Boiler protection valve or not?

[NCFord]

I am wondering if I should have boiler portection valve, in the attch. diagram from econoburn there is
no valve. When I talked to dale at econoburn he said I did not need one but I don't see how the incoming water will be hot enough. (I did not ask why) My system is not the one in diagram, however just picture mine with the boiler just heating the storage tanks. So where the primary on the top is correct, the bottom just comes from the storage. My concern is that the incoming water temp will be very low much of time, since all I'm doing with the boiler is charging the tank,

 

[ewdudley]

Are you saying your system does not have what is labeled as 'near boiler pump' in the diagram?

 

[NCFord]

first, my system is still in design, in fact I have most all the materials on my workbench ready to install except a boiler valve. And I do have the near boiler pump but in the diagram right below the near boiler pump is just a tee.
I seem to see most everyone having a near boiler pump and some sort of boiler protection valve. I am no expert, I just
don't want to have to change anything after I install it.

 

[ewdudley]

first, my system is still in design, in fact I have most all the materials on my workbench ready to install except a boiler valve. And I do have the near boiler pump but in the diagram right below the near boiler pump is just a tee.
I seem to see most everyone having a near boiler pump and some sort of boiler protection valve. I am no expert, I just
don't want to have to change anything after I install it.

I think the way they intend it to work is that the 'near boiler pump' boiler-recirculation-flow is supposed be voluminous enough and hot enough to mix with the return-from-storage-flow and still maintain minimum return temperature. Also it requires a sensor in the top of the boiler, or on the return line, that turns off return-from-storage-flow when the boiler starts to fall behind.

If their controls are set up right it can work perfectly well. Instead constantly mixing boiler-recirculation-flow with return-from-storage-flow, they turn return-from-storage-flow on and off to achieve the same result, namely boiler return temperature above the minimum.

 

[NCFord]

Thanks! That is a very good explanation. That's what I was thinking,but did not know how, also I have not gotten to the wiring side of things yet.

 

[heaterman]

EW is exactly right. The near boiler pump, commonly called a system bypass pump in the trade, is controlled by an aquastat in the boiler. When the temp of the boiler is below 140-150* the near boiler pump runs and diverts water from the supply directly back into the boiler before it can go out to the system. This allows the boiler to come up to temperature much faster than a diverter valve such as a Termovar mixing setup would. The down side (usually inconsequential) is that until your boiler reaches that internal temp, there is no flow at all to your "loads" be that storage or directly to the system. This is the way boiler protection has been done here in the US for decades and it works very well.

 

[goosegunner]

The econoburn controller is one or the other for pumps. If storage return temp is low it will drop the boiler well below 150 before it stops the primary circ and kicks in the near boiler pump.

gg

 

[NCFord]

So if the the return temps are low and drops the boiler well below 150* is that a problem?

 

[BadgerBoilerMN]

All boiler combustion chambers must be kept hot. In solid fuel boilers with short stacks this is particularly true. There are many ways to keep a boiler hot by controlling the return starting with primary/secondary piping. In a static load system e.g. on zone, one boiler steady loads. This can be done in crude fashion by simply throttling a by-pass valve at the boiler.

From there a 3 or 4 way mixing valve can be employed with various degrees of control including outdoor reset. We use the Taco 5000 mixing valves on smaller economy systems but prefer injection whenever the system warrants the expense for solid fuel, gas or oil boilers. For injection the Tekmar 352: (broken link removed). This may seem expensive until you burn through a couple boilers or burn a few extra cords.

 

[NCFord]

I understand that keeping the boiler hot is critical. The set-up in the above post is way more than I would need with my system. With my set-up I will simply be charging the stroage. I have a seperate closed loop feeding the Load side. With the boiler side I just have a coil in the stoarge tank that is used solely for charging, the boiler loop is not connected to the load side in anyway. My plan is to load and fire and charge the strorge when I have time, as this will work best for our schedules. The boiler will never idle at all. I am not sure if this makes any difference, but my set-up is about as simple of a system as one could design. I just want to make it right
and simple at the same time. Thanks

 

[BadgerBoilerMN]

Taco 5000

 

[goosegunner]

I understand that keeping the boiler hot is critical. The set-up in the above post is way more than I would need with my system. With my set-up I will simply be charging the stroage. I have a seperate closed loop feeding the Load side. With the boiler side I just have a coil in the stoarge tank that is used solely for charging, the boiler loop is not connected to the load side in anyway. My plan is to load and fire and charge the strorge when I have time, as this will work best for our schedules. The boiler will never idle at all. I am not sure if this makes any difference, but my set-up is about as simple of a system as one could design. I just want to make it right
and simple at the same time. Thanks

Sounds like the same set up as most. Charge storage with boiler, Heat the load off of storage. I guess I don't understand how yours would be any different. You will have a large amount of cool water in storage. Yes you run the boiler wide open with no idling I do that every day with mine also. It takes a few hours to bring up the temp of the bottom of my tank. The Danfoss makes sure the water going to the boiler is 150.
Think of it this way:
If the storage bottom is 100 degrees the near boiler pump runs until the boiler temp is 150, it will then stop and the Main pump will start.
The temp sensor on the Econoburn is in the top of the water jacket. As cool water returns from storage it will begin to drop the boiler temp. By the time it drops to 150 to stop the main pump and start the near boiler pump the boiler temp will be on its way down fast.

