Mitsubishi Ecodan not switching accoding to Cost Boiler selection
Hello!
I own a Mitsubishi Ecodan / Zubadan ASHP 14kW with a gas boiler attached as backup heat source. It can help in colder periods but it should also switch based on energy price.
Which states that it can be achieved but it is not technical.
The HP has an Intelligent operation mode where it can select Cost based between electricity and gas based on the price/kW of each energy.
I expect as example that at a certain outside temperature,
COP=3 and 3kW heating are produced from 1kW electricity
1kW electricity costs 0.6. But it produces 3kW heat with a cost of 0.2 /kWheat
1kW produced with gas costs 0.2 => it pdocudes 1kW heat with a cost of 0.2
=> it should stay as soon as the outside temperature drops and COP drops => it should switch to gas boiler.
Settings:
Service menu / Operation settings / Boiler Operation / Hybrid settings/Priority Mode: Cost
Service menu / Operation settings / Boiler Operation / Intelligent settings/Energy Price / Electricity: 0.6 */kWh
Service menu / Operation settings / Boiler Operation / Intelligent settings/Energy Price / Boiler : 0.2 */kWh
I can force a boiler operation when accessing
Service menu / Heat source setting (Standard/Heater/Boiler/Hybrid *7) : Boiler.
But when i select Hybrid as it should, it only runs on HP.
To test, I used a ridiculosly increase price for electricity and it soed not switch.
I can also force only boiler oepration using the settings:
Service menu / Operation settings / Boiler Operation / Hybrid settings /Outdoor ambient temperature: HP-Boiler when under -15 and Boiler to HP when over 1 (deg C). But it does not account the cost variable.
The manuals say very little about this topic. They say it should work.
if anyone has this setup and can advice or is an installer that did this before. thank you in advance for helping me out.
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Sorry. I don’t think any of the Ecodan owners who usually see this forum have a hybrid hp. You will probably find an answer to this and your other question on the renewableheatinghub.co.uk forum, there are lots of knowledgeable people there.
Good morning! Thank you for information, this is new to me - i will create an account there and post the questions. They are quite advanced, the system was built to take advantages of price variations on different energy market as well as backup if any of the sources have problems. I leave the topic open, maybe there are also people here that can guide me.
Sorry. I don’t think any of the Ecodan owners who usually see this forum have a hybrid hp. You will probably find an answer to this and your other question on the renewableheatinghub.co.uk forum, there are lots of knowledgeable people there.
Please pop back if you find out @Sorin it might help other community members in a similar situation
Hi @Sorin
Out of complete ignorance of your particular system I've read the instructions contained in your link and it says the costs of electricity and gas are stored on the SD card. Do you know what is programned for each of those?
Your electricity price (approx) would be either 22 or 0.22 (for pence or pounds) and your gas would be either 6 or 0.06. This will give you a energy cost of 22/3.2 = 6.8p / kWh for the HP with a COP of 3.2 (mentioned in the document) and 6/0.9 = 6.6p / kWh for gas (where 0.9 or 90% is a typical condensing boiler efficiency) which means the gas is cheaper all the time so it won't switch to the HP. As the temperature drops the COP will fall so your price per kWh on the HP will continue to rise and it will never be the cheaper option in this case.
For it to work dynamically (selecting the cheaper energy) the electricity price would have to be around 20p a unit. With a COP of 3.2 the HP cost would be 6.25p (cheaper than gas) or 7.1p when the COP is 2.8 at very low outside temperatures (more expensive than gas).
Any thoughts on what I have said here?
Peter
Does Peter E’s response help @Sorin?
Hi @Sorin
Out of complete ignorance of your particular system I've read the instructions contained in your link and it says the costs of electricity and gas are stored on the SD card. Do you know what is programned for each of those?
Your electricity price (approx) would be either 22 or 0.22 (for pence or pounds) and your gas would be either 6 or 0.06. This will give you a energy cost of 22/3.2 = 6.8p / kWh for the HP with a COP of 3.2 (mentioned in the document) and 6/0.9 = 6.6p / kWh for gas (where 0.9 or 90% is a typical condensing boiler efficiency) which means the gas is cheaper all the time so it won't switch to the HP. As the temperature drops the COP will fall so your price per kWh on the HP will continue to rise and it will never be the cheaper option in this case.
For it to work dynamically (selecting the cheaper energy) the electricity price would have to be around 20p a unit. With a COP of 3.2 the HP cost would be 6.25p (cheaper than gas) or 7.1p when the COP is 2.8 at very low outside temperatures (more expensive than gas).
Any thoughts on what I have said here?
