Hello all.

I have done numerous reading on this forum, and thanks to all who have posted various things over the years, a good read.

Our house currently has a small masport fire place, still a current model, in our lounge. Lounge gets toasty warm, rest of the house is cold. No surprises there.
The house is double glazed, and insulated well, but without a good heat source, its cold.

We moved in at the end of 2013, so this is our first winter, and we wanted to go through this winter to find out what its like before we made any changes.

I am a keen DIY'er and capable of have a good crack at most things, or getting most things done, as is my old man.
We were thinking if we installed a wetback in the fireplace (as its an option), we could use that is a closed loop system and install some radiators around the house, to take advantage of the fire, so not just the lounge is heated, everywhere gets a taste.
Being a small fire place, it will no doubt dampen the efficiency of the fire, however some heat around the house will be better than no heat.

The kids rooms have small electric radiator heaters and while they do the job well, I am guessing they are not that good on the power bill.
I work from home and my office is freezing. I sit at the computer with fingerless gloves, a beany, hoody etc, just so I dont have to use an electric heater all day long. Our power bill is high enough as it is.

So what I would like to discuss is this Wetback option, and radiators around the house.
I plan on installing a hot water pump in the line, pumping the water around. Have an expansion chamber and blowoff valve for safety, have drain to drain the system, and a thermostat to measure the water temperature and turn on the pump when the temperature is say more than 30 degrees at the fire place. Also potentially have an external radiator in case the temp gets too hot (but I doubt that would happen).

The option is that we upgrade the size of the fire too. We like the fire, don't have a free source of wood however have a good source of reasonably priced wood. Much cheaper than electricity imo, but that is for discussion elsewhere.

That is the first idea.

The 2nd was to have in parallel with that, with some smart solenoid valve, a bottled gas boiler (as we have no mains gas here), so we can run the radiators without the fire on.
The question is, how do you size the boiler. Simply looking at trademe and looking at options, I see ones from 5L all the way up to like 30L, which I assume is 5L/min increasing the temp from ambient to +25deg of ambient.
Can all of these instant hot water boilers accept a warm water input, to heat up the closed loop system? I dont see why they couldnt to be honest, but Im not expert on these. Not sure what the average units max water temp is, given a warm water input feed.

My parents have a pro installed mains gas instant radiator system in their house, no tank, just purely closed loop with instant heater, and it is amazing. The heating bill is very low, and the house is always the perfect temperature. They however paid about 10K to get that installed.
Talking to Dad, we should be able to do it for a fraction of that, doing it ourselves. 
Their boiler is 28Kw, 12L, and my dad believes the water sits about 85 degrees. They have about 7 radiators in their house. We are looking at a similar number.

Just wanting some input as to what people think.

I have no interest in discussing heat pumps, heat transfer systems or other forms of heating. I lived in Invercargill for 7 years, so I know what cold is. We have been through our share of good and bad heat pumps, fires, heat transfer systems etc, as we had 4 different houses down there during the period.

I just want to discuss wetbacks as the heat source for radiator heating, and also instant hot water boilers as the source of radiator heating.

My job is electronics design, so I have no drama with making a little controller to manage the systems, even having touch screen control etc - all a walk in the park. The heating itself however, I could use some help with making the right choice.

Very interested to hear what people think, or if they have experience with either.

Thanks in advance

WanaGo