We are designing a well insulated, double wrapped and well sealed off grid home. We would like a wood fire for our living room (more for cosiness and ambience rather than for heating) which has a small wet back to boost the hot water and an external air intake. I've been searching but having trouble finding one. Does anyone have a suggestion? If there's not one on the market is it just a matter of finding one with the wet back and having the external air intake added? Would this cause problems with wood heater regulations? We would like one with a glass door big enough to enjoy the visuals of a fire.
Wood heater with approx. 3Kw wetback and external air intake
(28 posts) (11 voices)-
Johnnojack
MemberI agree you need the external air intake. More important when the house is well sealed. Good luck finding a heater in Ozz with one. Couple of years ago I was at a home show, they had a big display of slow combustion heaters. When I asked about external air supply models the salesman had never heard of it, he then went on to say he had been in the heater business for 30 years. Some time ago there was an article in Renew mag where someone has fitted their own external air pipe and valve.
Posted Thursday 10 Nov 2016 @ 11:08:59 am from IP # -
Audrey
MemberWe are still having problems sourcing a suitable wood heater with small wet back and external air intake. What about the possibility of a wood-heater which has air vents under the ash tray at the bottom and then having an external air intake (that can be closed off) coming in under the concrete slab directly under this? Would this provide suitable air flow for the wood heater to draw properly and not create a vacuum in a well sealed house?
Posted Tuesday 10 Jan 2017 @ 12:03:17 pm from IP # -
Greg
MemberHave a chat to Pivot stoves, they seemed very knowledgeable with a reasonable range. The external air will be hard to find in Australia, may have to diy.
eg http://www.pivotstove.com.au/catalogue/wood/Wood-heaters-wet-backs/pyroclassic
Posted Wednesday 11 Jan 2017 @ 4:56:45 am from IP # -
Audrey
MemberWhat are the hoops one has to go through to diy external air intake and how would it affect insurance if there was a fire if it is a 'noncompliant' alteration?
Where would you get it done to get it passed by Australian Standards? Do boilermakers do this?Posted Wednesday 11 Jan 2017 @ 1:08:28 pm from IP # -
axess
MemberAudrey,
If you are designing a "well insulated double wrapped and well sealed off grid home" and still wish to incorporate a fire of some sort with a secondary requirement to heat water, then US or Canadian sites might be worth a look in.
I'm sure this would be a common request in their colder states or provinces and there is bound to be a U tube video of some kind.
Posted Wednesday 11 Jan 2017 @ 8:50:52 pm from IP # -
Johnnojack
MemberLook on the Mt Best site for an actual example
Posted Friday 13 Jan 2017 @ 10:38:35 pm from IP # -
tom rickard
MemberThe Mt. Best example is well done, and I read his paper on the benefits of an external air intake for his heater. Unfortunately it is a very flawed paper, while I agree that if you get an increase in air density you will get an increase in temperature under ideal burning conditions, most of the time you are not trying to burn a slow-combustion heater at ideal burning conditions. Hence the name "slow combustion".
It is unclear if the benefits listed in that paper are due to an inefficient initial design of the wood heater. I'd be interested to hear how much benefit is gained by simply having his extra air intake set-up open to the inside of the house.
If you have a sealed house, you will need a system to vent external air into the house in a controlled manner to have a suitable air quality. That is the system you need to be focusing on.
Posted Sunday 15 Jan 2017 @ 8:20:11 am from IP # -
Audrey
MemberThanks for the posts so far.
We are planning on having a Heat Recovery Ventilation unit which will bring fresh air into the house through vents in the ceilings and remove stale air.We have been told a wood heater will not draw properly unless it has an external air intake incorporated in it, or if it is vented underneath then a pipe can come up from the slab under the heater.
Getting a heater with an external air intake from overseas - there is apparently a lot of red tape and expense to get one certified for use in Australia. Metro from NZ used to sell them in Aus but now they aren't available.
I'm hoping someone out there can point us in the right direction as a wood heater is something we don't want to go without.
Posted Sunday 15 Jan 2017 @ 11:21:40 am from IP # -
Johnnojack
MemberGo to mtbest.net
Posted Sunday 15 Jan 2017 @ 12:30:37 pm from IP # -
tom rickard
MemberWho told you a wood heater will not draw properly without an external air intake?
