MHRV Units: Options?

Foiled Again

I'm looking for suggestions on which HRV unit to install. So far I know of VentAxia, Paul, ProAir and Ubbink. What other units are distributed and supported in this country?

Also interested in the economics of installing 2 smaller units vs one larger one for a new-build of 300sqm: any thoughts?

fclauson

I put two in so that units could run at 50% rather than 85% all the times

Works ok for me - we have a bungalow - bedroom end served by one unit - and kitchen/living by other

you will double you filter replacement costs

zrejvpx

We have a 278m2 split level house and thought we mightn't be able to get the ducts between the two sections so a quote for both ways - getting two units was 33% extra. It turned out that one unit was sufficient - we got a Vent Axia Sentinel Kinetic plus (from a different quote). But fclauson will have done a lot more investigation into this that I have...

runawaybishop

Foiled Again wrote: »

I'm looking for suggestions on which HRV unit to install. So far I know of VentAxia, Paul, ProAir and Ubbink. What other units are distributed and supported in this country?

Vortice

Foiled Again

Bump...

Surely there are more options and recommendations out there for HRV units?

BarneyMc

I'm looking myself at the moment and came across Beam and also zehnder/stork.

fclauson

there are many units out there but you need to look at two things
a) SAP/HARP rating
b) Passive Certified

The two methods of testing are not the same - for example the SAP/Harp number includes warmth from the motor - so a rubbish heat exchanger can be improved by motors which rung hot !! Its all very picky but important.

The most important thing is duct work & pressure loss - the narrow 2 or 3 inch type plastic flexible duct systems struggles over distance to carry the flow that you need - do the maths - the longer the run the more the loss - you will need multiple runs to make up for pressure loss

I went with 6 inch spiral with about 1M of acoustic duct at each outlet - you cannot hear my system at all (and I am fussy on this)

On where to run the ducts - keep everything inside the warm envelope and only have very short runs from the unit out through your insulation layer - there is a BIG risk of condensation here (that's why you have a drain on the unit) - especially if the warm house air comes into contact with the cold duct- you will get water (I get moisture on my exposed incoming water main for the 3 inches where its not insulated and that's at 7degrees)

Remember to have a drain from the unit which CANNOT FREEZE (i.e. not in the loft)
Make sure units are easy to get to for maintenance - filters need checking every month and replacing every xxx months !!

Put a fly/big muck filter just as the air comes in from the outside - you can use a low grade filter here but it gets rid of the big stuff - the windy weather this week turfed but all sorts in to the air which gets caught here - plus if you live in the country Harrowing, Harvesting etc causes dust and muck which you do not want in your ducts.

You should also look for automatic summer bypass - helps with natural cooling in the summer

Run boost switch lines to your bathrooms - boost on the way in boost on the way out - although I was reading some research which says that this is probably not necessary (but it is to comply with Part F)

hope all that helps
As feedback my house is never stuffy and during this summer even when we came back home after one of those hot summer days the house was neither hot nor stuffy

Scartbeg

Have 2 x Brink systems installed, same reason as above so that they are running at about 30% rather than 60% all the time. The power consumption is not linear, as fan speed increases power use ramps up dramatically.

The good news is they perform well - we didn't have them running for the first few months and were getting condensation in bedrooms at night. Instantly gone once the system was running.

Ideally have the units in a service room, within the heated building envelope. If they are in the cold attic (as ours) it just makes it harder when you want to tweak settings and service the system. Also as noted, you need some heat to stop the condensate drain from freezing. Make sure your intakes are away from soil stacks and prevailing wind. If I had thought ahead, I think I would have the units in a ground floor plant room and take air in through undergrounded ducts to pre-heat in winter, pre-cool in summer. +1 on a rough pre-filter to keep out flies and chaff if you are near fields.

Timed booster switches at kitchen and shower rooms would be advisable. We didn't put them in, and cost of additional control boards needed to add them to our system is prohibitive. Look for a system that includes them as standard. Moisture or CO2 boost sensors may also be an option.

Foiled Again

Thanks for the input folks. Decided to go with a Paul Novus 450. I got a good deal on the Frost protection jobby also. Metal Spiral ducting already fitted. Let's see how it all hangs together!

runawaybishop

What sort of frost protection comes with it, is it a pre-heater or bypass circulation?

fclauson

Foiled Again wrote: »

Thanks for the input folks. Decided to go with a Paul Novus 450. I got a good deal on the Frost protection jobby also. Metal Spiral ducting already fitted. Let's see how it all hangs together!

At what Outside air temp do you think you will need the frost protector ?

