Why does it have to powered from a battery? Is this in case of a power failure?

Yes ;-)

The answer is yes you can power a natural gas furnace with a battery,probably multiple batteries more so than one but that's a different question/discussion.

I am talking about a small battery that powers a thermostat. No fan. The heater with a pilot light. My friends use their NG Fireplace this way when they have a power outage. The question - doe something like that exist for a crawl space installation?

I would assume that fire codes in your jurisdiction may have some issues with a gas appliance in a crawl space. You may want to check with your local building codes. Regarding the frozen pipes, there are pipe heating tape that you can use on your exposed pipes to keep the pipes flowing in extreme cold.

Good luck!

If that's the sum total of your question,it might be simple. Many furnaces,fireplaces and heaters are controlled by a 24 to 30 volt transformer. If that describe's yours,all you need is a back up battery coupled with an automatic charger for a set it and forget it back up. Most any electronics supply like Fry's sale batteries and chargers. One could also extend two wires with clamps to the garage or other easy to access area where two automobile,boat or motorcycle batteries could be robbed from vehicles in an emergency,wired in series to supply 24 volts . There are also 120 volt t-stats and controls that are more involved and complex so let's not go there unless necessary.

"Regarding the frozen pipes, there are pipe heating tape that you can use on your exposed pipes to keep the pipes flowing in extreme cold."

These would also need to be battery powered to work in a power outage.

Sorry - heating tape will not work because of no-power situation.

I thought about power bank but is not a good option - I have a furnace in my crawl space and to power it from batteries I need to have $2000 system and it will work for 10 hours only. Ideal solution is to have a NG boiler with a pilot light that is not using electricity at-all to heat some water in a big tank with a few pipes from this tank across the crawl space narrowing diameter and an angle for a return pipe. I know that this kind of system exists but can not find them here in Canada ... Especially a small one so I can put it in my crawl space.

"I would assume that fire codes in your jurisdiction may have some issues with a gas appliance in a crawl space"

- I have no issue here - I have a NG Furnace installed in my crawl space.

Turn the water off. Drain the pipes.

Turn the water off. Drain the pipes. -

Not an option because I am there every 2 weeks :) Draining all water every 2 weeks is not going to be an interesting activity :-)

Maybe a furnace designed for a travel trailer? Convert to NG

edit: Google Atwood RV furnace

" I know that this kind of system exists but can not find them here in Canada "

Based on this short conversation,it does'nt surprise me that you are unable to track down a system. At the beginning I thought you were preparing for a diy project,I now realize that isn't possible. Stating your requirments in intirity at the begining will go a long way in helping others help you. You have given us information one bit at a time. That may very well be why everyone you call can't supply a system. Consumers are not expected to know what information is required but professionals will ask for it if you tell them what key you want the finished product singing in. It's out there,call any good hvac company,state all your conditions and let them find a system to fit your needs.

Draining the water is a heck of a lot more interesting that just staring at a pile of charred rubble and a refused insurance claim.

I see your point and I did contact a few - looks like they do not do that. They prefer simple installations and it makes me to find a solution (DIY or ready to go product - does not matter)

Found this one : https://www.wayfair.ca/6-000-BTU-Natural-Gas-Propane-Vent-Free-Convection-Wall-Heater-WDFT060-VF-TYV1000.html

Is it dangerous ?

You have to provide 120v to the furnace and thermost in order for it to operate during a power outage. You could install an UPS (uninterrupted power supply). You can one that could run the furnace for hours but it will be expensive.

Thank you all for the input.

I think I've found a solution :

http://www.gasheaterstore.com/Empire-RH50CNAT-50000-Btu-Vented-Room-Heater--Closed-Front--Natural-Gas_p_127.html

I am glad that you got away from the unvented. That would make it rain in your crawlspace. Be aware that the flue for the vented heater might need to rise over the roof to meet building code.

It is not a problem - I can do that.