Posted Wednesday 18 Jan 2017 @ 6:44:03 am from IP # -
Bushwalker
Membertom rickard said:
Who told you a wood heater will not draw properly without an external air intake?Anyone who is aware of a well sealed house would make the same statement.
The wood heater needs to draw air through the fire and out the chimney. If the house is well sealed, there is no effective draw.
Audrey is expecting to install an HRV which is a fair indication that the building will be well sealed...
Posted Wednesday 18 Jan 2017 @ 6:52:24 am from IP # -
tom rickard
MemberMy point is that a well designed HRV will draw in enough air to satisfy the requirements of a slow combustion heater.
Within the constraints of your desired humidity/temperature, the more outside air you can circulate within your house the better.
If you are skimping on air intake, having a fire that is hard to light is going to be the least of your problems.
Posted Thursday 19 Jan 2017 @ 7:26:02 am from IP # -
Audrey
MemberHi Tom
We are planning a wood heater with a glass front for the living room - more for the ambience - and not a slow combustion heater. We have been advised by several people we will need a separate air intake either in it or directly under/next to it in order for it to draw properly.
I have read MtBest website and it looks like we might be doing away with the wet back and consider having evacuated tubes to pre-heat water to an instantaneous gas heater with electronic control as suggested by Tom Chalko.
Keen to read the thoughts of others.......Posted Thursday 19 Jan 2017 @ 12:09:44 pm from IP # -
Bushwalker
MemberTom, a HRV will not draw extra air for a slow combustion heater. An HRV is balanced, it pulls air from outside and exchanges the heat from the outgoing air to the incoming air.
If we are talking about a well sealed house with an effective HRV, the air balance of the HRV is even. It intakes the same amount of air as is exhausted.
Having a combustion stove pulling air from within a well sealed HRV equipped home does have some issues. One is that it may not have enough draft to run the fire properly, where will it get the air from in a sealed house? Pull a vacuum in the house? If you have an exhaust system in the house (like a kitchen rangehood etc) then it may pull air down through the chimney and add smoke from the fire into the house. Not a good look. Some HRV's have a system that reduces incoming airflow when outside air is freezing but maintains outgoing air, therefore creating some internal vacuum. Also not a good look if a fire is running.
If you have a fireplace and a HRV, much better for the house to have the fireplace well sealed from the interior and pull air from outside.
Posted Thursday 19 Jan 2017 @ 1:03:01 pm from IP # -
tom rickard
MemberOK. Fair enough if you are building to Passivhaus spec.
In any case Audrey, you are on the right track by looking around at what others have actually implemented, and trying to find out what has been done that will work for you in the best way.
I would suggest that especially since you are planning on having off-grid power, look at the extra investment in your power system that will enable you to operate R/C airconditioning, and compare that to the extra investment in building spec that will allow you to not use any extra heating or cooling.
Posted Saturday 21 Jan 2017 @ 4:37:47 am from IP # -
Johnnojack
MemberAudrey, a glass fronted wood heater sounds a lot like a slow combustion heater? Or is this going to be built in? like an old fashioned open fire with glass door? I have been to many properties in the Adelaide hills which are off grid. Every single one uses a slow combustion heater for heating. Some heat water with them as well. When it is cold in winter it is also cloudy, so little sun = little power= no power for reverse cycle heating either. What then, run generator? Alternative, gas, big LPG tank, locked into high running costs and increasing prices. Your house should be quite efficient so won't need huge quantity of wood. If you are off grid you are more likely to be in an area where free wood is easy to find.
Posted Saturday 21 Jan 2017 @ 10:54:46 am from IP # -
Adamc73
MemberI have one of these fireplaces and most of the models have an external air duct. I believe they just opened a showroom in Adelaide http://www.eurofireplaces.com.au/
Posted Saturday 21 Jan 2017 @ 10:57:20 pm from IP # -
davross
MemberWe recently built a well sealed house offgrid with a HRV and slow combustion fireplace with wet back. I tried to find a heater with a wetback and external air supply but I couldn't find anything. In the end I went for a yunca monte with wet back. The additional air requirement was built into the HRV calculations and extra ducting was installed around the heater. The heater heats the house well and is easy to start I have had no issues. The only thing I would worry about is finding someone who can install the wet back properly. We had a plumber totally stuff up my installation. Once we had it fixed it usually takes a few hours to heat a 250L hotwater tank from approx 30 degrees to 50. I also have a sanden heat pump connected to the hotwater tank, but It rarely runs in winter because the wetback does all the work at night.
