HRV - Have you had to find a balance between cold and Air Supply.

jasperok

First Cold Season In the House
I have been going mad with how cold it has seemed all the time Especially In the morning its been a case of being able to see your breath!
So i went round all the Inlets and was mildly suprised to find just how much air and just how much ICY air is being pumped into the House Constantly!

What is the deal with these sytems - How safe/unsafe is it to run them at lower speeds?

A friend reccomended tunging the Unit off or putting it on a timer at least but seeing as the house is 99% totally sealed I dont want to be starving anyone of O2 especially wit the stove (heating ALL the rads in the House) is belting along as that does consume its fair share.

Ayway - If someone could give me advice or share similar experiences of dealing with HRV in the colder climate I'd really appreciate it

thanks

gizmo555

jasperok wrote: »

First Cold Season In the House
I have been going mad with how cold it has seemed all the time Especially In the morning its been a case of being able to see your breath!
So i went round all the Inlets and was mildly suprised to find just how much air and just how much ICY air is being pumped into the House Constantly!

What is the deal with these sytems - How safe/unsafe is it to run them at lower speeds?

A friend reccomended tunging the Unit off or putting it on a timer at least but seeing as the house is 99% totally sealed I dont want to be starving anyone of O2 especially wit the stove (heating ALL the rads in the House) is belting along as that does consume its fair share.

Ayway - If someone could give me advice or share similar experiences of dealing with HRV in the colder climate I'd really appreciate it

thanks

HRV is designed to be constantly pumping fresh air into the house. The heat recovery part of it though, should make sure that the temperature of the incoming air is not much lower than the exhaust air. If it's very cold, then either the inside temperature of the house was already pretty low, or the heat exchanger is not working efficiently. Another possibility is that the fans are working too hard and changing the air too often - no heat exchanger is 100% efficient and the more frequently the air is changed, the greater the heat loss will be.

My system is set up to do about 10 complete air changes per day. I don't find at that rate that it noticeably cools the house. I certainly think it's far preferable to the previous setup of passive ventilation with wall vents and trickle vents in the windows. I found that far too drafty and cold in windy weather, and muggy and damp in calm conditions.

So far as turning the system off from time to time is concerned - no big deal, there's no safety issue and no-one will suffocate. Air quality will deteriorate though, which kind of defeats the purpose of having it. Maybe have your installer check the system and make sure it's not overdoing the air change rate. Have a look here too, for some interesting discussion on HRV:

http://markbrinkley.blogspot.com/2009/11/whither-mvhr.html

jasperok

Interesting read thanks.

Do you see this:
Let's take your 58 m2 house. Suppose it has a generous 2.5 m ceiling height so its volume is 145 m3, and suppose we use a reasonably generous 0.5 ACH. That gives us 73 m3/hr, which 20.28 l/s.

thats an extract from the discussion.


I'd like to calculate that for myself but not sure how

My house is 200m2 and 1.8m high so thats 360m3
And i think my unit is rated at 85% efficient (orcon hrc300)

Does anyone know the equatio to calculate three air changes a day?

That way i could set the fan speed at x litres an hour to suit and see if that helps.

Cheers

gizmo555

jasperok wrote: »

I'd like to calculate that for myself but not sure how

My house is 200m2 and 1.8m high so thats 360m3
And i think my unit is rated at 85% efficient (orcon hrc300)

1.8m high? Sounds low! Should be about 2.4m celing height.

jasperok wrote: »

Does anyone know the equatio to calculate three air changes a day?

That way i could set the fan speed at x litres an hour to suit and see if that helps.

A cubic metre is 1,000 litres. By the way, in case you missed the correction I made, my system is running at about 10 changes a day not 3. I gather about 0.35 changes per hour is considered usual.

jasperok

oh thanks thats great

your right - dont know where i plucked 1.8 from !!

Mothman

I assume I'm stating the obvious but in case, my HRV has a summer and a winter setting. The summer setting bypasses the heat exchange. Make sure your HRV is on winter setting. My system is 12 years old and this is done manually. I think likely that this is automated in most if not all HRV installations now.

jasperok

Well something is definately wrong - no matter how low i set it the air is just freezing no matter how warm the house is.

The funny thing is if i turn it off after 20 mins you can notice how cosy the house becomes.

I am pretty sure i am on my own getting this setup right as the company i bought the unit from went bust.

And there's no real control panel - just an led light that flashes red whe the filters need changing.

CJhaughey

What is the unit? I am sure you can mention the make and model seeing as the supplier has gone bust!

jasperok

sorry not the supplier i meant the reseller.

its well over a year i have it anyway only this is my first winter in the house.

its a hrc-300 MHRV unit.

apparently 85% efficient.

I think the next thing i will do is the (extremely conclusive scientific) black bag test on the room feeds and extracters.

It might give me an idea of what is being moved or how much anyway.

I imagine the black bag test isnt as suited to the master outlet and inlet ducts due to the fact they are moving too many litres of air a second to measure.

is there such a thing as an airflow guage? like a hamster wheel with a litres persecond guage?!

runawaybishop

jasperok wrote: »

sorry not the supplier i meant the reseller.

its well over a year i have it anyway only this is my first winter in the house.

its a hrc-300 MHRV unit.

apparently 85% efficient.

I think the next thing i will do is the (extremely conclusive scientific) black bag test on the room feeds and extracters.

It might give me an idea of what is being moved or how much anyway.

I imagine the black bag test isnt as suited to the master outlet and inlet ducts due to the fact they are moving too many litres of air a second to measure.

is there such a thing as an airflow guage? like a hamster wheel with a litres persecond guage?!

As Mothman said it could simply be that the summer bypass is active, therefor the heat exchanging is not taking place. I would check that first.

i was considering the model you mentioned, but i calculated that it would not be sufficient to supply the one air change every 3 hours required (.33 exchanges an hour) unless it was ran on the higher setting in my 213 sq meter house. Could it be that it is running on the higher setting and thereby lowering the efficiency of the heat exchanger?

edit:
http://www.energyefficient.ie/images/data/gallery/1_1581_HRC_folder_UK.pdf
i believe this is the model you have?

For a 200 m^2 house with 2.4 m ceiling heights you are talking about shifting 1/3rd of this 480 m^3 (i.e 1 full change every 3 hours, which i believe is the recommended amount) - so 160 meters^3 an hour. This means you are probably running at the middle level at a minimum. That wouldn't take into account the resistance from the ducts themselves, vents etc, so it is possible that it is running at the higher level, which would indeed lower the efficiency of your heat exchanger.

I think you can get yourself an anemometer for about 20 quid off ebay, might be better than yon plastic bag test

hope this helps