This cycle will repeat itself over and over. The only way you could make sure the boiler isn't running with cold water is to never let the storage bottom to drop much below 140. Now that could be done but it would be a big struggle when you start with a cold tank in the fall or when first fill. My fill start was 55 degrees, the Danfoss kept the return where it needed to be.

gg

 

[NCFord]

Thanks gg,
You have a Danfoss, so that is my question, should I plan on installing it or not, instead of just the near boiler pump. I like the idea of the danfoss type boiler valve. It sounds like it would not be a bad idea but I am not sure. It is only about $250 for a danfoss boiler valve, that's not too bad considering the whole cost of everything.

 

[ewdudley]

If the storage bottom is 100 degrees the near boiler pump runs until the boiler temp is 150, it will then stop and the Main pump will start.
The temp sensor on the Econoburn is in the top of the water jacket. As cool water returns from storage it will begin to drop the boiler temp. By the time it drops to 150 to stop the main pump and start the near boiler pump the boiler temp will be on its way down fast.

This cycle will repeat itself over and over. The only way you could make sure the boiler isn't running with cold water is to never let the storage bottom to drop much below 140. Now that could be done but it would be a big struggle when you start with a cold tank in the fall or when first fill. My fill start was 55 degrees, the Danfoss kept the return where it needed to be.

It sounds like the Econoburn controls are not set up right for heating storage, and as gg says a thermostatic mixing valve would be about the simplest solution.

To do it without a thermostatic, mixing valve the near boiler pump needs to run constantly, and the flow from the injection pump needs to be limited according to the minimum return temperature from storage. For instance if the near boiler flow is 17 gpm at 175 degF, and minimum return temperature from storage is 90 degF, then the injection pump flow can be no more than about 11.5 gpm and the injection pump needs to be disabled whenever the boiler supply temperature drops below 175 degF.

So in this example the control would be: near boiler pump runs constantly, storage return temperature can be no lower than 90 degF, injection pump flow can be no more than 11.5 gpm. Whenever boiler supply exceeds (for instance) 180 degF injection pump is enabled and whenever boiler supply drops below 175 degF injection pump is disabled.

Charging a cold tank would require an additional temporary limit on injection flow. For instance at 55 degF, injection flow cannot exceed 7 gpm if near boiler loop flow is 17 gpm at 175 degF.

This can all be done with a sharp pencil, an aquastat, an 007, and a three speed 15-58, but a single 007 and a thermostatic mixing valve is a sure thing as well.

 

[SIERRADMAX]

I've heard from two people that the termovar is a better option than the Danfoss. I'm using the termovar and a single circulator on the return wired to the primary pump leads. If interested, Dale can get you the programming to alter the launch temp of the primary pump & alarm.

 

[jebatty]

gg and my setup are essentially the same, except that I use a Termovar plus a balancing valve. I usually drop the storage tank to no less than about 120-130F, but occasionally to as low as 100F. The balancing valve at storage of 100F is opened somewhat more than if storage starts at 120F to make sure return water is 140F+. The balancing valve helps to put maximum excess hot water into top of storage and available for system draw. This has been operating since the winter of 2007-08 trouble free, and the Termovar does not require electric power or an aquastat or other control to operate. Very simple.

 

[NCFord]

Thanks guys, I will get a thermostatic mixing valve and perhaps change the controls a little. I think this will keep things simple.

 

[NCFord]

So one more question: It looks like if I install the boiler protection valve I should install the near boiler pump between the valve and the boiler return?
Or does it matter?

 

[ewdudley]

So one more question: It looks like if I install the boiler protection valve I should install the near boiler pump between the valve and the boiler return?
Or does it matter?

With thermostatic mixing valve you normally only need one pump between the boiler and storage. It can be placed be on the return side between the mixing valve and the boiler, or it can be placed on the supply side between the boiler and the tee that goes to storage and down to the mixing valve.

 

[NCFord]

That makes perfect sense, I just eliminated a pump, can't beat that! Thanks!

 

[SIERRADMAX]

So one more question: It looks like if I install the boiler protection valve I should install the near boiler pump between the valve and the boiler return? Or does it matter?

while using one pump, you'll want to wire it to the primary pump. Near boiler pump, I believe, kicks off at 150 degF... Definitely don't want to do that!!

 

[NCFord]

Your right about the 150 degF though I think you can change it, but wiring it to the primary pump makes sense.

 

[SIERRADMAX]

Yes you can, I pulled up an old email from Dale. Here's the sequence. A1SP is primary pump.

 

[goosegunner]

Three years ago when I set my system up I was told by Econoburn that the near boiler pump would not provide boiler protection when using storage.

I went with a danfoss because I could get it in 1-1/2" to go with my 1-1/2" copper. The near boiler connection in the controller is not used.

Gg