oil boiler and wood stove

[stovepipe?]

I have a new woodstove and new boiler. I get my hot water off my boiler. Each has its own SS liner, stove liner is insulated, but they share a masonry chimney. I've got good draft on both, and the boiler liner has a barometric damper. When I run the stove (most of the time), the draft gets a lot stronger on the boiler flue since its is getting warmed up by the adjacent stove liner. I have been heating the house almost exclusively with the stove, but the boiler still cycles quite a bit to keep itself at temp for domestic hot water. I'm not sure, but it seems like it is more than normal-- increased draft caused by warm flue must be pulling cool air through it and cooling the boiler more rapidly. Do others out there have a similar set-up? how does it work for you?

Also, do people out there have thoughts on how to get hot water more efficently? I was thinkng about putting on an indirect tank-- I've had mixed accounts about whether that set-up is more efficient. (sorry, not exactly a wood-heat question). Would that help with the cycling issue? I would think the boiler would only kick on when the tank dropped in temp, and they are supposed to hold temp pretty well.

 

[Eric Johnson]

I have a similar problem, even though I have a gas boiler that I heat with a wood-fired boiler and heat exchanger. I just turn the gas burner off and use it to store and distribute hot water from the wood boiler. However, I noticed that I was getting warm air from the jacket surrounding the gas boiler going right up the stack. Makes sense. So what I did was stuff some fiberglass insulation in the gas boiler exhaust to keep the air from escaping. I also taped down and tagged the burner switch so that I (or someone else) doesn't try to turn it on when the chimney is blocked.

I know that doesn't answer your question. But I think there's no way to avoid losing some heat up the chimney if you want to use the oil boiler. And I also suspect that having a tankless coil in a boiler that is not generally used for domestic heat is probably not the most efficient way to go. The boiler was designed to provide hot water to your baseboards and/or radiators primarily. The hot water thing is kind of a secondary benefit.

So I think the answer to your question would be to buy an independent hot water heater. If you do that, you probably want to re-configure your boiler settings so that instead of maintaining temp, the burner only goes on when there's a call for heat from the thermostat(s) up in the house. That way you're not using oil or gas to maintain hot water temp that's not being used, but it's available when you need it.

 

[Rhone]

I have this problem. November last year I went through 75 gallons of oil costing me $162 for heating & domestic hot water. This November was a little warmer if I recall, I went through a half a cord of wood and 99 gallons of oil costing me $298. None of the oil was used for heating, and in summer we go through around 20-25 gallons a month. I figured out my boiler has to burn for 2 hours each day to go through that much oil, and none of it was for heating. It must be idling. So, I started paying attention and hearing my boiler going a few minutes every hour, so cold air must be drafting up my oil flue because of my insert warming it up, and that cold air is blowing over the tankless coils in my boiler, cooling it down and since my basement isn't heated cooling it down fast, causing it to kick on for idling. What you describe is correct.

We're kind of in a bind. The best solution is to install a new sealed combustion unit with a tank, but that's too expensive for me and impractical for you as you just bought a new unit. The next best option I think is to convert it over to a tanked system like you said. It will help your boiler idling, it does not stop the draft in your flue when your wood appliance is going so it will continue to suck air out of your basement which must be replaced with cold outside air. The cheapest method, and the one I did, is I shut my boiler off when not in use and turn it on when I'm doing dishes or about to take a shower. That has dropped my oil use from 99 gallons/month to somewhere probably less than 20. Since it's tankless, my boiler takes 5 minutes from when I turn it on, to shower ready temperatures so I turn it on, eat breakfast, shut it off, and take a shower knowing I've shut the thing off so I have a limited amount of hot water (usually that's about 15 minutes). Now, if only my wife were more like that. At night, we turn it on, it heats up the water, and as soon as it clicks off, we turn it off. That gives us enough hot water at night to wash our hands & rinse dishes. Not to say there isn't some risk involved with shutting off your oil boiler in winter. You have to be careful.

