undersized storage ? how much heat am i wasteing.

I'll defer to the storage experts but here's some thoughts. All parts of the system have to be in some kind of balance. Knowing your heat loss is really what should guide you the most as far as storing BTU's. Baseboards start to lose it down at your low temp (depending on your outdoor temp). The useable BTU's are in the 500g from 185 to 150 degress. A quick calc is about 146,000 I could be wrong here. Doesn't sound like that very much storage for 3000 square feet. If your boiler is oversized compared to small storage it will idle a lot. And it sounds like it is. The boiler should be piped to supply the zones and then put the extra into storage IMHO. That way it will run flat out for a longer period of time and be more efficient. I am not sure yours is piped that way. Doing it your way sounds like you need much larger storage to take advantage of a full burn cycle. You might want to get a heat loss number out here for the pros to suggest things.

Now for a cup of Joe.............

Mike

An extra 500 gal certainly would not hurt if you have room but in the mean time why don't you let your storage deplete more before firing the boiler.You would be surprised how low usable temps you could use if your house is all ready up to temp.

The other end of the teeter-totter is the option of adding more baseboard or radiant panels (especially in any rooms that you might like to keep a little warmer) so you can use more of the storage you have. Radiant underfloor installation might be easier depending on your access and the opinion of your interior decorator. You might be able to double the useful heat you could extract from the storage you have.

Do you have pressurized storage?

I only have 500 gallons of storage and my boiler hardly ever idles.
That's with a full load too. If your boiler is putting out more than the storage can use try smaller loads.

I would vote for trying to run your storage down lower, if your heat system can use lower temps that will leave more space to put the BTUs with the storage you have. From there I would load smaller loads of wood. I have learned that especially with my fireplace insert, a small hot fire will be far better than a big smoky one.

The way you have it described, it sounds like you're building a fire when your storage tank temperature drops down to 150 degrees. Then, because your system is set-up to do so, the boiler goes into idle when the tank temp reaches 185 degrees. This idle happens when there's still a lot of fuel in the firebox, apparently, and that is why you're asking how much heat you're wasting.
I have an open system and am always struggling not to get it too hot and get things boiling. By the way, this is the only wood boiler I've ever had so you should probably take this with a grain of salt, but I always thought that being able to run at higher temps, in order to reduce idling, was one of the main benefits of pressurized storage.
So I gotta ask, why not crank her up to 210 or some other higher number to help ensure a complete burn?

I would also let it go lower, and crank upper the temp up a little.

You will have to experiment to see how low you can go with temps,try 130 then 120 or maybe lower,I take mine down to 100 but every-ones situation will be different and its up to you to find out what will work best for you.

My boiler never idles I build the fire based on the tank temp and what I see maybe the the tempss outside for the next day, I use nofossil's burn calculator for storage, works quite well. I just started a fire and only put 8 or split pieces in to have a small fire, it will shut down probable in 3 hours, my tank temp was at 150 or so. if I have to I will load more wood in and let her go for another 3 hours.
Kinda play it by ear, so to speak.

Steve

Bernard, I'll bet your peaking out at 185* top of tank. Thats not hard to do with pressurized storage. While the top of storage may be 185*, middle and lower temps are much lower. Try moving your sensor to the bottom third of your tank and make that sensor control your boiler pump. I have my boiler aquastat set to go off at 210* I'll bet your boiler will stop idling.

I usually reload when my tanks are between 145-150 and with 1/2 a firebox I charge the tanks to 197 while still supplying all the zone demands.
I have 720 gallons storage, and I wish I had the space for a 1,000 but I don't.
That being said, try and adjust the wood amount as suggested, and let it burn flat out.
The only time I add a little more than I think I need is at night time if the temperatures are really low.

