HRV questions/checklist

Technophobe

Hi all,

I am meeting my Plumber soon to discuss the installation of my HRV unit and wanted to know if anyone had any pointers and/or thoughts on what I need to discuss with him. The system is an MTD ERV-350

From my research and the usual informative posts here, I know to quiz him up on things like:

- Making sure the ducting is highly insulated
- That balancing is carried out correctly.
- That the Controller is located in a sensible place
- Making sure the External Intake & Outflow vents are located an appropriate distance apart.
- For my kitchen, what should I discuss??
My thoughts here were to install a Cooker hood with graphite filters to deal with smells & grease and then have the HRV deal with steam…To effectively do this then, does the extract vent in the kitchen need to be close to the cooker? Does it then not risk being clogged up with the grease due to proximity?? I would appreciate any thoughts on this??
Ideally, I presume you don’t want a hole in the wall for an Extractor fan when you are trying to keep your house airtight…

- I have seen some people suggest that Extract ducts could (in theory?) be located beside a stove/burner to draw some of the rising heat and thus (after heat exchange) re-circulate it around the house. Does this make sense? Is it practical?
Would this work in the same way to locate an extract vent close to an open fire that draws it air from the outside via an under-floor pipe? (I know an open fire contradicts the ideal of air-tight etc but that’s for a different discussion!)

Anything else to ask him or ensure he does?

Thanks for any help;)

CJhaughey

You are right with most of the things IMO.
BUT if you are considering fitting an open fire and an extract vent but not having a proper extractor fan that exhausts air seperately to the HRV doesn't make sense,the filters will fill with grease and gunk very fast otherwise.
I would fit a stove they give much more heat and convect much better than an open fire, plus they are controllable.
I would fit a proper extractor that exhausts through a roof vent/Wall vent.
Make sure it has self closing flaps that close when it is not in use to slow air infiltration.

sinnerboy

Off topic but relevant - aim for air tightness of Q50/5 or better to achieve max energy efficiency . DEAP calcs I have done indicate that HRV at levels above Q50/5 tend to result in increase of overall energy consumption . Heated air is forced out through the leaky fabric .

beyondpassive

Best practice is to aim for <2 ach per m2 @ 50 pascals.

This is a cumulative hole less than about 200mm diameter for a 2000 square foot house.

sinnerboy

Technophobe wrote: »

- That the Controller is located in a sensible place

Make sure the fan unit is located so that filter changing is easy . Will you go the attic 3 or 4 times per year to do this ? Dirty filters not only affect the efficiency but can lead to contimnation of the internal air

Insist that ALL ceiling vents are fire dampered - intumsecent duct wraps do not act fast enough in case of fire

gman2k

sinnerboy wrote: »

Insist that ALL ceiling vents are fire dampered - intumsecent duct wraps do not act fast enough in case of fire

Sinnerboy, can you explain the logic behind the above?
I don't want to drag this thread off topic, but I've spoken to a good few suppliers and they say it's not necessary. and there does not appear to be regulations re same.
I know you could say good practice, but I'd like to hear the rationale.

sinnerboy

read through this

http://www.boards.ie/vbulletin/showthread.php?t=2055385732&highlight=fire

Start a new thread please if you to reignite the issue ( pun intended )

sinnerboy

And to the OP - add to the list

- the fan motor of the HRV unit must be linked to the smoke detectors system to power down in case of fire

imitation

If your after an installation check list this one does the job very well, its from the SAP appendix Q

http://www.sap-appendixq.org.uk/documents/MVHR_Installation_Guide_Final.pdf

The cooker debate is one were currently going through, on one had going through the MHRV will add cost and the possibilty of grease and what have you getting into the system. On the other hand an extractor fan goes against the air tightness plan. Were going to investigate the posssiblity of an extractor that is reasonably airtight when not in use.

One other consideration is recessed lighting, if it is installed below the attic space it may create an air leak.

For the stove, I think the most effective way would be to connect a back boiler and install a radiator in the inbound air duct. You might have problems with the air being too dry then.

Technophobe

hey,

thanks to all so far for the input....useful stuff as usual...:D

soldsold

imitation wrote: »

For the stove, I think the most effective way would be to connect a back boiler and install a radiator in the inbound air duct.

Sounds like a good plan, do you know of any available models? PM would be great if you dont want to post openly. Just ordering my HRV today.

Thanks,

Steve

CJhaughey

imitation wrote: »

For the stove, I think the most effective way would be to connect a back boiler and install a radiator in the inbound air duct. You might have problems with the air being too dry then.

What size of Rad will fit into the air duct and not obstruct flow?
My intake is 150mm same with exhaust. It would want to be a small radiator or a large duct.

imitation

I should have qualified what I had seen more carefully, I saw a one manufacturer who had done it, I`m not sure on the exact details. I think the air is heated just after the HRV unit. I wouldnt advocate this unless somebody researched it carefully themselves.

M cebee

sinnerboy wrote: »

And to the OP - add to the list

- the fan motor of the HRV unit must be linked to the smoke detectors system to power down in case of fire

that and i think vents need to be a distance from smoke heads

the flexible metal ducting can cause issues with earthing and bonding

when used in conjunction with foil backed slab

let the sparkie know what's goin in anyhow

JuniorB

Here's a list of questions for suppliers that I got from another thread a while back ...

