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77 posts

Master Geek
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Topic # 150383 20-Jul-2014 22:23
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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

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1748 posts

Uber Geek
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  Reply # 1092761 21-Jul-2014 00:17
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Met someone recently with gas heated radiators in Dunedin.
The house is fairly large, and probably not double glazed. But their gas bill can be $600/month for heating alone.

I'm curious about radiators on a wetback too. We sometimes boil our cylinder, seems like a waste of energy to have it blow all over the roof.

For getting the heat around the house at the moment, I just use a fan on the floor in the hall to blow cold air back to the lounge. It does a very good job.




Location: Dunedin

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  Reply # 1092774 21-Jul-2014 06:11
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GDay Wanago, looks like an interesting project. It may not worry you but have you checked with the local council re adding a wetback to your fire since they changed the rules a few years back.

For a pump, I have used a solar hot water pump that has run happily at around 90 deg sometimes in summer for 8 years so far, so that should work fine in your wetback system. Also while I realise you can design a controller, there are a few cheap solar controllers out there that should do the work of controlling the pump based on temp differential.

FYI I see there are a pile of radiators available on TradeMe currently.

Looking forward to following the thread.



 
 
 
 


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  Reply # 1092779 21-Jul-2014 06:53
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The downside to this is you have to keep a fire lit all the time. I had a fire when I bought my place, it was damned annoying to keep going, wood stacked, clean up, it only heated one room like yours, etc, so I removed it. Just removing it made the house a lot warmer, as cold air was getting in around the chimney. I put two heat pumps in and the house is MUCH warmer. If I was doing it again I'd get a combined central heat pump and ventilation system, one that you can shut of rooms when you don't need it.

Another idea for you is a simple heat transfer system. Of course for those you have to cut holes in the ceiling, which lets heat out. I think heating should be done through the floor where possible and practical.




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  Reply # 1092780 21-Jul-2014 06:55
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WanaGo: 

I have no interest in discussing heat pumps, heat transfer systems or other forms of heating. 

WanaGo


Cough.

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  Reply # 1092781 21-Jul-2014 07:03
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Check building regulations etc, I have feeling what you are wanting to do is not a DIY job and there are considerable risks with wet backs if done wrong. They can create a great deal of system pressure that has to be dealt with correctly. You insurance will be in jeopardy if things go wrong.




Mike
Retired IT Manager. 
The views stated in my posts are my personal views and not that of any other organisation.

 

 It's our only home, lets clean it up then...

 

Take My Advice, Pull Down Your Pants And Slide On The Ice!

 

 


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  Reply # 1092793 21-Jul-2014 07:44
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kiwitrc:
WanaGo: 

I have no interest in discussing heat pumps, heat transfer systems or other forms of heating. 

WanaGo


Cough.


Didn't see that bit. Seems a bit ostrich like.




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Master Geek
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  Reply # 1092819 21-Jul-2014 09:36
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Thanks for the replies

timmmay: 

Didn't see that bit. Seems a bit ostrich like.


Why do you say that. I have already stated why. I have had heatpumps. Daiken, Mitsubishi and Hitachi. Some worked fine to an extent, we don't want that sort of heat in our house this time. We found heatpumps draughty, as while they push out warm air, they also push around the cold air before it warms up. Also if you are sitting somewhere that may be in line of the heat pump, you are in a draft. Really not wanting to go there for this house, so no point discussing it further thanks. We got in 2 Heatpump companies to quote, we would need 3 large 8Kw units to heat our house. Not an option.

Our fireplace is not draughty at all when not in use, its not an open fire. And yes, you need to keep the fire lit, but we would be anyway, so its a non issue. I work from home, my wife is at home with the kids.... no issue.
It is not the lounge we are concerned about anyway, its the rest of the house getting warmth there.
And with a radiator system, you can also shut off rooms you are not using... don't need a fancy heatpump system to do that.

We dont have $8-$10K to play with.


