As you might have seen from the other thread I have taken the plunge and fitted a Komfovent R-450-V MVHR Unit - https://www.bpcventilation.com/r-450-v-bundle from BPC

First Ventilation Land - avoid! BPC did not have any 160mm fittings in stock, so I went to Ventilation Land - 2 x fittings damaged on arrival and over a week later I am yet to get the replacements. The CS is terrible.

The ports are in different positions on the new unit to the old one so it needed a little surgery. Happily all the pipework was the insulated flexible pipe of which I had a bit of spare still. However, I did find the supply pipe had quite a bit of debris in it which I was slightly surprised by. I am going to fit an inline filter to catch this before it gets to the Komfovent unit. The old unit was very accessible more by luck than design and in designing a house, I suggest anyone makes sure they can replace these units as I do think they have a limited lifespan. Getting a 60kg lump into a loft could be challenging!

If you go for this unit and have a computer/smart phone, then you can control the unit without the display screen (controller) for £250 odd quid. I was led to believe you did need the wall unit :(

Pleasantly surprised by the unit. gradually experimenting on what can be controlled by HomeAssistant, but so far plenty so should be able to reduce the power consumption considerably by controlling the flow depending on what is going on and who is home.

Finally, if anyone wants some Helios EC 500 spares, let me know!

Posted By: borpinThere is a small 1kW heater on the supply side that keeps the supply temp to the target temp

Thanks for the observations, they're useful.

That sounds unusual. The small heater on the intake on our Brink is called a 'pre-heater' and is only used to prevent icing in the heat exchanger. A heater on the supply side is called a 'post-heater' and ours is manually controlled (well externally by computer). It's an add-on external product; I didn't opt for Brink's built-in heater.

For Extract Temperature, again, I think that is the temperature of the air it is pulling from the house, not what it is sending outside. Again, I need to get a sensor in there and check that!

Extract should be internal return temperature, as you say. If it was external return temp it should be Exhaust. To measure temperature can you just measure the inside of the duct temperatures with an IR thermometer. The extract and intake are easily accessible via the filter slots on our MVHR.

I looked at the Vantilation Land site out of interest and spotted two interesting-looking devices. Firstly it seems Brink now do an 'e-module' that I may be able to use with my MVHR, but I haven't checked whether it does anything useful yet although it will work without WWW access. Secondly there's a product called 'EnviSense CO2 monitor with data logger' that apparently logs CO2, temp & RH and can export CSV files again with no WWW access required.

Posted By: borpin
Finally, if anyone wants some Helios EC 500 spares, let me know!

Might be interested in the he complete unit if it were potentially repairable...

That's a rediculous price for what should be a part that is expected to be replaced! Thanks, will send a contact

Posted By: borpin Happily all the pipework was the insulated flexible pipe of which I had a bit of spare still.

What product is this? The final connection from rigid pipe to our MVHR is the part of the install I'm least happy with and I've been considering redoing it (and also swapping the inlet and outlets on the roof - does anyone anticipate any issues doing this. I'm guessing the inlet will be the dirty one but making that the outlet wouldn't cause any issues. making the relatively clean pipe the inlet should thus be fine?)

Just to continue this (I might be talking to myself) - I am finding there are lots of nuances to getting the best out of this unit and the builtin logic is not always what you want or maximizes the potential of the unit.

For the last few days the sun has been out (that does happen sometimes in Scotland) but overnight temperatures have been relatively low and our sunroom temperature has increased significantly duing the day (so increasing extract temperature). However, the supply temperature setpoint was still set to minimise the use of the internal heater (but keep the supply temperature reasonable).

As the internal (extract) temperature rose, the unit tried to keep to the setpoint (unsurprisingly) by introducing colder air from outside. This is obviously a waste when the supply temperature is less than the Central Heating setpoint!

I manually raised the setpoint to stop colder air being brought in and noticed the supply heater stayed off, but the heat recovery part kicked in.

All this is possible to see because I record all the data from the unit using a combination of Home Assistant, Node-RED and Emoncms.

I have decided to trigger the adjustment of the setpoint using Home Assistant Automations, based on whether the supply heater is on or not. If it is off (i.e. it can achieve the supply temperature just using heat recovery) I attempt to raise the setpoint until the heater comes on. At this point the other Automation will kick in and reduce the setpoint so the heater stays off with a 'floor' temperature set. This second automation then controls the setpoint as the air outside cools, but as things stand, I'm not sure these two will play nice as the external temperature starts to fall. "Discovery requires experimentation and this experiment will take time."

I don't have a maximum setpoint limit set yet, but I'm reasonably sure this approach will maximise the heat recovery potential.

It's also the ideal weather to try these things out though. I suspect I may have the opposite problem in the summer!

I really am impressed with the amount of information I am able to get from the unit and then use.

Next automation is to control the fan speed based on number of occupants / CO² levels in the house.

If anyone is interested, I am publishing my Home Assistant configuration (new automations not included yet) https://github.com/borpin/ha_komfovent_config

Posted By: borpinJust to continue this (I might be talking to myself) - I am finding there are lots of nuances to getting the best out of this unit and the builtin logic is not always what you want or maximizes the potential of the unit.

For the last few days the sun has been out (that does happen sometimes in Scotland) but overnight temperatures have been relatively low and our sunroom temperature has increased significantly duing the day (so increasing extract temperature). However, the supply temperature setpoint was still set to minimise the use of the internal heater (but keep the supply temperature reasonable).

As the internal (extract) temperature rose, the unit tried to keep to the setpoint (unsurprisingly) by introducing colder air from outside. This is obviously a waste when the supply temperature is less than the Central Heating setpoint!

I manually raised the setpoint to stop colder air being brought in and noticed the supply heater stayed off, but the heat recovery part kicked in.

Not sure I fully understand but if you're talking about the setpoint for the summer bypass to open and difficulty in choosing the value, does your MVHR offer another setting for the hysteresis in that value? Ours does and I find that very useful - between it and the setpoint I have found settings that I never have to touch.

Posted By: djhNot sure I fully understand but if you're talking about the setpoint for the summer bypass to open and difficulty in choosing the value, does your MVHR offer another setting for the hysteresis in that value? Ours does and I find that very useful - between it and the setpoint I have found settings that I never have to touch.

Well, possibly. It is simply described as the 'setpoint' and it is the temperature you select for the supply side air, that the unit then tries to maintain. Too high and the supply side heater kicks in (not the best way to heat the house - see below), set it too low and heat is expelled from the house rather than being recovered.

So I am adjusting this setpoint so as to minimise the heater and maximise heat recovery.

Posted By: djhIn our case it's set to produce air at 45°C

Typo?

Posted By: RobLOur Sentinel Kinetic BH plus has a summer bypass mode.

My old Helios unit had that and it seemed to recover heat up to that temperature. I did not have as much data as I do now though so I have no idea how efficient it was.

Posted By: RobLI've never really understood why resistance heaters are added, I can't by hand really tell the difference between air at 20C or 18C. Is it your only heating?

You would not notice it to be fair, but the physics say that if you are expelling warm air and bringing cooler air in, it is reducing the temperature overall. The small heater puts a relatively small amount of energy in and I agree, not hugely useful, but I suspect quite efficient in maintaining/smoothing the temperature.

Posted By: djhAh, it sounds like something different. An attempt at a more 'automatic' system but they may have designed out one of the useful knobs.

I will easily be able to achieve the same thing, just in a more controlled way. Summer bypass is simply a means of expelling warm air and replacing it with cooler air from the outside - bypass the heat recovery.

Posted By: borpin

Posted By: djhAh, it sounds like something different. An attempt at a more 'automatic' system but they may have designed out one of the useful knobs.

I will easily be able to achieve the same thing, just in a more controlled way. Summer bypass is simply a means of expelling warm air and replacing it with cooler air from the outside - bypass the heat recovery.

You mean by controlling whether the summer bypass is open or not by means of external logic? Then I agree but I have found that by setting the hysteresis as well as the opening temperature, plus the inbuilt logic the Brink has, I've managed to find settings that work for us without having to implement any external logic.

Posted By: WillInAberdeenLess automatically, we turn off the electric fan and open the windows during summer.

We open the windows too. Stack effect or a breeze provides a lot more air change than an MVHR when conditions are suitable, and we've now got fly screens on all the windows we use

It seems to me that the time you want to use “summer” bypass and/or more ventilation than is needed for IAQ is anytime the outside air temperature is in the direction you want to move the indoor temperature. I.e., when either:

a) the indoor air is cooler than desired and the outdoor air is warmer than the indoor air currently is or

b) the indoor air is warmer than desired and the outdoor air is cooler than the indoor air currently is.

Am I missing something?

Yep, “desired” isn't a single air temperature; it's a temperature band. Its bounds will vary with time of year, building fabric temperature, recent temperatures the occupants have been exposed to and maybe other things (humidity?).

Posted By: JontiIt maybe old fashioned but I find airing a house is something that needs doing most days…

Do you have MHRV?

Posted By: Ed Davieshumidity

There's a lot of scope for MHRVs to be cleverer and think ahead

- purge ventilate at very high flow during mid morning to dry out the fabric of the house, when the outside air is warming up but not yet humid/dusty, and the occupants are active and tolerant of cool/noise, or have gone out

- ventilate less for the rest of the day and let the fabric buffer the humidity

- reduce ventilation temporarily during rain showers

- reduce ventilation during cold weather when the outside air carries much less humidity and you want to conserve heat

- during heatwaves, purge ventilate in the early morning and the evening to cool down the fabric, then minimal ventilation during the hottest part of the day.

- during 'shoulder' months, ventilate more in the afternoon than overnight, to bring the air in at the time when it's naturally warmest


Most people use these strategies when they open windows, it should be possible to automate them with a MHRV with indoor and outdoor humidity sensors.

Most people open windows selectively, eg to ventilate the bedrooms that are occupied but not the spare bedroom, ventilate one bathroom while shower is in use, ventilate the kitchen while pots are boiling etc. The current state of MHRV is to boost ventilation in every room simultaneously, but maybe in time there will be ability to control individual rooms. Eg with duct valves, or d-MHRV.

Posted By: WillInAberdeen- purge ventilate at very high flow during mid morning to dry out the fabric of the house,

My issue is the opposite, the fabric is too dry.

Posted By: WillInAberdeenMost people use these strategies when they open windows, it should be possible to automate them with a MHRV with indoor and outdoor humidity sensors.

Yes, the trick is getting the overall balance right between Energy conservation / temperature / humidity / CO². There is no one size fits all in terms of the setup.

Interesting thoughts on increasing ventilation based on outdoor v indoor humidity. Might tinker with that to increase internal humidity.