On the side of efficiency, the longer your boiler runs the more efficient. With a tankless system, your boiler kicking on for a couple minutes every hour is not as efficient as a tanked system where your boiler will kick on for a longer period of time and stay off for a longer period of time. That's negated by the larger surface area of the tanked system losing more heat than that of the tankless. Also, a tanked system needs an additional pump, whereas a tankless system uses regular water pressure. That pump is a failure point and electricity to run. In the end, with situations like this if the tanked system stops you from idling so much when using your stove, the tanked system will be better. If you do tank it, get a tank wrap to go around it as it's one of those things that should pay for itself usually within a year. Also, make sure you insulate the pipes (tankless or not).

 

[fbelec]

i don't know if these dampers can be used with oil burners but if you get a motorized damper installed on your boiler you can have the best of both worlds. these dampers come on new gas boilers that don't come from the factory with a inducer fan. the damper stays closed keeping the heat in the boiler until the boiler needs to come on then the damper opens then the boiler comes on. the boiler can't come on until the damper is wide open. i know they're for gas boilers but never seen then on oil. might be a code against putting them on oil burners.

 

[babalu87]

I have a powervent on my oil boiler and I havent burned enough oil to have it register on the gauge this season

We have 4 people in the house and the kids get tubby time every other day..........unless one day is pasghetti day

I will be going to a Boilermate before Summer (have one line up and I can get the coil at cost)

 

[elkimmeg]

There are 3 things that can make an older oil burener more effecient. A fire retentioner a motorized damper. and changing the nozzel angle and flow rate.
This post I am sticking with the motorized damper. It works the same as a power vent without the inducer motor
One it holds the heat longer in the boiler and 2 prevents down drafts from cooling the fire box and coils in the burner. It is wired in to open just before the combustion cycle and wired to close x time after completion
Fbelec is correct this is an allowable and energy saving device for oil burners. code only requires it to be installed according to manufactures specs. The hardest part with the installation is getting an electrician that know what he is doing. Or one that will take the time and read the wiring instructions. Simmilar wiring to a Powervent There is a fail safe system that the boiler will not fire till the return signal to the motorized vent is reconised the motorized damper does not open the boiler cannot fire.
I am pressed for time but after bowling tonight I will try to point out other precautions une should consider shutting down your oFHA system with the wood stove and give the pros and con of hot water addon storage systems and other alternatives

 

[Eric Johnson]

Thanks for the information on the motorized damper elkimmeg and fbelec. That sure sounds like a much better solution to my problem than stuffing insulation up into the pipe. Do you think a non-electrician who took the time to read the wiring instructions could wire the thing up, elk?

 

[elkimmeg]

You seem to be very cleaver I think you will be able to wire it in to the right relay curcuits. If you have a problem e-mail me and we should be able to figure it out. My last electrician screwed it up. I figured it out. Part of the problem is we added a zone as well for the adition. He failed to consider that the transformer was designed for only 3 zones and that wiring in 4 dropped the voltage to all zones. This in short time will burn out zone valves. Then he adds another 3 zone transformer.
He so f up the wiring I was getting 18 volts one zone 52 another 28 inbetween. Finally after trying to figure out how messed up it was, I went out bought a new 5 zone transformer and re wired the entire setup. It was easier than trying to figure out what he did. That might also explain why the powervent did not work. It too neded the signal to open which valve when the demand call came in

 

[Rhone]

By the way, the electronic dampers I believe are referred to as Vent Dampers. Doing a search on electronic damper didn't produce anything, but a search on vent damper is a damper placed in the vent itself, that's electronically controlled, closes when the boiler is not running to prevent heat escaping up the chimney and coming down, and prevents the boiler from firing if it's in the closed position. Sure sounds like what's being called an electronic damper.

 

[Rhone]

And, you can see and read about them here http://oee.nrcan.gc.ca/publications/infosource/pub/ici/eii/m92-242-2002-10e.cfm?Text=N&PrintView=N

 

[Eric Johnson]

Thanks for the link Rhonemas. That's a significant savings, and that's at 2000 gas prices.

 

[stovepipe?]

hi all, thanks for all the good info.

elk-- how clever does one have to be do to put in a vent damper do you reckon? I've done plenty of basic wiring-- new circuits to the panel, etc, but nothing too complex. but have a good head on the shoulders. How complex a job was it for your electrician- did it take him an hour? six? also, any further thoughts on the costs/benefits of an indirect tank would be much appreciated.

again thanks for all the good info on this forum-- though with new england weather like this, doesn't seem like the time to be thinking about heat.

