Another Launch Temp Thread......

[BoilerMan]

I've been wondering this for awhile. Those with storage, how do you get your boiler to shut down the pump or loading unit after the storage is hot top to bottom?

For Example:
I load up the boiler, fire it up, boiler temp hits 160, pump launches, gasification for three hours or so, and as the coals are consumed, and the flue temp drops below setpoint, fan turns off. Pump runs till boiler is down to 155 (160 pump launch - 5 pump hysterisis), then residual heat launches pump again at 160, load only returns water at 149 (min return temp) and after 10 min of very little heat drawn from boiler due to margional delta allowed by min return, boiler back to 155, pump turns off.

This cycle repeats itself usually about 5 times, or around an extra hour of total pump run time with little heat drawn from the boiler. I with I could set the pump launch higher than 160, as the min return temp is a high 149F (65C) which is only 6 degrees below pump drop out temp. If I set the pump hysterisis lower it cycles during ramp-up, I thought 5 degrees was a bit narrow. Any thoughts? I hope this all made some sense......

TS

 

[maple1]

My loading unit pump is turned on & off primarily by flue temp stat. Therefore at end of burn, the pump stops when flue cools to setpoint and the rest of the heat coasts to storage by convection.

I say primarily as the power to the pump also goes through an aquastat that will start the pump if by chance something happens to the flue stat & the boiler gets to 190 or so.

 

[kopeck]

Well, if I overload my boiler (which is kind of what I think you are talking about) it will just cycle until it moved the heat or the fire is done.

It never seems to "give up", it's tries to finish the burn. I guess if things got bad it would go into an overheat and open up my largest zone to dump heat.

The key is matching how you load to your boiler to the heat load. I find one full load is good for about 40 degrees of rise in my tank. Of course if it's really cold then the house is going to suck up some of that so you mileage may vary.

Then aging maybe I'm completely missing the boat here!

K

 

[BoilerMan]

Not overheating, or overloading, it always happens at the end of the burn. I am only allowed to return water to the boiler at 149, and the pump drops out at 155 so it takes several cycles of this until the coals are out and not heating the water jacket back to 160. I've set my flue temp to 210, but maybe thats too high, it doesn't leave me with much charcoal to start the next fire.

TS

 

[kopeck]

Not overheating, or overloading, it always happens at the end of the burn. I am only allowed to return water to the boiler at 149, and the pump drops out at 155 so it takes several cycles of this until the coals are out and not heating the water jacket back to 160. I've set my flue temp to 210, but maybe thats too high, it doesn't leave me with much charcoal to start the next fire.

TS

OK...Hmm.

Mine is set to 90 C (194 F). I've thought about bumping it up a hair because my blower runs forever after the fire has died out. I often see people talk about there being some coals left over to reignite their fires when the time comes. My boiler leaves me with nothing but dust.

It's set per the manual.

K

 

[BoilerMan]

It seems like it's either the fan that runs forever of the circulator.......

TS

 

[goosegunner]

It seems like it's either the fan that runs forever of the circulator.......

TS

I like to run my 1000 gallons of storage up to 185 top to bottom. That will really make your pump run a long time if bottom of storage is 180+.

I have my controller wired to a switched outlet to pump. I can turn it off if I am around after the load burns down and boiler cools a little.

gg

 

[maple1]

So am I understanding right, that your fan is controlled by flue temps, and your pump is controlled by water temps?

 

[Fred61]

I only heat my unpressurized storage with my boiler and distribute to load from heat exchanger coil immersed in the tank. I can get away with this set-up because I have such a light heating load. If I remember correctly you are also super insulated. I removed the circulator launch from the boiler controller and set it up using a Tekmar 156 solar control and am able to make use of the differential temperature and max temperature features. The boiler combustion fan which is still controlled by the boiler control will still cycle, keeping the boiler at operating temperature until the fire goes out or it runs out of wood and goes into low temperature shutdown.
Since I only burn one three or four hour fire a day and am usually present or not too far away during this time and have a pretty good idea how much wood to load, most of these controls are usually meaningless to me. I have developed a sixth sense to gauge when the storage is hot enough and I just go down and shut off the boiler master switch. If there is too much wood in the boiler and the coals insist on glowing instead of going out, my overheat circulator launches and pumps water through my overheat coil in the bottom of the storage tank. It's usually a small amount of heat and normally doesn't change the temperature of the storage at the top where I take my reading.

 

[dogwood]

Kopeck, that's a useful bit of information about your getting around 40 storage temperature rise out of a burn, if the house isn't sucking up too much of the heat as you go. How many gallons is your storage tank and what are you typically burning to get that result?

Boiler and storage size would also make that figure vary for others, along with the type wood you're burning, but I'm guessing 40 rise is a good ballpark figure. You must need to know how to size your load so as not to overheat your tank and run into the situation Taylor is asking about. I wonder what kind of temperature rise per full load others with storage are getting.

Thanks for raising this question Taylor. I hope you get a clear answer or post what you figure out is your solution. An ounce of prevention is worth a pound of cure, but sometimes you might need the cure, in this case the shut down you mention. I'd like to hear your solution and hopefully work it into my wiring schematic as I'm moving on to that phase of our install. I'd like to have any and all fail-safes in place for overheating, electrical outage, circ failure, or anything else, so my wife can safely run this system when I'm away half the week at work. (I'm also thinking about smoke alarms, CO2 detectors, and a sprinkler heads, but that's off-topic).

