Cold start boiler, power venting and other issues

[muncybob]

I've had two installers to my house to get an idea on installation costs. Neither has ever heard of a gasifier and neither has installed any type of boiler utilizing water heat storage...both of these situations make me nervous but to this point I have not found anybody else in my area to do the install.

The 1st person and I discussed power venting the oil boiler to use as a back up unit and free up the existing chimney for a wood boiler. Problem is he stated it would be against code due to location of windows. 2nd person stated this also but then asked why I had not considered another part of the house and run the ducting through a crawl space to power vent apprx. 22' away from the boiler and be well within code....made me wonder why #1 installer had not thought of that? My concern is the crawl space gets very cold and wouldn't the pipe create some condensation if the boiler was used on a cold day? The vent outlet would be on the side of the house which gets prevailing winds...is this a concern?


#1 installer had suggested an indirect dhw tank and said he could make my existing oil boiler a cold fire unit. It is an old Axeman-Anderson boiler with hot water coil. Does this sound legit? Wouldn't an indirect tank benefit me since my oil boiler has very little water storage regardles if it's cold fire or not? He stated that the Newmac combination boiler would not benefit from the indirect tank since it had to keep it's much larger volume of water storage up to temp all the time?

#2 installer thought water storage makes sense but was concerned about running wood boiler at full burn if house is not calling for heat and water storage tank was up to max temp? He also thought the water storage tank(hopefuly a propane tank) would be like a large radiator and make the basement it sits in too warm even if it's insulated. I do want some heat in the basement but not such that it gets too warm.

Finally, the Mrs. is very concerned about having a wood boiler in close proximity to the oil boiler(may be only 2' apart).

Any thoughts on these "issues"

 

[Dredknot]

As an installer of oil boilers, I can say not to converty your Axeman into a cold start. Two common poroblems with this is the boiler vessel will shrink a little when if falls down to room tempeture and the gasket at the coil plate will most likely leak. The second problem is the amount of scale that may build up in the boiler when it fires off from a cold start, this will possably cause the vessell to plug up if not serviced annually.
I believe that the wood boiler has to be 36" away from walls or other appliances.
My opinion on an indirect is it is a good way to store heat from the wood boiler inbetween fires, I would heat it to around 160 degrees and use a mixing valve to temper the out going water to 120 degrees. Also they are very well insulated and most manufacures claim a 2 degree loss of heat in a 24hr period, so they do not emitt that much heat into the basement.

Hope this helps,

 

[muncybob]

Thanks for the info on the Axeman. I'm beginning to wonder if I should use installer#1 as he seems to either overlook some things or just be wrong. He stated the dealer of the Newmac said not to use the indirect tank since the Newmac boiler has 65 gallons onboard water storage and the indirect tank would not be very efficient due to this?

 

[jebatty]

#2 installer thought ... the water storage tank(hopefuly a propane tank) would be like a large radiator and make the basement it sits in too warm even if it’s insulated. I do want some heat in the basement but not such that it gets too warm.

I would not be concerned about this. I use a 1000 gal LP tank as a radiator to heat my space. It's 19' long and insulated with 6" fiberglass, except for 6' left open to act as the heating radiator. Fully insulated, even if you need more than 6", should be no particular issue.

#2 installer thought water storage makes sense but was concerned about running wood boiler at full burn if house is not calling for heat and water storage tank was up to max temp?

I guess the question is why would you fire the wood boiler when you don't need the heat? Second, if the heat is not needed, the wood boiler will go into idling mode, not desirable from an efficiency perspective but not dangerous and not supplying unneeded heat. This is a non-issue.

 

[steam man]

"The 1st person and I discussed power venting the oil boiler to use as a back up unit and free up the existing chimney for a wood boiler. Problem is he stated it would be against code due to location of windows. 2nd person stated this also but then asked why I had not considered another part of the house and run the ducting through a crawl space to power vent apprx. 22’ away from the boiler and be well within code....made me wonder why #1 installer had not thought of that? My concern is the crawl space gets very cold and wouldn’t the pipe create some condensation if the boiler was used on a cold day? The vent outlet would be on the side of the house which gets prevailing winds...is this a concern?

