How are you going to run any equipment, save for some select units, with no electricity?
Ventless units will require you to open doors and windows while operating the furnace to feed the combustion air supply and to vent the moisture and products of combustion

 

Maybe look at RV heates with solar bank to charge a battery to run it. Not sure if the make them for NAT gas or not.

 

Easier yet I guess a small wall furnace or vented console type heater.

 

Direct vent through the wall heater with a millivolt or snap action valve. Williamson is one possible mfg.

 

Williamson thru the wall

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Juan and DJ,

Thanks for the knowledgeable reference. Williams looks perfect to warm the springhouse. Will get electric up there someday when we need actually pump more flow, but even then I don't want the place to freeze when the power goes off for 5 days in an another ice storm like two years back.

Williamson 7400btu fills the bill. No power, pilot, direct vent. It's pricey @ $755, but looks solid. (Home Depot)

Noticed Williams also makes a 14kbtu no power unit for $582 ... scratch ... scratch ... twice the heater at 75% the price? OK ...

They probably just don't have the volume of sales for the 7kbtu unit and are sending the message to folks to buy the bigger unit and run it half the time :^)

Looks like I need to gear up for $600 to get this done.

Thanks!
Best regards,
Bruce

 

direct vent Williams wall heater.

 

With no disrespect, you need to go back and rethink this and/or you did not provide enough detail.

You say this is Spring/Pump house. "pump house" doesn't it need electricity. If you do have an electric pump, you have power and could possibly add a circuit from the pump power supply, 100 sqft.? That's about what my well house is and at -20F I can keep it above freezing with a 200 watt light bulb. I'm willing to bet you do not need the heating capacity you think. Have you done a load calculation. I'm thinking with that small of a space, closed up tight, you'll end up with performance problems using a gas heater, CO problems, condensation problems, make-up air problems

Just some other thoughts, solar electric with inverter and low wattage heat trace, Solar warm air heating (convection air flow)

 

If this is a flowing spring and all you want to do is to keep it from freezing just putting the building around it will probably accomplish that.

 

Should have said "future" pump house to be exactly precise if my first post. No electricity there now. Evolving project with possibilities.

Gas is there/never affected by wx outages/clean/very inexpensive to operate.

Spring water heat ... now that would be the ultimate, but the terrain/flow prevented construction at the outflow. Plus I have some other stuff stored there I would prefer reliably not to freeze.

Solar is uneconomic. Too much batt capacity required, solar insolation too low Jan/Feb and its in the trees anyway. Used to do remote radio solar for a utility. Was eco there compared to paying to string three miles of primary through the forest and keeping the trees cut back. Still a PITA for the maintainers. Finally justified a 500 gal propane tank/gen because of outages/overtime/overheads after all was said and done. I am tech agnostic. Most workable, reliable and economic with capex and opex gets my vote. Every job is different.

Appreciate the comments!