ohhh just as I posted the above I have found Ecodan controller which suggests all 5 (heatmiser & honeywell) thermistat don't send back temperatures to the FTC5. Meaning not only did the installer set up a compensation mode based on the temperature of the garage, but also installed 6 thermistats around the house that work with compensation modes? 😮 somebody please tell me I go this wrong...

@greekgoddj, I don't think you're wrong. We've not been using weather compensation for a similar reason. Our main control for the ASHP is in the utility room cupboard so the temperature is always above 25C. In addition to this, our Heatmisers and other controllers are connected to call for heat, but don't feed temperatures back. 

The fact that you're getting readings from the garage will also affect performance (in my opinion) because it'll always be warmer in the garage than outside. We have several weather monitoring sensors (not for the heat pump) outdoors and the one in the garage is usually over 10C warmer than the sensor that is monitoring the outdoor temperature.

I'm just surprised that the Ecodan doesn't have its own temperature sensor. Most heat pumps do.

I'll let Derek and the other Ecodan guys comment further.

Posted by: @editor

The fact that you're getting readings from the garage will also affect performance (in my opinion) because it'll always be warmer in the garage than outside. We have several weather monitoring sensors (not for the heat pump) outdoors and the one in the garage is usually over 10C warmer than the sensor that is monitoring the outdoor temperature.

I'm just surprised that the Ecodan doesn't have its own temperature sensor. Most heat pumps do.

Hi @editor , firstly great work from you and your partner on the site!

Many thanks for your response. To clarify, the outside unit has its own outdoor temperature..that bit is fine. The inside unit and the water tank is in the garage and that is where the “indoor” sensor is. So the issue isn’t that the indoor sensor is reading 10C higher than outside, but that it reads 10C lower than what the actual inside of the house (livable space). So I assume this means the compensation curve is working out a higher flow rate than needed? Either way it is messed. 

Will ring the fitter in the morning but am not optimistic… will update on here in case I learn something useful for others too.

Thanks

@greekgoddj ,

the weather compensation function on the Ecodan only uses the outside temperature, not the room temperature.  I think the sensor for outside temp is built into the outside unit. The Neostat thermostats act like on/off switches and will call for heat when their detected room temp falls below their set values. The ASHP will then produce hot water and pump it round until the room temp reaches the thermostat set value, then it will stop. The temperature of the hot water it produces will be as per the settings on the Ecodan controller, either via the weather compensation curve or a constant setting.

The Ecodan doesn't 'know' the temperature of the room in this setup.  As Mars says, the thermostats don't communicate that with the Ecodan. That's how mine was set up by the installer, although my controller is in the airing cupboard, not the garage, and reads about 27C.  This works OK, although there may be more efficient ways to run it (which is what I'm trying to find out).

If you try and use the room temp setting (auto adaptation) on your controller, it won't work properly because as you say, the room temp it's sensing is in the garage.      

Kev

Posted by: @greekgoddj

ohhh just as I posted the above I have found Ecodan controller which suggests all 5 (heatmiser & honeywell) thermistat don't send back temperatures to the FTC5. Meaning not only did the installer set up a compensation mode based on the temperature of the garage, but also installed 6 thermistats around the house that work with compensation modes? 😮 somebody please tell me I go this wrong...

Hi DJ,

The first thing that you need to do is look at the screen on your FTC controller and see to which mode your controller is set. If you look at section 7 of the FTC controller manual you should see pictures and tables detailing the information displayed on the screen. 

Your system will only be using the thermistor inside the FTC controller as a temperature measurement, if your system is selected for room temperature control. If your system is set for water flow temperature control, then the thermostats inside your home will be switching the ASHP on and off. If your system is set for weather compensation curve control, then the thermistor, located inside the ASHP unit, will be measuring the outside air temperature, and using this value to calculate the required water flow temperature, dependent upon the setting of the compensation curve. If the indoor temperature gets too high then the indoor thermostats should switch off the heat pump until the temperature falls.

I think that I should explain the difference between thermostats and thermistors in case there is any confusion.

A thermostat is an on - off device, in that it switches on when the temperature falls to a set level and then switches off when the temperature increases to a higher set level. It can therefore be used to turn your ASHP on and off.

A thermistor is a temperature measuring device, which can be used to measure the actual temperature as it varies. It is a resistive sensor, which varies its resistance with variation of temperature. The FTC controller measures the resistance and interprets the measurement to give the actual temperature reading.

Hi @kev-m, thanks I confused myself with the need for an accurate interior space sensor on the Auto Adjust mode, but yes I see now why compensation curve doesn't need it. Thanks for that.

@derek-m I have confirmed it is indeed on compensation curve. I found one of your posts in another thread and saw your suggestion for how to set the curve (45@0-25@20) and have set that up for now and will monitor how it goes. The curve so far was setup in a way that the flow temperature was quite higher I think.. and have in the last year 12 months averaged a COP of 2.8 🙄 . It was a case of the heating coming on, warming the place up, and then switching off for longer periods of time. I hope the new "run at lower flow temperature but more regularly" will help. many thanks for that.. learning lots.

And also thanks for the thermistat vs thermistor bit, as I did find myself searching online for a difference.

merci!

@greekgoddj each house has its own weather compensation sweet stop. I'd advise starting with @derek-m suggestion and seeing how you get on. You can easily raise or lower as you see fit. Just try to find the setting that is most consistent at whatever air temperature you're aiming for inside.