Power consumption, summer?

[JamesJJJ]

I completely get the benefit of mhrv in the winter, but I am struggling to see the same in summer.

 

We recently moved into a house which has a villavent system installed, it has been serviced recently and is working to spec.

 

I noticed high energy usage and tracked it down to the villavent. In normal mode (with summer bypass) it is chewing through approx 130w and in minimum mode approx 60w. It is also noisy at 130w.

 

In the winter I can understand that heat loss would outweigh the power consumption,  but in summer I can open a few windows and get fresh air with 0 cost?

 

Is this level of power consumption typical for a 5 bed system, or is it pointing to a potential issue?

 

Tia,

[PeterW]

Your system will be filtering out the dust and pollen so that’s a significant benefit in the summer. 

 

130w sounds like boost mode - has it got an automatic override ..??

[MikeSharp01]

Welcome to THE forum - there will be people who understand in depth along shortly. Sorry @PeterW this post crossed with yours and was not intended to insult. 

Edited August 10, 2019 by MikeSharp01

[JamesJJJ]

Thanks. Boost mode seems to add another 60-100w ontop of normal mode. 

[Jeremy Harris]

Doesn't sound far off for a system in a 5 bedroom house.  Our (smaller) MVHR uses around 40 W or so in normal background ventilation mode and this rises to around 85 W in boost mode.  It rarely stays in boost mode for long, though, as it only switches to this during showers, or if there's steam coming from cooking in the kitchen.

 

As @PeterW mentions, there is the benefit of very much higher indoor air quality, both from the big reduction in stuff like pollen, and from the massively improved whole house ventilation, which significantly reduces the risk of condensation and stale air build up.  Opening windows isn't that effective at providing proper ventilation, I found.  I measured the CO₂ concentration in the bedroom at our old house, and with a window open 24/7 the CO₂ still rose to around 1600ppm or more in the middle of the night (a healthy level would be lower than around 800 - 1000ppm).  In this house, with MVHR, I've never seen the CO₂ concentration get higher than about 650ppm, and that's only when we have guests around, so there are more people breathing the stuff out.  The air quality improvement alone would be enough for me to insist on fitting MVHR to any future house, and the ~£0.16 per day running cost* seems a small price to pay.

 

 

*  Ignores the fact that most days the PV system in the roof generates more than enough to cover the daytime running cost.  The true cost is probably less than 8p/day.

[nod]

Sorry hijack 

 

Omitting MVHR is the only thing I regret from our build Wonderful warm home in winter Cheap to heat 

It takes such a  long time to cool down in summer. We were advised to set the UFH to 19 in summer It would be great if the in house temperature   dropped to 19

[PeterW]

1 hour ago, JamesJJJ said:

Thanks. Boost mode seems to add another 60-100w ontop of normal mode. 

 

Do you have the model number of the MVHR ..??

[Jeremy Harris]

Also worth checking to ensure the filters are clean.  I find that the power consumption of our MVHR rises when the filters get dirty.  Filter change intervals for an MVHR depend very much on how clean the local air is, here I can just about get away with cleaning/replacing them every 6 months.  I know that others have found they need to clean/replace filters more often than this, though, so probably worth checking yours, @JamesJJJ, if you haven't already.

[SteamyTea]

45 minutes ago, JSHarris said:

others have found they need to clean/replace filters more often

May depend where you live. Near a busy road, or an arable farm, or very close to the sea. All those throw up a lot of particles, all the time.

I live just off one of the most polluted roads in the UK, hard to believe that in windy, wet Cornwall. The dirt I get in my windows is the worse I have known.

[JamesJJJ]

1 hour ago, PeterW said:

 

Do you have the model number of the MVHR ..??

I think it is this:

https://www.systemair.com/xen/Villavent-UK/Products/UnPublished/VR-400-EEC-warmtewiel-WTW/

 

 

Have ordered an air monitor so I can compare windows vs mvhr.

 

I also need to work out how to make it quieter, my wife cannot sleep when it is running in normal mode. None of this is an issue now but I need to sort it before winter...

[Jeremy Harris]

1 hour ago, JamesJJJ said:

I think it is this:

https://www.systemair.com/xen/Villavent-UK/Products/UnPublished/VR-400-EEC-warmtewiel-WTW/

 

 

Have ordered an air monitor so I can compare windows vs mvhr.

 

I also need to work out how to make it quieter, my wife cannot sleep when it is running in normal mode. None of this is an issue now but I need to sort it before winter...

 

The main things to monitor are CO₂ concentration and humidity, as they are good indicators of how well ventilated the house is.

