gc100 Posted February 22, 2021 Share Posted February 22, 2021 I'm not sure my MVHR is right. I just been running the fan speed at 100%. When I put my hand over the Exhaust vent outside I feel a good strong air flow. However when I put my hand over the supply vent outside I feel no air going in - putting a tissue is front it appears not to be pulling any air in. However when putting my hand over the supply vents inside the house I feel a good flow. So this is the first odd thing. The next thing I notice is the air coming in the supply vents within the house is really quite cold. Looking at the temp information on the MVHR unit I see this: Now according to this document http://www.cres.gr/greenbuilding/PDF/prend/set4/WI_25_Pre-FV_version_prEN_13779_Ventilation_for_non-resitential_buildings.pdf Exhaust air is the air going to outside whereas the extract air is the air coming from the rooms. It seems to be that the temporatures are back to front? and also given the supply temp is also low. Shouldn't it be : Exhaust air : 9 oC Extract air: 15.1 oC Supply 15 oC back into the house? Link to comment Share on other sites More sharing options...
Mr Punter Posted February 22, 2021 Share Posted February 22, 2021 Something wrong there. If the system is balance the intake and exhaust air flows should be about the same. Is the building occupied and up to temperature with the heating on? Link to comment Share on other sites More sharing options...
MJNewton Posted February 22, 2021 Share Posted February 22, 2021 Have you checked the right ducts are connected to the right ports on the unit? All too easy to make a mistake with the supply/extract/intake/exhaust nomenclature. Even more confusing when symbols are use instead! 1 Link to comment Share on other sites More sharing options...
gc100 Posted February 22, 2021 Author Share Posted February 22, 2021 Ok, so just doubled checked everything. The ducts are all connected correctly. I just took the panel off the front of the unit (Nibe) and it seems the extract fan is not running. I've checked the settings and the extract/supply speed are matched so perhaps the fan is broke? I will contact the suppliers. As a side note I've had nothing but issues with the Nibe MVHR and also ASHP. Not recommended at the moment. Link to comment Share on other sites More sharing options...
dpmiller Posted February 22, 2021 Share Posted February 22, 2021 are both fans actually running? Link to comment Share on other sites More sharing options...
gc100 Posted February 22, 2021 Author Share Posted February 22, 2021 Just now, dpmiller said: are both fans actually running? See above - no. Link to comment Share on other sites More sharing options...
MJNewton Posted February 22, 2021 Share Posted February 22, 2021 If the extract fan isn't running howcome you can feel a strong flow out of the external exhaust vent? Link to comment Share on other sites More sharing options...
dpmiller Posted February 22, 2021 Share Posted February 22, 2021 looks like we crossed... Check it's plugged in and free to rotate, and that there are no anti-frost protections in play. Link to comment Share on other sites More sharing options...
gc100 Posted February 22, 2021 Author Share Posted February 22, 2021 3 hours ago, MJNewton said: If the extract fan isn't running howcome you can feel a strong flow out of the external exhaust vent? I know right. So strange, I can only presume because only one fan is running its pushing/pulling air differently through the unit. But it makes no sense to me as the air has to be coming from somewhere to push into the house and out of the unit... Link to comment Share on other sites More sharing options...
dpmiller Posted February 22, 2021 Share Posted February 22, 2021 Once the house is pressurised air will follow the extract route quite happily Link to comment Share on other sites More sharing options...
MJNewton Posted February 22, 2021 Share Posted February 22, 2021 1 hour ago, dpmiller said: Once the house is pressurised air will follow the extract route quite happily I'm wondering how the house is getting pressurised though if the intake vent is barely pulling a tissue... Link to comment Share on other sites More sharing options...
Ultima357 Posted February 22, 2021 Share Posted February 22, 2021 Those figures are complete nonsense or it indicates something seriously wrong with the unit/installation. Extract air temperature should be roughly the temperature of your wet rooms , say 21 to 22 deg. Exhaust air should be lower, and how low depends on the external incoming air or outdoor reading in your display. Supply temperature should be only a degree or two under your room temperature as the heat exchanger does its business to warm up the outside supplied air temp which in turn cools the exhaust temperature. My Brink at 10 deg outside is currently supplying 21.7 fresh air. House is running at 22 generally but 23 in ensuite and kitchen warm after evening cooking. The Brink gives volume flow rates for both fans so I can see what is happening. Link to comment Share on other sites More sharing options...
gc100 Posted February 23, 2021 Author Share Posted February 23, 2021 The extract fan is broken. I still don’t understand why air is being forced out of the external supply. I’ll see what Nibe says. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 23, 2021 Share Posted February 23, 2021 7 hours ago, gc100 said: The extract fan is broken. I still don’t understand why air is being forced out of the external supply. Path of least resistance maybe. Link to comment Share on other sites More sharing options...
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