MVHR long term efficeincy - drop off after 3 years

[Simon R]

It looks as though the efficiency of my MVHR is diminishing and I've not a clue why so I thought where better to get some input than BuildHub.

 

I'm running a Blauberg SB 550 unit which is possibly a little oversized for our build. When commissioned  the air flow temperatures suggested I was getting pretty much 94%, today, three years later it looks as though its running at about 80%. The filters are clear(newly fitted), the heat exchanger core and internals of the unit and clean and indeed look like new.

 

When commissioned the air entering the house was less than 3.3C colder than the air leaving the house.  

 

 

 

Now it's pretty much 5.3C cooler. That's a big enough difference to notice as a draft. The figures looks like it has to be the heat exchange unit unless I'm getting a lot more air into the house than is leaving it through the MVHR. Our build ACH of 0.6 was, testing the flows should let me know if this has changed.

 

I've contacted Blauberg who made some suggestions about possible causes. Imbalanced flows,  dirty filters, dirty heat exchanger etc. I also asked them if they monitored and kept efficiency data for the long term operation of their units, they don't (or won't share it?).

 

I've added myself to the anemometer wait list so I can check flows and compare them to those at the time of commissioning, however as no settings have been changed I'd be surprised if it's a factor.

 

There must be a good number of BuildHub members who have long term data of the efficiency of their MVHR systems heat exchangers. I'd like to know if others have seen a drop off and indeed if they haven't.

 

Here is a copy of the heat exchanger washing instructions:Cleaning Poly brochure_EN.pdf

 

 

[ProDave]

When mine (different make) started to seem non optimum, investigation showed the stainless steel inlet vent has a Gauss filet on the input that had become almost entirely blocked with dust.  Cleaning that out restored normal operation and is now on my annual maintenance list.

[Simon R]

4 minutes ago, ProDave said:

When mine (different make) started to seem non optimum, investigation showed the stainless steel inlet vent has a Gauss filet on the input that had become almost entirely blocked with dust.  Cleaning that out restored normal operation and is now on my annual maintenance list.

Thanks, that's one area I've not checked. I'll take a look and report back......only snag is it's 7M up so I'll need to get the staging out.