Hello - Mitsubishi Ecodan ASHP constantly shutting down and immersion using lots of KW

[Caroline]

Hi 

 

Thank you for adding me.

 

We had a 11.5 Mitsubishi Ecodan ASHP fitted to a newbuild house in 2019.  We also have a neighbour newbuild with the same heat pump by 9 KW size.

 

Our first issue was that they are using in the 10s of units for their immersion, I understood this only kicked in when it did its salmonella? monthly thing.  Our heat pump is in the thousands so using much more than the neighbour, any suggestions to why.

 

In the last couple of weeks the ASHP is louder than usual and the system keeps shutting down, I reset it and it works for an hour or two then shuts down.

 

My installer has had a look can't work out why.  They sent Mitsubishi various codes and Mitsubishi said they couldn't detect any fault from the codes sent to them.

 

The installer has recommended Mitsubishi come out, the ASHP is still in warranty but the cylinder has expired in Dec 2021.  Misubishi have said if they attend and can't find an issue they will charge us £350 plus VAT.

 

I know there are some wise people on this forum so would appreciate any help.

 

I am so stressed as my husband has Stage 3 colon cancer, is undergoing chemo/radiotheraphy and the house is cold and water tepid around 40 deg atm but has been down to 27 deg (when we went out and system was shut of for a couple of days).

 

Thank you. 

[MikeSharp01]

29 minutes ago, Caroline said:

Our heat pump is in the thousands so using much more than the neighbour, any suggestions to why.

IS the heat pump running all the time, when it works, or are these the immersion units? Assume it is immersion units - which means your HP is not working correctly at all as I see it.

[Caroline]

Hi Mike

 

The ASHP and Immersion should be running to provide our under floor heating (our only source of heating) and the immersion which runs off the ASHP for hot water.

 

Kind regards

Caroline

[ProDave]

When the ASHP "shuts down" it should give a fault code. Post here what it says, picture of the controller if possible to show what it says.

 

High immersion heater use from new might be poor set up.  Ideally you want your hot water tank set at no more than 50 degrees, that's about the limit of good performance from an ASHP.  Many of them, if you set the DHW temperature higher, they default to using the ASHP up to about 50 degrees then the immerrsion heater to get it hotter.  Any competent electrician or plumber or even a competent teenager could read the manual and check through the settings to see how it was set up by installer.

[Caroline]

Hi Dave

 

Thanks for your post.  The fault code is P8.

 

I believe the water is set at 50 deg.  Because I am working from home today when the system shuts off (which is very regularly) the water is between 42-48 deg, depending how quickly I find the fault flashing.

 

Kind regards

 

[MikeSharp01]

Looks like the P8 problem can come from various sources. In this document https://ohmenergy.co.uk/heat-pumps/ecodan-fault-codes/ it mentions flow rate as the problem, maybe your pump is failing. Has it ever worked properly?

[Marcin]

Hi Everyone. I hope this is right place to post my concern. I had moved in to the property with heat pump and solar panels 5. Weeks ago. Since day one things are nightmare. Ecodan Mitsubishi pump. Floor heating downstairs and 3 radiators upstairs. 
Query 1
Not sure where to start. Initially had no hot water or heating and P0 error came up. Electrician came could not diagnose issue and stated he has bypasses something and now I can use immersion to heat water. Hot water was working however outside pump never engaged.
P0 error was still there and shutting down system. I have rang helpline from Mitsubishi and they advised to change battery in downstairs thermostats. I did that and error was gone but than changed to P1 error. 
P1 advise from manual and mitsubishi person has not helped. I was advised to change sensor settings to main RC and P1 error should resolve. This has not happened and when I put heating to curve mode or target flow temperature and want hot water system engages two pumps light up and after few minutes error P1 comes back. 
When I put heating to target room temperature and heat water, pump works few minutes and than there is loud clank and bolt appears on panel. Bolt is present all the time when water is heating and pump do not spin outside, this does not sound normal to me do you agree? Also when I stop water heating there is even louder clank from control board and bolt disappear. 
I believe P1 error is something to do with thermistors, i can only see five of them but all are tucked in under foam and touching pipes around cylinder. They are not even connected to anything but only to control board. One of them is freely hanging and not inserted anywhere. 
Contractors sent by developer had no clue what to do and one even said pump is not commissioned for different heating mode and he does not see issue. It is just nightmare and not sure where to head anymore. Any advise or support would be appreciated. 

