Storage Tanks

Smitty what do you have your triple aquastat set at? and does your stoker stoke every single time there is a heat call?

This system is very large.

CoalBurner5 wrote:okay so turn up the aquastat to what? Should I adjust the differentials? Does it make sense that the stoker stokes every time there is a call for heat? It just seems that it there should be times that the heated water in the boiler is enough to satisfy the heat call without the need of stoking...

Any guess to how many gallons are in you "large system"?

How many zones?
Where is the thermostat wired into?
Do you use the tankless coil for DHW?
Was this an old gravity hot water system?

Hard to advise w/o info.

CB5, I don't have a triple hooked to the stoker - that has it's own 4006A. I set that to 170° with a 15° differential. Works well in these temps, but I may have to bump that up 10 or 20 degrees in super-cold single-digit January/February temps. It keeps the boiler water between 155°-165°. The stoker only runs when it drops below 155°.

I have the triple on the boiler set with a 155° low limit and a 20° diff, just to keep the circ. from running when the water is too cold. That aquastat controls the T-stat calls and zone valves, and the indirect HW tank just as it did on the oil boiler alone.

EDIT to add pic: The 4006 is connected to a Reading idle feed rate control box. I keep that set to minimum. The 'stat connects to the T-stat terminals on the bottom of the unit, and when shorted together, cause the stoker/blower to run.

I have 3 zones.
zone one is a house all by itself with cast iron radiators. It has 9 large radiators and about 30 feet of baseboard.
zone two is cast iron 8 inch basesboard 65 feet of baseboard
zone three will be infloor heat consisting of 5 loops of 250 ft.

Boiler does have jacket on it my current settings are:low limit 150 with 10 differential, high limit 170 with 10 differential and I am running a honeywell L7224 triple aquastat.

Yesterday alone temp was 42 degrees and I have one full bucket of ashes.

Wow you've got some gigantic zones there!! Maybe the boiler is too small??

CoalBurner5 wrote:I have 3 zones.
zone one is a house all by itself with cast iron radiators. It has 9 large radiators and about 30 feet of baseboard.
zone two is cast iron 8 inch basesboard 65 feet of baseboard
zone three will be infloor heat consisting of 5 loops of 250 ft.

Boiler does have jacket on it my current settings are:low limit 150 with 10 differential, high limit 170 with 10 differential and I am running a honeywell L7224 triple aquastat.

Yesterday alone temp was 42 degrees and I have one full bucket of ashes.

I use a L7224...you can remove it's cover and watch and read water temp in real-time.

I'm no hydronic guru...so I'll step aside and leave this to those of a higher authority...Peace Out.

yes the system is huge.

but i'm still worried that I have something screwed up with the wiring of this aquastat. What can I do in hopes that the stoker will not fire every single time there is a call for heat. I do have a boiler bypass on the system.

Should I raise my low limit? Should I raise my high limit? Should I adjust my differentials? Should I rewire something? Just confused.

Hello CoalBurner5....Although you have huge zones... I would turn down the low limit to 135 and the high limit to150.
It is your high limit setting that is causing your stoker to run all the time on thermostat call....When thermostat calls for heat, it is the
high limit setting boiler aims to achieve. In my opinion too many people run way too high
water temps on their aquastats...I think high temps waste coal. Heck, I run my temps at lowlimit 130 and high limit 155 works perfect
and with a good cold day boiler will drift up to 180 to 200 sitting idle, waiting for next heat call. Right now temp is sitting at 185F
Now house will not heat up as fast, I like a slow rise in temp. Once house is up to temp 69/70 temp. All baseboards are running warm
and stoker runs alot less. I know these are lower aquastat settings but they work fine for me. Especially that I have ok draft and
on standby boiler water temp creeps up to 180/190 anyway... it all balances out...also to save more coal, Sometimes, such as in shoulder season... I run my TT off the low limit instead of the high limit...that helps conserve even more coal. I don't think you need storage tank. Just more patience waiting for temp to rise to meet a hopefully lower high temp limit on aquastat...and with all that big cast iron radiation heat rise will take longer, but I think you can do it without overly burning hot rads....thus saving coal. Now I am no expert by far, but I have been burning black rocks since 1981. Coal heat is the best... I have oil heat as back up and I have probably used about 50 gallons in the last two years.
Ken

I like this advice of the previous post. Let the low limit trigger the TT terminals. The circulater will run longer and radiators stay warm longer for more comfortable heat. Temperature of the water depends on how adequate the installed radiation is. You might have to raise temp. in real cold weather.

franco b wrote:I like this advice of the previous post.