Foiled Again

It kicks in at -3degC rather than shut down the exchanger.

http://www.paulheatrecovery.co.uk/components/defroster/

I hadn't intended to get it originally but as I say I got a great deal on it.

fclauson

see http://www.paulheatrecovery.co.uk/components/defroster/

frost protection is only actually need at -10 (which is very rare in Ireland)

at the recent PHI conference this was discussed - an amount (all be it small compared to a normal house) of energy is wasted turning on the frost heater too early

BarneyMc

Can I throw in a question about the ducting here and ask what range of duct diameters are used for the main HRV units. Is there a min recommended size?

fclauson

BarneyMc wrote: »

Can I throw in a question about the ducting here and ask what range of duct diameters are used for the main HRV units. Is there a min recommended size?

Barney - its all about air flow and volume -
Bigger duct - slower airflow - less noise
Small duct - speedier airflow - more noise

typically its 180mm and 150mm which is used in a domestic if you are going for metal spiral wound duct

runawaybishop

fclauson wrote: »

see http://www.paulheatrecovery.co.uk/components/defroster/

frost protection is only actually need at -10 (which is very rare in Ireland)

at the recent PHI conference this was discussed - an amount (all be it small compared to a normal house) of energy is wasted turning on the frost heater too early

-10 is not rare in fairness

2011: -9.8
2010: -18.7
2009: -10
2008: -8.8
2007: -8
2006: -8.6

The frost protection should be automatic once a certain minimum is reached and the more efficient the heat exchanger the sooner it needs to kick in (can be as early as -2). There are usually 2 methods: an actual air heater that warms incoming air and a bypass valve: this forces the unit to bypass the heat exchanger extraction and circulate warm air around the unit. For our climate a bypass value should be sufficient but they can force your unit to run at 100% for a minute or two, lower the efficiency and increasing the noise.

theoptimist

Hi guys, hoping to resurrect this old thread! fclauson and scartbeg did you guys install yourselves? you sound like you have a certain amount of technical knowledge on this. I have done a lot of reasearch but Google can only take you so far! I have had three or four installers recommended to me but I've had negative feedback re noise on one of these from a recent client of theirs.

The areas of our build that I am happiest with the end result are the areas where I had educated myself sufficiently to feel confident making my own decision, often going against the opinions of builder etc!
Are the principles of the heat recovery straightforward enough that I can oversee/check installation and not be at the mercy of an installer?

One installer recommended the smaller flexible ducting, but fclauson that sounds like a pretty simple principle, 'bigger duct = less noise!' and accoustic duct? nobody I've spoken with has suggested that!
If I have a checklist of the important stuff .....
Rigid vs flexible is another issue that people seem to differ on
and how bout cleaning your ducting?

BarneyMc

Wide, rigid ducting is best from what I hear and it makes sense.

runawaybishop

theoptimist wrote: »

Hi guys, hoping to resurrect this old thread! fclauson and scartbeg did you guys install yourselves? you sound like you have a certain amount of technical knowledge on this. I have done a lot of reasearch but Google can only take you so far! I have had three or four installers recommended to me but I've had negative feedback re noise on one of these from a recent client of theirs.

The areas of our build that I am happiest with the end result are the areas where I had educated myself sufficiently to feel confident making my own decision, often going against the opinions of builder etc!
Are the principles of the heat recovery straightforward enough that I can oversee/check installation and not be at the mercy of an installer?

One installer recommended the smaller flexible ducting, but fclauson that sounds like a pretty simple principle, 'bigger duct = less noise!' and accoustic duct? nobody I've spoken with has suggested that!
If I have a checklist of the important stuff .....
Rigid vs flexible is another issue that people seem to differ on
and how bout cleaning your ducting?

You can install it yourself, its very simple. Use big rigid ducting where you have the room, use bafflers near the unit.

howman

MHRV units

are they worth it?

Air to air heat exchange at low temperature differential - surely the h/e efficiency is horrendous?

then add in the kw used by the fan? and the installation costs?

just not convinced

theoptimist

How about rigid vs flexible ducting?
And cleaning of ducts?

I like the acoustic duct detail. That makes sense and I don't know why I haven't come accross it before. I've had three quotes and no one has mentioned that.

theoptimist

theoptimist wrote: »

How about rigid vs flexible ducting?
And cleaning of ducts?

I like the acoustic duct detail. That makes sense and I don't know why I haven't come accross it before. I've had three quotes and no one has mentioned that.

I must be losing my mind, posting a question that I've already asked! and worse, that barney and runaway already answered...

I don't know how i didn't see their posts (or mine!)

Sorry, it must be past my bed time....

theoptimist

runawaybishop wrote: »

You can install it yourself, its very simple. Use big rigid ducting where you have the room, use bafflers near the unit.

So the bafflers reduce vibration in the heat exchanger? or between heat exchanger and ducting?, tackling noise at the source?

How about the acoustic ducting that fclauson mentioned?

runawaybishop

howman wrote: »

MHRV units

are they worth it?