@kiwitrc - Regarding wetbacks - yes I have seen the regulations, and I don't think this will be an issue where we are, however that said, our fire place has an option to change the way it breaths when you add a wetback, to increase the efficiency a little bit. Thanks for the concern though, but I think we are OK there. I will definitely check more on this though.

@kiwitrc - Regarding solar - not 100% how this system works. If its 2 degrees outside, not sure what solar is going to do for us. 90 degrees in summer? Why do you want heating on in summer? Or do you have yours running your hot water system, rather than a radiator system...? I'm a little confused.

@kiwiNZ - regarding DIY - obviously we would get this all checked out by a professional plumber etc before firing it up. But yes, a good point to take note of. Having an expansion chamber and pressure relief in a system where you cannot accurately control the temperature (being a wetback), you do need to be careful. However there are a number of ways to protect yourself and your house.


Thanks for the replies. Doesnt seem like anyone has really done this wetback radiator system so far, maybe its old hat and people move on to Heatpumps and the like.

Ill continue to do more reading.





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  Reply # 1092821 21-Jul-2014 09:40
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WanaGo: .

@kiwitrc - Regarding solar - not 100% how this system works. If its 2 degrees outside, not sure what solar is going to do for us. 90 degrees in summer? Why do you want heating on in summer? Or do you have yours running your hot water system, rather than a radiator system...? I'm a little confused.




Sorry for the confusion, I was recommending a pump type that would be a good option to move the hot water around reliably, in my case it just happens to be on a solar system.



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Master Geek
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  Reply # 1092824 21-Jul-2014 09:43
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Ah right, yep fair point.

I have found a pump which can pump 95 degree water, 3 speed, max 10 bar, max 27L/min. Put that on the return and we should be good to go as that is the colder side of the system. Normally run around 85 degrees or so anyway, so it could go on the hot but probably last a bit longer on the cold side.

Thanks


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  Reply # 1092826 21-Jul-2014 09:50
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I worked for a Plumbing supply company many moons ago G. Methven & Co, we had a photo in our tea room of what can go wrong if a hot water system gets too pressurised. The cylinder burst with such force it went through the roof and took out a large chunk of the house. Quite impressive actually.




Mike
Retired IT Manager. 
The views stated in my posts are my personal views and not that of any other organisation.

 

 It's our only home, lets clean it up then...

 

Take My Advice, Pull Down Your Pants And Slide On The Ice!

 

 


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Master Geek
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  Reply # 1092838 21-Jul-2014 10:00
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This is great timing, I've been keeping half an eye on the web over the years regarding people who are doing similar things.

Over the weekend we talked to a company at the Home Show about a gas radiator system (and whole house was somewhere around 8k estimate, can't dump that cash on system unfortunately), great looking system. $2k I think was the 28kw boiler and they have many customers who do radiators over a number of years to cut costs.

Back to DIY, I had been wondering if viable to build a second circuit to separate radiators for a wetback circuit (the pressure issues have always been of concern but proper design I presume would be fine). The Gas system if installed would kick in if the wetback system wasn't maintaining a decent temp (especially early morning when the fire is out). I like your idea about using valves and maybe have it on same system to switch between the 2 systems as needed. When reading the brochure the gas boiler does mention solar input so I wonder if can be used with wetback as well.

Solar, even if 2 degrees outside, if the sun is out then you will get a large amount of heat via solar systems. Checkout http://www.builditsolar.com/Projects/SpaceHeating/GregCanCol/GregCanCo.htm I've got a tiny 7 can test system stuck together, 20 degrees in and 45+ out last week (in full sun, no fan just natural movement of heat), very keen to build a large one when time allows. A group in Wellington are doing a similar system (from memory crowd fundraising for low income houses). Once built, if using solar fan then it costs NOTHING to run :). Commercial outfit in USA with 240 cans had their system sized at producing up to 3kw of heat. Sorry for getting off topic but if you have a wall on house that gets lots of sun this could be a cheap source of heat during day.