Peter
Hi Peter. Perfectly logical. Thank you for looking into the document also and explaining the thought process. The values are stored on SD card and in the menu of the programable controller inside the unit.
To your question: :what is programmed for each of those”
The programmed values are close to the the ones in my example from the post. Also (good remark) the efficiency of gas boiler is a parameter ( currently set up to 100% but it allows values from 50% to 150%. I have a condensing gas boiler that declares around 105% efficiency at some water temperatures under 60? is i remeber well.). I do not wish to have the last p saved … therefore approximation in decent limits is acceptable.
The issues is that the HP never switches to gas, even for a 1000x higer electric energy price (specially entered for testing purposes). It always runs on electric power. The installer is not experienced with hybrid setups, maybe i find here someone that solved the same issue.
@Sorin thanks for coming back to the discussion. I run a discrete hybrid system (separate gas boiler and air to air heat pump) but I run it (manually) against the Agile Octopus electricity price (dynamic half hour pricing) and that is cheaper except during the peak (4pm-7pm) when I run the gas boiler or more often a wood burner to save using gas.
Given the current prices of electricity and gas it is always going to be cheaper to run gas with your system but you could choose an artificially low electricity price to get the HP to take some of the heating load and save gas.
However, it seems your actual issue is something else causing it not to switch to gas; most likely another setting buried in one of the menus something like HP Override set to On possibly. I'll try and get a User Manual and have a dig through to see if there are any settings that could be causing this. I'll come back either way.
In researching hybrid systems it seems these are popular in the USA where they run the heat pump down to 0C/32F and a gas heating system (both air ducted systems) below that when the COP drops to a low value and you start getting very frequent defrost cycles.
Peter
I don’t know if there’s some misunderstanding here
The issues is that the HP never switches to gas, even for a 1000x higer electric energy price (specially entered for testing purposes). It always runs on electric power. The installer is not experienced with hybrid setups, maybe i find here someone that solved the same issue.
The Heat Pump itself doesn’t run on gas and so will never ‘switch’ .. or do you mean that the whole system never switches to your gas boiler?
Hi @BPLightlog
We can wait until @Sorin comes back but my reading of the issue is that the HP runs when electricity is cheaper (with the COP) and provides a ‘handover’ signal to the gas boiler when it isn't. That is why the HP has both prices stored in the SD card. I might be wrong but I think the HP is not handing over even when very high electricity prices are entered so I'm figuring that the gas boiler handover signal has been inhibited for some reason, possibly by a setting in one of the menus. I can't find a user manual atm. I have seen Sorin’s request on another forum though so I'm in the right ball park.
Another possibility is the HP can't see the gas boiler (if it's designed to look for it) so it will keep on going rather than shut off and give a handover signal. We need a manual.
I don’t know if there’s some misunderstanding here
The issues is that the HP never switches to gas, even for a 1000x higer electric energy price (specially entered for testing purposes). It always runs on electric power. The installer is not experienced with hybrid setups, maybe i find here someone that solved the same issue.
The Heat Pump itself doesn’t run on gas and so will never ‘switch’ .. or do you mean that the whole system never switches to your gas boiler?
Hello! The HP is the electronic brain that decides to switch. It has a simple relay interface connected to the thermostat entry of the gas boiler turning it on/off when needed. This is working and could be tested from HP LCD interface when i tell to operate only on boiler. But i need the ‘Intelligent’ functions to kick in. Thank you!
That's good to know that the HP is able to switch the gas boiler. As you say, now to crack the intelligent switching.
As a side note, if you are on the SVR or a Fixed Price tariff it it might be better to switch the gas boiler on temperature when we know the COP is going to be lower. I've always seen ‘electricity price switching’ in the context of dynamic electricity pricing when you get cheap off peak (or half hour slots) in exchange for very expensive peak prices but I'm happy to continue to try and diagnose the price switching issue.
As a matter of interest have you inherited the system because if you had it fitted then a user manual should have been provided with it and that would be useful to have at this stage.
Peter
PS BPlightlog and I are forum volunteers and we happily take on challenges like this for customers
Hi Peter!
You are very kind and I will explain why this setup to understand why . There are backup advantages, eco-green benefits but the price is the most relevant as my house consumes 22.000 kWh heating during the winter.
