Big Toe Bullseye--Bill Clinton

Bill Clinton

Tried my best to do things the easy way and got shot in the foot again. I have a large radiant job complete: 40 condos, over 40,000 sq. ft radiant heat; 65 zones, Buderus Thermostream, 660,000 btu natural gas input. Matched the input size to heat load and that part works fine. Relied on Buderus ability to handle low temperature returns and that part isn't working. Those floors are soaking up heat too fast and I'm getting condensation dripping out of the boiler onto the floor. This isn't a matter of setting the aquastat too low, it's a matter of the boiler warms up slowly and sometimes can't achieve a non-condensing temperature.

The question is: "What to do?" I'm not anxious to repipe the boiler room (3" copper) if I don't have to. Here are some thoughts on possible fixes:

1. The easiest and to my preliminary guess probably the most effective: Add anti-freeze. We don't really need it here, but it can serve a useful purpose for corrosion inhibition. My understanding is that a 50% solution will knock several percentage points off heat transfer (efficiency). That should get the boiler back where it likes to be.

2. Add an end of the line bypass with a thermostatic valve that will close off as temperature increases (There is already a differential pressure bypass installed there). This would effectively reduce the flow rate through the floor and might decrease the systems ability to soak up btu's. Since a lower flow rate through the floor would increase temperature drop, I suspect I would get minimal effect from this, but maybe some. I just need a coupla percentage points to make this sucka work.

My guess is #1 is a good shot. Would welcome feedback and ideas. Thanks.

Bill

Mark Hunt

Have you considered the HS-2107 control with the built in condensation protection?

Just a thought.

Mark H

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hr

Can you T- drill a bypass

into the piping some how. Seem like that may be a bunch cheaper than (how much) glycol at 9 bucks a gallon, plus filtered water if needed.

hot rod

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Bob Bona_4

scrap the

antifreeze option. First because that is a TON of the stuff=service headaches/$.I liken it to poison injected into a hydronics bloodstream. Is it on Primary/Secondary?

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J.C.A.

How about.....

A system by-pass, or a boiler by-pass set up ?
Keep the water going back to the boiler at a more steady temp , and re-direct the cost of putting in a mixing/constant temp. valve .
I'm kind of new to this game , but my thoughts go back to the payment part . If it takes you less time , it costs the customers (or you as the contractor fixing it for free) less .
Ask Glenn Stanton for some advice on this . He also has some great drawings as to the difference between the 2 . It may help to solve your problems . Good luck.

Paul Pollets_2

Mixing

Bill, Buderus boilers are designed for mixing valves for low temp applications. Their controls (ecomatic) will do the job easily. a 3" 4way valve and actuator will solve your problems. If it was a radiator job, I'd use a 3way. Try calling Chris Rorke at Blueline in Wyoming. His number is 307-733-3953. He's the most knowledgeable fellow I know for commercial Buderus applications and troubleshooting. He's also an engineer and intimately involved with Buderus.

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Bill Clinton

bypass

I've considered t-drilling a bypass but am trying to avoid it. I'd have to drain the whole system, then worry about little chunks of copper remaining inside to lodge on zone valve seats. Not to mention I don't own a t-drill. Also, space is very tight. That option looks to me like three days work, so it's not attractive from that point of view either.

A small diameter bypass (1 1/4" or less) seems to me might be an excersize in futility. I've got a 3/4 horse flat curve B&G in there and it can increase its gpm radically with not a large change in delta p. If delta p doesn't change much, flow rate through the floor doesn't change much either and heat-load doesn't change much either, bypass or no. Also, even if I can affect the flow through the floor, I'm still faced with the fact of an offsetting increase in delta t through the floor.

It seems to me the only piping solution is a fairly large (probably 2") boiler room bypass with motorized valve and electronic control. With hindsight, I should have done that in the first place, but it's a nightmare to contemplate now.

Again, I'm attracted to the anti-freeze/corrosion inhibitor solution. Don't I recall your having mentioned there are some permanent anti-freeze products on the market? If I can just get overall combustion efficiency down a coupla points, I'm home free.

