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Master Geek
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  Reply # 364235 6-Aug-2010 13:43
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Yeah, I have had a Brivis central heating system in place for years now... works a charm, no issues, and very reasonable costs even churning away most of the day most days... (young family)

would happily recommend

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  Reply # 364243 6-Aug-2010 14:03
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One quick note is that a modern flued gas unit uses a heat exchanger principle, so no combustion exhaust gases actually touch the air flowing into the house. Removes any negative reference to the moisture problems associated with Gas in the past.



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  Reply # 364251 6-Aug-2010 14:24
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Awesome, thanks for your feedack guys.  The Brivis unit's have been reliable for you then?

bluedisk:  As we work from home the heating is on 24/7. It used to cost an arm and a leg to run until we took out the chimney, sealing the house better, insulated with pure wool ceiling insulation and installed draught stoppers around the ext. doors.

Since we did this 6 months ago our house is a lot warmer and our heating bill has dropped by a third


I've already gone through this insulation exercise.  The house has been fully renovated and the walls stuffed with batts and relined.  The ceiling and underfloor are well insulated too and i have a few draught stoppers sealing off the worst of the leaks.  This alone took one room from average unheated temperature of 8deg up to 16deg+. This room (20m2, 60m3) now only requires a tiny 5 fin electric oil filled heater on level 1 or 2 to keep a constant 19 or 20 deg overnight instead of level 3 or 4.  At the price of electricity, thats already a big saving.  Oil fin heaters dont really do a good job of heating the entire house though.

I didnt mention this earlier, but my celings are all 3m stud and i'm told that heat pumps dont handle that nearly as well as the 2.1m or 2.4m heights.  I was looking at a much more expensive central heatpump system to fit.




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Master Geek
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  Reply # 364259 6-Aug-2010 14:32
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I didnt mention this earlier, but my celings are all 3m stud and i'm told that heat pumps dont handle that nearly as well as the 2.1m or 2.4m heights.  I was looking at a much more expensive central heatpump system to fit.


Yes I was told the same thing. BTW is has been a very reliable system, even though its 13 years old its still going strong. Its had a service every two years with nothing much needed to be done, and the installer thought it would have a reasonable life left in it. 

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Master Geek
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  Reply # 366347 11-Aug-2010 17:17
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I have ducted gas central heating which I had installed when the house was new in the 1990s.  If I was doing it all over again I would not bother with gas.  I would install heat pumps instead.  Basically the reason is because heat pumps are cheaper to run for the same heat output.  Also the the grossly excessive daily fixed charge for gas that can run out at over $1.50, including GST is a big turn off.  I am paying nearly an extra $50 per month for what?  Actually nothing.  It costs me this amount even if I use no gas at all.  I can buy a lot of heat from a heat pump for this amount.



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  Reply # 366368 11-Aug-2010 18:20
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login: I have ducted gas central heating which I had installed when the house was new in the 1990s.  If I was doing it all over again I would not bother with gas.  I would install heat pumps instead.  Basically the reason is because heat pumps are cheaper to run for the same heat output.  Also the the grossly excessive daily fixed charge for gas that can run out at over $1.50, including GST is a big turn off.  I am paying nearly an extra $50 per month for what?  Actually nothing.  It costs me this amount even if I use no gas at all.  I can buy a lot of heat from a heat pump for this amount.


if you compare a 1990's gas central furnace efficiency with a 2010's heat pump efficiency, of course you are going to get a big difference. 

if you have a well insulated house, and a modern 90% or 98% efiiciency gas furnace then the numbers are going to be much closer.  take a look at the following link i found:

http://www.warmzone.co.nz/running-costs/4533589501

and note the following comment:

* Interestingly, this 4 bedroom home with a family of  5 compared their energy bill with an all electric household (3 x heat pumps) of the same size house and family.
The outcome was the all electric household paid on average $100 more per month on their energy bill.


I'm taking nightly gas and electricity readings for *before* i get something installed, and then i'll do the same after and report back on the usage - along with what i end up installing.




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Reply # 366371 11-Aug-2010 18:23
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login: I have ducted gas central heating which I had installed when the house was new in the 1990s.  If I was doing it all over again I would not bother with gas.  I would install heat pumps instead.  Basically the reason is because heat pumps are cheaper to run for the same heat output.  Also the the grossly excessive daily fixed charge for gas that can run out at over $1.50, including GST is a big turn off.  I am paying nearly an extra $50 per month for what?  Actually nothing.  It costs me this amount even if I use no gas at all.  I can buy a lot of heat from a heat pump for this amount.

Wow $1.50, my daily gas charge with Nova is $0.45.




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  Reply # 366376 11-Aug-2010 18:29
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gas heating is oone of the cheapest options at 6c per kWh - assuming you have reticulated gas.


