Steamed

Well good evening guys. I am sure I am going to get flamed for this and that is okay because I probably deserve it. So here is the setup. Vermont Basement Heater coal stove. SS hot water coil inside the top of the fire box. SS comes out the top of the stove and goes into about three feet of copper pipe. Then goes into CPVC and runs about 50 feet across the basement to the hot water heater. Half way between the stove and the hot water heater is a copper coil attached to a fan. The water is diverted to the copper coil/fan if the temp goes above 160 F. If it does not it goes into the top of the hot water heater and then is pulled from the bottom of the hot water heater and of course goes back to the stove. In the middle of the circulate is a grumb water circulation pump. So... This evening I got the stove fired up for the first time and water moving around and I had a small leak so I shut the power off to the circulator pump and of course 3 min later KUUUBHHHHSSSSHHHH I have steam melt and blow off the CPVC pipe that is attached to the copper pipe about three feet off the stove. Of course I shut everything down and cut the pipes and drain the system. Sooo... Obviously the cause of the steam issue was because I did not have water circulating through the hot water coil. If the pump had been running this would not have been an issue. So what if the power goes out. How do I make sure this kind of thing does not happen again should say the pump fail or power outage? Thanks guys,
Glenn

use copper the whole way


Eric

For a truly fail safe system you need to:

1. Eliminate the pump and depend on thermal gravity flow.

2. Use all metal pipe.

3. Provide an expansion tank.

To do #1 successfully the tank needs to be higher than the coil in your stove. Larger sized pipes and insulated pipes will increase the flow rate.

You can use a pump to speed flow, but you must design the system such that when there is no electricity, the system drains or stores the expanding heated water until the fire goes out. Above all you can not allow the coil in the stove go dry. Using a stove to heat domestic hot water is not a great idea in my opinion, unless you can do #1.

I am sorry but that really is not an option. I am already going to extend the copper for another 6 feet from the stove and I am going to put a blow off valve near the stove and vent that through the wall. I also thought about putting a valve near the pump so that if the electric/circulating pump fails it will allow water to by pass the pump and gravity circulate. Any other ideas?

Thanks,
Glenn

Sorry replied to the first post and when I did the second post had posted. Expansion tank sounds like a great idea and I can diffidently do that. As far as the gravity fed system... I will have to play with that. The stove is rather high of the ground but the pipe does go up about 4 feet to the basement ceiling and then runs pretty much flat across the basement to the hot water heater.


Thanks,
Glenn

That doesn't sound like the tank is higher than the stove.

As was said, needs to be large pipe and cold return outlet of tank must be higher than stove water inlet for thermosphion to work. It's the Laws of Physics...can't get around them.

It's really simple and works excellent, when played by the rules.

no flow = steam

This is physics and the nature of the beast.

You need a pressure /temperature relief valve at the very least in the system near the heating coil. Pipe discharge to a safe area. It will blow on loss of flow.

Since you apparently don't want to spend the money for copper the whole way to the tank, how about pex-al-pex? it has a much higher pressure rating, even if the temp is still rated at around 200*,,

Having a potential steam bomb is pretty dangerous.. you can get some very significan't burns from 212* steam, it has much more heat than 212* water. Don't let your wife or kids or pets anywhere near this plastic pipe if the stove is burning.

Gravity flow and all metal is the way to go. Are you using cpvc for the cold return to the stove as well?

Greg L.

Hey guys,
Thanks again for the assistance. I ended up running an additional 6 feet of copper pipe from the stove to PCVC. Also the question that was asked about the intake like, yes that is CPVC as well. I added a blow off valve coming off the hot water coil and ran galvanized steel pipe off of that out the basement wall and vented it in the crawl space under the front porch. Will start things up again on Tuesday.

Thanks again,
Glenn

It would appear that the coil is just too large for the job at hand. I got everything hooked back up again and it took my 30 gallon hot water heater that at the time was full of cold water and had the water temp up to 108 in under a half hour. All I had was a small wood fire going in the stove at the time. Thought about taking the coil back to the weld shop and telling them to make it much smaller or thought about trying it on top of the stove (out of the fire box) between the top of the stove and the air jacket. My only concern is that the air being drawn over the top of the stove and externally mounted hot water coil would cool the coil to where it will not heat any water for the hot water heater.

Thanks,
Glenn

Run a secondary loop off the 6' of copper, put a aquastat in the main line, any time the water in the main line exceeds 210*, start a pump in the secondary loop to feed either a length of finned baseboard, or a modine as a heat dump.

You can warm up the water in the holding tank to 200*, but must have a mixing valve somewhere for safety's sake.

Try it with a coal fire, the flames from a wood fire are actually pretty hot.

Greg L

Yeah those pipes get HOT! I wouldn't want any plastic anywhere near the pipe - let alone be MADE of plastic ....

This is my foam insulation about 5' feet away from coil exit ...

Greg,
I have it setup like that now: At 160 it changes over and sends it to a copper coil that I have on a 18" fan. Obviously it does not cool the water fast enough and I need something that can dump WAY more heat. The hot water coil is just way too large for the application. I am off brake though and have been working quite a bit so I have not had time to work on the project. The first thing I am doing is getting rid of the CPVC and putting in galvanized and copper pipe. Just a thought I had, what if I left the coil alone and even added two more and ran a hot water to air heat exchanger in the furnace plenum and then ran a smaller "new" coil to the hot water heater? Along with this pack the air jacket around the stove with insulation to make the stove more efficient.


Smitty,
Wow... That is hot. That looks very much like my CPVC when it melted down.

Thanks,
Glenn