Background hum in MHRV systems

BigGeorge

Going to install a MHRV in a new build but am concerned at the background hum - in particular the one you'd hear late at night

Am looking for suggestions , either components to add or design features to minimise the background hum

Lantus

If this unit will run all the ime then you'd really need to consider an acoustic consultant. Air handling units generate noise across the entire spectrum from 250hz to 8hz and low frequency noise can be a huge issue.

Ensuring you have a really quiet unit would depend on a number of factors: -

1/ The measured noise generated by the unit (should be inc on fac specs.)
2/ It's location relative to the sleeping areas.
3/ Acoustic isolation to limit virabation through the structure.
4/ Acoustic insulation to prevent breakout from the casing and fans.
5/ Silencers to prevent in duct noise. (note that these increase fan pressure and need careful and proffessional sizing.)
6/ Acoustic quality of walls and all gaps and doors/access of the room or area the unit will sit in.


Acoustics in Ireland is 20 years in the dark ages. Unless you give this attention you may well end up annoyed. Remedial works can be expensive to come back and fix later.

sunnysoutheast

BigGeorge wrote: »

Going to install a MHRV in a new build but am concerned at the background hum - in particular the one you'd hear late at night

Am looking for suggestions , either components to add or design features to minimise the background hum

Our units are suspended in a cradle from the roof rafters rather than sitting on the ceiling joists. There is a low background hum from the units but our guests have actually commented that their kids in our guest room have slept better in our house than theirs....they've been back a few times now so I don't think they're just being nice.

We find that there is some noise transmission but this is far outweighed by the improvements in air quality HRV brings. In any case, unless you live in the quietest place in Ireland, you will be getting noise through the wall or trickle vents you'll otherwise have to put in.

"acoustic consultant"?

SSE

BigGeorge

The plan is to have the unit in a well sound insulated room at the other end of the house. As regards external sounds, between triple glazing & high levels of acoustic insulation there wont be any other back ground noise....which is part of the issue I suppose
The issue then appear to be how to reduce the induct noise which is like a faint steady low frequency hum

sunnysoutheast

BigGeorge wrote: »

The plan is to have the unit in a well sound insulated room at the other end of the house. As regards external sounds, between triple glazing & high levels of acoustic insulation there wont be any other back ground noise....which is part of the issue I suppose
The issue then appear to be how to reduce the induct noise which is like a faint steady low frequency hum

To be honest we don't find the noise any sort of a problem, it's quite reassuring TBH. I think that a very low level of low-frequency noise can be beneficial to sleep, but that's just my opinion...

SSE

BigGeorge

Its all very very subjective, what reassures one person (you SSE) will drive another crazy ( my wife!) -

its the steady hum which will be a problem so I need to make sure sensible design suggestion are incorporated when the system is still on the drawing board rather than on site when it'll be a lot more expensive

Technophobe

From my experience of living with it, it is not noticeable in terms of the ceiling ducts .....the hum is inaudible to my and her ears....

Only area I can generally hear any sort of low hum is the rooms where there is an extract vent and again, it is very low and not anything that would put you off....

In terms of the unit itself, again it is about where you locate it and I have it located well away from any bedrooms, but my house design allowed me put it in such a location.....:)

MicktheMan

Also from experience of living with one, nobody has ever mentioned noticing any noise. I certainly don't hear it but then again herself is always telling me I'm deaf:D.

Ours is located in the loft, suspended from the rafters. If I were to do it again I would possibly locate it somewhere more accessable for routine filter maintenance.

BigGeorge

thanks - thats great to hear, its reassuring. Does it get much nosier when the system ramps up?

MicktheMan

BigGeorge wrote: »

thanks - thats great to hear, its reassuring. Does it get much nosier when the system ramps up?

I assume you mean on the "boost"function.
This is really the only time we hear anything and it is the sound of the extra air moving through the vents. This is not a humming sound, more like a slight air gushing sound. The system is set up to run on boost for 20 mins after the boost button is pressed. I would absolutely not consider this an issue at all.

CJhaughey

The system we have has mufflers on both the exhaust and supply duct runs.
The mufflers are pretty big and bulky but seem to do a good job, I can't really hear anything if I am in a room with a vent.
No-one has ever remarked on being able to hear the thing running.

muffler

CJhaughey wrote: »

The mufflers are pretty big and bulky

Oi! Watch it

CJhaughey wrote: »

but seem to do a good job

Thanks. Nice to get a wee bit of praise.







Sorry, couldn't resist

MicktheMan