MEEEEEEEEE 2

but then I have been preaching lower temps and longer circulation times for years

okay I will turn down the aquastat to 135 low limit, 10 differential high limit 150 with 10 differential, but won't my stoker still run every time there is a call for heat.

CoalBurner5 wrote:I do have a boiler bypass on the system.

Do you have it adjusted to temper the water going to the radiators?

When you have a large boiler and multiple small zones, starting the stoker with every heat call will inevitably drive the boiler temperature up to the high limit. In this case, the strategy described by Ken will certainly save some coal and reduce the standby losses of the boiler.

When you have a system with a lot of mass like yours, unless you make use of the bypass piping or turn the circulators on and off, the boiler will quickly get flooded with cool water and be running at a low temperature anyway...regardless of the high limit setting on the aquastat.

If this were my home, I would repipe the boiler in a primary/secondary fashion, and run the zone circulators independently of the stoker and primary circulator...that way you can turn the primary circulator on and off to protect the boiler, and in the mean time the zone circulators keep on running. This would ensure that all the radiators get ample & continuous flow during a heat call. I understand that repiping the system might not be an option at the moment, so lets explore other options.

Back to the bypass, get that adjusted so the EFM doesn't get slammed with cold water every time something calls for heat.

If you want to experiment with controls, Honeywell offers an outdoor reset module for your aquastat: http://www.pexsupply.com/Honeywell-W8735S1000-Out ... oor-Sensor

The outdoor reset module will allow you to set a "curve" for the boiler temperature based on the temperature outside...Honeywell claims up to 15% savings. It is just an electronic means to get the circulators to run more and the stoker to run less. Sting has been after us for years to get things balanced out...he is right.

I agree with the concept of running the circulators longer but at a lower temp.. I can see the benefits there. My problem is that I believe the l7224 was not wired correctly in the first place. I believe that the stoker is wired into the l7224 and it will run (regardless of what the temperature is) as long as any circulator pump is called on.

I think there is the problem. But again i'm not a hvac guy. I'm just trying to figure this out because there is noway I should be burning this much coal.

CoalBurner5 wrote:I agree with the concept of running the circulators longer but at a lower temp.. I can see the benefits there. My problem is that I believe the l7224 was not wired correctly in the first place. I believe that the stoker is wired into the l7224 and it will run (regardless of what the temperature is) as long as any circulator pump is called on.

I think there is the problem. But again i'm not a hvac guy. I'm just trying to figure this out because there is noway I should be burning this much coal.

Well, that doesn't sound right.

I have the L7224 on mine, and it only turns on when the LL is hit. Of course, since I have about 75 gallons of water in the two zones, it get's hit every time I get a tstat call.

CoalBurner5 wrote:okay I will turn down the aquastat to 135 low limit, 10 differential high limit 150 with 10 differential, but won't my stoker still run every time there is a call for heat.

Stoker will (should) run when thermostat calls for heat only if the boiler water temp is below the HI Limit 150F setting.. Lets say boiler has been sitting idle with no call for heat and temp has creeped up to 175F.
When thermostat calls for heat, the stoker motor should not come on until the boiler water temp falls below the 150F, the High limit setting... I think I am correct here...even though my mental circuits were fried years ago..

Now I realize too, that you have a huge huge demand load with all that cast iron and three zones with one zone being a separate house and all those big rads...Wow...so you are going to consume some coal....when you said you had one ash bucket a day..I did not find that too abnormal. Send us some photos of your unit and the surroundings... I sure would like to see an outside shot of this separate house...I can get an idea of demand/load .....we like photos..!

By the way, that EFM stoker boiler you have is a fine unit.. I hope EFM company is around for a long time.
Coal Stokers with a FIREPOT are the best way to stoke coal.....Right Rob R ??

Can you tell us where you are located, I don't see it in your profile.
Ken