Ecodan heats water only to 39C with heat pump

[FrankG]

My Ecodan only heats the DHW (Domestic Hot Water - in the boiler) to 39C by using the heat pump while it is 30C outside.
I have to use the immersion heater (= pure electric) to increase the temperature further!?

 

My installer tells me that this is normal, because heat pumps are designed/optimized to work in moderate temperatures.

To me this sound not very logical.

I've read the user manual, service manual, but did not find useful/relevant information.

 

Who can help me?

[JohnMo]

Sounds like a load of old tosh.  Almost all heat pump will provide 55 degC water some over 60 degC.

 

Does you cylinder have a heat pump coil in it?  If it doesn't that may be reason.

 

What is your flow temperature, when heating you hot water cylinder?

[ReedRichards]

It is without doubt a load of old tosh.  Either your installer did not know what they were doing or they knowingly did something wrong but don't want to own up.  

[HughF]

Yep, incompetent installer. Now there’s a surprise 😂

 

[LA3222]

My ASHP is an Ecodan and gets the water temp up to 55 fine without using the immersion. I can't see what has 'physically' been done to cause you this issue, my gut instinct is that something is not quite right with your settings in the FTC controller. A good read and familiarisation of the manual will help you to scroll through it all.

[TW9]

My Ecodan heats to 55 degrees so there's no reason yours shouldn't be able to. What happens when you try to increase the temperature on the controller?

[Dan F]

@FrankGWhat model Ecodan?

Edited July 15, 2022 by Dan F

[FrankG]

@JohnMo My cylinder (I assume you mean the cylindrical boiler) gets its initial heat from the hidrobox. And it has an electrical immersion heater (that should not be needed in summer).
Where can I see the flow temperature?

 

@LA3222, i read the user manual twice, compared notes and all settings with the installer. I guess I will have to read the Service Manual now?

 

@Dan F My hidrobox is the Mitsubishi EHSC-VM2D.UK.

[FrankG]

@TW9I just ran the experiment: set max temp from 50C to 55C. Heat pump stops again at 38C (the power consumption go down), and the FTC shows on the display that the immersion starts (see attached picture).
I also tried to set the DHW (hot water) mode in Normal, or ECO - does not make a difference ...

What I do notice in my power consumption (I have solar panels, so I can see this almost real-time) is that the heat pump only uses 1.3 kW when in use. I remember in winter that this was a lot higher!?

Edited July 19, 2022 by FrankG

[JohnMo]

Can you see what the return temperature is when you flowing at 55 degC?

 

Also what make/model cylinder are you trying to heat?  Is specifically for a heat pump?

[ReedRichards]

1 hour ago, JohnMo said:

Can you see what the return temperature is when you flowing at 55 degC?

 

Assuming the flow temperature reaches 55 C before the heat pump gives up?    

[JohnMo]

No, the return will be lower than 55.  If it's reaching 55, then the coil within the cylinder is not suitable for a heat pump.

 

Assume you changed the cylinder when you upgraded to a heat pump.  If you didn't or just installed a normal cylinder that is your issue.  The coil within the cylinder is too small to transfer the heat from the lower temperature heat pump, compared to a gas boiler which with would be flowing at around 70 degC.

 

The cylinder name plate will have all the info.  You take a photo and post on here?

[FrankG]

@JohnMo, my house (so also the whole installation) is new - installed in 2020.
See attached the plate of the boiler (sorry, in Spanish ...)

Edited July 19, 2022 by FrankG

[JohnMo]

Looks like your internal heat exchanger coil is 1.5m2 area, I think it more normal to a see a 3m2 coil when connected to a heat pump.

 

So your issue is related to the DHW cylinder and it's internal coil being too small most likely.

 

Did you install yourself or was it specified and bought by the plumber?

 

Also looks like there is an anode to replace to prevent internal corrosion, these normally need to be replaced annually.

[Temp]

I think I would try measuring the ASHP flow and return temperatures before doing anything drastic with the tank. See if the ashp is even trying to make >38C.

[PhilT]

Menu item 3 in the DHW settings determines operation time. Mine is still set at the default 60min which will not be enough for yours if your coil is only 1.5sq m. Until you find a more permanent solution try setting it to the maximum 120min

[FrankG]

@JohnMo, @ReedRichards and @Temp, your questions lead to a small test I just did.

Attached picture says it all - the temperature of the heat pump / hydrobox does not get above 44C!?
Already after 18 minutes the heat pump stops. Not sure why. The operation time is set at 60 minutes, max temp at 50C.

What setting (FTC or dip switch) could be wrong here?

What's next to test?

Edited July 19, 2022 by FrankG

[HughF]

1.5m2 is fine for a heat pump coil. Ideally you’d see 2m2 or above but sometimes you just can’t get that size into the cylinder. My vaillant slimline heat pump cylinder is 1.5m2.

 

 

 

 

[HughF]

1 hour ago, HughF said:

1.5m2 is fine for a heat pump coil. Ideally you’d see 2m2 or above but sometimes you just can’t get that size into the cylinder. My vaillant slimline heat pump cylinder is 1.5m2.

 

 

 

 

And by comparison, the non-heat pump vaillant cylinder of the same 150ltr capacity is 0.69m2 coil area. The 300ltr only gets a 0.8m2 coil.

[PhilT]

It's fine if time is not an issue but in the depths of winter the DHW cycle needs to be as short as possible

[SteamyTea]

26 minutes ago, PhilT said:

It's fine if time is not an issue but in the depths of winter the DHW cycle needs to be as short as possible

Not if the CoP of the ASHP suffers and frosting up takes place because it is trying to run at an elevated temperature.