 

It shouldn't make any noticeable noise if it's installed and set up properly.  Set up after installation is fairly important, as the flow rates need to be balanced, the ventilation rates measured and the fan speeds set to give adequate ventilation without noise.  Ours is silent in background ventilation mode, it cannot be heard at all, even in the middle of the night when the house is quiet.  The fact that you can hear yours makes me suspicious that it may not have been properly commissioned, or may not have been properly installed.  Often silencers are specified as being a requirement in the main duct runs to the unit; the manufacturer of our unit stipulates that these must be fitted.  I didn't follow this advice initially, and there was some noise from the unit, but after fitting silencers the noise went away.

[PeterW]

Doesn’t look too complex - do you have the commissioning sheet as normally that is the reason why you have noise when the vents are done up too tight. 

 

Manual is here - if you can get the cover off and take a photo of the DIP and Rotary switch settings it may help. 

 

[Gone West]

4 hours ago, JamesJJJ said:

I also need to work out how to make it quieter, my wife cannot sleep when it is running in normal mode. None of this is an issue now but I need to sort it before winter...

As others have said it's either because the filters are blocked or the system hasn't been set up properly. Our system is too quiet to hear. Do you know if it was set up to SAP ventilation rates.

 

[JamesJJJ]

2 hours ago, PeterW said:

Doesn’t look too complex - do you have the commissioning sheet as normally that is the reason why you have noise when the vents are done up too tight. 

 

Manual is here - if you can get the cover off and take a photo of the DIP and Rotary switch settings it may help. 

 

Thanks, that is a useful doc. 

 

Dont have the commission doc but do have the engineer report from when it was serviced. This shows flow rates in the 8-13 l/s for all rooms with the kitchen extract highest. This flow rate was achieved on 'norm' setting which is definitely audible...

 

The filters look pretty black and dirty, I will try to get some replacements.

[MJNewton]

23 minutes ago, JamesJJJ said:

Dont have the commission doc but do have the engineer report from when it was serviced. This shows flow rates in the 8-13 l/s for all rooms with the kitchen extract highest. This flow rate was achieved on 'norm' setting which is definitely audible...

 

Those flow rates are what most would aim to achieve for 'boost', and that's in the wet rooms not the main living areas/bedrooms. If you turned the whole lot down a bit for 'normal' you should still get the ventilation required but with much less noise.

Edited August 10, 2019 by MJNewton

[Jeremy Harris]

13 minutes ago, JamesJJJ said:

Thanks, that is a useful doc. 

 

Dont have the commission doc but do have the engineer report from when it was serviced. This shows flow rates in the 8-13 l/s for all rooms with the kitchen extract highest. This flow rate was achieved on 'norm' setting which is definitely audible...

 

The filters look pretty black and dirty, I will try to get some replacements.

 

 

The flow rates look pretty high to me.  Do you know the volume of the house/rooms?  Building regs require the background ventilation rate to be at least 0.3 l/s/m² of floor area, so  the flow rate sum of all the extracts (or the sum of all the fresh air supplies - should be the same as the extracts) should be the total house floor area multiplied by 0.3.  For example, our house has a total floor area of 130m², so requires a whole house ventilation rate of 0.3 x 130 = 39l/s.  We have a total of 6 fresh air supply terminals, so each only needs to provide about 6.5l/s.

 

If your are supplying 8 to 13l/s then that suggests that the house may be being over-ventilated, and that may be a possible reason for the noise.  13l/s is the highest extract rate needed under building regs, for the kitchen terminal.  Building regs also require that bathrooms and utility rooms have an extract rate of 8l/s and WCs 6l/s, but those rates can be provided by the boost function, I believe.

 

[PeterW]

So in the manual there is a guide to setup - what’s the total area of the house (all floors) and the ceiling height ..?

 

From that you can set the power on the dial, and then there is a also a night time setting to reduce the speed also. 

 

Where are you in the UK..?

[PeterW]

1 hour ago, JamesJJJ said:

The filters look pretty black and dirty, I will try to get some replacements.

 

When was it serviced ..? 

 

Docs seem to say max 9 months between filters, should be a 5 minute job to change them. They are two different types, @JSHarris had a good link a while back to non-branded filters that weren’t too expensive. Every 6 months seems to be the norm. 

[JamesJJJ]

1 hour ago, PeterW said:

So in the manual there is a guide to setup - what’s the total area of the house (all floors) and the ceiling height ..?

 

From that you can set the power on the dial, and then there is a also a night time setting to reduce the speed also. 

 

Where are you in the UK..?

