@sandman1600 What controller do you have there are good videos from mitsubishi on how to set weather compensation, I will assume you have an FTC7 controller as its a new system so this video is probably best for you.

Thank you. I’d literally just found that video as I couldn’t figure out what was meant by “Control Logic”. 

I tried reducing the flow temperature to 35 degrees this morning and I planned on monitoring the temperature in each room to see how each room operated with the lower flow temp. 

However now I’ve activated Weather Compensation I now seem to have no control or indication of what the flow temperature is doing. 

I haven’t messed with the weather curve so I’m running off these defaults until I can get my head round how it works.

@sandman1600 so what that is showing is that at -3C outside your flow temperature is 55C and at 25C outside your flow temperature is 25C. 

Between those two outside temperatures the flow temperature is varied on the straight line   

I would change them to -3C and 50C for the second and 16C and 30C for the first, then see how it goes for a couple of days. 

@bontwoody That’s great. Thank you.

And is it normal that when the weather compensation is activated, I can’t make any manual adjustments to the flow temperature?

Since Monday I’ve lowered the flow temp from 55 (as set by the installers) down to 37 today and things seem to be working okay. (Obviously this is just with the current weather conditions.)

If I now activate weather compensation, is that not going to just ramp up the flow temperature to help reach the higher thermostat temperatures? 

@sandman1600 Control logic is either auto adapt, weather comp or fixed flow you want weather comp the graph symbol in the image below

What is telling the heat pump to turn on do you have separate wireless mitsubishi controllers, or 3rd party controllers?

How many actuators do you have on the UFH manifold's and are these controlled by separate thermostats?

If you do these are bad for heat pumps as they will shut off, reduce water volume and cause the heat pump to cycle more frequently.

@sandman1600 That’s correct. The weather compensation takes over control of the flow temperature according to that little graph that is shown. 

It’s highly likely you can go lower than my suggested flow temperatures but I would start there and if you are warm enough try lowering them a degree at a time and see what’s that like. Obviously you need cold and warm days to check out the two extremes of the curve. 

Posted by: @gary

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@sandman1600 

What is telling the heat pump to turn on do you have separate wireless mitsubishi controllers, or 3rd party controllers?

How many actuators do you have on the UFH manifold's and are these controlled by separate thermostats?

If you do these are bad for heat pumps as they will shut off, reduce water volume and cause the heat pump to cycle more frequently.

The Polypipe UFH system is set up with two manifolds (one on each level of the house) and a thermostat in every room.

I’ve attached a photo of the manifold and I’m assuming we have individual actuators for every room. They’re currently all open as we’ve set a high temperature on the thermostats as recommended earlier on this thread to keep the heatpump running (at a lower flow temperature). 

It’s a bit depressing if the anctuators are going to cause an issue with the heatpump as I can’t really justify the cost of having the system replaced. 🤦🏻‍♂️

@bontwoody Thanks. I really do appreciate the advice from everyone. It’s all helping get my head around the new normal of a heat pump.

You need to follow a process

• Turn all room/central thermostats up to maximum
• Set the heat pump to run 24x7
• Ensure that the Ecodan is in weather compensation mode

This will disable any external controls, your house should overheat

• Slowly reduce the target flow temperature at the left hand end of the curve.  Change by no more than 1C per day (if the house overheats a lot then you can initially make a bigger change, 55 is silly so start at 35-40).  Keep reducing it until the house is just heated to the right temperature

If your rooms settle at different temperatures you may need to balance the loops (by restricting the flow rate through the loops where the rooms get hottest).  Not sure how you do this with that manifold TBH but someone else will be able to comment, it probably involves replacing the actuators with manual heads, unless there is another valve in each loop.

Your heat pump is now operating at its most efficient.  DONT reinstate the external controls, or if you do reinstate any then set them 2C above the desired temperature so they act as limiters (eg in the case of solar gain) not controllers.

There may be some subtle tweaks from this position particularly if you heat pump is oversized, but 24x7 operation on WC alone is almost without exception the best starting point.

Edit

I just found this which explains how to adjust the loop flows manually if that needs doing.  Dont bother unless it proves necessary.

@sandman1600 you've got a 14kw in a 130m2 well insulated house. I think you might be oversized there too.  I've an 11.2 KW heat pump in 260m2 average insulated house. And at one point I though it was undersized, but after learning how to work it better, I think it just about covers it.... but its tight. 

I have a lot of UFH, and depends on the design and pipe spacing, but if you run it 24/7, you'll be surprised at how cool you can run it.  I rarely ever need the flow above 33. 

@sandman1600 

Thinking about it, my head was in radiator mode. Using under floor heating you can probably knock 5C off both of my suggested flow temperatures and still have room to decrease them further if the rooms are warm enough.

@sandman1600 

If you unscrew all of the actuators then the circuits will always be open regardless of what the thermostats are doing, then you just need 1 thermostat somewhere to limit the house temp to your maximum.

Follow James directions for weather comp curve 55C is ridiculous for UFH it could damage your flooring.

Do you have the wireless adaptor and Melcloud app once you have it running consistently the hourly temperature plots under reports are useful to see the last 24 hours of temps and whether its cycling or not.

Here is my 8.5kw Ecodan running today at 32C

and then defrosting at 12 before returning to heating