Mitsubishi Ecodan 8.5KW with Polypipe Room Stats and UFH system

[PaulF11]

We recently moved into a new build property with underfloor heating throughout and a Mitsubishi 8.5kw Air source heat pump to provide the heating and hot water. 

The house is a 4 bed detached property of 150m2. Each room has a Polypipe programmable room thermostat. These are on 24/7, on a comfort setting of 18.5°c from 6am until 11pm. Our setback is 17/17.5°c.

We are having problems with the heating side of the system. 

When rooms are all up to temperature and no hot water is required, our Mitsubishi system will continually switch from pause to play despite no demand from any of the Polypipe room controllers. We have even switched the room controllers off completely but the ME system still switches on / off. The system is off for 1.5 minutes, then back on for 12 minutes before repeating continually. The cycle appears to be; the heating mode switches to pause and the heat pump in the garden stops, 2.5 minutes later the circulating pumps will stop for 1.5 minutes before the heating then switches to play, the circulating pumps start up and then fan outside starts up again and runs continually for 12 minutes. 

However, sometimes when the Polypipe room thermostats are searching for heat, the Mitsubishi Electric main controller for the Heat mode will switch to pause despite the rooms searching. Today, we had 1 room upstairs searching (it was at the comfort setting of 18°c but it had to achieve another 0.5°c to stop searching) and one room downstairs which required 1°c plus the 0.5°c to stop searching)

The ME system is set up as two zones, zone 1 upstairs and zone 2 downstairs. 

The room upstairs has now achieved 18°c plus 0.5°c but zone 1 is still on play
The room downstairs is still searching. 

Our Polypipe room thermostat manual states that they have a function called "Optimum Start" which is enabled on our controllers. It is meant to learn the warm up time of the room and start the heating at a time to achieve Comfort by the time required i.e 6AM. Our comfort setting runs from 6am until 11pm. Most days when a room is searching at 6am, it can take 12/15 hours to achieve an increase of 1°c by which time we've gone to bed and the we have the same situation the next day. 

We've had the house builders team of plumbers and electrician's here to investigate why the system is switching on/off but they can't resolve the issue. The plumbers have slowed the flow rates to 1 l/m, but the flow meters on the manifold don't move from 0 - are they not working or just not enough pressure now to move the gauge within the flow meter? What should the pressure be for UFH?

[MikeSharp01]

Interesting. Three thoughts, biggish picture so maybe not understanding the detail, 1. is there any connection with the external temperature gradients. I wonder if the Optimum start function is just trying to get ahead of the external temperature curve somehow. 2. Once all the rooms cease searching does it continue? This may be linked to 1 above a little because if the external temperature is equal to internal and internal is at the set point and it still runs there is a bigger problem - I suspect not. 3. Are there any odd interactions between the ground floor temperature and the first floor because heat rises and, if you have one, is getting recirculated cooler air via the MVHR tending to average out things albeit this effect will be quite small.  

[scottishjohn]

mimium pressure fro my ecodan to work is 0.5bar--but engineer says he likes 0.8

[scottishjohn]

10 hours ago, PaulF11 said:

We recently moved into a new build property with underfloor heating throughout and a Mitsubishi 8.5kw Air source heat pump to provide the heating and hot water. 

The house is a 4 bed detached property of 150m2. Each room has a Polypipe programmable room thermostat. These are on 24/7, on a comfort setting of 18.5°c from 6am until 11pm. Our setback is 17/17.5°c.

We are having problems with the heating side of the system. 

When rooms are all up to temperature and no hot water is required, our Mitsubishi system will continually switch from pause to play despite no demand from any of the Polypipe room controllers. We have even switched the room controllers off completely but the ME system still switches on / off. The system is off for 1.5 minutes, then back on for 12 minutes before repeating continually. The cycle appears to be; the heating mode switches to pause and the heat pump in the garden stops, 2.5 minutes later the circulating pumps will stop for 1.5 minutes before the heating then switches to play, the circulating pumps start up and then fan outside starts up again and runs continually for 12 minutes. 

However, sometimes when the Polypipe room thermostats are searching for heat, the Mitsubishi Electric main controller for the Heat mode will switch to pause despite the rooms searching. Today, we had 1 room upstairs searching (it was at the comfort setting of 18°c but it had to achieve another 0.5°c to stop searching) and one room downstairs which required 1°c plus the 0.5°c to stop searching)

The ME system is set up as two zones, zone 1 upstairs and zone 2 downstairs. 

The room upstairs has now achieved 18°c plus 0.5°c but zone 1 is still on play
The room downstairs is still searching. 

Our Polypipe room thermostat manual states that they have a function called "Optimum Start" which is enabled on our controllers. It is meant to learn the warm up time of the room and start the heating at a time to achieve Comfort by the time required i.e 6AM. Our comfort setting runs from 6am until 11pm. Most days when a room is searching at 6am, it can take 12/15 hours to achieve an increase of 1°c by which time we've gone to bed and the we have the same situation the next day. 

We've had the house builders team of plumbers and electrician's here to investigate why the system is switching on/off but they can't resolve the issue. The plumbers have slowed the flow rates to 1 l/m, but the flow meters on the manifold don't move from 0 - are they not working or just not enough pressure now to move the gauge within the flow meter? What should the pressure be for UFH?

my first question would be   does this used a pre  plumbed cylinder from mitsubishi as well or just the ASHP

are these plumbers approved ecodan trained men ?

I have an ecodan pump+preplumbed cylinder  which is running faultless and i have 8 zones  on my system ,none of problem s you are talking about 

[scottishjohn]

just a thought --where is the temp sensor for the ashp --.could it be its just circulating water around your piping that feeds the actual UFH and its sensing drop in temp there which is then causing it to come back on for short time then going off again 

 

sounds like your polypipe controller is not linked correctly to ecodan .

maybe a plumber who is ecodan trained?

[PeterW]

Questions @PaulF11

 

Whats the flow temperature on the UFH manifold set at..?

Does the UFH manifold have actuators fitted..?

Does this only happen in heating mode..? 

What brand UFH is it..? Manifold photo would help 

 

The fact you’re not hitting the comfort setting is one thing - that is down to flow and flow temperature alone. Reducing the flow will make that worse. What is the Ecodan output temperature set at for heating ..?

 

I would reprogramme the controllers to begin with - are you on E7..?? Remove the smart start or whatever setting, use the stats as binary time switches. Set them on for 4-9am, set back 9-4pm then on from 4-9pm, set back 9pm-4am to start with. Then check the flow temperature on the manifold is set to 38c and run the system. 

 

From that you can start to eliminate the issues as you have a baseline to work from 

 

[ProDave]

The bit of the description that worries me is you are not seeing any flow on the flow meters on the manifold.

 

You need someone that actually understands UFH to check it all out. Make a room call for heat, check the actuator(s) for that room are actually energised, check the UFH pump is on, check water is fowing, check the temperature of the water that is flowing.

 

It is not rocket science but does require a slow careful methodical check through the system one stage at a time.  A lot of "heating engineers" don't understand it if it's not an S plan or Y plan with radiators.

 

Also look through the controller to see if it has registered any fault codes?