[AliG]

TBH I am just reading on the internet here, so you may have already seen this yourself.

 

The "bolt" is a lightning bolt. This means that it is using the immersion heater instead of the ASHP to heat hot water.

 

The electrician has done what is shown in this video -

 

He has changed the heat source from Standard to Heater. I would change it back. The sound you are hearing is the relay switching on the immersion.

 

P1 error seems to be for reading the flow temperature. It may be that the P1 error is caused by it using the immersion and not the heat pump as there wouldn't be any flow to measure. Or it may be something else. Can you change it back to Standard using the instructions on the video and then see if that resolves the error. If not something else is the issue.

 

 

 

[ProDave]

Try these two

 

 

 

[Marcin]

On 20/09/2023 at 13:30, AliG said:

TBH I am just reading on the internet here, so you may have already seen this yourself.

 

The "bolt" is a lightning bolt. This means that it is using the immersion heater instead of the ASHP to heat hot water.

 

The electrician has done what is shown in this video -

 

He has changed the heat source from Standard to Heater. I would change it back. The sound you are hearing is the relay switching on the immersion.

 

P1 error seems to be for reading the flow temperature. It may be that the P1 error is caused by it using the immersion and not the heat pump as there wouldn't be any flow to measure. Or it may be something else. Can you change it back to Standard using the instructions on the video and then see if that resolves the error. If not something else is the issue.

 

 

 

So Installer came and straight away stated issue with wiring. Further, temp sensor for tank was not even connected. Now I have hot water. I can see pump working, however immersion seem to be kicking in on the end of the cycle. Not sure if this is ok, water set to be heated to 55 degrees. Heating seems to be working ok at the moment. 

[AliG]

If you turn it down a little bit that should stop the immersion kicking in. 55c is at the limit of how hot it can get the water. In fact that’s as high as the flow can go so if the tank temp is set at 55 it will need the immersion to get there.

 

The description of the temp sensor wiring did sound very dubious although I didn’t think that wasn’t the main issue.

 

 

 

 

[Marcin]

9 hours ago, AliG said:

If you turn it down a little bit that should stop the immersion kicking in. 55c is at the limit of how hot it can get the water. In fact that’s as high as the flow can go so if the tank temp is set at 55 it will need the immersion to get there.

 

The description of the temp sensor wiring did sound very dubious although I didn’t think that wasn’t the main issue.

 

 

 

 

Hi. Thanks for the reply. Main issue was wiring. Guy was able to sort things out to the point that heating has started working. Sensors THW 1,2 and 5 connected to the board but nowhere else. Not sure how system could know how hot water was in the tank. Temp is set in 55 as this was installer recommendation. I will decrease this to 50 and se what will happen. 

[JohnMo]

9 hours ago, Marcin said:

will decrease this to 50 and se what will happen. 

The ideal temp is as low as it will go without actually running out of hot water. The other thing is set your timing to heat the cylinder, either in a low price period if you have a low rate tariff or towards the middle of the day when it's likely to be warmest outside so you get the best CoP. Worst time to heat without a low tariff period is first thing in the morning, when it's likely to be the coolest outside.

[Marcin]

4 hours ago, JohnMo said:

The ideal temp is as low as it will go without actually running out of hot water. The other thing is set your timing to heat the cylinder, either in a low price period if you have a low rate tariff or towards the middle of the day when it's likely to be warmest outside so you get the best CoP. Worst time to heat without a low tariff period is first thing in the morning, when it's likely to be the coolest outside.

