MVHR dripping!!

[Pete]

As you know we have just moved in and it is a steep learning curve with all things ASHP and MVHR. When it was freezing on xmas day I noticed the casing on the Vent Axia Sentinel was dripping slightly. I checked the controller and it was flashing anti-frost. With it being xmas day I just turned it off for now but just wondered is this the norm for it to drip? Have I not got enough slope when I fitted as I assume this is what the condensate drain is for? I wrapped the inlet/outlet pipes in armaflex and then the flexible pipe insulation from BPC so all should be ok there. Have people come across this before and if so what did you do please? 

I am trying to come down from the exertions of the last month of trying to get in the new house before xmas and my head is a complete mash of new tech and mundane issues that need sorting. TIA

[dpmiller]

might pull the covers off and check that the H/E is fitted centrally. If it's moved in transit it could be leaning on one or other of the covers, distorting it away from the foam seal.

 

/ mine's normally absolutely dry, but currently- extracting a tonne of water from the screed- there's a weep from the bottom of the front panel...

[RandAbuild]

Check the inlet pipe into the Vent Axia from the outside vent is very well insulated. We have the same model and I hadn't insulated the plastic spigot into the unit well enough. Warm air in the house was condensing on this small area and created a lot of water over a few cold days.

[jack]

Water condensing inside the unit is perfectly normal. You can get a lot of condensation on cold days as the warm moist internal air is rapidly cooled inside the heat exchanger. That's what the drain is for.

 

You should not, however, have water dripping from the casing. That suggests that water is finding its way out of the designed drainage path.

 

We had this with our Brink unit on the odd very cold day. In our case, it was because there was a region along the bottom of the heat exchanger where capillary action could cause water to be pulled into an area outside where it could be drained. The result was that in certain conditions, water would accumulate where it wasn't meant to, then work its way through cracks in the internal insulation until it ended up on the inner surface of the bottom casing. It would then find its way out of a join in one corner.

 

To Brink's credit, they sent out an engineer for free, over four years after we bought the unit. He applied a fix in the form of a strip of aluminium that redirected water around the danger area. Unfortunately, it wasn't a very robust solution, but I re-did it myself with some plastic, and it's worked fine since. 

 

First thing to do is to make sure your drain is working properly.

 

The next thing is to see whether there's any water pooling inside the unit where it shouldn't (you'll probably need to remove the front casing to see this - at least, that's how it works on our Brink unit). If there's water where it shouldn't be, work your way back from where it's pooled to see where it's coming from.

 

You need to make sure there isn't condensation coming from either of the external ducts. Both the inlet and outlet get very cold in cold weather, so either could be the source of unwanted condensation. That said, depending on where it enters the unit, such condensation should still find its way to the drain.

[joe90]

Our indoor RH is quite high, and the outside RH very high. Our MVHR has an enthalpy filter and no drain, I do wonder if we had a different unit without an enthalpy filter and had a drain our internal RH might be lower. I will go and check the filter later and see how it is inside.

[Declan52]

Is the connections from the top dripping down and running inside and out the bottom. If it's not sealed fully at the joint then you could get condensation here.

[PeterW]

@joe90 what do you call “high” internal RH..? Running the same HEx as you - so no drain - and seems to sit at 58-62%

[joe90]

3 minutes ago, PeterW said:

@joe90 what do you call “high” internal RH..? Running the same HEx as you - so no drain - and seems to sit at 58-62%

just popped upstairs and it’s 74% (on a very cheap Chinese thingy), conservatory (non heated and ventilated) is at 85%.

[MikeGrahamT21]

You talk about slope on the unit, mine is a different one to yours (vortice), but this one has to be totally level as the polystyrene inside the casing is already preformed with the correct slope to remove the water, so check the install guide and ensure yours is correct to whatever it says.

 

ive not had any water escape so far, normal heat exchanger, house sits around 50% RH

 

[phatboy]

I had this issue a couple of months back... not especially cold but very wet weather so high RH.  Sentinel Kinetic BH.

 

My issue was the unit was not mounted quite level (Had rotated a bit of it's screws into the roof beams), and so some of the collected water was passing the drain hole behind the Summer Bypass, and running to the front of the unit.

 

The front PCB got wet, and the unit went haywire, reporting weird errors and fans spinning up and down.  I levelled up the unit this time bolting it to the roof timbers, and a helpful friend cleaned up the circuit board for me, and everything is now fine.  I keep checking the unit in the loft, and 2 months on no liquid has been seen.

 

 At the time I also cleaned the drain hole behind the Summer Bypass, and removed the bung to the front of the drain (I use the rear one), and checked it was all clear, and poured a little water in to be sure.

Edited December 27, 2020 by phatboy

[Eric]

I have the same unit with similar problems, mine is in the attic & the heat exchanger keeps filling up with water.

I’m hoping that some insulation around the unit will help.

[dpmiller]

One other observation on my system- what kind of trap do you have on the drain? If airflow is imbalanced (too much extract) the extract fan is powerful enough to pull water UP the drain pipe from where it'll flood the H/E drain area and even flow over the bottom of the fan when it'll splash water into the extract outlet duct. Suggest checking the drain pipework is well sealed and the trap functional...

[Eric]

I don’t have a trap fitted on my unit yet, I just have it draining into a bucket. I either have to drain it outside or to the soil vent pipe.

It’s balanced very well.

 

Does it matter that water is accumulating in the heat exchanger? 

[Pete]

Since the initial dripping I have not had anymore and have not had the cover off the unit. I wonder if the airless trap was stuck together as I had this with a sink upstairs. The weather is colder and I would have thought I would have had more dripping if there was a problem so will just keep monitoring under the unit. 

[jack]

3 hours ago, Pete said:

Since the initial dripping I have not had anymore and have not had the cover off the unit. I wonder if the airless trap was stuck together as I had this with a sink upstairs. The weather is colder and I would have thought I would have had more dripping if there was a problem so will just keep monitoring under the unit. 

 

You'll get less dripping when it's very cold, because there's a lot less moisture in the air. Very low single figure temperatures with high humidity will give you more condensation than when the temperature is sub-zero.