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Re: Off peak slab heating v oil heater

PostPosted: Thu May 26, 2016 8:58 am
by australsolarier
a long time ago i met a canadian. he said: keeping warm is easy. when you feel cold just put another layer of clothes on. in our case another layer of blanket. (you will be amazed how many people do not know about this)
i used to sleep regularly in -25c temperatures (inside the room). it is very cold at first then after while you are cosy warm. no electric blanket needed. maybe a water bottle.
the people there had a baby and it probably went to 0 degrees in their bed room. last i heard he was still alive and going strong. must be somewhere around 40 now.
logic says, it does not really matter how cold it is, as long the baby is cosy warm.
just imagine the eskimos trying to heat up their igloos to 18 degrees.

concerning the wood heater, it being 26 degrees, it depends where you measure the temperature. i measure the hot plate at 400 degrees, but the furthest room being heated then is 20 degrees. the wood heater also creates drafts which means added cooling effect. so 26 degrees next to the wood stove is probably alright. basically you want to feel warm no matter what the thermometer reads. some people think 16 degrees is hot and some think 22 degrees is cold.

Re: Off peak slab heating v oil heater

PostPosted: Sat May 28, 2016 9:36 am
by bpratt
davidg wrote:
jimbo wrote:The wood heater is at one end of the house and our bedroom where the baby will be sleeping is at the other. Right now its 24 in the living room and 18 in the bedroom but over night when we choke the heater down it will drop a few degrees. We would like to maintain a room temp of around 18-19 degrees.

Too warm, believe it or not general temp for night sleeping is far better at 13-15 max people including babies get better sleep.

Just thinking about it, and what you say makes great sense.

I agree with a bedroom/house is around 13-15 degrees, I do get a good nights sleep. If the room is any warmer, i.e. 18+ degrees I tend to get a bit restless, as I'm getting too hot in bed, and of course when the room goes below 10 degrees you become restless by semi-awaking when you move to colder parts of sheets.

Of course, I've never had the experience of a baby in the house, so things might be a bit different there, but I can't easily see why.

Re: Off peak slab heating v oil heater

PostPosted: Sat May 28, 2016 9:41 am
by jimbo
Sorry guys but I never asked what temp to have the room. Just in case i hate the room under 16 degrees myself and get a bad sleep.

Re: Off peak slab heating v oil heater

PostPosted: Sat May 28, 2016 2:52 pm
by Smurf1976
Power for the slab heating costs about half what power for the plug-in electric heater will cost (off-peak versus peak).

Downside of the slab heating is that you'll be heating the room constantly, it will be warm day and night (that's how it works - the slab stores heat when the power is on and releases it constantly).

If you want to keep the room warm constantly then the slab heating will definitely cost less than using a plug-in electric heater. But if you only want to heat it for a few hours each day, well the plug-in heater has the advantage of easily being turned off.

I'd use the slab heating. Won't cost that much if it's only heating one bedroom and it's an inherently safe system with nothing to go wrong that poses any danger (versus the never zero risk associated with any portable device that gets hot and has a cord attached). Also causes no draughts, makes no noise and so on and the thermostat should be far more accurate than with a portable heater.

Just make sure the slab heating is actually connected to off-peak power and isn't running during peak times (check!). It'll send you broke if it's running on peak rate power.

Times have changed though. I remember we had ice form on the inside of the windows when I was young kid. No heating overnight, oil heater (that's an oil burning heater, not an electrically powered heater filled with oil) lit in the morning and slowly warmed the house up. Not many oil burners around these days and now we're talking about keeping kids warm overnight. Probably a good thing - do whatever the experts recommend with that one.

Re: Off peak slab heating v oil heater

PostPosted: Sun May 29, 2016 9:33 am
by Gordon-Loomberah
Smurf1976 wrote: I remember we had ice form on the inside of the windows when I was young kid. No heating overnight, oil heater ...

That was a regular occurence for me when I was young too, back when oil heaters were common. Ice inside the windows behind the curtains was very frequent in winter - often lovely ice ferns, and we even found thin ice on the top of a glass of water on the kitchen sink one particularly cold morning. I was nice and warm under the doona though, but we did use electric blankets in really cold weather.

Regarding the cost of space heating- if you use a modern efficient reverse cycle air conditioner with COP >5, you effectively cut the cost of heating to 1/5, so it will be significantly less expensive running that on regular tariff than electric slab heating with off-peak.

Re: Off peak slab heating v oil heater

PostPosted: Wed Jun 01, 2016 5:14 am
by Privatteer
I've been using a oil heater to keep a small room at about 20deg. I have not been tracking it too closely but its been probably averaging about 4KWh a day. Outside temp getting down to 0deg at nights.

That said the window has an insulated roller shutter, double heavy material curtains and roof is insulated.

Re: Off peak slab heating v oil heater

PostPosted: Wed Jun 01, 2016 8:17 am
by australsolarier
just to do a bit boasting of sleeping in chilly rooms, i remember the snooze at the tip of the nose being frozen in the morning when sleeping at my grandmother's place.

i have three heating systems in my house:
air conditioner
wood cooking stove
radiators (heated by 100 heat pipes and storage of 3000l of water)

the most pleasant heat seems to come from the radiators, although floor heating would be better and more energy efficient, as lower temperature could be used.

the next pleasant is the aircon.

last is the wood cooking stove. it also heats the hot water. it creates draft, the temp in the kitchen is 30 degrees to be comfortable in the lounge. it is also messy. but an excellent back up when that sun disappears for a couple of days.
however if you go for the very expensive agar or the like with central heating jackets the spreading out of heat could be overcome. tied in with a solar space heating system and storage, it would be the ideal situation. however those wood cooking stoves are very expensive, though they probably last a life time.

Re: Off peak slab heating v oil heater

PostPosted: Wed Jun 01, 2016 8:46 am
by jimbo
I have had the slab heating on for a few days (been -2 over night lately) so last night i switched off the hot water and read the off peak meter. It's showing that we only use 3.6kWh over night which is not bad at all. The room sits at around 17 degrees.

BTW there are 2 circuits with readings on the meter, would the hot water be on the other one or is that if i force it to run during peak times? It didn't change last night.

Re: Off peak slab heating v oil heater

PostPosted: Sun Jun 19, 2016 10:41 am
by jimbo
A bit of an update for those interested.

I finally figured out which circuit everything is on (slab heating has its own meter).

With a little oil heater on from around 8pm to 8am our peak electricity usage went up around 4-5kw and the room felt nice and warm. We could probably drop it a degree and use less. On the other hand the slab heating uses between 16-20kw (yes only 1 room) between 11pm-8am set at cooler 19 degrees. Yes the room stays warmer for a while after but by the afternoon it has already cooled down to 17 or so.

I think the slab heating will be turned off and just use the small oil heater when needed.

I have also been surprised at the electric hot water, seems to use 2.5kw per shower person. So when i'm home its 4-5kw but when just the girlfriend around 2.5kw (this is with no solar input). With off peak rates it works out very cheap and for 6 months of the year the 3 panels seem run the system fine. I can see why people chose the simplicity of solar with electric backup over a more expensive gas unit (we don't have lpg here)