Hi. Thanks for sharing. I have same tariff for electricity through the day and night. 
i have set max temp at 50. When water was hot I had only heat pump engage to keep temp. Today when water started not been so hot, I had pump automatically engaged but only worked for  10 minutes and went to switch to immersion. Is this what should happen? Outside temp is 13 degrees. 

[JohnMo]

3 hours ago, Marcin said:

Hi. Thanks for sharing. I have same tariff for electricity through the day and night. 
i have set max temp at 50. When water was hot I had only heat pump engage to keep temp. Today when water started not been so hot, I had pump automatically engaged but only worked for  10 minutes and went to switch to immersion. Is this what should happen? Outside temp is 13 degrees. 

The logic could be

You have a demand for cylinder heating

ASHP starts and heats the cylinder, if the cylinder fails to get to full temperature (50), before the heat pump gets to its max temp, the immersion will start.

 

Its not ideal if the immersion is stating every time you have a demand for cylinder heating.

 

Can you see the flow temperatures to and from the heat pump and the cylinder temperature? If so, it would be helpful to record what is happening to max sense of exactly what's happening

[Dave C]

4 hours ago, Marcin said:

Hi. Thanks for sharing. I have same tariff for electricity through the day and night. 
i have set max temp at 50. When water was hot I had only heat pump engage to keep temp. Today when water started not been so hot, I had pump automatically engaged but only worked for  10 minutes and went to switch to immersion. Is this what should happen? Outside temp is 13 degrees. 

 

Certainly isn't what should happen! Some thing happened on my Ecodan after it was installed - heat pump would come on to heat up hot water cylinder, it would start heating OK, then in under half an hour would give up and switch over to the immersion, which I guess is the fall back behaviour for "we need hot water and the heat pump can't run for some reason". Turned out it was insufficient flow rate causing the heat pump to shut down - installer needed to reconfigure the water pumps.

 

Could try turning the water pump speed up, if it's a separate pump plumbed in and it's just got a simple dial or push button to switch between different pump speeds.

Edited October 12, 2023 by Dave C

[AliG]

There could be something funny in your hot water settings.

 

This video explains all the hot water settings. It is pretty simple, could you tell us what the settings are. I assume that you are changing the DHW Max temperature and not the flow temperature. If some of the other settings are incorrect they might be causing this.

 

It would also be useful to know the size of your hot water tank and the capacity of your heatpump.

 

 

 

[Marcin]

This is my water cylinder. I have similar setting as on video. I wanted to ask about sensor he is talking about. Where does it need to be with size of my tank? Same as his at the bottom? As mine seems to be at the top. I will post picture of the pump in next post. 

[Marcin]

Just now, Marcin said:

This is my water cylinder. I have similar setting as on video. I wanted to ask about sensor he is talking about. Where does it need to be with size of my tank? Same as his at the bottom? As mine seems to be at the top. I will post picture of the pump in next post. 

 

[Marcin]

16 hours ago, Dave C said:

 

Certainly isn't what should happen! Some thing happened on my Ecodan after it was installed - heat pump would come on to heat up hot water cylinder, it would start heating OK, then in under half an hour would give up and switch over to the immersion, which I guess is the fall back behaviour for "we need hot water and the heat pump can't run for some reason". Turned out it was insufficient flow rate causing the heat pump to shut down - installer needed to reconfigure the water pumps.

 

Could try turning the water pump speed up, if it's a separate pump plumbed in and it's just got a simple dial or push button to switch between different pump speeds.

Pump is on max speed. Does it also need to be changed on controller in installer settings? Its on speed 3 but can go up to 5

[Marcin]

3 minutes ago, Marcin said:

 

Also. On that video he can see temperature of hot water on FTC controller. I cant see any temperature. Is there way to set this somewhere?

