update on toe bandages-Bill Clinton

Duncan_2

[Hand waving wildly from the bad boy section in the back of the class] Can't I get at least partial credit on this question???

After all, removing baffles does increase secondary air like I initially suggested, and I was on the right track.

I really need a good grade, it's a self-esteem thing!

Bill Clinton

update on toe bandages-Bill Clinton

Learning a lot on this subject (nobody likes my anti-freeze idea). Had good conversations with Steve Grady and Lou Vorsteveld that gave me a new appreciation for Buderus. Here are remedies in the order in which I will try them:
1. Check the firing rate. Underfiring can cause condensation. This is a long-shot as I have already checked gas pressure and the power burner was operated and certified at the factory. Can't hurt though.

2. Pull the baffles (a big nod to ME who suggested this right out of the shoot--although I wasn't sure what a baffle was). This is a 660,000 btu Thermostream which is a three pass Scotch boiler. There are four chunks of finned cast iron shoved in on the burner end. Saw them when installing the boiler; couldn't figure out there purpose. Turns out, at least one purpose for these things is to save my neck. Pull them out and you decrease efficiency slightly, increase flue gas temperature exiting boiler; probably eliminate condensation. No, decreasing efficiency is not a problem; the problem is that it is too efficient at the temperatures its now operating at. (I'm fairly confident this will do it.)

3. Install some more bypass regulated by thermostatic valve.
My guess is this will have only a small effect but if the first two steps haven't done it, I'll try this.

4. Install a logamatic control with condensation protection. My understanding is that this will work by turning the pump off when the boiler is below a certain temperature. Burner would be on only when pump is off, thus there would be no cold water rushing in to super-cool flue gasses. When the temperature is up again, pump can come on. Turn pump off again when temperature drops. Repeat until all is ok. This sounds to me like a good strategy when needing to bring a large system up from very cold conditions. Not sure how much I want to try it here. Seems like the pump would start and stop pretty often. Still, if push comes to shove, will try it.

5. Tear it all out and do over again with 4-way motorized valve, a second pump, and electronic controlsl. A nightmare as we're talkin 3" copper in a tight space. Might have been good to do it this way in the beginning, but don't wanna now. Still, if it turns out to have to be, that's what will happen.

Despite the hassle, I'm enjoying this. Hydronics never ceases to be interesting.

Bill

Mike Kraft

Bill

Please keep us up to date with your decisions and ultimate cure.Great attitude!

cheese

Mark Eatherton1

K.I.S.S.

Glad you got it figured out. I still think a variable speed pump at start up would eliminate the spiking the boiler sees. I've got thermographs of my partners Bluedareus boiler, and it looks like a disaster waiting to happen.

I think modulation is the key to proportionate control...

The loads vary, why shouldn't the heat source.

Let us know how it goes there Doc!

ME

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Duncan_2

Mr. Eatherton, Mr. Eatherton!!! Oooo!!! Ooooo!!!

[Hand waving wildly from the bad boy section in the back of the class] Can't I get at least partial credit on this question???

After all, removing baffles does increase secondary air like I initially suggested, and I was on the right track.

I really need a good grade, it's a self-esteem thing! Hey, no-one told me it was a power burner! No fair!

Mark Eatherton1

You get...

an AA. Always Accurate! Ifn' you'da known it was a Bluedareus power berner, you'd said the same thing.

You should come to work for us. We could use good help. :-)

Good to see you.

ME

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Duncan

Thanks, teach.

My self esteem was really hurtin' after that last thin pour job.

Hey, I'd come to work for you guys in a second if ya didn't live in the big city. But Tom would have to re-train me not to drop so many 1/2" Zip-In screws ;-)

Anyway, I learned something: over-firing and de-baffling makes a burner run hotter, which can get rid of condensation in marginal cases.

I have to confess, I was approaching it from a dilution air standpoint, not a heat standpoint: more air through the combustion chamber carrying off more moisture. Probably not as effective as higher combustion chamber temperatures.

Bill, I hope you take a before and after efficiency check when you do the work, and give us a full report. Why would you guess more bypass would only have a small effect? The massive flow rates involved? Pump curve?

Bill Clinton

effect of bypass guess

My reasoning is:

The water temperature in the boiler has to be raised to prevent condensation. The only way to raise that water temperature is reduce the btu load the system places on the boiler. A bypass can perform this function be lowering the pressure differential from supply to return, thereby lowering the flow rate through the floor which in turn increases the delta t through the floor. Increased delta t means lower average temperature: lower average temperature means less heat given up the floor, therefore a reduction in heating load. The problems with this approach, I think are two:
1. Cutting the flow rate in half results in about a 20% reduction in output (so I'm told). Therefore you need a substantial reduction in flow rate to shed much load.

2. The pump I have installed is a 3/4 horse B&G with a pretty flat curve. To drive the supply to return pressure differential down very much would require a pretty large amount of bypass.

Anyway, this is all theorizing: I don't know from experience. I'm bettin on the baffles.

Bill

hr

If you do have to repipe

Could you loop the 3" building together together and loop the boiler lines together and use a V/S injection arrangement. This would, as you know let the building loop isolate itself from the boiler loop hydraulicly, give you boiler protection, and the ability to reset. Dollar wise you may come out better than a 3" 4 way motorizied mix valve.

Hard to see the "least painful" way of correcting the problem without being there.

Some of the Viessmanns I have installed use that aquastat inserted into the boiler for protection by shutting down the pump as you mentioned. A $50.00 setpoint control ( Ranco, Goldline take your pick) and basic wiring could install this set up. The Viessman uses a simple well mounted Honeywell aquastst.

A strap on sensor setpoint control would not even require "wetside" tie in. A cheap and easy fix if indeed you are that close to "right" with the "baffle shuffle" I not sure a short cycle problem would be created with that much boiler mass.

hot rod

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Steve Ebels

Hey Bill

Just for kicks, stick that Testo in the flue and see what Combustion Eff. that thing is running at while condensing.

I've had excellent results with the 2107 controll from Buderus. They know how their equipment operates and that control matches it well. Also take whatever Lou tells you as the truth. He's a straight shooter and very sharp when it comes to these boilers.

Good Luck
Steve

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