Size calculations/safety checks for heated driveway

Skender823

 Hello,
The house I moved into has part of a heated driveway set up. There is a powervent water heater, most of the pipes needed, a heat exchanger on the wall and a manifold in the garage. The problem is I have no idea how much pipe is under the driveway, not sure how to pressure test the system under the driveway and how to figure out the rest of the parts I need to make this work. I know I need 2 pumps but don't know how to figure out what size, also an expansion tank. I've been trying to do some research but its hard when I don't know all the variables involved. Any help or advice is appreciated and I can provide pictures. Thanks in advance.

Here are some pictures of the setup. The manifold is in the garage. My driveway is about 24x24 and the distance from the heat exchanger is probably 35ft. I don't know anything from the previous owner. I think it was at least two owners ago.For a pressure test would I do that from the red and blue pex in the picture or from the manifold?

EBEBRATT-Ed

I am assuming this isn't presently working. Before you invest any $$$ in this system the first thing is to pressure test the underground tubing.

Also identify what brand of tubing it is if you can. There should be antifreeze in the system.

Snow melt takes a lot of heat and burns a a lot of fuel.

That's the first step.

Do you know any history of the system from the previous owner?

hot_rod

Find out what type of tube you have, buy the cheapest fittings, tees and plugs to connect them and pressure test with air. If they hold air, then move on to a design.

JosephTonozzi

A power vent hot water heater is going to use a energy to melt snow . It uses a lot with even a high efficiency boiler system . But the way some people’s driveways are I guess it’s a necessity. If we keep melting the snow we will not need to in the future. Covered Bridges ?

Zman

Some pictures of what you have and the size of the driveway would help.

Daveinscranton

If it doesn’t leak, I would hook it up correctly and try it.  By correctly, I mean proper boiler and mix valve and pump.   And glycol.  Probably an expensive experiment.  Might be fine.  I did a snow melt set up on my driveway 30 years ago at my old house.  Mostly a pad 24’ or so by 24’. Worked great.  Pretty sure I used 1 foot of fancy hose per square foot of concrete.  Dog liked it a lot.  He would be asleep on the driveway with snow (half an inch or so) on his nose.

hot_rod

The amount of heat or energy you can throw at it depends on tubing size and length. And the size of the boiler or heater determines how fast you can melt the snow.

If you can see the tube you can determine the diameter. If you really need to know how much tube you could fill it, purge the air, then measure how many gallons comes out. The tube manufacturers will indicate how many gallons per 100' typically.

Ideally you would have 5/8 or 3/4" tube, inside diameter.
3/4" pex would be 7/8" od, for example.

100 btu/ sq foot of driveway is a good number. A common water heater may be around
30,000 BTU/hr output, so 300- 400 square feet of driveway. look for the label on the heater to see the BTU rating.