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837 posts

Ultimate Geek
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  # 1750469 30-Mar-2017 07:55
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kindagot:

 

We went with a Rinnai flued gas heater a few years ago and it was the best decision. I did loads of research and it it 5kw and heats the whole house (108m2) albeit in Auckland. It brings fresh air in and we have had zero mould in the house since installation. It is really cheap to run and the heat just finds its way everywhere. I would definitely recommend it, friends that have heat pumps just don't seem to get very much out of their 5kw, they find it hard to keep the heat moving. The Americans seem to love them and the video for their market explains the heat transfer https://www.youtube.com/watch?v=fmNTpijYQ84

 

 

 

 

Heat pumps just don't give the same heat experience as fire, not possible.


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  # 1750513 30-Mar-2017 09:13
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We also have a 100 year old Wellington house - however not on a hill. Due to the original layout of the house (read lots of rooms) and the fact we are not looking to change this anytime soon we have installed gas central heating which has been working great. We looked into heat pumps, ducted heat pumps, multiple heat pumps on one outdoor unit and found that installed gas central heating was the cheapest and most effective way to heat multiple rooms in a smallish house.

As we are already using gas for cooking and hot water - the install was roughly $8K for 14 vents (one in each room on the floor - two in the lounge and extra large vent in main bedroom) the gas burner (braemar) sits outside of the house (like a heat pump unit) the vents are ducted to this unit and blow hot air with a return air grill located in our hallway sucking the air back to get re-heated.

 

I believe it was so cheap to install due to the ground clearance under the house (being an old house on piles). I am not sure if this would work for multi story but worth a look? 


 
 
 
 


neb

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  # 1751398 31-Mar-2017 23:37
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Hmm, heating the basement of a wooden house... is it OK if it's a one-off heating event, or do you need the house around for more use later?

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  # 1753355 2-Apr-2017 19:31
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timmmay:

 

Gas burning produces carbon dioxide and water. Flued I guess takes some of that away, but it doesn't seem like a good thing to burn inside your house. Burn it outside and bring the heat in.

 

 

 

 

A flued gas heater takes all of the moisture and CO2 from burning the gas outside. If some is getting inside it means there is a fault in the flue system. Alot of the newer Rinnai gas heaters use fan assisted balanced flue system. meaning the air that is needed for the gas burners comes from outside, and the flue gasses also go outside. Rinnai use a pipe inside a pipe system. The inner pipe carries the flue gases, and the gap between the inner and outer pipes carries the air to the burners. This gives better efficiency as some of the waste heat then pre heats the incoming air.

 

 

 

Because the heat exchangers in gas appliances run at higher temperatures. Holding your hand in front of the room air outlets on a Rinnai gas heater when it is running on full output is like a fan heater or hairdryer. Compared to a heatpump which moves lots of air, but that air is not very hot.






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  # 1753381 2-Apr-2017 21:03
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Aredwood:

timmmay:


Gas burning produces carbon dioxide and water. Flued I guess takes some of that away, but it doesn't seem like a good thing to burn inside your house. Burn it outside and bring the heat in.



 


A flued gas heater takes all of the moisture and CO2 from burning the gas outside. If some is getting inside it means there is a fault in the flue system. Alot of the newer Rinnai gas heaters use fan assisted balanced flue system. meaning the air that is needed for the gas burners comes from outside, and the flue gasses also go outside. Rinnai use a pipe inside a pipe system. The inner pipe carries the flue gases, and the gap between the inner and outer pipes carries the air to the burners. This gives better efficiency as some of the waste heat then pre heats the incoming air.


 


Because the heat exchangers in gas appliances run at higher temperatures. Holding your hand in front of the room air outlets on a Rinnai gas heater when it is running on full output is like a fan heater or hairdryer. Compared to a heatpump which moves lots of air, but that air is not very hot.



What temperature does a gas heater output? A heat pump will supply air at 40+ degrees. The important thing is that they are sized and zoned correctly for the house.

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  # 1753409 2-Apr-2017 22:36
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eddieddieddie,

 

It is easier to heat from the bottom of the house than from the top of the house because less dense air, such as heated air, rises. You can overcome this natural convection with fans blowing air from the second level to the first level. But you should also try to make an artificial convection current with flows in the other direction such as a ducted fan drawing the coldest air from the downstairs to upstairs.

 

See this example of moving hot air downwards http://www.treehugger.com/gadgets/totally-tubular-innovative-fans-redistribute-hot-ceiling-air-floor-warmer-rooms-lower-heating-costs.html in the same room . If the tube went down another floor then there should be another duct to prevent pressurisation. It doesn't sound like the downstairs is open plan so any air you blow down there will pressurise the rooms and force air out of any gaps in the external walls, effectively wasting that heat. That's also why people are saying insulate, insulate, insulate - it normally has the best return of any heating investment.

