Placement of Hot Water Heating Loop in Stove?

[tla100]

I picked up a stainless steel U-Coil online, I plan on installing it inside my woodstove. It will preheat my boiler for floor heat in my 50'x32' garage. Stove is in basement right before my boiler, so I can tap right in to the inlet of boiler with no problem. I will run circulation pump constantly and still have boiler hooked up so it will kick in when I am gone.

I am just looking for input on if I should install in my firebox, under secondary coils. Stove is a Heatilator WS-22, manual is here: Look at illustration 12.1 on page 12 for pic.

http://downloads.hearthnhome.com/installManuals/7057_128.PDF

Or above the secondarys/ceramic blanket, directly under the top of the stove. I am wonder if it will effect the airflow up the chimney. Loop is 1" stainless tubing about 7" wide. Or am I overthinking this, just hate drilling holes in cast iron. I can't weld cast. Want it done right and don't want to re-plumb it as the system is pressurized.

Directions from coil site says to place where it is hottest.

 

[NSMaple1]

If doing this I would likely put it above. Then it would be less likely to interfere with the effectiveness of the secondary burn tubes.

But I don't think it is something I would do - I am thinking it won't give enough heat to your boiler system to be worth the effort and it might make for a creosote maker inside your stove especially with the low return temps that are typical of in-floor heating. And the coil will likely dirty-up in short order & you won't get very good heat transfer to it. Then there's the chance an insurance company might not like a mod like that done to a stove if you ever have an issue where you'd need them.

Just my quick thoughts...

 

[jr27236]

Don't they make stoves with something more effective and designed for your purpose such as this
http://www.charmaster.com/hotwater.html

 

[kingOFgEEEks]

Yes, my charmaster has the loop. In the back of the firebox. Makes plenty of domestic hot water, but I don't know how much volume you need for floor heating, it might not keep up.

 

[ChoppyChoppy]

It certainly won't be enough to heat the floor. Much too small of heating area/water vs the water being heated.

I'd be worried about putting it in contact of direct flames. How about making a bigger coil and putting it on top of the stove?

My Dad had a loop in his stove for domestic hotwater (homebuilt stove), it was on the side of the firebox, about 3ft long 2 feet wide 1.5" K coppper. It heated water for the house for almost 30 years trouble free... enough for a family of 5.

 

[tla100]

Well thanks for the replies. I think I will run it in the firebox, top under secondary tubes. I was afraid the water temps were going to too hot, that is why I went with a smaller look. If it does not keep up, I will plumb that to my water heater and run bigger coil for my floor heat. I keep garage at 55-58, that is with boiler temp set at around 120 degrees. So I think this should be just fine, keep the pump running all the time, just won't have a lot of temp control, can do that with 3 speed pump hopefully.

This is 1" stainless pipe, 24" long x 7" wide, with a lifetime warranty. The guy said send it back if it fails and they will replace it.

 

[Highbeam]

Definitely above the insulated baffle. If you place that cold coil under the tubes in the firebox you will quench the secondary combustion, you won't have as much room to load the stove, and you may not be able to replace the baffle when you break it. Up above the secondary baffle all of the clean burning has already taken place. The heat you steal up there is stolen from flue temps, not firebox temps.

 

[mga]

pressure relief valve as well?

 

[cmsmoke]

When I ordered my D.S. Machine 110, I had it ordered with the loop. It would have went on the left side looking in the door, vertically. I changed my mind because I didn't know about burn times and didn't want to effectively loose firebox size. I was also leary putting this in my living area and trusting the circulator pump and pressure relief valve to keep from making steam and having a possible explosion. My oil furnace has the upper water temp limit set at 140 degrees. I think having a loop might have evened out the temps throughout my house, but would have made way to much heat with the circulated air/ heated water combination with cast iron radiators.
There was a coal boiler here at one time, which the few times that I had it lit, we had to have the windows open, because it was oversized for my house. Bottom line is as long as you make enough hot water to keep up with the heating demand, you will be fine. Remember this isn't like an oil or gas furnace that turns on and off when called for. A continuous fire will make a lot of hot water. I believe that once the slab is up to temperature, keeping it there won't be an issue. Did you get any specifications on the possible output? I would be more concerned about where to dump the extra heat. My brother is building a garage 32x56 with heat in the floor. It will be very well insulated. He is going to use what I see as a "glorified water heater" in it, made for that type of system.
Edit: Inside the firebox will be much hotter than on top of the insulating blanket. The stove is designed to extract as much heat as possible, before it goes up the chimney.

