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Heat storage on for gassafire boilers.

Started by Joe Hillmann, November 06, 2014, 11:56:10 AM

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Joe Hillmann

My father in law has a gassafire boiler made in Germany.  I don't know much more about it than that.

The problem he is having with it is it can't run all night.  He has to feed it in the middle of the night or the fire goes out.  And it isn't even cold here yet.  He is heating a 1,500 or so sqft shop with heat in the floor as well as a 1200sqft or so log cabin with pex tubing nailed under the subfloor.  The shop is pretty well insulated,  the cabin walls are not insulated.

I have suggested to him that it may have been designed to heat a large tank of water, let the fire die out and then use the heat in the tank to heat the house through the rest of the night.

My questions are: Is it common/does it work to use heat storage with gassafire boilers?  And how many gallons of storage would be needed?  He has a 250 gallon tank he could use but I am thinking more like 1000 gallons would be needed.  Is there a way to calculate the heat storage and how much heat the cabin and shop require?

pook

Hi,

One question, does the fire die out or does all the wood burn up?

Joe Hillmann


doctorb

Lots of questions:

1.  Is this a new boiler to him or just a new problem on a boiler that has worked well in past years?
2.  Does the water heat up appropriately while the boiler is running?  In other words, does the boiler cycle on and off raising the water temp and then kicking back on again when the water cools?
3.  How fast does the water cool once the boiler cycles off?
4.  Is the piping for the system the correct size?  If the pipes are too small, then the water returning to the boiler is too cool and the boiler can never catch up with the heat demand.
5.  How many gallons of water does the furnace hold?

You are right.  Something is dramatically wrong.  Could be user error, but this sounds like a system problem to me. 
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

pook

your heating area is small enough that even a small boiler should work but that was my first thought that maybe your boiler is too small for the area your trying to heat.

doctorb hit on many other questions I should have asked though.


pook

do you know what the BTU output of this boiler is?

Joe Hillmann

I can't answer most of your questions.  I don't know much about the boiler.  I think he said all his lines are 3/4"  I know for sure they are larger than 1/2".

The boiler is new to him but used.  Last year he had a different boiler but heating the same shed and house.  On the coldest days (-35) it could maybe go 10 hours before running low on wood.  On fall days it only had to be tended once a day and even then it wouldn't have used up all the wood.  The firebox itself on this one is maybe 3/4 the size of the old one but this one is supposed to be much more efficient.

I don't know how much coolant the system holds.  He had 150 gallons and still has 25 gallons left but one time the blow off valve opened and some was dumped on the ground.

I don't know if the system cycles on and off like it should. But he has experience with traditional boilers so I think he would notice if it was staying on all the time.

I have no idea on how quickly it cools off.

I don't know the btu output.

gspren

   Sounds like either the controls are set wrong or they are malfunctioning.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

doctorb

My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

WmFritz

Joe, I just spent a half hour typing a detailed post, switched screens to use the calculator and lost everything.  >:(

I'll try again with the amended version.  :D

Most if not all European Gassers that I know of, recommend storage.  I have one that I've run for two years without. Think of storage like a battery. You charge the battery when it's convenient, then the system can draw on the battery when it needs to.

As far as storage size... I've read the Pro's recommend a minimum of 7 gallons of storage to every 1000 btu's your unit is rated.

For example, my boiler is rated @ 85,000 btu's. That would require a minimum of 595 gallons, were I to add storage.  7x85=595.  My unit holds 20 gallons of water in the jacket. It heats a very poorly insulated 1200 or 1500 sq ft ranch (I forget) with a full basement through the  gas forced air furnace. The t-stat is set @73°-74° all winter and gets fed 3 times a day on the very coldest days. Gassers have to have dry, seasoned splits.

You need to do some homework and find out what unit we're talking about... German? Maybe Froling...Tarm? There's a laundry list of European Gasser's. If it has Lamba controls (expensive) or conventional?
~Bill

2012 Homebuilt Bandmill
1959 Detroit built Ferguson TO35

Holmes

A 1000 gallon tank can hold about 12 hours of useful heat, heated to 180 degrees.  1000 gallons x 8.3 lb per gallons = 8,300 lbs x 60 degree delta t [ useable water temperature 180 to 120 degrees} 498,000 btu's  divided by 42,000 btu per hour heat loss = about 12 hrs of heating capacity.
  Is this an indoor boiler?
Think like a farmer.

WmFritz

As far as how much heat the buildings require... you'll need a heat loss calculator (Google is your friend).  You need to plug in all the buildings criteria and get an estimated heat loss for your areas heating degree days. There are free calculators online.
~Bill

2012 Homebuilt Bandmill
1959 Detroit built Ferguson TO35

Joe Hillmann

Quote from: WmFritz on November 06, 2014, 07:00:05 PM

You need to do some homework and find out what unit we're talking about... German? Maybe Froling...Tarm? There's a laundry list of European Gasser's. If it has Lamba controls (expensive) or conventional?

