Servicing a Vent Axia Sentinel Kinetic Plus B - 8 years old unit

[Stones]

Following on from this original topic, I have today just completed the annual main clean and service of my MVHR unit, now 8 years old.

 

With our unit now located within the heated envelope of the house (rather than our cold loft as it was originally), the blocked condensate drain issue has not arisen again.  There is always some evidence of mould growth on the extractor fan blades and extract fan chamber, but given this is a cold and damp / wet part of the unit, that is hardly surprising.  I did however uncover 2 new issues:

 

1. The summer bypass, which consists of a plastic louvered fin assembly in a rectangular frame, opened and closed by a solenoid, was stuck in the closed position, i.e. on summer bypass.  Closer inspection revealed the end of the solenoid which allows the unit to switch from heat recovery to summer bypass had broken off.  On attempting to operate the louvres by hand, they were stuck solid.  The screws securing the louvre assembly to the frame had corroded to such an extent that they prevented movement, which in turn caused the solenoid to break. The screws were so far gone that they dissolved on contact with a screwdriver.  With the gentle persuasion of a mallet, I was able to tap open the louvre assembly to the heat recovery position.  This means that I now have no summer bypass as there is no means to close the louvres.  Not an urgent problem given the time of year, but something I will have to think about getting a replacement part for.  Top tip therefore, lubricate the screws to try and slow / prevent corrosion.

 

2.  Eight years of removing and re-inserting the core has torn / destroyed one of the seals (pictured hanging).  Fortunately, I had some neoprene adhesive backed tape which I used to replace.

 

Other than that, (and a previous fan bearing replacement) the unit is still going strong. 

 

[Stones]

[Russdl]

@Stones thanks for that update/great reminder.
 

Apart from filter changes I’ve not opened mine up yet. It’s been on my ‘to do’ list for a while, as have many things, I’ll put it top of the “things to do when it get warmer” list. We’re only 3 years in so hopefully no big horrors lurking inside. 

[Andehh]

Yep, we're 18 months in ourselves! Interesting points to keep an eye on though.

[Pocster]

Where’s the summer bypass grate ? . I had mine open due to leakage issues and I do t recall seeing anything like that .

[Stones]

At each end of the louvre assembly, the 3 slats you can see closed.  The bypass forms when the solenoid closes the main louvres, and opens the 3 slats at each end.  This prevents air cycling through the heat exchanger by guiding the airflow (with the aide of foam on each end of the heat exchange core) around the heat exchange core.

[DOIGAN]

Hi Stones, interesting that you mention mould on the inside, our unit is covered in it and gets very wet inside, you mentioned the location, ours is in the loft where builders put it, not really an option to move it either, ant suggestions about the mould and how to stop the inside being wet?

Cheers

Andy

[Stones]

On 23/11/2024 at 14:39, DOIGAN said:

Hi Stones, interesting that you mention mould on the inside, our unit is covered in it and gets very wet inside, you mentioned the location, ours is in the loft where builders put it, not really an option to move it either, ant suggestions about the mould and how to stop the inside being wet?

Cheers

Andy

 

Sadly, nothing to offer other than a regular clean and treat the moulded area with bleach.  I find that when I remove the heat exchange core, and angle it over, a fair amount of condensate drains out, but generally this remains free of mould.  The plastic louvre grill tends to have mould grow on it, as do the extract fan blades, so I clean the lot, and make sure the drainage hole and pipe run off is clear and free flowing.  

 

Having measured the temperature of supply air into the house, my unit seems to operate at 90% heat recovery.  Added to that the higher relative humidity and moisture levels, it's perhaps not surprising there is so much condensation - but at least shows the unit is working.

 

 

[Daragh]

I am having trouble removing the side panels of the unit to get access to the exhaust fan to clean the mold fully. Has anyone removed the side panels what are the steps?

[mouldman]

Daragh, did you manage to remove the side panels? They are a bit fiddly but I think it is just a case of making sure front and back are removed first. Then sort of jiggle one of the sides and it should slide and then you can lift the top up a little and remove the side.

 

Stones, your unit has held up much like mine, now 9yrs old. I need to get some replacement draft sealing style tape and also my bypass motor has broken too. I am contemplating just going up to the attic and manually putting the bypass mode on when temps are consistently over something like 18C at night.

[KineticBuser]

On 22/11/2024 at 16:51, Stones said:

 

So would this be Summer Bypass Mode on or Off? Mine is currently set like this with the Summer Bypass Mode on

By togging the mode to On or Off should i immediately be able to see the solenoid change?

[KineticBuser]

1 hour ago, KineticBuser said:

 

So would this be Summer Bypass Mode on or Off? Mine is currently set like this with the Summer Bypass Mode on

By togging the mode to On or Off should i immediately be able to see the solenoid change?

Sorry i mean the Central Grate being open means Summer Bypass Mode is not On? If thats the case and mine is set to open with Summer Bypass On, then the solenoid is the most likely culprit?
I presume thats the case so i have removed the solenoid and closed the grate manually - which i presume is ok and forces Summer Bypass on constantly?

Has anyone found a solenoid replacement cheaper than from Vent Axia?

 

[dpmiller]

IIRC it's not a solenoid but rather an electrically-heated wax motor. Takes a few minutes to open and close as it heats or cools.

[KineticBuser]

15 minutes ago, dpmiller said:

IIRC it's not a solenoid but rather an electrically-heated wax motor. Takes a few minutes to open and close as it heats or cools.

