Question for Glenn Stanton

Pstef

I have a Crown Freeport ODV just installed 8 weeks ago. Feeding off of 1-1/4" bypass loop, four zones, fifth zone BoilerMate, heating 2000sf home. I noticed the other evening, which was cold and damp that there was water vapor being exhausted from the DV. I see there is a lot of concern about condensate with these small capacity (water) boilers. I have two questions, How do you prevent such when the system is designed to fire form a cold start, is there not a certain amount of condensate in unit no mater what bypass design used? How about the intake combustion air, what happens to the water content of such when it is used for firing? Does the change in humidity change the firing efficiency?

Unknown

I can't neccessarily answer for Crown

because I don't work for Crown. They are a part of the Burnham Holdings family of heating equipment manufacturers but run as a seperate company. I can, however, speak regarding low-mass boilers like this such as our LEDV and the possiblity of condensation in the flue gasses. There will always be a certain amount of moisture content in the flue gasses with oil. Not nearly as much as those properties of Natural or LP gas but its still there.

What we recommend with these cold-start low-mass boilers is to install a "System Bypass" whereby during its operating cycle, the circulator will divert a certain amount of heated boiler supply water across the bypass to the return where it blends with cooler return water to always keep the boiler above the dew point or above 140F. This will keep condensation to an absolute minimum all during the running cycle. Depending on the venting distance and the ambient temperature of the boiler area you may have some condensation form in the vent pipe also. Follow the manufacturers guidelines as far as proper pitch to be able to deal with this possibility. eel free to contact Crown Boiler at the link or phone number below. Hope this helps.

Glenn

www.crownboiler.com

1-215-535-8900

Constantin

I saw that last night...

... Our boiler ran out of #2 dino juice thanks to the insulation guys hitting the shut-off valves on both Roth tanks during the day. By the time I got to the boiler, it was flashing the error signal and was shut down.

After I figured out how to reset the Vitoflame and clear the error, I could observe the movement of the 4-way valve that controls our main manifold temperature as the boiler fired and fired to bring the water temp up throughout the system.

At first, the valve was sending 100% of the water back into the boiler. I did a quick back-of-the-envelope calculation as to how long it would take for the boiler water to re-reach its 111°F setpoint. 5 minutes later and I could see the valve cracking open further and further as the rest of the system got re-heated as well.

It was pretty nifty not only to properly predict the amount of time it would take for the boiler to reach its setpoint, but also to observe the 4-way valve doing its part to protect the boiler from condensation.

Pstef

Appreciate help

How about the humidity in the intake air, would you see this discharge as water vapor when firing at >90% humidity (water) in the combustion air? Would it be different at cold start as compared to already at working (140F) temp start-up?

I understand that Crown may be different than Burnham but the raw mechanics/physics should be the same. I really appreciate all the help.

Thanks
Paul

DaveGateway

The byproduct of any combustion

is some water vapor plus there's relative humidity at ambient combustion air temps. But you must remember that any high efficency oil boiler still must produce a flue gas temp of 300°+ and the burn temp at the cone must be well over 800° so as long as cold return water temps don't suck all the heat out of the flue gas, any condensation that starts to flow back down the flue from an initial cold chimney should vaporize before getting back into the boiler. A cold start boiler might see a few minutes of condensation as it first fires but I'm sure it quickly dries as the burner overcomes the low temp.