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Wetback with underfloor heating or radiators?

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Wetback with underfloor heating or radiators?

Posted 13 Sep '10 04:45 PM

We are building a 110 square metre home. We are planning to have a wood burner with a wetback as we have a continous supply of firewood. Has anyone experienced using a wetback with radiators or underfloor heating along with it heating the hot water. We would only need about 4 radiators, but if we used underfloor heating we would put it throughout. I would be very appreciative of any ideas, tips or suggestions.

Re: Wetback with underfloor heating or radiators?

Posted 22 Sep '10 03:46 AM

I don't have any personal experience but got this information recently when researching.

(1) heating engineer told me that a wetback is only good enough to support 2-3 rads maximum.

(2) our friends just took over a house with a wetback, and strugged to heat the house. The wetback (for hot water only) was oversized they discovered and sucked all the heat out of the fire. They could run it for several hours without it getting hot enough to touch. So I guess that correct sizing is key.

(3) we are going to take the wetback out of our place as part of a general renovation and replace with with a pellet boiler (not a fire) running radiators & hot water. The wetback is just not controllable, we keep overheating the cylinder just to keep the room warm on these snowy Dunedin days.

I saw there are several wood boilers available - they come in lots of different sizes and so could be sized to handle the hot water and rads/underfloor comfortably. But would need to be stoked etc.

Hope this helps, good luck. Nick

Re: Wetback with underfloor heating or radiators?

Posted 22 Sep '10 04:42 AM

I do, what fire are you going to be using?

Re: Wetback with underfloor heating or radiators?

Posted 25 Sep '10 05:05 AM

Thank you for your helpful comments Nick - obviously we are going to have to work all this through. We have not chosen what we are using yet, as still researching what we want the fire to do for us. We want to make the most of the unlimited supply of wood we have.

Re: Wetback with underfloor heating or radiators?

Posted 06 Nov '10 07:01 AM

if you are going to use a wet back, as other posts suggest this can suck a lot out of the fire, suggest you research a cil or sleeve around the chimney! truely wast heat it has been done & works well. where are you guys planning on building?

Re: Wetback with underfloor heating or radiators?

Posted 29 Dec '10 09:19 AM

would like to hear from you re wet bac and rads,. wat heat source etc and rads etc

Re: Wetback with underfloor heating or radiators?

Posted 06 Jan '11 07:23 PM

Hi 2oldies.

While Nick_B's info may be correct about being able to only heat 2-3 radiators, that leaves out some important facts:

- How powerful the fire is (Usually measured in KW) - How well designed the system is. i.e. v.important especially in NZ to ensure your plumber/engineer has experience in designing and installing such systems. I have heard way too many stories about central heating performing badly becuase it appears it was designed badly from the outset. - How well insulated the house is. Ask your builder if you can over-spec the insulation - we did.

Any good seller of fires or manufacturers (see Harris Flame for their "Woodsman" range, I hear they are good) will be able to quote you the kilowatt (KW) heat equivalent output of the fire.

As an example, we have 6 beefy old cast iron 4 column radiators in each room of our new replica villa. They are heated directly from a wood-fired Kitchen Range (A reconditioned Rayburn - check out classiccookers.co.nz) which, depending on the type of wood used and how well seasoned it is can chuck out well over 16kW of heat which has been *easily* enough to do the rads, boost our 400L water cylinder (it's primarily heated via a 30-tube solar collector). *and* heat water enough for x2 300W equivalent towel rails in the 2 bathrooms.

So you should therefore have no problem with 3-4 rads and the underfloor providing:

- The system is well designed and installed - The fire is powerful enough.

As Nick_B says you could also use a boiler which are designed especially for just such a case, and there a multitude of types, sure it would need to be stoked, but so would any fire.

Also, find out exactly how much heat you actually require to heat any one room. Sounds logical now that you think about it. You can then use a calculator online to calculate the amount of heat required to heat any room, once you punch-in the room's dimensions, glazing type, insulation, orientation (North, South etc)

It sounds like a lot of work, but it really isn't and you learn so much about your home that you simply would not have done otherwise.

I found an immense amount of satisfaction having done all the legwork beforehand and it paying off last winter. Sure, there are things about the house as a whole I would have done differently if I had my time again, but doesn't everyone!?

Online heat calculators:

I used the calculator here: http://www.theoldradiatorcompany.co.uk/btu-calculator I also just found this: http://www.theradiatorcompany.co.uk/heatoutput/

You can use this site: onlineconversion.com to convert BTUs (British Thermal Units) to Watts/Kilowatts.

Good luck. Russ

Re: Wetback with underfloor heating or radiators?

Posted 06 Jan '11 07:27 PM

...Oh the the bonus with something like a Rayburn (Or Wamsler or any of the other makes) - as if heating water and space heating weren't enough - is you can cook on them too.

I love cooking on ours..here's a piccy:

http://theruss.com/gallery/kapiti-off-grid/DSCF0431.JPG.html

Cheers Russ

Re: Wetback with underfloor heating or radiators?

Posted 25 Mar '12 09:29 PM

Did you end up getting the right solution here?

Re: Wetback with underfloor heating or radiators?

Posted 14 Sep '15 12:35 PM

i understand you have to get the old cast iron rads to 50 - 60 deg c before they are efficient where as under floor is around 20 deg c. hope this helps.
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