 

I've seen houses with open wells or atriums. Hot air upstairs hits a colder wall surface at the outside of the atrium causing the air to fall thereby creating natural convection currents where hot air is actually going down and mixing with the air below. A little help from a ceiling fan can get that air down close to the downstairs floor.

 

In old buildings there can be air flows between the downstairs ceiling and the upstairs floor which can strip heat out of the building. So it is worth insulating there to impede such air flows. I lived in a an old brick mansion in Dunedin where there was half a meter of space between the floors and the air flow whistled through taking a lot heat out the side vents. A good convection current or flow can move a lot of heat.

 

I'd probably prefer flued gas heating central heating at the bottom of a house if I'm already using gas. My only concern with gas central heating is that a failure at the heating unit must not result in carbon monoxide (which is less dense than air - about 97% from memory - and it would be hot so even less dense) rising into the living areas. If it can then I'd probably install a CO detecter to warn me. You can put central heaters outside but that will increase heat losses and maintenance costs due to being exposed to the elements.

 

Heating from the bottom of the house would work well for heat pumps except that heat pumps prefer to be in the warmest spot outside to ensure you get the best efficiency. You've already said the downstairs rooms are shaded and cold so a heat pump would suffer from some disadvantage as heat pump efficiency reduces at the temperature difference increases between the outside temperature and the desired indoor temperature.

 

If the downstairs rooms are also damp and there is no ventilation then I'd look at running a dehumidifier to remove water from the air and provide a little heating.


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  # 1753412 2-Apr-2017 22:45
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We used these panel heaters in our wooden wellington bedrooms. Cheap to purchase, easy to install, very cost effective to run. They lift the ambient temperature by a few degrees and help keep damp bedrooms dry. We left ours on 24/7 over the coldest months of winter. Can't recommend them highly enough.

 

 

 


 
 
 
 


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  # 1753413 2-Apr-2017 22:46
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Kickinbac:

What temperature does a gas heater output? A heat pump will supply air at 40+ degrees. The important thing is that they are sized and zoned correctly for the house.

 

The output temperature depends upon a lot of factors like the air speed. Our heat pump has never provided air as hot as our flued gas heaters did. They'd have a temperature rise of 40C-50C in the room which meant we often get air hotter than 50C. They often have humidifier tanks whereas I haven't seen a heat pump with on. Also the manuals tell you not to lie down/sleep in front of them.

 

Standalone units aren't allowed to be built in so there may well be issues with dangerous heat levels if they are. The surfaces could get too hot for young children and the manuals warn to keep children away.


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  # 1756074 4-Apr-2017 02:23
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Kickinbac:

 


What temperature does a gas heater output? A heat pump will supply air at 40+ degrees. The important thing is that they are sized and zoned correctly for the house.

 

Often around 70deg. Gas heaters are rated at their max output. Often the manufacturer will quote a temp rise over the ambient temp, for air at appliance inlet Vs outlet temp. Also it is perfectly fine with gas appliances to only turn them on when you need them. As their efficiency doesn't reduce just because of cold starts. The higher air outlet temps are good for people who like to sit in front of a heater. Elderly people especially seem to like that feature.

 

As for safety - a modern balanced flued gas heater will have to have multiple serious failures to put carbon monoxide into a room. First the burner or it's controls would have to have a failure serious enough to cause incomplete combustion. Then the heat exchanger would have to crack or rust out. yet lots of flued gas heaters put the combustion fan in the flue gas outlet stream. So the fan is sucking the gasses through the heat exchanger. And the room air fan pushes air through the heat exchanger. So often even a leaking heat exchanger still won't allow flue gases into a room. Kids and building the heater in  - Virtually no floor level heater can be 100% kid safe. And of course a heater won't work properly or be unsafe if you build it in or enclose it. Except as the manufacturer allows you to.

 

I personally think those econopanel heaters are pointless and just cleaver marketing. As you can get a dehumidifier, which will use similar or a bit less power. And all of it's waste energy is heat. For every litre of water it removes from the air - you get 0.6kw/hr of free heat. (Google latent heat of water if you want to know how / why) The drier air in the room has less thermal mass - so easier to heat. Plus all the other benefits of a dryer room.

 

If you still want to use electric heating. It makes much more sense to use a 1.2kW or 1.8kW electric resistance heater for 8 hours per day. Than a 400W or 600W econopanel heater for 24 hours a day. Same total electricity usage. And if you set the thermostat on the 1.2 or 1.8kw heater to a sensible setting. the room might actually reach the thermostat setting. So the heater will cycle on / off instead on being on all the time. Even lower power usage compared to the econopanel heaters.






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  # 1756083 4-Apr-2017 07:01
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My heat pump is 55 degrees at the unit, but that cools down rapidly as it's blown around the room.


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