 

[tla100]

Yes MGA, pressure relief is installed already on boiler.

Highbeam, good point on baffle replacement. That might be the deal breaker. Once it is in, it is not coming out.

All good points made. It would be nice to have out of fire box, I usually cram it as full as possible. Wife is also home at noon for lunch and she usually checks and adds if needed.

CMSMOKE I have thought about this too. That is what is shown in the instructions, installed in firebox on left side vertically.

 

[NSMaple1]

Depending on how far this coil is from the relief on the boiler, it might not do you much good. You could have a flash event at the coil, that might damage that and your stove before the relief on the boiler sees the event. I think that relief valve in the package in your pic is meant to go right at the coil, in addition to the one at the boiler.

I still don't think you will be satisfied with the performance, at all. Rough calcs using a 5gpm flow rate that is typical for a circulator on low speed show that the water will only spend about 2 seconds in the coil on its way around the loop. That isn't much time for heat transfer to take place, especially once the cold water accumulates some soot or creosote buildup on the pipe in the box.

Curious to see how this works out though.

 

[tla100]

Well, it is in and running. Temp gains are only about 4-6 degrees. I am just reading with an infrared temp gauge. The boiler does not seem like it runs much, although outdoor temps have been pretty mild except the past week. Thermostat at 55, and inside temp is 56-57, and have only seem it call for heat a couple times in 5 days or so.

I have not been burning 24/7 yet. So, I should be able to tell in a couple months if it is helping. I think it keeps the slab a little more consistent temp.

The loop is covered with nasty creosote, it did not take long. So I may need a long wire brush and scrape it off once a week.

 

[Highbeam]

Well, it is in and running. Temp gains are only about 4-6 degrees. I am just reading with an infrared temp gauge. The boiler does not seem like it runs much, although outdoor temps have been pretty mild except the past week. Thermostat at 55, and inside temp is 56-57, and have only seem it call for heat a couple times in 5 days or so.

I have not been burning 24/7 yet. So, I should be able to tell in a couple months if it is helping. I think it keeps the slab a little more consistent temp.

The loop is covered with nasty creosote, it did not take long. So I may need a long wire brush and scrape it off once a week.

Let's see some pics? What flow rate to get that 5 degrees rise?

 

[tla100]

Loop in, cut firebrick where it went thru. I had to pull shields off to get nuts on backside.
Ended drilling 5 holes total, 2 thru firebox and 3 thru shields. Took longer than expected. Probably 3 hours total.

First fire....

Used 1" copper to go from loop to 1" PEX. Loop is 3/4" stainless pipe thread, used a bushing to get to 1" pipe thread. Then street 90 to a 1" sharkbite fitting, fast and easy. I cut the 1" PEX and used 90 degree sharkbite fittings to connect to 1" copper line.

Pump is on Low, not sure what flow rate is.

 

[jr27236]

You probably loosing a lot of heat from the bare copper pipes and pen tube before it gets to the floor. What's the temp of the pipe coming out of the stove to the floor?

 

[tla100]

Well, my basement will vary in temp from 65-85 depending on how much the stove is cranking out, or not on. If anything, the copper should be absorbing more heat than cooling. Floor temp in garage as of right now varies from 55 along the edges to 57-61 thru shop. Air temp says 59-60.

Not sure the infrared is giving me an accurate reading on such a small surface. But, it should be coming out of garage at around 55 and leaving close to 60. Give or take a degree or two. Outside got around 36-38 today, tops with some sun. So it is raising temp a little, and will hopefully maintain once I am burning full time.

 

[Deleted member 83629]

wrapping the stove pipe with copper tubing will give a limited hot water supply if you want to try that.