condensate

Brad White_9

Typicaly most ModCons in my experience want to be individually vented. A few times I combined two and these were Viessmann Vertomats.

Almost all boilers in this size want SS stacks, AL29-4C or 316L material positive pressure systems.

With Aerco Benchmarks there is also some leeway to combine but for simplicity (especially where these were in a penthouse) it was simpler on one particular job to just pop up through the roof with combustion air drawn in laterally to each unit. In your case you seem to have a lateral opportunity for both.

There is a newer unit, the HydroTherm KN series which now is available in 600 MBH, 1.0 and 2.0 million input versions. These seem to be very forgiving of combination venting but the inventor, Ken Cohen, strongly suggests that any combined venting system (his or anyone elses) have a pressure-based draft inducer such as an Exhausto at the stack outlet. I have seen a KN in action and it tracks CO2 nicely across it's full range and if the OA is restricted it modulates and downfires accordingly. Turndown is 4:1.

BTW: What I like about the KN is that it will work on 2 inches of gas pressure. Big help here in Boston where the gas company only guarantees 4 inches.

As far as condensate retrieval, generally the venting should pitch back to the boiler anyway. Most outlet connections are at the low point or at least "bottom out" at the boiler low point, so with that arrangement I am not sure you can get more condensate than is produced. Hope this helps.


Brad

Keith_8

Condensate

Looking at design build project for a large commercial boiler room. In the neighborhood of 6,000,000 BTU's.

I would like to go with mod/cond boilers but I'm concerned about the venting. From my perspective it apears that the venting considerations are the one variable that can be a disaster. This boiler room is @ ground level and there is a outside wall to install direct vents.

Is it possible to capture additional flue condensate before it leaves the building? It seems to me if you can reduce the condensate in the flue gas before it exits the building you reduce your ice build up.

Keith

Keith_8

Thanks

Brad,

Thanks for the responce. Good food for thought. It never entered my mind that you could twin a couple of the boiler vents together for a direct vent. A draft inducer would create a steady negative draft.

We have used the S.S. sealed chimney sytems a few times. Nice product.

Keith

Brad White_9

I think you will like the Exhausto

product line. They make inducers but also laundry dryer exhaust and combustion air supply units. All have VFD's for fan speed control based on maintaining a specific pressure. Very smooth and reliable. Not all ModCon manufacturer's recommend twinning though. Each should stand on their own for flue/combustion air balance is the theory. Go by the manufacturer's recommendations always of course.

Brad