Internal vs. External HX

Alan (California Radiant) Forbes

I have a customer in SF with a failed CombiCor, pouring water out of the top of the unit.  They live in a 4-unit condo; each unit has radiant heating with 4 CombiCors lined up in the garage.  If you look at the radiant side pressure gauge on the other units, they all read around 80 psi, so you know all of the other HXs have failed as well, but they are just not showing it via the leak path yet. 



As I see it, I have 2 choices:



1) Install a new, improved CombiCor, or



2) Install a high recovery 50 gal water heater with a Taco X-Pump Block.



Your thoughts?

EricAune

Combi system fist if given a choice

Split the eggs into two baskets.  Likely to be higher cost now but with added efficiency of system (ODR with X-block) that cost may see return throughout time. The week link is a relatively low cost replacement.



I have had a bad taste for the combi-cores for a while now, new and improved or old. 

kcopp

how about a combi....

boiler? wall hung... TT excellence or one of the Embassy/ Cosmo Gas rigs..... it would last a lot longer than a Std. water heater.

hot_rod

what's in your Water

I've found that plate Hxers used on DHW applications may to be flushed out fairly often.



I installed some of the early Danfoss ZCP with plate HXers for radiant via a DHW tank. In one case the exchanger is removed yearly and taken to a radiator shop for an acid bath.. The external HX will cost you the pump electricity also.



The improved Combi with the large coil has been a very strong and long lasting HXer. That would be my first choice.



Has the no lead law kicked in in that area yet? I've heard there may be a "grace' period for compliance? Does it apply to circulators used on DHW and heat exchangers?



hr

Mark Eatherton

Riddle me this...

I went to the BWC web site and pulled the specs up on the CombiCor heater. It appears that the appliance is a conventional 80%er. But as you read through their literature, as a combined space heating appliance, it has an AFUE of 82%, which is 2% higher than its thermal efficiency.



How does THAT work?



I've always said that AFUE is a bogus number, but really...



http://www.bradfordwhite.com/images/shared/pdfs/specsheets/553.pdf



ME

SpeyFitter

Common or Dedicated gas piping/metering?

So I'm assuming each individual combicore has it's own gas supply off of its own meter?

Alan (California Radiant) Forbes

Combi System

It would be tough to install a combi boiler because the heating plant is in the basement garage, far away from an outside wall; venting would be difficult if not impossible.  It would also be at least double the cost.



I've never had problems with corroding HX's in this area, probably because we're blessed with excellent water.



The "Lead Free" law is active and enforced in SF.  All wettable surfaces must conform and I'm told by my supplier that Taco is about to release their compliant X-Pump Block (XPB).



Before I spring for another CombiCor, I'd like to hear some success stories in my area.  Like Eric, I've still got a bad taste from all the CombiCor and PowerCor failures that I've had.



Yes, each unit has it's own meter.



What I like about the water heater/XPB combination is that when the water heater fails, it's not a big expense to replace it.