Nuaire MVHR high energy consumption?

[NewbieJ]

Hi all,

I was wondering if someone would be able to advise if something is wrong with the MVHR in my one bed flat. I recently moved into a new build flat that has the Hybrid system MRXBOXAB-ECO5-AE(OH)CV installed.

I have noticed that the amount the electricity that required to run the MVHR seems to be extremely high.

At first, I did not know what the cause of my high energy bill was, however after getting the smart meter display, I can now clearly see that the MVHR using around 550W just to run it.

I would be grateful if anyone would be able to advise if it is normal? And if I have missed something.

Thank you in advance.

[Nickfromwales]

2 minutes ago, NewbieJ said:

Hi all,

I was wondering if someone would be able to advise if something is wrong with the MVHR in my one bed flat. I recently moved into a new build flat that has the Hybrid system MRXBOXAB-ECO5-AE(OH)CV installed.

I have noticed that the amount the electricity that required to run the MVHR seems to be extremely high.

At first, I did not know what the cause of my high energy bill was, however after getting the smart meter display, I can now clearly see that the MVHR using around 550W just to run it.

I would be grateful if anyone would be able to advise if it is normal? And if I have missed something.

Thank you in advance.

Hi. Does it have an electrical pre heater in it? This would be to uplift the temp of incoming air, and that would likely be the culprit. 

[NewbieJ]

Hi Nick,

 

No not I am aware of. In fact, I thought that the incoming air is actually rather cold.

It is more like the cooling mode is running, but I actually have it switched off, therefore I am not sure if there is something wrong or not.

[Nickfromwales]

10 minutes ago, NewbieJ said:

Hi Nick,

 

No not I am aware of. In fact, I thought that the incoming air is actually rather cold.

It is more like the cooling mode is running, but I actually have it switched off, therefore I am not sure if there is something wrong or not.

If it cools then it has an inbuilt heat pump. In the last bit of cold weather I suspect this has been sporadically heating, maybe overnight. Is the 550w consumption constant? Fan should be sub 200w. 

[NewbieJ]

14 minutes ago, Nickfromwales said:

If it cools then it has an inbuilt heat pump. In the last bit of cold weather I suspect this has been sporadically heating, maybe overnight. Is the 550w consumption constant? Fan should be sub 200w. 

Yes, the 550w is constant.

[Nickfromwales]

 

Ok, so 550w divided by 230v is  = ~2.3amp draw, so seems a bit odd.

 

I’d suggest going through the programmer again to confirm what ‘state’ it is in, eg it is cooling or heating or neither, currently. Maybe perform a factory reset. 
 

Also, does it have a display of the 4 ports, with the 4 temps (supply > fresh in / extract > exhaust) etc?

[NewbieJ]

Inside of the cover it has 6 dials which adjust the speed at which the fans rotate.

 

[Dreadnaught]

22 hours ago, Nickfromwales said:

Does it have an electrical pre heater in it?

 

@NewbieJ, you may have misunderstood how (and why) and pre-heater works. A pre-heater is to ensure that the heat exchanger doesn't freeze up in the coldest weather. The heat generated does not however enter the house, the majority of it instead heads straight out of the exhaust port as that is how heat exchangers work. If your pre-heater was accidentally running when it shouldn't, it might possibly explain (at least part) of your overly high power consumption. But it would show not as warm air to the house but actually as surprisingly warm air at the exhaust port to the outside.

 

A post-heater is different – that one heats the house.

[Nickfromwales]

20 hours ago, NewbieJ said:

Inside of the cover it has 6 dials which adjust the speed at which the fans rotate.

 

This is mostly for commissioning the correct flow rates to the spaces served by the unit. Not seen one like that before, so the unit must have (I assume) 3 fans or more. Can you post a link to the actual user / installation manual if possible, please? A bit tricky to pin down the exact instructions for the unit, seems to be a few different offerings. 
 

FYI, I would expect (hope) that if doing active heating or cooling, the fan speeds would increase to convey additional volume of air (and heat energy) as at trickle rate the usefulness of those functions would be borderline pathetic.

 

Do you have a pic of the display saying which mode it is in? Does it mention heating and cooling specifically, and can you leave it in max cooling for an hour then go to max heating for an hour, to test these functions at the air inlets? 

[JohnMo]

1 hour ago, Nickfromwales said:

Not seen one like that before, so the unit must have (I assume) 3 fans or more.

Looks pretty similar to Titon units, but they only have 4 potentiometers. Setback speed is just a calculation.

 

So speed one (assume a setback speed) one pot for extract and one for supply fan. Then same for normal and boost. So just two fans and adjustable flow rates for each speed of the fans.

