Hot Water and Radiant Heat Plumbing Question

Hot Water and Radiant Heat Plumbing Question

PostBy: traderfjp On: Tue Apr 10, 2007 11:32 pm

Hi,

I have an Alaska Channing stove that I love and with the price of oil I want to get more out of it. Here is my plan. I want to get two SS coils custom made and mount them inside my stove (side walls). Each coil would flow into the drain valve of my 30 yr. dry base oil fired boiler in a loop. I would then add another zone to my boiler and feed a Bock hot water heater with a mixing vavle so temps don't get out of hand. The hot water heater is oil fired with its own retention head so it could easily kick on if need be. Right now I live in a 2 story colonial with a basement. Our coal stove heats 95% of our two floors so the hot water from the coild would only have to heat the basement (stays at 50 degrees with no heat) and our domestic hot water.

I'd like to hear opinions on this setup. Please don't suggest a coal boiler because it's not doable.
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3

PostBy: coaledsweat On: Wed Apr 11, 2007 9:27 am

I would guess that it is probably asking a little much from a stove, but it might work. It may also trigger your oil boiler to cycle.

Don't be so sure a boiler wouldn't work for you. Is it cost or configuration that prevents it?

There is no better way to use coal than a boiler.
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

PostBy: traderfjp On: Wed Apr 11, 2007 9:52 am

My wife's mom is in the basement and I don't want to have to see her that much and I want her eto have her privacy. Also it would be a huge expense to add a boiler.

Right now I used 180 gallons from 2-11-07 to 3-11-07, from 3-11-07 to 4-11-07 I used 100 gallons. The basement is being kept at 73 and we all use a lot of hot water. I have a seperate oil fired hot water tank too. So even if the boiler and hot water fires occasionally I think in the long run I would be saving dollars. I've used about 3 tons so far which I think is excellent since the downstairs is at 77 and the upstar bedrooms are staying around 70. This summer I'll add floor registers to help move more of the heat.
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3


PostBy: coaledsweat On: Wed Apr 11, 2007 9:56 am

As long as you are not having trouble heating the house, I would try one coil first. If that works and you can still heat with no problem, add the other coil.
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea

PostBy: Bob On: Wed Apr 11, 2007 11:06 am

traderfjp wrote:My wife's mom is in the basement and I don't want to have to see her that much and I want her eto have her privacy. Also it would be a huge expense to add a boiler.

Right now I used 180 gallons from 2-11-07 to 3-11-07, from 3-11-07 to 4-11-07 I used 100 gallons. The basement is being kept at 73 and we all use a lot of hot water. I have a seperate oil fired hot water tank too. So even if the boiler and hot water fires occasionally I think in the long run I would be saving dollars. I've used about 3 tons so far which I think is excellent since the downstairs is at 77 and the upstar bedrooms are staying around 70. This summer I'll add floor registers to help move more of the heat.


The oil consumption in the basement --300 gallons in 2 months is roughly equivilent to 1.5 tons of coal. That 1.5 tons of coal would be a 50% increase over the 3 tons you cite for the stove (over what period). In thinking about this project is it realistic to push 50% more coal through the stove?
Bob
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea/Anthracite

PostBy: traderfjp On: Wed Apr 11, 2007 11:11 am

Bob: I'm not an engineer but my hope is that the coil in the stove will not steal that many BTU's. There isn't a heat exchange in the stove I'm thinking that the coil may only add a marginal amount of coal to my current consumption. I have no data to back this up so there are many unkowns on how this would all play out. I think it may be an interesting idea and with the cost of oil it may make sense.
Also, my stove's coal consumtion was from October to April.
Last edited by traderfjp on Wed Apr 11, 2007 6:02 pm, edited 1 time in total.
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3

PostBy: Bob On: Wed Apr 11, 2007 4:32 pm

traderfjp wrote:Bob: I'm not an engineer but my hope is that the coil in the stove will not steal that many BTU's. There isn't a heat exchange in the stove I'm thinking that the coil may only add a marginal amount of coal to my current consumption. I have no data to back this up so there are many unkowns on how this would all play out. I think it may be an interesting idea and with the cost of oil it may make sense.
Also, my stove coal consumtion was from October to April.


Given that your stove coal consumption was October to April it seems that the BTU's required to heat the basement/water are a lot more than to heat the upstairs (I am assuming that 3 tons of coal, which is approximately equal to 600 gallons of oil, heated the upper two floors for 6 months while you used nearly 300 gallons in only 2 months for the basement and water.

This suggests to me that it would not be reasonable to expect one or two coils added to the stove will come close to heating the basement and the water.
Bob
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea/Anthracite

PostBy: traderfjp On: Wed Apr 11, 2007 6:04 pm

Bob wrote: Given that your stove coal consumption was October to April it seems that the BTU's required to heat the basement/water are a lot more than to heat the upstairs (I am assuming that 3 tons of coal, which is approximately equal to 600 gallons of oil, heated the upper two floors for 6 months while you used nearly 300 gallons in only 2 months for the basement and water.

