I'm Torn Between KA-6 and Harmon VF3000

Hi Hollfeld,

I was torn between the same 2 boilers and went with the K-6. I think both are great boilers but the deciding factor was that you can pick up the phone and call Keystoker directly and speak with the owner Jim, they even have an after hours emergancy number to call. The 2 Harman dealers here have never sold a boiler and have no knowledge at all, which seems to be quiet common from some of the other members comments on here. I'm sure that the Harman is a great boiler but I like the customer service you get from Keystoker direct, which to me is worth the extra money . As far as the wait for the K-6, I spoke to Keystoker last week and they are making the K-6 now and should be shipping them out within the next 3 weeks.

Sting wrote:If you truly want automatic and fault tolerant fail over from coal boiler to oil hot water heat - install one appliance for coal and one for oil in parallel on your load. (This can be as automatic or as manual a fail over installation as you wish for - or can afford - of care to tinker with) The coal boiler will work better because its designed for one fuel use and so will the oil boiler. In the long run you will save $$$$$

Dual fuel appliances are dual headaches -- but there goes my opinion again

I have to agree with Sting here, not only is it a lot cheaper and more efficient but gives you 100% backup. I personally would avoid dual fuel units like the plauge.

Tarm dual fuels tend to burn holes in the baffle between the solid fuel and oil side when the oil is used a lot. They have inherent problems no matter what the brand.

The KA-6 can be vented out of a 6" flue. To switch from coal to oil on the KA-6 requires that the oil nozzle be installed, and a flick of the switch. Total time to switch, less than a minute. The KA-6 makes the Harman seem like a toy, plus Keystoker has never gone into bankruptcy and customer service is second to none.

Mike

The KA-6 can be vented out of a 6" flue

The k6 calls for a 8" flue in the specs. You might get away with a 6" depending on your chimney.
but you might have a problem in the summer when it is trying to Idle when making DHW.
I remember reading some posts that the K6 fire goes out sometimes when Idling.
maybe it is because it is not connected to the proper size chimney.

The 6" flue will actually help out in the summer, as it will take less heat to keep the draft going, and in the winter the 6" flue is more than large enough for it. Keystoker even has given a 6" flue its blessing. I have several in the field running on 6" flues with no problems.

I spoke to a factory rep for the K6 and asked about how critical the 8" chimney is and he kinda hemed and hawed and said "well maybe you will have enough draft with a 6" but then again maybe not"

Another thing.... it is against code to reduce the stack pipe to a smaller size.

There's another potential problem with dual fuel coal boilers that's never mentioned. Notice I said potential problem, depending on operating conditions. All coal has some sulfur in it, hence the exhaust gases and/or fly ash has sulfur in it. The other fuel oil, natural gas, propane produces H2O during the combustion process. Under certain operating conditions like low return water temperature the H2O will condense and combine with the sulfur to make highly acidic sulfur components that can harm your boiler and will harm your flue pipes. When do you get low return water temperatures? Some radiant heat system designs always have low return water temperatures. If the coal fire goes out and the manual or automatic switch over allows the system water to cool, you will have low return water temperatures. Two separate fuel boilers with individual chimneys don't have this problem.

I don't believe that a Ka6 will have any problem with a 6" chimney.. I agree with Mike on the summer scenario, a 6" will pull a more reliable draft in warm weather.

The only time I see where maximum chimney capacity is needed is when the stoker is running with a full bed of coal.. which would be when it is under full load, which is when the weather is really cold,, Cold weather provides a greater temp differential for the chimney and you have more draft..

I know they are different animals, but if an AA or AHS 130 can work with a 5" flue and the 260,000 BTU version work with a 6" flue,, then I don't see the 6" a limiting or safety factor for a Ka6 with much lower BTU output [hot exhaust gas output]..

And yes the AA and AHS use induced draft but in my instalation, I see a negative draft all the time when the combustion fan is running,, and this is with an AA260 with 6" flue pipe. My chimney is only 18' high..

I'm not sure which state would say it is against code to reduce a flue size... if it always pulls a negative draft in the combustion chamber then the chimney draft is adequate..

Greg L

While reducing the flue size from 8" to 6" may work under some operating conditions, flue sizing is based on the maximum possible demand and should not be reduced. If that boiler would work under all conditons with a 6" flue, it would have been built with a 6" vent. It is clearly designated as requiring an 8" flue on their website. I assume Keystoker is tested by UL or Warnock-Hersey or some other llab. If so it was tested and listed with an 8" flue. Unless you get it in writing from Keystoker, I would not reduce the flue.

All dual fuels that I am aware of are oil/coal. Yanche is correct that if you were to run gas and coal, or gas and oil together there would be serious problems with the condensation inside the flue. I believe that what the "single appliance per flue" code is set up for are those two possible combinations plus wood and any other type of fuel together as the possibility of a chimney fire with a resulting blockage from the fire.

Mike

I actually have the opposite problem. My chimney is 12x12. With the Harman I have to line the chimney since the required flu pipe is quite small compared to the area of my chimney. I just talked to Keystoker 5 minutes ago about the KA-6 which requires a 8" pipe and they said it will work just fine with my 12x12 chimney and no liner is required. "No problems drafting in the summer". Figure the cost of the liner is at least $400 so the size of your chimney can be a deciding factor in stove selection.

Also if you are looking at the oil burner option for the Keystoker they use a Becket gun which is a little better or at least more popular than the oil gun you get on the Harmon.

The KA-6 I just sent out has a 6" collar on it. It is set up for a power vent. To convert it from power vent to natural vent requires that the fume switch be taken out of the loop, and connect that 6" collar to the chimney with 6" pipe and off you go. My Alaska 140, which is rated at 170,000 btus, vs. the 122,000 btus of the KA-6 and it runs all day on that 6" flue with a .04 draft. I too have spoken with Keystoker a couple of times, and a 6" flue is no problem on it. The proof is in the pudding.

Mike