Another problem is that this unit may not be installed in crawl space because of clearance issues to the ceiling ,,, fire hazard as I understand :(

Just looking at that site, why not use a Floor Furnace, which actually sits in the crawl space and also needs no electricity:

http://www.gasheaterstore.com/Empire-3588XNAT-32500-Btu-Floor-Furnace--Natural-Gas_p_131.html

A lot of '60's homes in Northern California have old-style versions of these with a grate on the floor, and natural convection rather than a fan seems to bring the warm air up into the room.

Interesting. Will look into it too. Hope it is vented. Also clearance could be an issue too. (in crawl space there is no ceiling.)

Why no one manufactures anything especially for crawl space !!! or I just can not find.

You could put in a hot water loop from the water heater and then install a water pump set to a temperature switch the farthest from the water heater. This temperature switch would activate the pump and circulate the water when the temperature drops below a set temperature.

Then insulate both the cold and hot water lines really well. Set your furnace for inside the home to 55 degrees or so.

This system can also serve as an instant hot water solution.

Austin Air,that is surly a modern,forward thinking and creative idea. I have the same situation as op at my cabin. I have been draining the plumbing but would love a system like you are talking about. What appeal's to me most is it's ability to to maintain not only the crawl space but inside home at 55 degrees during power outages. What supply's power to run the system during extended power outages?

power outages means no power to run a pump. But ! If you run all pipes correctly from bigger diameter for hot water output to smaller diameter when cold water returns and some slope - then you do not need a pump or any power. All will work by itself. The only thing you need if a electricity free water boiler and it is no an easy thing to find :)

In my case (crawl space) it is hard to do because hot pipe should be much higher than cold one ...

Here it is :

http://www.free-ed.net/free-ed/Courses/05%20Building%20and%20Contruction/050207%20HVAC%20Heat/HeatSys00.asp?iNum=06

Correct, I think it has been a long time since one-pipe hot water systems have been at all common as new projects.

My first thought at this suggestion was that this needs to be code compliant and there are problems in combining water for heating and water for DHW, however, making the loop part of the hot water supply would skirt that. Will there be enough heat transfer from simple pipe to provide the heat necessary? I doubt it.

If a circulator pump were to be installed it has to be of they type used for potable water, stainless steel, IIRC, not an hydronic heat circulator. Obviously the whole system needs to meet potable water standards.

Klem,

I am a control freak by nature and these kinds of systems I worked on what seem like a life time ago when I was working in facilities maintenance for what is now mostly a defunct cell phone manufacturer.

Realize this system does not provide the heat to the structure... it is not a boiler type system. It is your hot water system on steroids. You already have the hot water that is in the hot water tank. The pump is merely a way to circulate it. The pump would come via commercial type application. The thermostat is merely to turn the pump on or off via a predetermined set point. Bell & Gossett are a well known brand some 20 years ago for this kind of application.

That might be something ser1140 can use but I'm afraid it's far more elaborate than I have in mind. I can't afford something like that for my primary residence much less a vacation cabin just to prevent freezing pipes. I'll just continue draining lines when temperatures threaten. Thanks all the same.

Total material parts most likely under $1100.

Run return pipe back to water heater - copper return piping- $200

--- install shut off valve $20

install circulation pump $300-500

install thermostat and pump controls: $150

Install check valve. $20

Install hose bib and shut off valve at water heater. $40

Tie pipe into water heater drain port.

Run electrical to pump. $100-200

Costs above are to do it yourself. This is elaborate?

90% of homeowners certainly think it's elaborate,they don't have back up generators sitting in their primary residence yards,much less cabins that are on the grid. People post every day about hvac contractors making multiple return trips to re-lick their calf and they are still without air. That contraption is far more complex to troubleshoot and install than a furnace fan or condenser contactor. Elaborate enough that you overlooked the back bone of the system. " install a generator that would kick on to run your furnace, power the water heater and the pump and controls of the system" = $???? Your estimate also overlooked automatic transfer switch= $????. Yes,much to elaborate just to prevent freezing water lines at a vacation cabin.

Yeah money can be the bigger of the two problems. I stand corrected.