Part of the equation is also based on where your sensor is that says your down to 150... is it low or high or in the middle of the tank? and just how far down the tank does the 150 go? Just the top or all or only half way down and is your water a turbulent mix or do you have stratification? (supply your 185 where the 150 appears for comparison) you need to know where your temps are at to tell you how much hot water you really have. With your current set up chuck172 nails it with smaller loads but the question you are then going to have is "is the amount of heated water you have up to temp going to last you until your next scheduled fire?" If it won't then you can deduce you need added storage. If it will last until the next scheduled load you are in a very sorry predicament. You cannot load any more wood and cannont use that as an excuse to dodge doing the dishes (especially if you let the little lady read the post). You may suffer from knowing he wood you have now will last you longer than anticipated so that means fewer trips to the woods. As well you will have to tie yourself to the whipping post and give yourself 40 lashes and promise yourself you will not waste wood by overfilling the boiler again in writing 1000 times (the sentences must be legible). :lol: sweeet!

On the other hand you could do a test and run your max temp to 195 or so (if your controller will let you) and do a wood consumption analysis gauging your wood consumption in idle vs full bore run time and wood consumptio vs your current set-up consumption etc. You may find that a full bore run with a smaller load and a little/no idling works well. I found with my open system in the summer I could put in a partial load and shut down when my dhw reached temp. (I had a circ running 24-7 to protect the boiler from over heat). The next day I would have some wood and a lot of char and start the process all over. Two face cord would last me most of the summer and practically eliminated my lpg bill for the summer.

chuck172 said:

Bernard, I'll bet your peaking out at 185* top of tank. Thats not hard to do with pressurized storage. While the top of storage may be 185*, middle and lower temps are much lower. Try moving your sensor to the bottom third of your tank and make that sensor control your boiler pump. I have my boiler aquastat set to go off at 210* I'll bet your boiler will stop idling.

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I would also get the sensor in the lower third of the tank if possible. I have a solar tank with two sensors in the same well and even they don't read the same unless the tank has been idle for a time. Sensor placement can make a big difference in how your system responds.

Mike

Stratification is your friend. Should be a bigger dif between top and bottom.
Will

Jeff S said:

An extra 500 gal certainly would not hurt if you have room but in the mean time why don't you let your storage deplete more before firing the boiler.You would be surprised how low usable temps you could use if your house is all ready up to temp.

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I agree. I no longer let my house cool during the day, I keep it a constant 68 or 70. I find that it will maintain easier from a cooler tank than trying to warm it up form say 60.

Try doing a search on stratification. You may find that mixing the water is just robbing potential from your storage. In my mind it is ideal to heat the whole tank to the 185 but drawing the heat out then returning the cooler water and mixing it well in the tank robs the energy you used to heat the water. Making use of a stratified system is more complicated but ensures you ae using the hottest water at all times. I built a simple spreader in my small storage tank from pex for my open system that seems to work well. There is no visible turbulence.

I’m heating about 2000 SF with baseboard and have 500 gallons of storage. I let my storage temp get down to 120 or so before I worry about starting a fire unless it’s a timing issue. My Tarm rarely if ever will idle and generally I’ll heat the tank to 175 to 185 degrees. I usually have one fire a day with about two fireboxes full of wood, give or take depending on temperature.

I echo what many above have said. Hard to believe but my Johnson Controls aquastat on the water coming into my basement (350' from boiler thru UG pex) is set at 88 degrees. So the autostat controls the blower on my air handler and also the pump that circulates water thru the HX in the plenum. I believe the probe tucked under the pipe insulation is probably reading about 10* less so it might be more like 98*. At any rate the temp of the air out of the registers is lukewarm and about the same as what the heat pump puts out. Even baseboards would still give off some significant heat between 120 and 150 I would think. If you have room the extra 500 gal would be great. I think I would try waiting until tank is down to 120 before firing and maybe running up to 190. Maybe this would put you in the ideal situation where the boiler runs flat out keeping house warm and charging tank right up to 190 when it runs out of wood. The extra 500gal would definitely help with this and give ability to have longer periods without firing which fits my work schedule and possibly yours too.