#1 installer had suggested an indirect dhw tank and said he could make my existing oil boiler a cold fire unit. It is an old Axeman-Anderson boiler with hot water coil. Does this sound legit? Wouldn’t an indirect tank benefit me since my oil boiler has very little water storage regardles if it’s cold fire or not? He stated that the Newmac combination boiler would not benefit from the indirect tank since it had to keep it’s much larger volume of water storage up to temp all the time?"

I have a cold start power vented boiler. They normally stay warm all year because of DHW use during the summer along with heating in the winter. This prevents the leaks, condensation/corrosion issues. Mine has gone cold at times (room temp) but the basement is dry and I haven't seen any problems in 18 years. Power venters have issues and can fail and be a maintenance headache. However, stay on top of it and it would will work fine. I am not sure what the power venter has for maximum pipe length. It may work but I would probably suggest a stainless steel Field Controls SWG (5?) with all stainless piping and the outside air kit.

My system is going to utilize the storage as a buffer tank for the wood boiler. When the oil boiler calls for heat it will decide between the tank or firing the burner. I may be in the minority about heat losses through an oil boiler but keeping it warm and operating will reduce corrosion/leaking issues. Again, going against the grain you could pipe your wood/oil boilers in series (and charge a tank) and have a cold start with an indirect set up. I am not sure of the performance of the Axeman boiler using a cold start but I would think you don't want a large water volume.

Mike

 

[BrownianHeatingTech]

The 1st person and I discussed power venting the oil boiler to use as a back up unit and free up the existing chimney for a wood boiler. Problem is he stated it would be against code due to location of windows. 2nd person stated this also but then asked why I had not considered another part of the house and run the ducting through a crawl space to power vent apprx. 22' away from the boiler and be well within code....made me wonder why #1 installer had not thought of that? My concern is the crawl space gets very cold and wouldn't the pipe create some condensation if the boiler was used on a cold day? The vent outlet would be on the side of the house which gets prevailing winds...is this a concern?

Running that far will likely require insulated stainless pipe. Add the cost of a powerventer and the insulated stainless pipe, and you might as well put up a chimney, most likely.

Venting into the prevailing winds will be problematic, as well.

Joe

 

[muncybob]

Jim, I guess what I was trying to ask is could there be a situation when the boiler is on full, house does not need heat(already brought up to temp) and storage tank is at max temp is there a problem? If all is working properly the boiler should go into "idle" I think.....I believe installer was concerned about if the boiler did not go into idle how do I avoid a problem. I countered with using a dump zone that is activated if the boiler goes over temp or if there is an electrical interruption. Since I only vaguely understand everything happening here I sometime wonder if I'm not clear enough on what I'm trying to say.

Joe....so true on the cost factor. I believe the vent, needed piping and labor will be well over a grand. I have a chimney person coming tomorrow to give me some estimates on several things and one of them will be a new double flu chimney. I'm guessing the problems with power venting into prevailing wind side of house will be possible fumes coming back in through open windows on that side?

Mike, I too think a parallel set up is the way to go.

I have given both of the installers this web site and I do hope they use it to gain information from you guys since they have little or no experience in setting up 2 boilers with heat storage. I wish I had the tools and the confidence to attempt this myself but I don't think my heating system is the best way for me to start learning from my mistakes!

 

[BrownianHeatingTech]

Joe....so true on the cost factor. I believe the vent, needed piping and labor will be well over a grand.

I don't know about prices in your area, but with 22 feet of insulated pipe and the powerventer, and wiring and install labor and such, that would be in the two to three grand range around here.

22 feet is a decent chimney, just laid down horizontal instead of vertical.

I'm guessing the problems with power venting into prevailing wind side of house will be possible fumes coming back in through open windows on that side?

That's an issue, as is the potential to discolor the siding, but the real problem is the variability of the draft, which can cause the burner to lock out. Powerventers on the windward side tend to have frequent nuisance lockouts, which become more than a mere nuisance if they happen when you are away from home.

Joe