Mike

 

[maple1]

Could you simply try upping your pump launch & hysterisis (differential) a bit? Say to 165/10?

Maybe if that sees some improvement but not enough, go another 5° on both?

Just thinking a 5° differential seems pretty small.

 

[kopeck]

Kopeck, that's a useful bit of information about your getting around 40 storage temperature rise out of a burn, if the house isn't sucking up too much of the heat as you go. How many gallons is your storage tank and what are you typically burning to get that result?

Boiler and storage size would also make that figure vary for others, along with the type wood you're burning, but I'm guessing 40 rise is a good ballpark figure. You must need to know how to size your load so as not to overheat your tank and run into the situation Taylor is asking about. I wonder what kind of temperature rise per full load others with storage are getting.

Thanks for raising this question Taylor. I hope you get a clear answer or post what you figure out is your solution. An ounce of prevention is worth a pound of cure, but sometimes you might need the cure, in this case the shut down you mention. I'd like to hear your solution and hopefully work it into my wiring schematic as I'm moving on to that phase of our install. I'd like to have any and all fail-safes in place for overheating, electrical outage, circ failure, or anything else, so my wife can safely run this system when I'm away half the week at work. (I'm also thinking about smoke alarms, CO2 detectors, and a sprinkler heads, but that's off-topic).

Mike

I have a Tarm Solo Innova 30 feeding an 820 heat bank (http://www.americansolartechnics.com/heatbank820.html).

I had the fellow that sold me the boiler over to commission it and he said to expect a 40 degree rise per load. That was just a well educated guess as like you said there's some variables in there but I've found that with little load from the house, burning red maple, cherry and some red oak it almost works out perfectly to 40 degrees.

It's a pretty easy number to work with when you are figuring a load as well. When the cold really sets in I just fill the box and walk away. At night that might mean throwing a few more sticks on before I go to bed if it's really cold out and the house is sucking up the heat before it goes to storage.

K

 

[stee6043]

For those of us with "old school" boilers there is really only one way to automatically shut off the pump after your storage return temps exceed the max pump-on temp on the boiler and that is with a differential setpoint controller. They are pretty affordable and readily available, similar to what is mentioned above.

I personally just slow my pump down during the last part of the burn and let my pump run until I get up to go to work in the morning. I swing by the boiler and shut it off manually. My burns usually quit at 2 or 3AM so I only really have a few hours of "wasted pump on time" during an average day.

 

[BoilerMan]

So am I understanding right, that your fan is controlled by flue temps, and your pump is controlled by water temps?

Exactly.

TS

 

[BoilerMan]

Could you simply try upping your pump launch & hysterisis (differential) a bit? Say to 165/10?

Maybe if that sees some improvement but not enough, go another 5° on both?

Just thinking a 5° differential seems pretty small.

160F is the highest it will go...... I wish I could go 165/10. I've tried 160 (highest) and 10 diff, but the min return is 149F and turning off the boiler at 150 with a 1 degree delta means the pump will run for hours and hours moving basically no heat.

I'm not heating storage pre se, it's a really thick slab, but I have a Taco (Tekmar) injection controller, with the return sensor after all loads back to the boiler, so the injection control will back off the injection circulator if the return water to the boiler ever goes below 149F no matter what other loads are calling (electronic return protection). So this leaves me with 6 degrees to work with (160-5) at the end of the burn. If I turn the diff up to 10 then 160-10 is 150 pump shutdown and 149 returning to the boiler.........

I too only burn one 3-4 hour run/day, and have to turn off the circ manually, which is fine. But even with the boiler back to 155, the live coals still will raise the small (32 gal) water jacket back up to 190+ in 30 or 40 minutes. My conclusion is that a higher pump launch temp and wider differential would solve this whole problem, keeping all the temps well above the min return temp and allowing me to effectivly pull the heat from the boiler. All without excessive pump run time, and excessive cycleing of the pump at end of burn.

TS

 

[Fred61]

I'm not sure if I an correctly understanding the whole scenario. What about adding another temp sensor and circulator like I have for overheat, set to launch at ~say around 200* and let them run independently of all other controls through the same heat circuit.

 

[Armaton]

Taylor, if I remember correctly, some of the EKO users were getting erroneous launch and shutdown temps due to the insulation and placement of their sensors, and adjusting the placement of them helped to correct it. Could you move yours and "trick" it into thinking it was a touch cooler than it is? Then may be possible to launch at actually 165-170 and still get your 10 degree diff? Just a thought.

 

[ozzie88]

Set your boiler to shut off pump&fan at a certain temp, like 180* or so your tanks may only be 160* or so,like my unit boiler runs 20* hotter than tanks. Then wire in a snap-switch set at likke say come ON at 180* and off at 160*, this will put rest of heat into your tanks and keep from over-heat, when unit gets down in temp again it will come back on, works fine on my unit it I explaned it ok to you??

 

[Armaton]

Doesn't have storage, except for the thermal mass in his floor, and uses "Bang Bang" for boiler protection.

 

[BoilerMan]

Not exactly "bang bang" just not a thermostatic recirculation valve. Still prevents water from ever going below 149. This is really the problem......the 149 min return temp is it were lower, or the launch temp higher. 160 is the highest, and 149F (65C) is what is stated in the manual for return protection. Any other thoughts, I've been doing what others are I guess by simply turning it off manually.

TS