The gas boiler system was installed some time ago and is still working fine. But with the gas prices spiking when russia started the war in Europe => i installed a PV system. No government incentive but there is a benefit that allows me to store the produced electricity in the network until 2030. It means that the PV produces 16.000 kWh during the summer and i consume when i needed paying some fees for transport and distribution (0.5 /kWh) . Electricity needs, except for heating, are 9.000 kWh. The rest of 7.000 for heating (with a COP around 3 to cover for the 22.000 kWh heating needs stated above). The entire system was calculated and it is ok. But the gas price now is low and i should take advantage of this, the savings are important on the 22.000 kWh heat
I also run HomeAssistant smart home connected to everything, including HP and PV and i am able to change temperatures in the system, on water flows, and make lots of logical switchs. But the options do not include any Configuration changes as to force switching on boiler. These are done from the unit LCD disply and are done with the system completely shut down (the display informs you the the system will shut down to change these settings). Smart home looks like a smarter remote :)
Mitsubishi has this facility in the options, i checked all the menus, read the manuals, again and again and it looks fine.
I am pretty sure that it is somewhere something to activate. etc.
Ok. Needle in a haystack time! I could wade through all the controls and figure out what each setting should be or do one of my favourite tricks when we have a complex piece of equipment not working and compare it to that.
There is a shed load of DIP switches on page 16 and 17 and as the Default is for a working system it would be useful to know if there are any differences beween the Default and what is set on your unit. Probably best to print the pages out if you can then fill in the results and let me know any differences. It also gives me a chance to think of a Plan B if that doesn’t work and to read through the other document.
Peter
Many thanks for that. I've had a quick scan and I've noted that there are switch setting for different models and fitment options. Do the switch settings agree with what is fitted in terms of the HP model and the various ancillary units fitted?
I must admit that the very obvious switch settings that would have caused the problem are correct.
Another point which is worth noting, as a former software engineer, is that board fitted switches are normally ony read once just after the power up reset period and are never read again. If the HP unit has never been switched off and on it may be worth doing that. It would happen anyway after a power cut so it it is likely to occur from time to time anyway.
Peter
Hello!
The switches reflect the system configuration
there is a gas boiler attached
there is a Domestic Hot Water tank 300 liters (too small for my girls :))
on Heating/Cooling there is a buffer tank of 50 l calculated by the installer and seems ok for my house.
Model ERSC-VM2D - first on the list at point SW5 + internal heater 2kW
Regarding the reading of the switches, the HP was restarted several times (complete power cut off) since the DIP switches were set up.
Ok. It looks like we've exhausted the easy wins. I'll need to read the other document and will get back to you soon.
Starting from page 28 is the system setup (makes a strong cup of coffee) …
On page 30 there is something I don’t understand
I’ve got to Intelligent settings/Energy Price and I get the Electricity setting but what is the Boiler setting?
Can you also tell me what you have set for the others in this area?
I believe Hybrid settings should be set to Priority/Ambient/Cost/CO2
Thanks
Peter
The next thing I have discovered is this setting
Page 19, you need Boiler selected according to this
19
Signal inputs - IN4 - Demand Control Input –
Open Circuit (Normal)
Short (Heat Source Off)
Note *3 - To turn on the boiler operation, use the main remote controller to select “Boiler” in “External input setting“ screen in the service menu
@Peter E : Yep, I know the setting but it requires an external relay to trigger gas Boiler switch on/off, regardless of the Intelligent settings in HA.
It is an option if I can reinvent the hot water :)) and rewrite all the logic outside HP:
calculate the COP curves (although they can only be guessed from specs) outside the HP intelligent settings - e.g in Home assistant or in ESP microcontroller
evaluate cost /kWh heat and decide when to switch + margins to avoid frequent switching on borderline …
Program another ESP8266 or ESP01 + relay to fulfil this function. I have a few of them already connected to different devices
I could also force some improvements via Smart Grid functions - to heat DHW or raise water temperature when the energy is cheaper or from PV (autumn / spring)
i exclude any option where I will trigger manualle any switch - I am full of automations in my house and any additiona long term maintenance will make me serve the automation not the other way around
But these are workarounds. I am able to program the microcontrollers to do the job but as a last resort.
The challenge now is to make it work as it was designed by the manufacturer.
Starting from page 28 is the system setup (makes a strong cup of coffee) …
On page 30 there is something I don’t understand
I’ve got to Intelligent settings/Energy Price and I get the Electricity setting but what is the Boiler setting?
Can you also tell me what you have set for the others in this area?
I believe Hybrid settings should be set to Priority/Ambient/Cost/CO2
Thanks
Peter
To answer the above message that i overlooked (sorry)
You can choose from the Priority option one of those Cost/CO2/Ambient. I chose cost, of course. The setup allows to prioritize CO2 if you go greener than others
The price is *kWh price for electricity or boiler fuel (boiler can be gas, petrol or whatever) but it still has a cost/kWh and an efficiency (see HeatSource/Boiler Efficiency).
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. There are backup advantages, eco-green benefits but the price is the most relevant as my house consumes 22.000 kWh heating during the winter.
