CivilWausau

Thanks for all the replies. I'll crunch some numbers with the info from CaptainPanic. I installed a coil (since I had some excess material available) in the upper 200F chamber and was only getting a few degrees increase in temperature - very disappointing. If I shut off the pump and let the water sit, it heats up to 200, but the constant flow is too much for the 40' coil configuration to get a significant increase. If the calculations don't show much better by changing the temperature from 200 to 400, it'll be time for a shopping trip to simply get a boiler. I needed the pump, valves, etc. to hook up to a boiler regardless, but thought I'd at least try it first using heat that is already available. My goal was to not have the basement be less than 60F when we have fires going (usually at least 4 nights/week). I know I could get plenty of hot water in the fire box, but I wanted to avoid doing anything inside the firebox due to the risk of steam and explosions or leaks. I know I could get the temperature that way, but it had way too many variables for me to experiment in my living room with. Does anyone think that using aluminum fins, similar to baseboard radiators for hydronic heat, would make a difference? I was contemplating less length of pipe, with a larger diameter and the fins may be more effective since it'll transfer the air temp better and the water will flow slower with a larger diameter of pipe? Any thoughts?

I can take a picture of the fireplace and post it, but it'll be a few days until I'm back by the unit to do this. The simple schematic is an air space that maintains heat at 200F with 40' of 1/2" copper inside it, water coming in at 1-3 GPM at 60F and I'm trying to figure out what increase in temperature I could expect to see at the outlet. I also have the second area that is heated around 400F, but it is smaller and less accessible for construction. Thanks for the input - I'll work on getting a photo out.

I'm attempting to extract some additional heat from an existing fireplace and wondering if anyone can help me with the rate of heat transfer from air through a copper pipe to water. Here's what I have....a fireplace with two chambers outside of the firebox where air can be blown to other rooms via duct work. Rather than blowing air, I'd like to install a copper coil of 1/2" flexible copper tubing and heat water to pump through my in floor tubing in the basement. The question is, if I have 40' of 1/2" copper tubing in the chamber with water flowing through it at a rate of 1-3 gallons per minute (if I set my pump on low speed and only open 1 of 4 loops in the floor it is at 1 gpm, if I open the system up and set my pump on high speed it can push about 3 gpm) can I increase the water temperature from 60 F to 90 F? I checked the temperature in the two chambers; during an average fire, the one closest to the firebox is at about 400F and the secondary one is at about 200F. The secondary chamber has better access for construction and would be preferred for use, but I don't think 200F is enough heat. The system is set up so it flows into an open tank, so it intentionally isn't a closed loop system to avoid the chance of boiling waterm high pressure, expolosion, etc. I'd appreciate an assistance in calculating if this might work, as well as any other suggestions for stripping the heat from the air and getting it to the water (i.e. radiator fins similar to hydronic base boards). Thanks for any assistance!