Are they using an SAP Appendix Q certified machine.
How do they integrate the extractor fan in the kitchen into their system.
Have they made any provision for a fire out break in the home, fire rated valves, electrical cut out etc.
Ask what ducting they are using and why plus do they insulate it and with what.
Can they show a calculation of how they sized the units suitability for your home.
To answer this topic, can they give a reason for you to install one, that doesn't sound like them simply making a sale.
Have they had any independent (not a 30 min session from the manufacturer) training on how to design and install a HRV system.- http://www.bsria.co.uk

Advice...
- get the rigid ducting not the flexible stuff
- get anti-microbial ducting to the supply ducting
- get a boost function for showers etc.
- get a summer core which does not do heat exchange
- put an extract in your laundry/utility room so you can dry clothes

gizmo555

Technophobe wrote: »

My thoughts here were to install a Cooker hood with graphite filters to deal with smells & grease and then have the HRV deal with steam…To effectively do this then, does the extract vent in the kitchen need to be close to the cooker? Does it then not risk being clogged up with the grease due to proximity?? I would appreciate any thoughts on this??
Ideally, I presume you don’t want a hole in the wall for an Extractor fan when you are trying to keep your house airtight…

This is exactly the setup I have. My system was installed about 8 months ago, with a recirculating cooker hood directly over the hob and an exhaust vent for the HRV in the ceiling about 3 ft horizontally from the hob. I only run the hood fan when frying, or cooking something with a strong smell. If I'm doing something that just produces heat & steam but no smell, say boiling pasta, I leave the hood fan off and let the HRV deal with it on its own. I find this works well.

In the period since it was installed, I've cleaned the hood several times and there has been the normal amount of grease on it that you'd expect. After reading your post, I just got up on a chair and gave the HRV vent a close visual inspection for the first time since it went in. There was a small amount of dust mixed with a very light coating of grease on the inner surfaces of the vent.

CJhaughey wrote: »

You are right with most of the things IMO.
BUT if you are considering fitting an open fire and an extract vent but not having a proper extractor fan that exhausts air seperately to the HRV doesn't make sense,the filters will fill with grease and gunk very fast otherwise.

I clean the filters on my HRV system regularly and there is no sign of any grease getting as far as the filters. When I vacuum them, all the dust comes off easily, which you wouldn't expect if there was any grease on the exhaust filter for it to stick to.

CJhaughey wrote: »

I would fit a proper extractor that exhausts through a roof vent/Wall vent. Make sure it has self closing flaps that close when it is not in use to slow air infiltration.

I'd have to disagree. It makes no sense to me to be going to the trouble and expense of installing a HRV system and then separately putting in a fan to exhaust large volumes of warm air from what is usually the hottest room in the house.

CJhaughey

gizmo555 wrote: »

I'd have to disagree. It makes no sense to me to be going to the trouble and expense of installing a HRV system and then separately putting in a fan to exhaust large volumes of warm air from what is usually the hottest room in the house.

I guess it depends on the house, My house overheats very easily if I don't run the extract from the kitchen during cooking.
If there is dust and grease in the duct then over time it will build up, in areas that you can not clean easily.
I don't like the idea of that, thats why I use a separate extractor plus when cooking stuff like stirfrys etc I need to have the hood on max to get rid of all the steam and fumes, the HRV would not be able to cope with that amount by itself.

gizmo555

CJhaughey wrote: »

If there is dust and grease in the duct then over time it will build up, in areas that you can not clean easily.
I don't like the idea of that, thats why I use a separate extractor plus when cooking stuff like stirfrys etc I need to have the hood on max to get rid of all the steam and fumes, the HRV would not be able to cope with that amount by itself.

Your posts and the OP's intrigued me so I've checked a little further. I unscrewed the "mushroom" in the centre of the kitchen exhaust vent so I could see up into and touch the inside of the duct behind it. There is no trace of any grease in the duct, beyond the very small amount I already described as being deposited on the vent itself. We're a hungry family of five, so the cooker gets a lot of use too!

All I can say is that from my experience, this is a non-issue. I can't see why a moderate amount of dirt and dust in the exhaust ducting would be a problem anyway, as long as it wasn't getting to the point where it was restricting airflow.

So far as the ability of the HRV to cope with cooking goes, the thing which generates the most steam for me is boiling pasta and it deals with that no problem.

Quack13

sinnerboy wrote: »

And to the OP - add to the list

- the fan motor of the HRV unit must be linked to the smoke detectors system to power down in case of fire

Who would generally be responsible for hooking this up. The HRV installer or Electrician (assuming he is putting in alarm)?

larrym

Where do you get replacement filters (have an mtd350) ?

gears

larrym wrote: »

Where do you get replacement filters (have an mtd350) ?

From MTD ?

http://www.mtd-solutions.com/index.htm

M cebee

Quack13 wrote: »

Who would generally be responsible for hooking this up. The HRV installer or Electrician (assuming he is putting in alarm)?

the sparkie

he needs to run a control pair from any interconnected smoke head back to the board or mhrv unit to switch a contactor

you need a relay base w/battery backup to do the switching(EI do them)

alternatively if you have smoke heads connected to a security panel .the panel will prob have a contact in the panel

BigGeorge

Is there any consensus / opinions on the correct controls for a HRV in a new build

e.g. boost buttons ( say 15 mins) in kitchens & WCs, shoulds WCs be on humidity control etc...