 

I would leave these settings well alone. Look for a duct heater upstream or downstream of MVHR unit. Switch it off does it fix the issue?

[Nickfromwales]

The 550w constant is what gets me, as with heating or cooling you’d think it would be on off thermostatically or at least a curve to the consumption?

[JohnMo]

The unit may have a cooling module. Which I assume is a small heat pump. You can adjust the set point at which this operates, factory set point is 23. But if altered from this say to 20, and the extract air is 21, then cooling mode will run continuously. Worth a look.

 

 

hybrid_cooling_brochure_1_.pdf

[Mike]

5 minutes ago, JohnMo said:

The unit may have a cooling module

And, in addition to the set point question, the User Guide also indicates that there's a manual switch to select either summer or winter mode, and that "Selecting “Summer Mode” means that the MVHR will target a lower internal temperature during the warmer months."

 

If it's currently running in Summer Mode it would be fighting against the heating system, which may also explain the power usage.

[NewbieJ]

On 28/02/2025 at 21:21, Dreadnaught said:

 

@NewbieJ, you may have misunderstood how (and why) and pre-heater works. A pre-heater is to ensure that the heat exchanger doesn't freeze up in the coldest weather. The heat generated does not however enter the house, the majority of it instead heads straight out of the exhaust port as that is how heat exchangers work. If your pre-heater was accidentally running when it shouldn't, it might possibly explain (at least part) of your overly high power consumption. But it would show not as warm air to the house but actually as surprisingly warm air at the exhaust port to the outside.

 

A post-heater is different – that one heats the house.

Thanks for the explanation! Yes, I am clueless on this. 

[NewbieJ]

On 01/03/2025 at 10:41, Nickfromwales said:

This is mostly for commissioning the correct flow rates to the spaces served by the unit. Not seen one like that before, so the unit must have (I assume) 3 fans or more. Can you post a link to the actual user / installation manual if possible, please? A bit tricky to pin down the exact instructions for the unit, seems to be a few different offerings. 
 

FYI, I would expect (hope) that if doing active heating or cooling, the fan speeds would increase to convey additional volume of air (and heat energy) as at trickle rate the usefulness of those functions would be borderline pathetic.

 

Do you have a pic of the display saying which mode it is in? Does it mention heating and cooling specifically, and can you leave it in max cooling for an hour then go to max heating for an hour, to test these functions at the air inlets? 

Thanks Nick.

Yes, there is 3 sets of fan, the first one is the usual mode. the other 2 are boost mode.  One is connect to the bathroom, and the 3rd one is in the kitchen.

 

There is a thermostat at the wall that is connect to it, which has a Summer mode and Winter mode that can be switched on and off. My understanding is that when Summer mode is on, the cooling will kick in when the temperature reach the set point. On the other hand, if the Winter mode is selected, this will switch on the heat recovery mode. 

 

Please find the user guide and installation manual below for your information. 

 

MRXBOXAB-ECO5-AECV.pdf MRXBOX-ECO5-AECV User Guide.pdf

[NewbieJ]

8 hours ago, Mike said:

And, in addition to the set point question, the User Guide also indicates that there's a manual switch to select either summer or winter mode, and that "Selecting “Summer Mode” means that the MVHR will target a lower internal temperature during the warmer months."

 

If it's currently running in Summer Mode it would be fighting against the heating system, which may also explain the power usage.

I have switched it to Winter mode, but I am wondering if it is stuck at summer mode.

[NewbieJ]

9 hours ago, JohnMo said:

The unit may have a cooling module. Which I assume is a small heat pump. You can adjust the set point at which this operates, factory set point is 23. But if altered from this say to 20, and the extract air is 21, then cooling mode will run continuously. Worth a look.

 

 

hybrid_cooling_brochure_1_.pdf 9.3 MB · 1 download

Thanks John, I switch to winter mode, so the cooling mode in theory if working correctly, it should not kick in. All very strange. 

[Mike]

1 hour ago, NewbieJ said:

there is 3 sets of fan, the first one is the usual mode. the other 2 are boost mode.

There will only be one pair of fans (one for supply, the other for extract), but they can both run at 3 different speeds. Speed 1 is for when the house is empty, 2 is for normal use, and speed 3 for boost. The installer should have set the dials to move the correct amount of air for each of these speeds to suit the design, which takes into account the layout of your flat.

 

Presumably you have a controller that can switch between all 3 speeds, as well as between summer & winter - so 6 possible settings. If you can measure how many Watts it uses in each of these 6 settings, then that may provide us with some clues.

 

Edited March 2 by Mike