I think that's a big assumption isn't it?  Just how many households in the country would have access to reticulated gas, not many I think.
 




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  Reply # 366546 11-Aug-2010 22:55
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login: Also the the grossly excessive daily fixed charge for gas that can run out at over $1.50, including GST is a big turn off.


i'm paying 88 cents per day with genesis for the fixed daily charge, and then get 45 cents off that as some discount they are running for another 12 months, so the net daily charge i pay for gas is only 43 cents.  compare that to the fixed daily charge for electricty of 98 cents per day for electricity.

i.e. gas daily charge is actually cheaper than electricity daily charge - even before discount - not sure how it could be called excessive.

on top of that, gas costs me only 6.41 cents per kWh, whereas electricity costs me 21.29 cents per kWh. 

i'm not sure what the output heat is per input kWh for 90%+ efficient gas furnace versus an electric heatpump, but it cant be that much better for the heatpump when you are paying 3-4 times the price for each kWh power supplied..




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  Reply # 366551 11-Aug-2010 23:00
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sleemanj:
 
gas heating is oone of the cheapest options at 6c per kWh - assuming you have reticulated gas.


I think that's a big assumption isn't it?  Just how many households in the country would have access to reticulated gas, not many I think.
 


i wasnt implying gas was the cheapest option for everyone, just suggesting that gas could be one of the cheapest options *assuming* that you have access to reticulated gas.  i think you misread the sentence.




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  Reply # 366646 12-Aug-2010 09:41
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Regs: on top of that, gas costs me only 6.41 cents per kWh, whereas electricity costs me 21.29 cents per kWh. 

i'm not sure what the output heat is per input kWh for 90%+ efficient gas furnace versus an electric heatpump, but it cant be that much better for the heatpump when you are paying 3-4 times the price for each kWh power supplied..


This hits it right on the head.

300% efficient heat pump at $21.29c per unit, works out at 7.10c per 100% efficiency (rough way of working this out, but need to compare somehow)

85% efficient gas heater, at $6.41c per unit works out at 7.37c per 100% efficiency, so basically exactly the same.

The efficiency of the heat pump drops off significantly the larger the difference in temperature between inside and out.  So when it's cold outside and you're wanting to keep it warm inside then the cost to run it rises.  At say 200% efficiency, you could easily be looking at 10.6c per 100% efficiency.

I'm not seriously in one camp or another, but I just don't think it's entirely right the way the heat pumps have been pushed as the only energy efficient heating option.  Naturally you do have to pay a gas line charge of some sort as well, so that really is worth considering if you are looking for gas for heating only.  If it does hot water, heating and cooking then that's a different story. 

I probably wouldn't look at gas if I was building from new for instance.  But just my thoughts anyway though.  The above figures are probably a stupid way to try and compare each, and if need be could be rejigged to be more 'proper' but it should convey was Regs is saying in that a heat pump is real efficient but it's energy cost is higher per unit, and gas is not that efficient, but the per unit costs are really cheap, so they work out about the same, until the heat pump efficiency drops when it gets colder.

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  Reply # 366656 12-Aug-2010 09:50
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"until the heat pump efficiency drops when it gets colder."

That one sentence sums up the problem with "heat' pumps, they don't work as well when it gets cold which is when you want them to.


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  Reply # 366666 12-Aug-2010 10:10
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langers1972: "until the heat pump efficiency drops when it gets colder."

That one sentence sums up the problem with "heat' pumps, they don't work as well when it gets cold which is when you want them to.



That's true of air source heat pumps, but ground source heat pumps are a different matter entirely (because the ground temperature is pretty stable once you get a meter or so down).




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  Reply # 366672 12-Aug-2010 10:34
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sleemanj:
langers1972: "until the heat pump efficiency drops when it gets colder."

That one sentence sums up the problem with "heat' pumps, they don't work as well when it gets cold which is when you want them to.



That's true of air source heat pumps, but ground source heat pumps are a different matter entirely (because the ground temperature is pretty stable once you get a meter or so down).


Yes, but the cost of installation is higher and messier,  and  not really something that can be easily done on existing section.

On a new build on vacant land sure, but the original OP was talking about putting gas central heating into an existing house, on a presumably established section.

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  Reply # 366676 12-Aug-2010 10:45
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I had a friend install a pellet burner for his house in dunedin.

It is digitally controlled and maintains the house at a very comfortable 20~22C during the day and can be dropped to 18~19C overnight.

He retrofitted it to the radiators that were already there but I'm sure you could get something similar. The pellets were very inexpensive for the amount of heating but I cannot recall figures. Something like $150 ~180 for the whole of winter IIRC.

Good luck.

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