Posted Monday 23 Jan 2017 @ 12:45:37 am from IP # -
Audrey
MemberThanks for feedback so far.
Looks like we might be doing away with the wet back and consider having evacuated tubes to pre-heat water to an instantaneous gas heater with electronic control as suggested by Tom Chalko.Davross I am interested in knowing which HRV you went with , and how it is going, how often filters need to be changed, do you have a designated area for the 'workings' of it, do you turn it off when windows open?
Posted Monday 23 Jan 2017 @ 4:04:41 am from IP # -
davross
MemberWe went with a Stiebel Eltron LWZ170+. There are cheaper options around now, but i'm not sure how they perform in comparison. The system asks me to change the filters every 7/8 months. I live rural so If you lived in a city you would probably need to change them more often. I usually clean the filter and reuse them because most of the debris in the filter are small bugs the system sucks in from the outside. The most basic filter (there are a few options) is $100 for 10, they are much cheaper from germany via ebay.
I leave the system on even with the windows open. The system will know when it needs to run based on the air quality sensor. In winter I don't open the windows at all so the hot air doesn't escape.
The system itself sits in a utility room with the hot water tank inside the house. It mounts on the wall. You wouldn't want it in plain view because of the ducting, make sure you have a utility room with adequate space.
Another option for heating your water with a wood fire is a water jacket that fits on the flue http://www.axeman-fireflue.com . This way you could get any wood fire that has an external air intake and fit one of these to it. Also if you are offgrid make sure you get a wood fire with thick steel plate on the top so you can do some basic cooking if you run out of power. I use an induction cook top, and a small steam oven normally so its good to have a backup just in case, although we have never had to use the generator or even come close to it.
Posted Monday 23 Jan 2017 @ 5:58:01 am from IP # -
tom rickard
MemberThanks for sharing your information davross. It is good to hear from other people that have successfully built an off-grid dwelling.
It's a shame there is so much misleading information given by people with vested interests.
The other advantage of designing your HRV to accommodate combustion devices is that it allows you to use a regular gas cooker. (Something my wife insisted on)
Posted Wednesday 25 Jan 2017 @ 3:56:36 am from IP # -
Audrey
MemberThanks Davros
How much space does an HRV need in a utility room? We have a room put aside for the hot water cylinder and the workings/ ducting of the HRV currently on the plan at 2300 x 1200. Sound big enough?We are looking at the 'Lopi Rockport hybrid fyre' which has an external air intake and cook top. Interested in knowing if anyone else has feedback on this heater.
Posted Wednesday 25 Jan 2017 @ 11:40:02 am from IP # -
davross
MemberThe LWZ 170 dimensions are: Height 602 Width 675 Depth 525 and weighs 35kg. You could probably mount it off the ground on the wall close to the ceiling if needed. There is a lot of ducting in the roof space so you might want to make sure you have enough room here also. Check all this with the installer because you might require a more or less powerful unit depending on the size of house, house configuration, occupants etc. My house is 150m2 as an example.
When you are selecting a heater, make sure that you are not selecting one that produces too much heat for the house. My house is only single wrapped/taped and if I had a heater any bigger than the yunca monte I would be too hot. On a sunny day in winter the internal temperature of the house can be 19/20 degrees and most of this heat is maintained during the night. We live an hour away from Canberra so the winters here are really cold, but as long as there are a few hours of sunshine the house will be 15 degrees or more when the outside might be close to 0. If you are getting someone with experience installing the air tight wrap you will probably achieve even higher temperatures. I didn't have the budget to go with a builder which had experience with these things but the builder was willing to work with me and I am really happy with the result.
Posted Thursday 26 Jan 2017 @ 12:20:46 am from IP # -
Davebintas
MemberTry the Flue Company in Kingston. I bought a heater from them that has an external air intake. The heaters are made in Europe and have a good efficiency rating. I bought a smaller model and when I've had it burning, it'll pump out so much heat, I have to sleep with the windows open. I live south of Hobart up in the hills, so it gets pretty cold in winter. Some of the more expensive models (none are particularly cheap) have features that enable hot water and hydronic heating to be incorporated. The model I bought is the Euro Fireplaces Falun. While the firebox only accepts a small amount of firewood and uses very short log sizes, the fire burns overnight easily. Pivot fires sells them in Victoria.
Posted Thursday 2 Feb 2017 @ 9:50:00 am from IP #