[AliG]

The little grey box is where the normal thermostat on the cylinder would be. Can you point to where the thermostat is please as I can’t figure it out. If it is near the top of the cylinder then it likely won’t get hot enough to hit the target temperature as the heating coil is near the bottom.

If the temperature of the tank is not showing as in the second picture then it suggests to me that the controller still is not correctly connected to the tank thermostat.

 

I don’t have direct Ecodan experience so someone might chip in.

 

That is an extremely untidy looking install if you ask me and there are a surprising number of loose cables.

 

Also on your pic of the ASHP are those drops condensation or ice? My parent’s ASHP was bone dry this morning, it’s not that cold. It suggests to me that the ASHP is running very hard. It might be too small.

 

 

 

[Marcin]

1 hour ago, AliG said:

The little grey box is where the normal thermostat on the cylinder would be. Can you point to where the thermostat is please as I can’t figure it out. If it is near the top of the cylinder then it likely won’t get hot enough to hit the target temperature as the heating coil is near the bottom.

If the temperature of the tank is not showing as in the second picture then it suggests to me that the controller still is not correctly connected to the tank thermostat.

 

I don’t have direct Ecodan experience so someone might chip in.

 

That is an extremely untidy looking install if you ask me and there are a surprising number of loose cables.

 

Also on your pic of the ASHP are those drops condensation or ice? My parent’s ASHP was bone dry this morning, it’s not that cold. It suggests to me that the ASHP is running very hard. It might be too small.

 

 

 

Hi thank you for reply. Grey box is not even connected hence why I believe there is no temperature on the screen. Can you advise where this should be connected on FTC control board?

Hanging cables are thermistors/sensors. These are THW 1,2,5. THW 5 has two coming out of control board. I believe these should be inserted into spaces on the tank. See picture, I am unsure if both in the same space or in two separated places. First pic is top of the tank and second is bottom. Do you know where these would go? 
Droops on ASHAP pic are rain so nothing to worry. 
I agree this is set up messy and was like this from day one. As it is not my house I keep asking but people dont take any notice so I try and sort it myself. 
thank you for your help and would appreciate more thoughts on above. 
 

Ps. Looking at above video with water setting, I have found out from comments that actually this type of Mitsubishi pump R32 only heats water to 48 degree after which immersion kicks in if you want it hotter. Apparently system calculate what would be quicker and most efficient way to get to temp above 48. 

[AliG]

Maybe setting it to 48C is the answer. I think that is the temperature quite a few people use.

 

TBH that should be warm enough, a shower is usually at around 40C.

 

The tank is not that large, however and will cool down quickly as you have a shower, so if the temperature is set at 48C I would set the temperature drop when the ASHP kicks in to 8C, you will have to play around with it. It depends on how much hot water is used. Running at 6kW it will take almost an hour to recover back to 48C from a 100l use for a shower. 

 

I am afraid I cannot help on the thermistors, I have never seen a hot tank set up like that, I don't know if that is normal for an Ecodan.

 

 

[Marcin]

4 hours ago, AliG said:

Maybe setting it to 48C is the answer. I think that is the temperature quite a few people use.

 

TBH that should be warm enough, a shower is usually at around 40C.

 

The tank is not that large, however and will cool down quickly as you have a shower, so if the temperature is set at 48C I would set the temperature drop when the ASHP kicks in to 8C, you will have to play around with it. It depends on how much hot water is used. Running at 6kW it will take almost an hour to recover back to 48C from a 100l use for a shower. 

 

I am afraid I cannot help on the thermistors, I have never seen a hot tank set up like that, I don't know if that is normal for an Ecodan.

 

 

Hi. I have set it up pump to 47 degrees. I have put 2 thermistors in the bottom and top of the tank. Pump now heats to set temperature and does not use immersion. Looks like positive sign. All resolved by myself and people like you with advice. I am hoping all will continue in good way.