HRV Condensate
moose_head27
| Posted in General Questions on
Hi, could anyone troubleshoot potential problems with my HRV?
From my understanding a HRV should produce condensate in the winter months. Currently its been extremely cold in my area (-20- -30 degree C) and the relative humidity in my home sits around 50% @ 21 degree C when the HRV is turned off. When the HRV is on, shouldn’t there be condensate forming and draining from the unit? The drain pipe is dry and when I open up the unit there’s no condensate on the pan.
Shouldn’t I be getting some condensation with my conditions? Or am I incorrect?
Thank you
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Replies
Yes, under the conditions you state I would expect condensation from your HRV. A lot.
I do have to say however that I find a value of 50% RH indoors at 21C (70F) very unusual for a home in cold winter conditions. I am not sure how you are measuring this, but my first suspicion is that you are actually much lower that 50% RH. In cold winter conditions it can be hard to maintain something like 35% RH, even with a humidifier running with warmth of 21C indoors. If you are actually at 50% RH and it is -30C outdoors your windows (normal double pane) would likely be dripping with condensate. My bet is that you are using an inaccurate hygrometer and that your actual indoor humidity levels are much lower than you are assuming.
Hi, thanks for the reply. My thermostat displays RH. I'm not sure how accurate it is though.
As for my windows(double pane) they are sweating a lot. Reason for the high RH is that I have a visitor that is sensitive to low RH air so I've generally been keeping the HRV off and only let it run at certain times.
Even before my visitor came and in previous years, I ran the HRV on low all the time in the winter. Not a drop of condensation from the HRV. I managed to keep my RH usually around 30% at that time.
Thank you
That's strange. Is it possible that it's a ERV rather than an HRV? Other theories would be that something connected up wrong, something is broken, or the moisture is all freezing up. I guess it could be that the way the defrost works on your unit, it cycles the frost that has formed back into the house.
Some things to try include checking the temperatures of the air coming out outside and the supply air coming in inside, as well as confirming air flow in both those channels. And letting us know the make and models so we can look at its defrost system.
I have a swappable-core HRV/ERV, and when I swap the core from HRV to EVR mid-fall, it's a soggy mess in there.
Some older HRVs could also be pretty inefficient, which means it won't exchange enough heat to create much condensation.
It could also be that your unit is out of balance.
If you have a set of decent thermometers (digital meat thermometers are great for this), you can measure the temperature of the fresh air supplied to the house and the stale air exhausted to the outside. If the unit is roughly in balance, the difference between outdoor temperature and stale exhaust temperature would be about the same as the difference in fresh air supply and house temperature. If these two temperature deltas are way off (ie the fresh air supply is very close to house temp while the outdoor delta is far apart) you need to rebalance the unit.