It may work out like that on paper but I can tell you if I didn't have the stove I would have used around 1200 gallons.
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3

PostBy: LsFarm On: Thu Apr 12, 2007 12:37 pm

Hello trader. If you recover any heat from the coal stove and add it to you boiler system it will help reduce your oil consumption. But I don't think you will be able to get by without using some oil.

The amount of heat captured by a SS coil in the stove is not a lot, it will slowly heat a tank of hot water, or help keep the boiler warm, but it won't be able to replace the heat used by burning oil.

Just take a look at the surface area that is heated in a boiler, then compare this area to that of a coil of SS tubing. You only have so much area to transfer heat from the firebox to the water. So the amount of heat transfered to the water is not great. But a little heat 24hrs/day adds up and will help reduce the oil use.

It's worth a try.

Greg L

.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

PostBy: traderfjp On: Sat Apr 14, 2007 12:03 am

LS Farm: Do you think I would be better off with 2 coils and running a coil to my hot water heater and the other to my boiler? My other option is to run both coils to my boiler and then create a zone off the boiler and feed my oil fired hot water heater from the boiler. Obviously I would keep both appliances on so if the stove couldn't keep up the burners would pickup the slack?
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3

PostBy: LsFarm On: Sat Apr 14, 2007 11:52 am

You will have to keep the appliances on, I guarantee that even two coils will not heat enough water for a dishwasher and a teenager-shower or load of laundry at the same time.

Most coil-in-stove heat recovery systems heat a tempering tank of water that feeds prewarmed water to a domestic hot water tank. This way there are two resevoirs of hot water for domestic use. Your oil boiler heat system is probably set to work at 160-180*, so you will need to run the coils very close or over the fire in the stove to get a good temperature differential for heat transfer.

It will help, but I doubt that even two coils will heat a lot of square footage.

One member here put in radiant floor, which needs only 100* water in a small room he was remodeling, and used a coil to heat it. With a resevoir tank. I can't remember the rest of the system. Or the member's name. When I get time I'll do a search.

Like I said, it is worth a try, especially if you can get a coil made for your application and do it yourself, the return on invested money and time will be shorter.

Greg L
Last edited by LsFarm on Thu Apr 19, 2007 7:35 am, edited 1 time in total.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

PostBy: traderfjp On: Thu Apr 19, 2007 1:13 am

LSFram: I usually keep my boiler at 110-140. I find that I save more oil and that 140 degree hot water is more than enough to heat my basement. I have no idea how many gallons of water my boiler holds. But the water circulates through the baseboard heat in the basement quite a bit. Do you think I would be better off putting in a tempering tank and then feeding this to my boiler (in boiler drain/out relief valve)?

Out showers are not at the same time so I'm thinking the coil will have plenty of time to heat our 30 gallon tank and if it falls short then the oil burner on the hot water heater will pickup the slack. I guess I will need a tempering valve too which I've never installed so that may be fun.

I wish the coils that can be bought had more loops in them. They seem to use large radious bends.

What do you think?
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3

PostBy: LsFarm On: Thu Apr 19, 2007 8:10 am

The large radius bends are for water flow. Many of the coil instalations use gravity or thermosiphon flow to circulate the water. This requires as little resistance to flow as possible.

I don't think a tempering tank would work with a boiler, only with a domestic hot water tank. Use the boiler itself as the 'tempering tank'. Any captured heat will be in the boiler to use the next time the circualtor pump calls for heat.

You will be able to recover some heat from adding loops into your stove, but I don't believe you will be able to recover enough to heat the basement. I don't know how big the rooms are or how well insulated they are in the basement. You don't want to try to heat rooms with concrete floors and walls. The concrete absorbs huge quatities of heat.

If you hook one coil to the boiler you will get some residual heat in the boiler, it would only be a fraction of what is needed to heat a basement though.

If you hook one coil to a tempering tank in the cold water supply side to the domestic hot water, this will provide quite a bit of heat overnight for hot showers in the morning.

There just isn't a lot of heated surface on the coils so the amount of heat captured by the water is not great. But if it keeps recirculating all night or all day long, then you can bring a 40 gallon tempering tank up to 180-200*, it depends on so many variables. In the winter, with the stove really cranking, you will get a lot more heat from the coils. In the fall and spring, not so much 'cause the stove will be idleing a lot of the time, if you turn up the stove to get more hot water, you will get chased out of the house by the heat.

So if you get creative, you will gain some hot water from your coils, but I just don't believe you will see a huge reduction in oil use. Depending on the cost of the coils and instalation costs it may not pay. There was a thread about a year ? ago titled 'was it worth it' author wenchris I think try a search for it.

I would keep the domestic hot water coil separate and dedicated to domestic water. Keep the second coil dedicated to the boiler. Boilers should not have fresh water with fresh oxygen added to the system this promotes corrosion in the boiler. Domestic hot water heaters are designed to have fresh oxygenated water circulating through them.


Lots of variables and options, Experimenting will tell what works

Greg L.

.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland