OK - changed Water Law to 32 & 45 degrees. At the moment I'm having wierd HW problems - the cylder temp drops by about 10 degrees before it fires up again. Over the weekend the cylider dropped to 30 - had to heat it back up to 52 with Eddi. Three port valve problem?

Is there an Error Log somewhere? I'v found one but it's greyed out.

As for thermostats - e-mailed Homely a few times - no reply. Have they gone bust already?

Question - has anyone used Kaiflex Solar 2in2 pipe? They used it on my installation betwee the HP and three port valve and then across the loft to the heating circuit. It's 25.4mm inside diameter, stainless steel 'corrugated' pipe. I've spoken to a distributer and e-mailed the company in Germany. No replies. All I'm trying to find out is how does it compare to 28mm copper. Flow rate specs?

Power wise - see below. The control panel says it's running at a COP of 5.2. I suspect it's lying ...

@raiph Homely were still ‘at home’ this morning as I was chatting to technical support and sorting out a few things. As to the pipework; is corrugated pipe smooth on the inside? If not, then surely this is going to cause flow problems? Regards, Toodles.

@raiph Hi Ralph

It would be useful if you could annotate your graph with what is using the power at different times. Ideally you want to minimise any usage outside your overnight cheap rate.

A COP of 5.2 at the moment isnt outrageous during this warm spell at your flow temperature.

Are you heating your domestic hot water in a timed block or is it set up reheat when the cylinder temperture drops by a certain amount?

@bontwoody Hot water - at the moment it's on 'Standard' - it re-heats when the temperature drops 4 degrees from the set temperature. I'll add a graph at the end. I've switched to 'eco' - just to see what it does. I have set a hot water schedule which forces it to re-heat first thing in the morning. One problem - how do you change the time on the Control panel (i.e. MIM controller)?

A few questions:

Stll cannot find out about the Kaiflex Solar 2in2 pipe - specifically the flow rate - how does it compare to 28mm copper?

Diverter valve used - Honeywell Home 272889. Not exactly reliable due to its rubber ball. Is there an alternative (with the same port layout) that has a rotating shoe (self cleaning) that can handle the high flow rates of an ASHP? I'm trying to avoid the Swiss ones - wrong pipe/port layout plus expensive (EBSE).

At the moment I'm in the observation phase - no fiddling until I know what's going on. As an aid I've been using an EliTech Temperature Data Logger (£26 from Amazon). Great for the price.

Observation - 1 to 1.5 Degrees between flow and return measured at the Kaiflex to original pipework junction (i.e where it connects to the radiator circuit).  Will monitor it at the HP connections. Bit low?

I've been trying to balance the rads with an IR camera - really need cooler weather. I have noticed the heat losses from the junk in the loft i.e. 3 port valve, 25l volumiser 28mm flow restrictor, Y strainer and about six valves. None of them lagged. Time to build an insulated box ...

No temp graph - doesn't like JPG files ...

Try again ?

@raiph So it will be cheaper to heat your domestic hot water overnight if you have a large enough tank to meet your daily needs. I dont heat my DHW using the heat pump so havent used the controller to set it up. I image its in schedules, you could try searching on youtube.

The flow rate of the Kaiflex pipe could be estimated from its internal diameter, I would think that it is fine for an 8 kW unit

Are you saying that your flow and return water temperatures are 1.5 C difference? If so that is too small. Ideally a 5C difference is stated, but certainly more than 3C. Have your radiators been sized correctly?

Posted by: @raiph

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One problem - how do you change the time on the Control panel (i.e. MIM controller)?

Go to Settings - Options - User Mode - Wired Remote Controller - Current Time

Thanks Mike, time now correct.

HW cylinder in 'eco' mode. Possible feature(bug). Switch to eco. After the scheduled Off/On time it reverts to Standard mode. Will have a word with Samsung.

Radiator sizing. All sized to a flow temperature of 45 degrees C. Most OK at 43. Confirmed with Heating Engineer and Heatpunk software. All depends on the materials used in the Heat Loss Calcs. The other major factor is the ACH. Complicated by an MVHR system. Possibly the lowest heat loss of 4.3kW was correct or even an over estimate. Heat pump too big? The installers ignored the HLC and just fitted an 8K unit. I sized and changed the rads.

Kaiflex pipe. My concern is that it's a corrugated pipe so the water flow through it will not be laminar. An inner diameter of 25.4mm should be OK for a 8K HP. Looks like Kaiflex make the lagging and someone else produces the pipe, hence they have no idea of flow rates.

Delta T across the rads. So many factors involved. Flow rate for heating 19lpm. Hot water 26lpm. Do any of the MIM FSV settings control the pump speed i.e. is the high flow rate causing the low Delta T?

@raiph I would assume you could manually alter the pump speed, or if it is of a compatible type it can be controlled via Pulse Width Modulation directly from the HP controller. Ive done that and it works very well. What pump do you have?

The corrugation probably will have an effect but difficult to know how big.

If you mean the 1.5C delta T is across the rads then that might just be that the flow temperature you are running at cant dump more heat into the house.

@bontwoody My HP - it's the variant that has everything in the box i.e. pump, expansion vessel et al. Will read the MIM controller manual to see what control there is for the pump. RTBM ...

@raiph So if its all in the box, my guess would be it is already using PWM to control the pump. It would be madness not to given that the facility is already built into the Gen 6

Posted by: @raiph

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Kaiflex pipe. My concern is that it's a corrugated pipe so the water flow through it will not be laminar. An inner diameter of 25.4mm should be OK for a 8K HP. 

To quantify the greater pressure drop of your corrugated pipe you could try using an online calculator like https://www.pressure-drop.online/  

For example, at 20 l/min a 25.4mm corrugated pipe (5mm high corrugations every 10mm) has five times the pressure loss per metre than a 28mm copper pipe. 0.010 bar vs 0.002 bar per metre. 

Your pump(s) will be using more energy to overcome this pressure drop than would be the case if your pipes were 28mm copper.