25KW or 40KW?

[__dan]

Dan, although your posts sound professional and impressive, they give me the impression that you don't actually operate a gasser.

Do you have the real world experience of running one? Just curious.

I have pictures in the install thread and 10 years experience as a low bidder wiring boiler changes for schools, as a sub. I wired about 50 schools all over the state in that time, power and controls. No small ones, only big ones. I will find the picture posts later.

 

[velvetfoot]

That sounds like a real nice setup-warm floors would be nice.

 

[__dan]

So are you going to operate the boiler the exact same way after you add storage?

The boiler operation now is to put the wood in, make sure the fire starts if it's first in the morning (wait for flue gas temp over 120 C), and walk away. How could I change anything?

Burn time is ~ 3 hours. I cannot touch it for 3 hours because adding wood or poking it to make it burn faster would exceed demand. After 3 hours I may add a few splits on the coal bed. The boiler would be off and restart, but still hot and maybe the circs still on and scavenging heat from the boiler, coals burning when off. Fuel from under the porch burns perfectly to ash. Fuel from the tarped pile that got a little rained on may need to be poked at the end of the burn.

I burn large uglies that barely fit through the door with smaller pieces thrown in alongside. Small splits would burn too fast. A mix is best.

What the 400 gallon buffer tank will do for me is reduce loading cycles and allow more fuel per load. No other changes are foreseen. Tank with the slabs for storage will be sweet, but there is no one locally that I know of who has a better system than what I have now (unless they have utility methane)

It was unexpected how much I would like making fire every day. Loving the heat and unlimited DHW.

 

[__dan]

That sounds like a real nice setup-warm floors would be nice.

Basement slab surface runs 85 to 95 F depending on where the tubes are. The constant heat penetrates every surface so scanning the rest of the house, both floors with an IR gun, you will not see more than 2 deg F difference anywhere in the house on the IR gun.

 

[maple1]

The boiler operation now is to put the wood in, make sure the fire starts if it's first in the morning (wait for flue gas temp over 120 C), and walk away. How could I change anything?

Well, you answered your own question later:

What the 400 gallon buffer tank will do for me is reduce loading cycles and allow more fuel per load.

So, with storage, you would increase your boiler output. With no change in your house heat load. Which I think goes to what some of us were saying - with storage in the picture, matching boiler output to house heat load is not quite so important anymore.

 

[henfruit]

You still did not explain turn down capacity? How do you do it?

 

[__dan]

You still did not explain turn down capacity? How do you do it?

It is built into the Froling, kind of an undocumented feature as the boiler requires storage (constant load) which I do have.

There are two Belimo motorized operators, one for each, primary and secondary air valves, a high quality commercial grade TEFC variable speed induced draft fan, and a factory custom programmable microcontroller control board.

So the Froling reads hot water supply (HWS) setpoint and as supply temp exceeds setpoint (currently 73 C for my application) the boiler starts to turn down by closing the primary air damper to the minimum 20% open and ramping the draft fan down to the minimum 35% speed. Secondary air is independently controlled to maintain 9% excess O2 using the lamda sensor. Under load it will modulate infinitely between max and min burn rate to maintain HWS setpoint.

Typically at minimum fire, secondary air is at the minimum opening, 10 or 20%, and the Froling by design and build typically burns steadystate at 12% to 16% excess O2. If I open it and poke the coal bed, secondary air will go to 60%.

Typically in my application max load is first fire in the morning, up from off overnight. After the first hour DHW drops out and the slabs are returning 90 or 100. As soon as the DHW load drops out, HWS continues up above setpoint and the boiler starts to turndown, and may be at min 20 minutes later.

Note that at this point the entire house load regardless of the weather is usually less than the minimum boiler output and HWS continues to creep up to 85 or 90 C, which is why I need the fuel 1/2 load to burn out after 3 hours. The load scavenges heat from the boiler and when HWS is back ~ 70C I can throw a few splits on the coal bed and restart the process.

I do need the tank, but for convenience or to save an inexperienced operator from overloading fuel and slumbering. My heat works perfectly and the only residue in the flue is light non combustible ash.

 

[henfruit]

So the Vigas and Froling run very similar. We can set our water out put temp also, the fan we use will modulate down to 1% if I choose to set it that low. The lambda system will also adjust as to what the o2 is sending to the controller.

 

[__dan]

So the Vigas and Froling run very similar. We can set our water out put temp also, the fan we use will modulate down to 1% if I choose to set it that low. The lambda system will also adjust as to what the o2 is sending to the controller.

Yes and no. Yes you have some turndown with the draft fan speed. But do you also restrict primary air with a motorized damper. When burning, the hot flue gas will create its own draft and throttling at the intake air damper will cut it back hugely.

The motor works on the principle of induction and "slip". Even the best quality 3 phase motors with VFD drives have a minimum speed of 25% to 30%. I believe you may be saying the control board has a 1% setting, but if you get the motor nameplate data and call the motor manufacturer for the minimum speed allowed by the factory, they will not say 1%. Depending on the motor type, they may not warranty any reduced speed control at all, which would be typical for single phase motors with inexpensive speed controls. There are several ways to do it which is why you need the motor nameplate and the call to the factory.

The new ECM motors are the best and natively variable speed, but they are new with very few, specialized applications. Likely, you have an older style system, not a 3 phase motor with a single phase VFD or an ECM.

You would want that number, minimum fan speed is probably in the 30% to 40% range depending on motor type (and may not be factory supported). Especially for heat which is a critical application.

You should look at the Froling for component and build quality.

 

[henfruit]

The motor we use is a ebm pabst. We do control our primary and secondary air with a belimo servo motor.The ebm Pabst is a single phase motor that is run through the controller using P I D. I think the Froling is a great product as is the Vigas but I do not think it is worth 30% more in cost.

 

[__dan]

Right, EBM Pabst is a brand name. That means factory support. Give them a call with the motor nameplate data, model number and they will tell you the minimum rated speed using a speed controller. The PID, proportional, integral, derivative, determines the target speed percentage. It does not say the method of how the speed is reduced.

You can see in my application that I absolutely depend on the boiler turndown capacity and the Froling was the only one I was aware of, and I hit the Spring Sale. I compare the cost of the Froling to the cost of burning oil. Over the life of the boiler I will save ~ 70% off the alternate fuel oil bills (it will pay for itself three or four times over).

 

[henfruit]

Thank You, I will check into that motor information.

 

[__dan]

Thank You, I will check into that motor information.

That's exactly what I would do, I call the manufacturer routinely when there's any question. I like to rate brands on their factory support. I sometimes have an expected range of where the question or answer will lay, but the factory support and specifications are essential as I'm sure you know why.