Air to air heat exchange at low temperature differential - surely the h/e efficiency is horrendous?

then add in the kw used by the fan? and the installation costs?

just not convinced

Around 95% efficient using brushless motors so they cost 20-40 euro for the year to run, you can install them yourself fairly easily. They are a must in any house going passive and make a lot of sense in any well insulated house anyway. They are very overpriced over here though and the install costs i was quoted were a joke.

theoptimist wrote: »

So the bafflers reduce vibration in the heat exchanger? or between heat exchanger and ducting?, tackling noise at the source?

How about the acoustic ducting that fclauson mentioned?

They reduce noise and vibration from the unit to the ducting and are sited next to the unit.

joeirish

runawaybishop wrote: »

Around 95% efficient using brushless motors so they cost 20-40 euro for the year to run, you can install them yourself fairly easily. They are a must in any house going passive and make a lot of sense in any well insulated house anyway. They are very overpriced over here though and the install costs i was quoted were a joke.



They reduce noise and vibration from the unit to the ducting and are sited next to the unit.

I have looked online but cannot find anything about these 'bafflers'. Can you tell me more or point me towards a site where I can get more information. thanks

runawaybishop

joeirish wrote: »

I have looked online but cannot find anything about these 'bafflers'. Can you tell me more or point me towards a site where I can get more information. thanks

They should come as standard with any unit i would have assumed -they will just be a flexible bit of ducting to absorb noise and vibrations.

http://www.ductplus.com/Products.asp?NodeCode=0001&gclid=CjwKEAjwns6hBRDTpb_jkbTv1UYSJACBhberrTeBDajeBG8M-TovdDLYvr1L5Xsv5RHET01eYDjSmRoC7HTw_wcB

^^ bottom item here is something similar - would probably do the exact same job.

romeonovember

Hi there,

sorry of hi-jacking this but it is kind of related. A MHRV supplier I was talking to recently was trying to inform that an individual supply/return to each inlet and outlet with a manifold was a much better system than the traditional one when you have Tees of the main ducts to each supply and return. he also said that the system with the manifold is easier to balance in that this is done at the manifold. is he right or is this just sales pitch? from reading online, he would seem to be talking sense. We are due planning for a 2900ft2 house with a provisional BER of A2 this week, so trying to get all these items sorted now before our architect does his detailed design. I was also interested in the -snip- are pitching as being the best thing since sliced bread, but I have not had any reply from them. thanks in advance.

romeonovember.

runawaybishop

romeonovember wrote: »

Hi there,

sorry of hi-jacking this but it is kind of related. A MHRV supplier I was talking to recently was trying to inform that an individual supply/return to each inlet and outlet with a manifold was a much better system than the traditional one when you have Tees of the main ducts to each supply and return. he also said that the system with the manifold is easier to balance in that this is done at the manifold. is he right or is this just sales pitch? from reading online, he would seem to be talking sense. We are due planning for a 2900ft2 house with a provisional BER of A2 this week, so trying to get all these items sorted now before our architect does his detailed design. I was also interested in the -snip- are pitching as being the best thing since sliced bread, but I have not had any reply from them. thanks in advance.

romeonovember.

It would be easier to balance alright but apart from that its not a much better system - If you are paying to have it installed they will balance it anyway (ask to see the readings from the balancing to make sure its done) so i don't really see a benefit to you for what i assume is a more expensive system.

Did he mention any other benefits? Out of interest what's the capacity of the model they are recommending?

MicktheMan

romeonovember wrote: »

Hi there,

sorry of hi-jacking this but it is kind of related. A MHRV supplier I was talking to recently was trying to inform that an individual supply/return to each inlet and outlet with a manifold was a much better system than the traditional one when you have Tees of the main ducts to each supply and return. he also said that the system with the manifold is easier to balance in that this is done at the manifold. is he right or is this just sales pitch? from reading online, he would seem to be talking sense. We are due planning for a 2900ft2 house with a provisional BER of A2 this week, so trying to get all these items sorted now before our architect does his detailed design. I was also interested in the -snip- are pitching as being the best thing since sliced bread, but I have not had any reply from them. thanks in advance.

romeonovember.

Imo, there is an issue coming down the tracks wrt mvhr ducting and that is how will the ductwork be cleaned. In my mind, if there is a manifold with individual runs to each in/outlet then this makes it a lot easier to clean.

romeonovember

he was going to spec the zehnder 550 comfoair for our house. from looking at the zehnder website, the 350 should do it.

runawaybishop

MicktheMan wrote: »

Imo, there is an issue coming down the tracks wrt mvhr ducting and that is how will the ductwork be cleaned. In my mind, if there is a manifold with individual runs to each in/outlet then this makes it a lot easier to clean.

Not sure why you think that is easier? There are less meters of ductwork the other way so you only have the clean the central direct run and then come up from the exit/entry in each room, rather than having to clean back to source with a manifold.