Itrium

After much playing around, I believe this is caused by the room sensor settings in the initial settings. It was originally set to ‘Main RC’. The pumps on the two zones would turn off by the third party thermostats but leave the heat pump running. Changing this to ‘Time/Zone’ and setting the time to always on, allowed the thermostats to turn off the heat pump as well. Unfortunately the room temperature is monitored as -33’C. The 2 zone configuration seems fairly common, Mitsu even supply a kit for this. Its a pity they don’t provide understandable documentation 😬

I’ve got the freeze stat setting turned off, set to **. At the moment the thermostats are set to close for turning off the heating. I was wondering if flipping the logic with the DIP switches so that the heat pump ran with closed thermostats would help?

I have an ecodan ASHP running in WC with third party on/off thermostats connected to IN1 and IN6 terminals. When both thermostats are satisfied, the UFH pumps turn off as expected. The heat pump goes into idle mode but the pump to the ASHP itself keeps running and the water in this primary loop is kept heated by the heat pump. It seems a waste of energy keeping this loop heated especially as the thermostats could switch off for several days in warm periods. Is this normal operation? If so, is there any way to switch off the heat pump besides manually turning it off at the controller? I would be interested to hear if this is common to ecodans using third party thermostats or if there is some setting to turn off the heat pump when idle.

After starting this discussion 18 months ago and seeing it is still active, it seems only right to share some of my experience. The first problem I discovered was the installers had left a lot of insulation off the external pipework. They came back and corrected that. The next problem was that the electric heaters were coming on at strange times. This I traced to the calibration of the flow and return thermistors. They were reading about 6’C low making everything hotter than it should be and the electric heaters kicked in to raise the temperature. The flow and return temperatures are easily checked with a digital thermometer. There is an option to calibrate the thermistors in the controller. Also, I disabled all the options for electric heating. I asked a couple of water companies about the risk of legionnaires bacteria in their supply and was fobbed off with remarks like keeping within legislative limits. Thinking this through, the water tank bottom will never reach sterilising temperatures. There is a lot of dead pipe in the supplies to shower heads where bacteria could live, these would be nicely sprayed out before any hot water killed them. Everything is a sealed system with no open tanks for stagnant water. All in all, it seems very unlikely there is legionella in the system and it would be flushed through by regular use anyway.I have set the tank to 40’C but it actually gets to about 50’C as the thermistor is towards the bottom of the tank. I’ve turned off the sterilising cycles and I am still alive! I mentioned about there being 8 thermostats in this small mid terrace house. They are a complete waste of time, money and space. It takes about 4hrs to warm up 1’C with the UFH. The thermostats may react to short events like the sun coming out but it does nothing to control the room temperature. For the upstairs rooms, the quickest way to warm a room is to open the door and let the down stairs heat in. I never use the upstairs heating, enough heat comes from downstairs to do the job. Down stairs I have unscrewed the valve actuators and wired in a TADO in the hall as an over temperature limit. This gives a limit to the house core temperature. I did try the auto adaptive control but this was not stable. I think I understand why the heating can be left on 24/7 in a well insulated house. The heat loss depends on the difference between the inside temp and the outside. For example, if it is 20 inside and 0 outside the heat loss will be 20*const. If the heating is turned off overnight and the temp falls 1 deg, the heat loss will be 19.5* const. The difference in heat loss is 2.5%. Extra heat has now to be put back into the building to get back to 20 deg. Not worth worrying about trying to save money by setting back the temperature. The conclusion is to use a slightly aggressive WC and let the TADO catch any over temp. I am currently trying to find the best WC settings by manually adjusting the flow temp now we are in a spell of much colder weather. I would be interested to hear if you have any thoughts on these changes.

The trade is full of warnings about the perils of undersizing or oversizing a heat pump. Symptoms vary from having a cold house to reducing life span from frequent stop-starts. In my mind, the only time a heat pump is the correct size is when it is supplying full power on the coldest day to give adequate warmth. At any other time, it will be running at reduced power… in other words, oversized. At the low power end, the pump will be just ticking over at the start or end of the heating season, a fraction of the full rating. To me this raises all sorts of questions about sizing a heat pump. Surely a correctly sized pump is simply one that can cope with the coldest weather? A larger pump is just a waste of money for unused hardware. As for the low power end, there will be a minimum cycle time determined by the temperature rise, volume of water and heat pump power. Besides scary stories from installers about wearing out or damaging heat pumps from short cycle times, has anyone seen real data about running a heat pump at low loadings and is there an acceptable short cycle time?

Thanks for these replies. Legionella cycle definitely gets turned off. I like the idea of just removing the main living area actuator for starters, it probably accounts for about half the heating load and would always give a good water flow through the ASHP. There is no buffer tank on this system. Has anyone tried the auto adaptive flow control on the FTC5? A controller that sets the flow temperature according to room temperature as well as outside temperature should be more responsive than a simple on/off signal from a thermostat. I suppose this could be Mitsubishi hype?

Hi Everyone, I have just moved into a new build 3 bed terrace-house which is heated by a 5 kW Ecodan ASHP, total floor area about 60 sq.m. Heating is UFH with a separate circuit in each room with its own neoStat thermostat, I guess this is to comply with building regs even though the smallest room is only 2 sq.m giving a total of 9 thermostats. Each circuit is fed through a manifold with electric actuator. The Ecodan is fired up when any of the thermostats call for heat. Ecodan flow temperature is controlled using the compensating curve method with the FTC5 controller. This is my first experience of heat pump technology and it all seems mindlessly complicated for such a small dwelling. I would be interested to hear your answers to a few questions about the system. I was advised by the installer to run the heating 24/7/365… does this mean there should be pumps working all the time or that the system should turn on if a thermostat calls for heat? The controller has a potentially expensive to run legionella prevention cycle. I have seen unvented HW cylinders with uncovered header tanks (including the occasional dead bird!) for years with healthy occupants… is this legionella prevention some health and safety scheme gone mad or jobs for the boys? Looking at the thermostats, it is quite possible for a single small circuit to be left active and calling for heat. Surely running a very lightly loaded ASHP will give excessive cycling on and off? Looking at the error log, I see several U1 error codes indicating an overheating Ecodan. I would like to improve and simplify the heating with the option of easily returning it back to its original state if there are warranty issues. It should be possible to use the auto adaptive flow control by using a thermistor sensor in the main living area which contains the kitchen, lounge and dining. There is a kosher Mitsubishi temperature sensor for about £100 but a 5k thermistor off ebay should do fine for a few pence connected with some bell wire. In my opinion, only the 3 bedrooms would benefit from thermostats. The intention is to disconnect and remove all the actuators except for the bedroom ones. Also, the call for heat function needs removing from the remaining thermostats. Thus the auto adaptive controller does the bulk of the temperature control with the bedrooms set to a lower temperature. Finally, switch off the legionella prevention and run the DHW as cool as possible to give a good shower. This leaves me with a system where the main living area has the optimum temperature control with the ability to have cooler bedrooms. Any fine tuning can still be done by adjusting water flow rates on the manifold. On paper, this sounds to me a far more sensible approach to what is already installed but I would appreciate comments from more experienced members.