested).

@judith i can't hear the heatpump but i can hear the external waterpump. Maybe i can try increasing the flow temp, reducing the flow rate manually through the manifolds and have the heatpump working for smaller periods. Is it generally preferable to have the heatpump turning on once or twice daily to get water temp to 38c from 10c or having it run continuously depending on thermostat temps?

@jamespa only able to measure delta t on primary circuit. If anyone with knowledge on hitachi heatpumps can suggest a way to see number of cycles, it would be great. I can remember reading somewhere that the particular model is rated for 200sqm spaces

Posted by: @iraknic

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. I can remember reading somewhere that the particular model is rated for 200sqm spaces

That will be the water pump capacity not the heat pump capacity, which is dependent on the house loss.

The water pump may be on longer than the heat pump.  However from what you know, roughly how frequently is it cycling and for how long on and off at what outside temperature.  Have you got any monitoring equipment at all for temperature or electrical power.  Could you put a mobile phone on record next to the pump and record the on off noises for an hour or two

Do you have an internet/WiFi interface on the pump, without this the monitoring options will be pretty limited.

@jamespa i was able to watch a 20 minute operation. In a 12c outside temp, the heat pump cycled off 2 times for 3 minutes at a time. When it cycled on it did not exceed 30% capacity. There is a setting for a minimum off and on time to reduce cycling. If i force it to stay on for longer how it will be able to stay within water temp limits? On the other hand if i force it to stay off for longer wouldn't it operate harder to get back to temp each time it cycles on?

Posted by: @iraknic

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@judith i can't hear the heatpump but i can hear the external waterpump. Maybe i can try increasing the flow temp, reducing the flow rate manually through the manifolds and have the heatpump working for smaller periods. Is it generally preferable to have the heatpump turning on once or twice daily to get water temp to 38c from 10c or having it run continuously depending on thermostat temps?

it’s much more efficient to run a heat pump continuously but for everyone in the end it’s about money. So if you were able to run only on the cosy cheap 8hrs or economy 7 then despite the efficiency being lower your costs would be too.