 

[Eric Johnson]

Maybe elk can answer both our questions with the following information. Here's my situation:

Gas boiler with 4 zones, each with its own circ. pump and relay. I have one transformer is wired to the burner control and a switch that allows the burner to be turned off. The burner (and appropriate pump(s) kicks on when there's a call for heat from one of the zones AND the boiler water temp is below the aquastat setpoint.

As I understand your last post, the motorized damper is essentially a zone valve, or at least is wired up like one.

 

[stovepipe?]

I have an oil boiler for a steam system, one thermostat-- no separate zones.

 

[elkimmeg]

Vent damper the mechanics are similar to working with any vent. you will have to cut your vent and reessemble it to include the space taken up by the vent damper unit. It helps to have tin snips and a crimping tool drilland sheet metal screws.
In the case of my electrician I sent him off to ty in the pannel while I figured out the mess he made. First you are at an advantage. You are not starting out with a messed up situation. What I did was follow the wiring diagrams in the instruction manual. Twisted the connections together firs before applying the small wire nuts, For zone valves the common voltage is 28 atleast the ones I used.
Following the directions, it should take no more than 1/2 hour to complete . Sorry if I scared a few off it can be done.
Rhome provided the links thanks, but this technology has been available since the late 60's Motorized dampers do retain heat in the boilers and prevent introduction of cold air from entering Ever see you Barometric damper flapping in the wind?

Other things to consider about your FHW system. While the water sits in the pipes it does get cold, Most radiators are llocated on outside walls and many times there feeds run threw overhangs. When it leaves the boiler at 180 drgrees warm water contains a
lot of air. The air promotes heat loose faster and is more susptiable to freezing. If water sits in a pipe and is exposed to outside cold drafts long enough it freezes. I have actually froze up my system 3 times in the 20 pluss years here. All caused by the wood stove producing enough heat that the furnace did not come on, so no circulation in the pipes, Circulating water has less chance to freeze. It will happen when we get that extended cold spell below zero, single digits day time. On the domestic water delivery system, I crack the most remote fawcets to drip one hot one cold. My heating system I charged the zones with antifreeze Rv type Panadol, which holds it antifreeze properties for about 5 years. Walmart $3 a gallon less than 15 gallons for the 3 zones. Problem solved.

Here is how one can tell your system is freezing. In the middle of the night if you wake up to all kinds of pipe banging and shaking sound of watter falls in your walls. You are dangerously close to freezing. Get up and nudge your thermo stats up, hopefully you just saved a DISASTER. YOU now know corrective measures are needed

 

[babalu87]

My heating system I charged the zones with antifreeze Rv type Panadol, which holds it antifreeze properties for about 5 years. Walmart $3 a gallon less than 15 gallons for the 3 zones. Problem solved.

My FHW system is also loaded with anti-freeze
When I finished the upstairs the plumber fill our system with anti-freeze due to the original plumber not running the return/supply for the boiler properly (no room for insulation)

DO NOT USE AUTO/CAR ANTI-FREEZE
It is not viscous enough for your little TACO pumps

 

[drizler]

So you guys are saying that my weil mclean tank storage system with my peerless oil boiler is MORE efficient than the coil method??? I always thought otherwise so I am all ears here since I was considering switching over to a coil when my 10 yr old stainless model craps out. Can you use one of those draft vents with oil. If anyone has any more on this like links ect let me know. I do like you guys and only use the boiler for hot water and when the "damned wimmen" grab for the stat. I should put a combingation lock on it or something. I have gone through about 1/2 tank of oil since early Nov for 3 people. How does that sound to you guys? Would rigging one of those dampers really pay for itself? Elk .. how low can you go on nozzle size with a 4 zone155K BTU peerless boiler using only 2 zones almost never, one capped off and one for dom hot water. It came with 1.5 and I throttled it down to 1.25 which was the plumb supply's word on how small a nozzle I could use.