When I have some time I'll be back and do more of a brain dump of ideas I've had :)

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Master Geek
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  Reply # 1092844 21-Jul-2014 10:19
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Great post by the way, we just converted our rental (Ohakune so it is very cold) to gas hot water and gas heating but we already have a wet back.  I asked the electrician about a radiator system but they said it was just easier to cut the pipes off as he said that the wetback sucks up to 20% of the heat.  So that is what they did, which is a shame as our fire puts out alot of heat so losing 20% to heating other rooms is fine by me.

The wetback is still there and I am keen to add a radiator system sometime in the future to heat the drying room and two back rooms that tend to be freezing.

So I will follow your post closely, to see what you come up with.









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Master Geek
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  Reply # 1092854 21-Jul-2014 10:31
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KShips: Over the weekend we talked to a company at the Home Show about a gas radiator system (and whole house was somewhere around 8k estimate, can't dump that cash on system unfortunately), great looking system. $2k I think was the 28kw boiler and they have many customers who do radiators over a number of years to cut costs.

Back to DIY, I had been wondering if viable to build a second circuit to separate radiators for a wetback circuit (the pressure issues have always been of concern but proper design I presume would be fine). The Gas system if installed would kick in if the wetback system wasn't maintaining a decent temp (especially early morning when the fire is out). I like your idea about using valves and maybe have it on same system to switch between the 2 systems as needed. When reading the brochure the gas boiler does mention solar input so I wonder if can be used with wetback as well.


Thanks for this.
What was the company you talked to about the boiler, and $2K for 28Kw? Would be interested to talk to them.
Boiler assisting the wetback could be very helpful indeed.



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Master Geek
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  Reply # 1092940 21-Jul-2014 12:10
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Got myself a range of Radiators off trademe. 
New Dehlongi ones I have been watching for a few days now.
Made contact with the seller, they are Centralheating.co.nz in Christchurch. Just selling off old stock as a new model of radiators has come in from Dehlongi.
$50 buy now for all sizes, they have a range available. 5 of some, 10 of some, 1 or 2 of some. 

Got 4 2Kw units, and 4 800W units.

This should work out nicely for us. Not sure if the wetback is going to be enough to cope with all that, but it might do for one or two to start with, and then move to a boiler once we have saved a bit of money.

At least got the radiators for a good price.
8 radiators for $400 with $80 shipping. Cant complain about that. New models they said are $150 to $450 each depending on the size.

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  Reply # 1093351 21-Jul-2014 22:35
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I have abit of experience on the wood burner side of things.
What model of masport is it?
Depending on the model it could be a tad too small to put out any meaningful heat to the wetback (ie 1kw or so) custom fitting a wetback is relatively simple and you can get hold of custom made wetback though these guys www.wagenerstoves.co.nz I possibly wouldn't bother going back to masport (glen dimplex) as they are likely to be more expensive and you have more options with wagner.

If you want a fire to put out a decent amount of heat into the wetback you will either need something big and way too overpowered for your lounge or a fire that does not comply with the clean air regulations. 
There are a few ways to get around this:
1. Have more than 2ha of land (clean air laws don't apply to you then) 
2. Or install a fireplace that is multi fuel burns coal and wood (depending on local council regulations this is a very good way to get around the clean air regulations)
3. Or spec the fire as a cooking appliance this can get around clean air requirements depending on your council 
4. Or don't get a permit and install what you want not recommended for insurance and legal reasons.

Option 2 is the best choice depending on where you live as you can get a fire that will pump 6kw of heat into the wetback, only 8kw into the room and get a permit :) 

I might consider having a small tank if you upgrade the fire as it would provide a good buffer as the output of a wetback will vary lots.  

There is NO industry way to determine the true kw output of a wetback so be sceptical.
If you have any questions feel free to ask I was in the industry for 5 years (left it around a year ago)

Bottled gas is a bad idea as cost for LPG is not cheap (vs natural gas)


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