Ah ok, maybe i need to leave it plugged in for 10 and see if the vents open / close then? Can you confirm the summer bypass and vent operation?
The vents are on the right, so if thats the incoming air, would make sense for them to be closed and force the air past the heat exchanger

[KineticBuser]

@Stones Did you manage to replace your actuator and find the part cheaper than from Vent Axia?

 

[Stones]

2 hours ago, KineticBuser said:

@Stones Did you manage to replace your actuator and find the part cheaper than from Vent Axia?

 

 

I decided in the end to see what the difference would be without an operational summer bypass in terms of summer internal house temps. Up until this point, can't say it makes any noticable difference.

 

I haven't got the details to hand but I recall finding an alternative and much cheaper supplier for the actuator. I also sought a price for a new louvre from vent axia.  That was going to be over £100.

 

On 27/06/2025 at 15:07, KineticBuser said:

Sorry i mean the Central Grate being open means Summer Bypass Mode is not On? If thats the case and mine is set to open with Summer Bypass On, then the solenoid is the most likely culprit?
I presume thats the case so i have removed the solenoid and closed the grate manually - which i presume is ok and forces Summer Bypass on constantly?

Has anyone found a solenoid replacement cheaper than from Vent Axia?

 

 

Central gate open = normal heat recovery mode.  Summer bypass the 2 smaller end louvre sections would be open, thus bypassing the core.

[ProDave]

"Summer bypass" is a poor description of this function.  It is in reality "heat exchanger bypass"

 

In summer when it is hot, the heat exchanger can actually work in reverse and COOL the incoming air.  Operating "summer bypass" then, would just allow ever hotter air into the house.

 

I have never used the bypass function on mine, I struggle to find the very few times it would actually be of any use.

[Nickfromwales]

15 hours ago, ProDave said:

"Summer bypass" is a poor description of this function.  It is in reality "heat exchanger bypass"

 

In summer when it is hot, the heat exchanger can actually work in reverse and COOL the incoming air.  Operating "summer bypass" then, would just allow ever hotter air into the house.

 

I have never used the bypass function on mine, I struggle to find the very few times it would actually be of any use.

+1, and it is a royal pain to have to try and explain this over and over again with each new client.

[jack]

2 hours ago, Nickfromwales said:

+1, and it is a royal pain to have to try and explain this over and over again with each new client.

 

On my (Brink) unit (and I imagine most other modern units), bypass mode mode is automatically entered based on (among other things) the difference between internal and external temps. Assuming an automatic system, what prompts clients to ask you about it? Do they tend to get concerned that it isn't coming on during hot days in summer?

 

18 hours ago, ProDave said:

In summer when it is hot, the heat exchanger can actually work in reverse and COOL the incoming air.  Operating "summer bypass" then, would just allow ever hotter air into the house.

 

Yes, but if it's automatic, summer bypass mode won't come on unless it's cooler outside than inside. Are there many/any current units that only have a manually-operable summer bypass mode?

 

For us, summer bypass tends to kick in during the evening on hot days when the outside temperature drops below a threshold. It turns off the following morning if/when the outside temperature rises sufficiently.

 

18 hours ago, ProDave said:

I have never used the bypass function on mine, I struggle to find the very few times it would actually be of any use.

 

Perhaps less of an issue in Scotland, where overheating is presumably less common?

 

That said, is your unit configured to operate automatically based on the difference between inside and outside temps? If so, why wouldn't you just leave it operating so you get the benefit of cooler air bypassing the heat exchanger overnight if your house is too warm?

[Nickfromwales]

1 minute ago, jack said:

Assuming an automatic system, what prompts clients to ask you about it? Do they tend to get concerned that it isn't coming on during hot days in summer?

Clients read up on these things, then ask how to implement / manipulate etc, and then I typically have to explain the pros cons and caveats and dissuade them ‘fiddling’ and just say to leave it alone to do its job. 
 

If a client knows it has a function, they want to fiddle with it.

[jack]

Just now, Nickfromwales said:

If a client knows it has a function, they want to fiddle with it.

 

Sounds like clients in every industry!

[Pocster]

37 minutes ago, Nickfromwales said:

Clients read up on these things, then ask how to implement / manipulate etc, and then I typically have to explain the pros cons and caveats and dissuade them ‘fiddling’ and just say to leave it alone to do its job. 
 

If a client knows it has a function, they want to fiddle with it.

Everyone likes a fiddle 😉

[Nickfromwales]

28 minutes ago, Pocster said:

Everyone likes a fiddle 😉

Lay off the bitumen, the fumes are getting to you. 

[jack]

52 minutes ago, Pocster said:

Everyone likes a fiddle 😉

 

No wonder you haven't finished the build yet.

[Stones]

1 hour ago, jack said:

 

Perhaps less of an issue in Scotland, where overheating is presumably less common?

 

That said, is your unit configured to operate automatically based on the difference between inside and outside temps? If so, why wouldn't you just leave it operating so you get the benefit of cooler air bypassing the heat exchanger overnight if your house is too warm?

 

Certainly where I am, ambient air rarely gets above what the internal house temp may be.  Overheating really is a function of solar gain for us, welcome in winter (like having a fire on), probably the most intense in April.  Given the comparatively low flow rates of MVHR, I can't say I've noticed much of a difference - ours was set to come into operation when internal house temps exceeded 22C.