Scotland. House is 175m2, ceiling height is 2.6m. I had a look at the unit and it seems fairly straightforward,  but I couldn't find the dip switches or rotary dial to check the current setting.

[JamesJJJ]

2 hours ago, MJNewton said:

 

Those flow rates are what most would aim to achieve for 'boost', and that's in the wet rooms not the main living areas/bedrooms. If you turned the whole lot down a bit for 'normal' you should still get the ventilation required but with much less noise.

Thanks, perhaps us gravitating towards the minimum setting is actually closer to optimal. 

[PeterW]

32 minutes ago, JamesJJJ said:

Scotland. House is 175m2, ceiling height is 2.6m. I had a look at the unit and it seems fairly straightforward,  but I couldn't find the dip switches or rotary dial to check the current setting.

 

Take both sides off the unit if you can -

possibly somewhere toward the middle unless for some surreal reason it’s mounted on the back of the control panel ..???

[Jeremy Harris]

47 minutes ago, JamesJJJ said:

Scotland. House is 175m2, ceiling height is 2.6m. I had a look at the unit and it seems fairly straightforward,  but I couldn't find the dip switches or rotary dial to check the current setting.

 

 

For a 175m² house, the background ventilation rate, at building regs rate, should be 52.5l/s.  If you count all the supply terminals in the house, and divide 52.5 by that number, that will give the average supply flow rate.  So it you have, say, 8 supply terminals, then the average flow rate for the background ventilation rate from each of them should be about 6.56l/s. 

 

It's quite important that the fresh air supply rate for the whole house matches the extract air flow rate for the whole house.  It can be a bit of a faff to set this up during commissioning, and I suspect that some systems are never properly set up. 

 

[JamesJJJ]

Have now had a good look inside the unit and control panel, no dip switches. Reading through the manual again it looks like the 400/e is configured through the control panel. The 400/ec (I assume a higher model) looks like it has a control panel and the dip switches, presumably to allow finer tuning of the configuration.

 

We ran the unit overnight on the min setting as usual and co2 reached a peak of 1543ppm. When we got up I switched it to normal mode (where the service measurements were taken) and co2 fell steadily to 876ppm in 2 hours. I then opened the outside door on our room and co2 fell to 434 in 25mins!

 

Tonight we are going to try the normal setting and see what happens to co2 levels. At some point I want to test with the villavent completely off and see if co2 rises significantly higher.

 

[JamesJJJ]

15 hours ago, JSHarris said:

 

 

For a 175m² house, the background ventilation rate, at building regs rate, should be 52.5l/s.  If you count all the supply terminals in the house, and divide 52.5 by that number, that will give the average supply flow rate.  So it you have, say, 8 supply terminals, then the average flow rate for the background ventilation rate from each of them should be about 6.56l/s. 

 

It's quite important that the fresh air supply rate for the whole house matches the extract air flow rate for the whole house.  It can be a bit of a faff to set this up during commissioning, and I suspect that some systems are never properly set up. 

 

This fits with the unit being configured for normal ‘high’, the switchover is 50l/s according to the manual...

[Jeremy Harris]

14 minutes ago, JamesJJJ said:

Have now had a good look inside the unit and control panel, no dip switches. Reading through the manual again it looks like the 400/e is configured through the control panel. The 400/ec (I assume a higher model) looks like it has a control panel and the dip switches, presumably to allow finer tuning of the configuration.

 

We ran the unit overnight on the min setting as usual and co2 reached a peak of 1543ppm. When we got up I switched it to normal mode (where the service measurements were taken) and co2 fell steadily to 876ppm in 2 hours. I then opened the outside door on our room and co2 fell to 434 in 25mins!

 

Tonight we are going to try the normal setting and see what happens to co2 levels. At some point I want to test with the villavent completely off and see if co2 rises significantly higher.

 

 

A CO₂ concentration as high as over 1500ppm suggests that the unit may not be set up properly.  As mentioned earlier, setting up and balancing an MVHR system can be a bit of a tedious process, and I strongly suspect that many systems are installed and never properly balanced.  If this is the case, then there's a fair chance that both the ventilation may not work as intended and that the power consumption may be a lot higher.  Blocked filters won't help, either. 

 

The normal outdoor CO₂ concentration will be a bit over 400ppm usually, and the house should be sitting just a bit higher (ours is currently sitting at 439ppm, but the MVHR is on boost from cooking lunch).  A CO₂ level, with the MVHR running at the background ventilation rate and the house occupied, should normally be around 600 to maybe 800ppm (ours tends to sit around 550 to 600ppm with both of us in, but the house is relatively large for just two people).