efficiency loss

efficiency loss

PostBy: cjkirvan On: Thu Nov 20, 2008 3:38 pm

My s260 is three years old and has worked well until this winter. I can't get the boiler to heat the water to 120 degrees. It levels out around 115 and stays there, running constantly. Any suggestions as to what I can fix to increase the efficiency? Where should I begin?
cjkirvan
 
Stove/Furnace Make: AHS Coal Gun
Stove/Furnace Model: S 260

Re: efficiency loss

PostBy: WNY On: Thu Nov 20, 2008 3:44 pm

not enough feed or too much water flow and it doesn't have time to heat up? Auqastat or something not turning off the pumps? to let the water heat up?
WNY
 
Hot Air Coal Stoker Stove: Keystoker 90K, Leisure Line Hyfire I
Coal Size/Type: Rice
Stove/Furnace Make: Keystoker, LL & CoalTrol
Stove/Furnace Model: 90K, Hyfire I, VF3000 Soon

Re: efficiency loss

PostBy: cjkirvan On: Thu Nov 20, 2008 3:50 pm

system is set up for continuous circulation with valves on each zone supply branch. I neck down the valves to decrease flow rate and increase residence time in the boiler. It seems as though the fire is not being pulled sufficiently into the firetube. It also looks like there are lots of clinkers and ash in the firetube, should I take the fan off and clean that out. Do you think it would help?
cjkirvan
 
Stove/Furnace Make: AHS Coal Gun
Stove/Furnace Model: S 260

Re: efficiency loss

PostBy: PatrickAHS On: Thu Nov 20, 2008 5:21 pm

There is a possibility that the heat exchanger has become plugged due to condensation mixing with flyash. This condensation is likely to have occurred if you haven't operated the boiler at high enough of a temperature. What temperature have you been operating the boiler at for the last two years? Have you checked heat exchanger and the cyclone for obstructions? Have you cleaned the boiler in the off season?
PatrickAHS
 
Stove/Furnace Make: Alternate Heating Systems LLC

Re: efficiency loss

PostBy: cjkirvan On: Thu Nov 20, 2008 6:07 pm

I'm ashamed to admit that I have not cleaned the boiler in the off season. I am going to florida for ten days and will let the boiler cycle off so I can clean it when I return. I'm pretty sure I know how to clean the cyclone (through the floo ring, correct?) How do I clean the heat exchanger? By removing the fan? And I have been operating the boiler at 125-140 degrees. what temperature do you recommend to eliminate the condensation?
cjkirvan
 
Stove/Furnace Make: AHS Coal Gun
Stove/Furnace Model: S 260

Re: efficiency loss

PostBy: PatrickAHS On: Thu Nov 20, 2008 6:50 pm

You can clean the cyclone by first removing the exhaust pipe, then unbolt the flange where the pipe connects to the boiler, that will give you access to the cyclone. Clean the cyclone with a wire brush. Then make sure ash is cleared from the funnel at the bottom of the cyclone. That hole can be accessed from the bottom as well.

Leave the cyclone disassembled.

Next, remove the fan assembly which will give you access to the swirl chamber. Clean inner and outer sections of the heat exchanger with a long handled wire brush and a shop vac.

Make sure you clear the hole between the cyclone and the heat exchanger. This is best done by running a brush through the hole from the cyclone side. Check to see if anything fell into the heat exchanger from cleaning that hole. If so, remove the debris.

Reassemble the boiler. It is best to install a new gasket at the cyclone flange.

Also, the Coal Gun should be operated at a high enough temperature to have 150 degree return water. That should eliminate condensation. Thus, your operating temperature becomes relative to the amount of return water in your zones. I would generally suggest 180 as the best minimum operating temperature.
PatrickAHS
 
Stove/Furnace Make: Alternate Heating Systems LLC

Re: efficiency loss

PostBy: U235a4 On: Thu Nov 20, 2008 8:36 pm

Here is what I found when I did a spring cleaning and repair this summer I'm not sure how long since the last cleaning but the boiler is a 1958 AA260m.

http://nepacrossroads.com/about6534.html
U235a4
 
Stove/Furnace Make: 1958 Axeman-Anderson
Stove/Furnace Model: 260M

Re: efficiency loss

PostBy: Yanche On: Thu Nov 20, 2008 8:47 pm

At the end of last season my AHS had similar symptoms. When I cleaned it I found ash in all the places Partrick suggests. There was caked ash between the two concentric cyclone tubes just under the exhaust pipe. Clearly it was restricting the combustion air flow through the boiler. I also had ash buildup where the combustion gases first enter the heat exchanger, i.e. right about the height of the burning coal. I attribute the buildup as a result of too high a burning fire in the boiler and ash flakes coming off the burning coal being sucked into the heat exchanger because the level of the burning coal was at the same height as the entrance to the heat exchanger.

My cone or funnel at the bottom of my cyclone has welding splatter which catches ash and leads to a buildup of ash.
Question to Patrick. Should the bottom of the funnel normally be clear of ash? Or should there be some buildup at the bottom of the cone which gets reduced each time the grate ashes?

On my boiler the top of the cyclone where the flue pipe connects did not have a gasket. Just an red RTV silicone made-in-place gasket. What remained after disassembly was sufficient to re-use.

In addition to Patrick's caution about return water temperature, I would suggest not to use wet coal, at least wet coal that gets into the combustion chamber. Adding moisture to the combustion chamber would likely increase the clumping of fly ash. Perhaps the heating of the coal hopper is sufficient to remove any water in newly added coal.

It would be interesting to use a manometer to monitor combustion air flow through the boiler. Similar to the use of a manometer to monitor degradation of filters in an air handler. Second question to Patrick. Which would be more appropriate. Differential measurement boiler exhaust breach to ash container area or differential measurement exhaust breach to closed inspection port door.
Yanche
 
Stoker Coal Boiler: Alternate Heating Systems S-130
Coal Size/Type: Anthracite Pea

Re: efficiency loss

PostBy: PatrickAHS On: Fri Nov 21, 2008 11:57 am

Yanche,

The thing to watch for with the hole at the bottom of the funnel is a permanent blockage / "plugged up".

It is fine to reuse the RTV silicone, as long as it is sealed.

If you were to measure air flow, it would be best to do from the sight tube with the boiler full of coal. This will give you a reading of the pressure from the fire pot itself.
PatrickAHS
 
Stove/Furnace Make: Alternate Heating Systems LLC

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