Can anyone help with my MVHR saga?

[Blooda]

13 hours ago, Deniance said:

Originally it was going to be loft mount but then changing filters would do my head in and the in and out would be close to chimneys and smoke, and the condensate was an issue as I knew the upstairs bathroom was getting moved downstairs, so yeah I didn’t have motivation to complete it, but new extension out the back made us gain a utility room between new extension and the house , it made sense for the in and out through the wall, makes sense for condensate, made sense for filter changes, just made the ductwork about a million times harder getting it up to the loft but hey Ho I’m sure I’ll get there in the end! All ducts were taped up when left and the unit had protective caps on it

 

Where does the small pipe come from that goes into the [condensate ?] line coming from the MVHR unit,  You may need a dry trap instead of the normal trap, as the condensate will not feed the wet trap with enough to create a seal. 

 

 

[Deniance]

 

why are the extraction rates higher for a kitchen than a bathroom? 
 

I was playing about yesterday trying to get the extracts right, and I assumed the bathroom would of had the highest extraction rates not the kitchen? 
 

my bathroom is the steamiest room of all

 

i did however manage to get nearly dead on 13 l/s and 8 l/s for the two extracts and it was barely above speed one , and the unit is barely moving! think it was 30 decibels stood in front of machine

 

So I didn’t even need to boost the machine to meet rates, but what should you set the boost at to clear a shower or toilet smell? Or are the rates in the table already taken that into account?
 

 

[Deniance]

On 06/10/2023 at 14:03, Blooda said:

 

Where does the small pipe come from that goes into the [condensate ?] line coming from the MVHR unit,  You may need a dry trap instead of the normal trap, as the condensate will not feed the wet trap with enough to create a seal. 

 

 

There’s a dry trap for the big condensate, but nothing has condensed yet , I’ve been checking, the smaller condensate takes whatever runs back down the extract , i angled to run inside rather than drip outside , this drips down and I’m using the trap right at the bottom to stop any smells , this is always kept full of water from the washing machine and it’s also in the extract pipe so any smells will go outside anyways , I hope

[Deniance]

Are these figures ok? Am I measuring in the right place? Poked the probes under the insulation and left them there for an hour, set heating to 22

 

extracting 22, outisde air in is 15.6 heat recovered air into house is 21.2

 

is this how you even measure it or do I need the temperatures at the grilled in the rooms?

[SteamyTea]

3 hours ago, Deniance said:

Are these figures ok?

The way to check is to run the numbers and see if it makes sense.

https://www.engineeringtoolbox.com/amp/heat-recovery-efficiency-d_201.html

[Deniance]

2 hours ago, SteamyTea said:

The way to check is to run the numbers and see if it makes sense.

https://www.engineeringtoolbox.com/amp/heat-recovery-efficiency-d_201.html

Think that’s the right way I’ve entered them? 0.97 doesn’t sound very good?

[JohnMo]

2 hours ago, Deniance said:

Think that’s the right way I’ve entered them? 0.97 doesn’t sound very good?

 

As it's not saying % it's the unit prior to conversion to a percentage efficiency, so would read 97.4%. As the temperature get a wider difference apart the efficiency will likely drop. Not really being asked to do much looking at your figures.

[Deniance]

Ok so I’ve finished the install!!!

 

I tried setting it up with the testo hot wire 405 Bluetooth probe in the 100mm duct as others have done

 

set the app to l/s and added the damping to stop measurements jumping about

 

i closed 3 out of 4 supply valves and opened the furthest one all the way, got it to 21 l/s by adjusting the pot, then opened the other 3 valves and fiddled and fiddled until I got all 4 valves at 5 litres per second as best I could 

 

then I did both extracts same way to get 21 litres per second, as best I could 

 

so when it’s measured they are there or there abouts for a balanced supply and extract 

 

but…… 5 litres per second in each room doesn’t seem very strong , can hardly feel it, don’t think it would even blow a candle out!  Is that right?

 

also even though they are nearly extracting and supplying the same the supply trickle pot is at a different position to the extract trickle pot

 

supply is say at 10 o’clock position and extract is at 12 o’clock position?

but I guess if I’ve measured all the valves and they balance out then the that’s just how it is?

 

is there anything else I need to do? 
 

if I meet the rates in normal mode , what should I set boost to? In this unit boost has to be higher than trickle 

 

 

[JohnMo]

6 hours ago, Deniance said:

supply is say at 10 o’clock position and extract is at 12 o’clock position?

Your pots being different positions it just indicative of the difference resistance (pressure drop) in the supply and extract.

 

My extract will just hold a bit of toilet roll up. So not much flow. Remember you are only extracting the whole house air every 2 to 3 hours, so flow rates are aren't huge

 

I set my boost to 25% above the trickle flow rate.

[Deniance]

I just thought that because my two extracts are very short , bathroom is 1.5m and kitchen is 1 metre and it exits the wall about 300mm above unit that the extract pot would be lower than the supply pot? The supply duct is 4 supplies and the last one has got to be about 20 metres and a few bends and reducers , just assumed the supply would have to work harder to get air to all the distant places

 

but I guess the anemometer doesn’t lie right? It all seems balanced 

 

I’ll have another go after work and make sure I’ve got it right

 

when I tried leaving the furthest supply wide open , like grille wound out so it looked silly, and tried to get 21 l/s to flow I just couldn’t get it, even turned the pot up and couldn’t hit 21 l/s, so I closed it down until it looked like a grille again and started getting the figures, so I guess I opened it too much and it couldn’t build any pressure? I’ll post some pictures later

[JohnMo]

You really need to start with all the terminals open an equal amount. Then start at furthest away terminal and set fan speed to get the room target about right. Now don't touch the fan speed or that room, but adjust the rooms getting closer to the MVHR unit and adjust the terminal to room to target flow rate.

 

Then go back to the start again and use the same method, furthest room fan speed adjustment to tweak flow rate, all other rooms the terminal. You may need to do 3 or 4 times to get it right.

[Deniance]

If a bedroom is 3x5x2.4 metres that’s 36m3 or 36,000 litres

 

if the room is getting filled with air at 5 l/s , 300 litres a minute 18,000 litres an hour 

 

then this room will take 2 hours to have all its air replaced with fresh air?

 

is that right? Too much or too little?

[Deniance]

How do I know if I’ve got the anemometer set correctly?

 

I have the 150mm cone that goes into the 125mm cone that goes into 100 mm duct about 400mm long with the anemometer stuck in the side in a stuffing gland

 

i set the testo to extract or supply and put 100mm as the diameter and I’ve balanced the supply and extract as well as I can, the supplies get divvied up from 21 l/s to 5 l/s to each of the 4 rooms, but the grilles are almost closed , there’s like about 5mm gap in the grille , the testo says there’s 5 litres coming out but it feels like it wouldn’t blow a rizla paper about

 

cindensation has certainly reduced by about 95% in the main bedroom but need a really cold night to prove it more, house doesn’t seem any fresher to me and it just makes me think the unit isn’t on fast enough or I’m measuring the flow wrong?

[Marvin]

10 minutes ago, Deniance said:

How do I know if I’ve got the anemometer set correctly?

 

I have the 150mm cone that goes into the 125mm cone that goes into 100 mm duct about 400mm long with the anemometer stuck in the side in a stuffing gland

 

i set the testo to extract or supply and put 100mm as the diameter and I’ve balanced the supply and extract as well as I can, the supplies get divvied up from 21 l/s to 5 l/s to each of the 4 rooms, but the grilles are almost closed , there’s like about 5mm gap in the grille , the testo says there’s 5 litres coming out but it feels like it wouldn’t blow a rizla paper about

 

cindensation has certainly reduced by about 95% in the main bedroom but need a really cold night to prove it more, house doesn’t seem any fresher to me and it just makes me think the unit isn’t on fast enough or I’m measuring the flow wrong?

Doing mine I used the diameter of the outlet by the flow rate to calculate volume.

[Deniance]

16 minutes ago, Marvin said:

Doing mine I used the diameter of the outlet by the flow rate to calculate volume.

Can you explain it to me like your talking to a child😂 all this flow rate stuff pickles me

[Deniance]

[Deniance]

[Deniance]

Added a few pics just to show grilles and condensation free windows!!

[Deniance]

This was on a cold night and we’ve gone from waterfall windows to mist! So mvhr does help with condenstion in an old leaky house!

[Deniance]

This was the big bedroom this morning , cold side of the house, still reduced from what it was but meh

 

i followed document F and divided the fresh air equally between the supply rooms so each room is like 5.5 litres per second , can I adjust the valves so the other rooms are less and this double bedroom gets a few more litres per second or am I just wasting my time as the windows are old and house isn’t airtight?

[Arudge]

or am I just wasting my time as the windows are old and house isn’t airtight?

 

You've already proved the benifits of your setup because you've got less condensate on the windows.

 What you have to consider is that the level of damp in your house is also in the plaster, the furniture, your clothes and anything that's absorbs moisture, it will take weeks to dry out, but it will.

 

 You won't get perfect results because you don't have air tightness, but if your system is balanced you'll achieve more than some say. 

 

 Think about it, if you have more supply than extract then that positive pressure will push out through whatever is leaking. If you have more extract than supply then the slight vacuum will suck cold air from outside through the same leaky bits, and you'll feel that as a draft. Keep the system as balanced as reasonably possible. 

 

[Deniance]

I had another try at it this morning , it was very windy , made sure my phone was charged and put new batteries in the testo, no joy it’s got to be the wind! I’ll try again in the morning!