 

[Sundeep Arole]

I have a new woodstove and new boiler. I get my hot water off my boiler. Each has its own SS liner, stove liner is insulated, but they share a masonry chimney. I've got good draft on both, and the boiler liner has a barometric damper. When I run the stove (most of the time), the draft gets a lot stronger on the boiler flue since its is getting warmed up by the adjacent stove liner. I have been heating the house almost exclusively with the stove, but the boiler still cycles quite a bit to keep itself at temp for domestic hot water. I'm not sure, but it seems like it is more than normal-- increased draft caused by warm flue must be pulling cool air through it and cooling the boiler more rapidly. Do others out there have a similar set-up? how does it work for you?

Also, do people out there have thoughts on how to get hot water more efficently? I was thinkng about putting on an indirect tank-- I've had mixed accounts about whether that set-up is more efficient. (sorry, not exactly a wood-heat question). Would that help with the cycling issue? I would think the boiler would only kick on when the tank dropped in temp, and they are supposed to hold temp pretty well.

Stovepipe, Rhone - I have been dealing with this as well since I started burning my insert. I've been thinking about this and why it might be happening, as it was hard for me to believe just the heat from the adjacent flue was responsibe for the increased draft. One counter observation I had was that the boiler cycling was just following startup, when the stove (or flue) wasn't as hot. Once the stove was up to temp with a intense fire going, the short cycling was much less. So what I suspected as the cause for the increaded draft in the burner flue was air being pulled up from it due to the venturi vacuum created by the rapidly exiting gases from the insert flue. This past weekend it was warm enough for me to go up the roof and try a experiment, and sure enough, it seems the cycling has stopped for this week. I took a small piece of liner I had left over from the install and used it to temporarily "extend" the oil burner flue so that it was about 2 feet higher than the insert flue; and this was apparently enough to keep the pressure disturbance caused by the insert flue far enough away that it wouldn't interfere with the burner flue draft; and it seems to have done the trick. Sometime in the summer I'll think about how to make the setup more permanant.

Your situation may be different, but just thought I would share this with you so you could see if this seemingly simple solution solves your problem.

 

[Sandor]

Am I missing something here?

Why not just install an electric water heater and be done with it?

For what some are paying a month for hot water (using oil), you could maybe get 6-8 months worth with electric.

 

[BrotherBart]

Am I missing something here?

Why not just install an electric water heater and be done with it?

For what some are paying a month for hot water (using oil), you could maybe get 6-8 months worth with electric.

Thank you Sandor. Exactly what I think every time I read the posts about all of this elaborate water heating gear. For $258 bucks I put in a new electric water heater a few months ago. Nifty little rig on top of it controls energy usage and the thing cost squat to run every month. I have never forgotten to call and have the electricity tank filled.

And finally I have one that takes either heating element off-line if the water level is too low. No more fried elements after power failures where the water heater starts before the well pump has time to refill it.

 

[Sundeep Arole]

Well, if I had the room for a tank, that would be a easy decision to make. But I don't. My boiler actually sits in the kitchen! Furthermore, the plumbing wouldn't be easy if I figured out a place for a tank in my garage or somewhere else, as all the pipes run under the slab. I have what I have, and have to make it work somehow.

 

[elkimmeg]

Driz Right now you are in noman's land Steel boilers can crap out any time after 10 years . A lot depends on your water quality minerals PH ect. It could last 15 years. If you used your boiler for constant heat than the tankless benifits in the winter with a constantly warm to hot fire box. Since your stove has shut the furnace down it has to cycle to warn the hot water and to some degree the fire box. I would say at this point if not cycling much forget fooling around with nozzels. The electronic damper might be the way to squeeze more effeciency out of it. Seriously do not over look insulating as much of your hot water pipes as you can. In the Ash Can I will be adressing homeowner tips and pointers to increase the effeciencies of your duct system

 

[BrotherBart]

Well, if I had the room for a tank, that would be a easy decision to make. But I don't. My boiler actually sits in the kitchen! Furthermore, the plumbing wouldn't be easy if I figured out a place for a tank in my garage or somewhere else, as all the pipes run under the slab. I have what I have, and have to make it work somehow.

I hear ya guy.