Buderus GC144-5 producing a lot of condensate

chrisalecia

Ironman said:

Your calc seems a little on the light side. I would think 55-60k btu's would be closer.
The 560 btu pr. ft. of baseboard is with 180*water entering the baseboard. A system with 180* supply and 160* return has an average water temp of 170* and 500 btu's per ft. of BB is the number to use. So, that would indicate that your BB is sized for 77.5k btu's.
This is a good thing since over-sizing the BB allows for lower water temps which means higher efficiency. The negative side is that it also means lower stack temps and greater likely hood of condensation.
An over-sized boiler will short cycle and that can cause excessive condensation also.

Did you contractor do a heat loss calc? It looks as though he just sized it off the old boiler.

Lower stack temps? Condensation? Short cycle?

Ding Ding, we have a winner. I think we have come full circle from my original post. That was pretty cool actually. Sad part is that the facts tell the tale. Yes, I think the new boiler was based off the old one and no a heat loss was not done. Contractor has been my plumber for 12 years. He did run the BB calc though.

I am having all 3 symptoms of an oversized boiler.

chrisalecia

Another engineering question:

I've read from here that the recommended burn time for a cycle should be 7 to 10 minutes. My boiler has a tank of 3.4 gallons. The boiler is currently burning from 3 to 4.5 minutes each cycle.

Question is how long should it take to heat up 3.4 gallons which is already at 120* to start with? My Low limit is 122* with an 18* differential. Logic would tell me that 7 to 10 minutes is way to long. Even with one or multiple zones open.

So how can 3 to 4.5 minute burn times be considered short cycling?

chrisalecia

Just to close the loop on this. I installed a SS liner and the condensation problem went away immediately. Case closed. Thanks to all who gave me great advice! Happy Holidays!

Ironman

Thanks for letting us know how it turned out.