I am not sure but there is a computer attached to it as well as wifi so it can be controlled and monitored from anywhere. I assume that would be the lamba control?

Joe Hillmann

Quote from: Holmes on November 06, 2014, 07:05:51 PM
A 1000 gallon tank can hold about 12 hours of useful heat, heated to 180 degrees.  1000 gallons x 8.3 lb per gallons = 8,300 lbs x 60 degree delta t [ useable water temperature 180 to 120 degrees} 498,000 btu's  divided by 42,000 btu per hour heat loss = about 12 hrs of heating capacity.
  Is this an indoor boiler?

It is an indoor boiler.  It is in the shed.

r.man

Firebox size is important to know as well and is the wood supply basically the same this year?
Life is too short or my list is too long, not sure which. Dec 2014

Joe Hillmann

Quote from: r.man on November 07, 2014, 10:12:50 AM
Firebox size is important to know as well and is the wood supply basically the same this year?

The wood supply this year is dryer and more hardwood than last year.  By the end of last year he was cutting trees to burn the next day.  Although the wood he has now was cut this summer so it isn't as dry as it should be for a gassafire.

I also just found out that the previous owner had a bulk milk tank that had a heat exchanger in it.  So it sounds like he had it filled with water to use as storage.


WmFritz

Quote from: Joe Hillmann on November 07, 2014, 10:49:31 AM
Quote from: r.man on November 07, 2014, 10:12:50 AM
Firebox size is important to know as well and is the wood supply basically the same this year?

The wood supply this year is dryer and more hardwood than last year.  By the end of last year he was cutting trees to burn the next day.  Although the wood he has now was cut this summer so it isn't as dry as it should be for a gassafire.

I also just found out that the previous owner had a bulk milk tank that had a heat exchanger in it.  So it sounds like he had it filled with water to use as storage.



Depends on the species of wood he's cutting. Ash.. he's good too go, oak ... can't use till next year.

Two more questions: 1. What was the old boiler rated for (or firebox size if you don't know) ?                                                  2. From the shed to the house,  are the lines buried or is the shed attached to the house?
~Bill

2012 Homebuilt Bandmill
1959 Detroit built Ferguson TO35

doctorb

Quote from: Joe Hillmann on November 07, 2014, 09:59:25 AM
It is an indoor boiler.  It is in the shed.

I have an outdoor boiler and it's in a shed.  While some manufacturers allow their boilers to be placed in either location, most do not.  Most indoor boilers are inside.
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

Gary_C

If the boiler is running out of fuel, you do not have a storage problem, you have a heat loss problem. Find out where the heat is going.
Never take life seriously. Nobody gets out alive anyway.

Cornishman

Have you good insulation under your under floor heating pipes.

Ford_man

You said it holds 150 gal but it only has 25gal in it now. Maybe the water thermostat is set to high, or it is not working like it supposed to and it is boiling the water away. water temp should be around 170-185. If the old wood burner worked alright then I would think there is something wrong with the new one. splitwood_smiley

bandmiller2

Does the furnace have grates or does the fire sit in the ash bed. Sounds like its getting too much air, and a hot quick fire that burns out too soon. Possibly try larger chunks of wood. Even with heat storage a fella doesn't want to have to relight his furnace every morning. Frank C.
A man armed with common sense is packing a big piece

Joe Hillmann

Quote from: Cornishman on November 17, 2014, 03:56:30 PM
Have you good insulation under your under floor heating pipes.

There is 3 inches of foam under the shed floor.  The pipe to the house is insulated with spray foam so it has 4 to 6 inches of insulation on all sides.

Joe Hillmann

Quote from: Ford_man on November 17, 2014, 04:56:28 PM
You said it holds 150 gal but it only has 25gal in it now. Maybe the water thermostat is set to high, or it is not working like it supposed to and it is boiling the water away. water temp should be around 170-185. If the old wood burner worked alright then I would think there is something wrong with the new one. splitwood_smiley

You misunderstood.  I meant out of the original 150 gallons of coolant he had  he still has 25 gallons left over that was never used in the boiler.

Joe Hillmann

Quote from: bandmiller2 on November 17, 2014, 08:35:00 PM
Does the furnace have grates or does the fire sit in the ash bed. Sounds like its getting too much air, and a hot quick fire that burns out too soon. Possibly try larger chunks of wood. Even with heat storage a fella doesn't want to have to relight his furnace every morning. Frank C.

It is a gasifier boiler so the the wood sits on a grate and once the fire is lit the flames are below the grate.  The draft created when it is running keeps most of the ash out of the fire box.

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