Teething issues with MVHR

[Tom]

We moved in three days ago and so fired up the MVHR unit (ventaxia sentinel kinetic high flow). It's recently been commissioned, air flow set at 30% with 9l/sec at the terminals. When I finally sat down in the sitting room at the end of the day and things were quiet I became aware of a background noise, hard to describe, with another noise like a running stream, which eventually I realised was coming from the supply vent. This noise seems to have got louder - or perhaps I'm just more aware of it. I had a fiddle with the flow controls on the ductwork, and when I open fully the one for the living area the noise reduces. I did notice also that the plenums were very noisy themselves, there was an air leak detectable from the supply plenum and both sounded like a running stream inside. It seems this noise is being transmitted to the terminals - which in my mind seems counterintuitive for a plenum. Attached is a picture of one of them. It does seem small for all the ductwork going in to it, so I can imagine the airspeed must be high with lots of turbulence. I paid a lot of money for this install but I have yet to pay the final invoice. Am I being too picky - or is this all to be expected?

[Nickfromwales]

Have they installed silencers / attenuators?

 

5 minutes ago, Tom said:

Am I being too picky - or is this all to be expected?

Nope, I'd be quite pissed off if my MVHR was audible. I've installed loads of MVHR systems for my clients and they're all silent or near silent at worst (at trickle).

 

Is the metal ductwork bringing air in from atmosphere insulated?

 

[Tom]

1 hour ago, Nickfromwales said:

Have they installed silencers / attenuators?

Yes

 

1 hour ago, Nickfromwales said:

Is the metal ductwork bringing air in from atmosphere insulated?

No. Its quite a short run and I could easily wrap it in mineral wool though.

 

Another complication is that the unit is currently running at boost and I can't seem to turn it down to normal flow. It seems to be gurgling inside so I wonder if there's some trapped condensation in there tripping the humidity sensor.

 

What's your opinion on the plenums? I'm assuming they shouldn't be making a noise?

[Tom]

Wider angle...

[Tom]

16 minutes ago, Tom said:

Another complication is that the unit is currently running at boost and I can't seem to turn it down to normal flow. It seems to be gurgling inside so I wonder if there's some trapped condensation in there tripping the humidity sensor.

 

Right, I've investigated further. I've actually had it running with the condensate drain not attached to anything, just draining in to a bowl. There seems to be lots of air being sucked up the short length of corrugated pipe, and this seems to be causing the gurgling. If I put my finger over the end and then take it off, some water drains out. I did this a couple of times until no more came out and the gurgling stopped. It seems that the constant flow of air up the drain pipe was preventing water from draining effectively. 

Is it normal for air to be sucked into the condensate pipe? I guess when I plumb the thing in, a ubend/trap would stop the air flow and the water would drain more freely?

Anyway, I've switched the thing off for the night as there is clearly a problem. 

[Adsibob]

25 minutes ago, Tom said:

Another complication is that the unit is currently running at boost and I can't seem to turn it down to normal flow.

This is your problem. It is normal in my experience at least for the system to be audible when boosted. But you should only boost it occasionally, after a very smelly session in the toilet, or a long steamy shower. Fix the boost issue first.

[Iceverge]

Is the unit itself directly on the floor? 

 

Maybe some rubber feet or paving slabs wouldn't go amiss. 

[Tom]

20 minutes ago, Iceverge said:

Is the unit itself directly on the floor? 

 

Maybe some rubber feet or paving slabs wouldn't go amiss. 

It's hung off a blockwork wall, all very solid and no vibration 

[Tom]

28 minutes ago, Adsibob said:

This is your problem. It is normal in my experience at least for the system to be audible when boosted. But you should only boost it occasionally, after a very smelly session in the toilet, or a long steamy shower. Fix the boost issue first.

Yes, I agree. Strange that I can't seem to turn the boost off though 

[Adsibob]

35 minutes ago, Tom said:

Yes, I agree. Strange that I can't seem to turn the boost off though 

The boost switches have probably just been wired incorrectly. They should be retractive switches, but there are different types so maybe the wrong retractive switch was used, or the right one was used but incorrectly wired. Easy enough to fix. I would just ask them to come back and address boost issue first and then any other issues. If you want an objective reading on the sound, you can get a decibel meter from Amazon for about £12.