An interesting side-light is that the Buderus thermostream is reputed to be good for temps down around 125 degrees. I suspect that would be true if oil fired. Firing with natural gas is different as it produces more water vapor for any given input, thus resulting in a higher dew-point temperature in the heat exchanger.
Bill

Steven Grady

Condensate protection

To solve the problem of the condensate in the boiler,you will require a condensate protection control.(Logamatic R2107) The statement that Buderus can accept low temperature return water is true, but you should not run the burner and the pumps below 122F on a G315 boiler. The Logamatic R2107 control has an adjustable pump logic built into it. This may be a redundant control depending on what type of system that is controlling your radiant. Please call me at 518-424-1490 so I may help you solve you this issue.

Duncan

Will glycol work?

Is there any way you can increase secondary air to the boiler burners? This might help keep the water vapor from condensing. Probably not enough of an edge, but possibly worth exploring if you're a hair's breadth away.

Stay away from glycol, it presents more difficulties to work with than water. You will probably increase your headaches, not lessen them.

Glycol finds leaks water will not. You will come back a year later and find blue stains and stalagtites at sweated copper joints and threaded fittings that work perfectly well with water.

The same for all rubber components (which glycol loves to eat). You'll find leaks at valve packings, flanges, boiler drains, anywhere ther's rubber, unless it's Viton.

A 50% glycol solution increase pump head required, it's more viscous.

It requires a flow rate correction - maybe no big deal in your case.

It requires annual water quality maintenance.

If you're thinking in terms of the glycol being a lousy conductor and not scrubbing as much heat off the boiler, the glycol is still cold, and in direct thermal contact with the iron. How would the boiler wall temperature increase? I'd like to hear more about this approach.

Considering the expense, and questionable success, is glycol worth the risk?

About the bypass solution (assuming the existing bypass it at the pump outlet)...

A thermostatic valve at the end of the (main?) line will only sense or system SUPPLY temps, and you want to look at RETURN temps. Maybe investigate a thermostatic valve with a remote bulb you can strap onto the return?

I'm really interested in seeing other solutions more elegant than my meager offerings, and what your final solution is.

Boilerpro

Low Temp protection with Tekmar 361

Just completed a job in which I used Tekmars 361 for low temp protection only. The boiler sensor is placed on the boiler return and the minimum temp is set on the control. The supply sensor is placed on the system supply. FYI I also used a 369 zone control connected to a 262 to control the zones and boilers. The boiler supply sensor for the 262 is placed on the system supply (not the boiler supply) and the 369 provides indoor feedback for 262 outdoor reset. Just some more ideas.


Boilerpro

Mark Hunt

So I guess the HS-2107 was a stupid idea? Drilling holes into the piping or changing the density of the liquid are better ideas.

Sorry I wasted your time.

Good luck!!

Mark H

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Mark Eatherton1

What about...

pulling some of the baffles in the combustion chamber. I know it works for me. If I see too low a flue gas temps, I pull a few (4 available for pulling) baffles and raise the flue gas temperatures.

There's also a small baffle plate that can have segments broken out of it to allow for more flue gas bypass from the primary chamber into the secondary flue gas passage ways.

I'd avoid the glycnoids if it were me. Expensive in more ways than one...

ME

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Mike Kraft

Bulls eye Bill...........

Sounds like a very impressive project.I remember you sometime ago posting that you found a boiler that makes sense to you.A boiler that will allow you to reset it to your curve without concern.I remeber respones to the post that told you the Thermostream is not a condensing boiler.But a boiler that will allow you to bring cool return temps to the edge of dew point.Its ashame that you have the puddles and I'm sure you are near seathing.

Mark Hunts suggestion is the quickest,easiest and least expensive alternatives that you have.I also understand that your view of this type of "control" is (to quote a freind)bang bang on off............or a over glorified triple aquastat.

May not be what you want............but thats what you got.

cheese

Mark Eatherton1

The problem with pump logic...

is that the control takes for EVER getting the fluid temp up to the point that the pump stay on. It works OK on over sized systems, but I've found that on cold startup, any kind of logic that interrupts the space heating circulator goes through a lot of start/stopping. Maybe a variable speed control that slows the speed of the main circulator would be less likely to compound the start stop scenario.

Just thinking out loud.

ME

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