[MikeGrahamT21]

100% get them back in for all the issues mentioned above, this is firmly their remit to sort

[Tom]

6 hours ago, Adsibob said:

The boost switches have probably just been wired incorrectly. They should be retractive switches, but there are different types so maybe the wrong retractive switch was used, or the right one was used but incorrectly wired. Easy enough to fix. I would just ask them to come back and address boost issue first and then any other issues. If you want an objective reading on the sound, you can get a decibel meter from Amazon for about £12.

There are no boost switches, just the internal humidity sensor and the manual overide on the front of the unit

[Tom]

1 hour ago, MikeGrahamT21 said:

100% get them back in for all the issues mentioned above, this is firmly their remit to sort

They said it was up to my plumber (ie me) to connect up the condensate drain. The problem is they are a commercial ventilation installers rather than domestic, if that makes a difference, so perhaps they see their remit slightly differently

[dpmiller]

there should be a wee squiggle symbol at the bottom right of the display if it's auto-boosting because of humidity

[Tom]

46 minutes ago, dpmiller said:

there should be a wee squiggle symbol at the bottom right of the display if it's auto-boosting because of humidity

Yep, it has that, but it seems to be boosting continually now, even when no one's had a shower etc.

Edited Thursday at 08:20 by Tom

[Tom]

I need to plumb in the condensate properly I think. My plan is to attach a hose (essentially a washing machine hose) to the stub that comes out of the machine, run this along the floor, up and over some metal trunking and through a hole in the floor to the plant room below, then T into the pipe that takes the tundish from the UVC.

Does that sound reasonable? 

Running the pipe up and over the trunking would effectively make a u-bend.

[Tom]

Stub pipe as it is now, gurgling and draining in to a bowl

[Tom]

T into this 32mm pipe, tundish just above

[dpmiller]

11 minutes ago, Tom said:

Yep, it has that, but it seems to be boosting continually now, even when no one's had a shower etc.

 take the humidity limit up a few % and see if it comes out of boost. IIRC ours was a bit oversensitive out of the box

 

and yes, get a trap on the drain

[Tom]

5 minutes ago, dpmiller said:

 take the humidity limit up a few % and see if it comes out of boost. IIRC ours was a bit oversensitive out of the box

 

and yes, get a trap on the drain

Good idea, I'll have a look at it. The manual suggests the sensor is set at 70% humidity to trigger boost, and the house is pretty much over this everywhere according to the Wunda thermostats

[Tom]

23 minutes ago, dpmiller said:

and yes, get a trap on the drain

 

My idea above, with the hose running along the floor then up and over some metal trunking would effectively make a trap - and this is unavoidable as the metal trunking is between the unit and the hole the hose needs to go through. I could add a trap nearer the 32mm pipe I want to T in to, but there might be an issue with having two "traps" in series? 

Edited Thursday at 08:57 by Tom

[JohnMo]

5 minutes ago, Tom said:

 

My idea above, with the hose running along the floor then up and over some metal trunking would effectively make a trap - and this unavoidable as the metal trunking is between the unit and the hole the hose needs to go through. I could add a trap nearer the 32mm pipe I want to T in to, but there might be an issue with having to "traps" in series? 

You need a proper dry trap, like Hep2O ones, close to the unit. The pipe needs to fall away to a drain point, you can take it up and over. A hose on the floor, is a bodge, water will collect become stagnant and you are potentially breathing stuff in you shouldn't.

[Tom]

The unit is only ~100mm off the floor and I have a ~50mm high piece of trunking for the hose/pipe to go over before it can drop down in to the plant room, so not much wriggle room. 

[Adsibob]

51 minutes ago, Tom said:

Does that sound reasonable? 

Not sure. Can you run a drain pipe upwards? Seems odd to me.

 

[Adsibob]

20 minutes ago, Tom said:

The unit is only ~100mm off the floor and I have a ~50mm high piece of trunking for the hose/pipe to go over before it can drop down in to the plant room, so not much wriggle room. 

You will need to drill through the floor to find a way. You really don’t want stagnant water anywhere near this system.