Old Radiators, New Boiler, and Slime & Sediment

LannyW

My partner and I are

planning to use a Triangle Tube Combi condensing boiler to supply 18 big, old

radiators, some existing hydronic baseboard (3/4 copper), some new radiant

(pex), and DHW.  We are well on our

way to designing for the various temperature and volume requirements (but would

welcome any bright ideas).  What we’re

really wondering about is . . .

Will there be a problem with

that old black slimy water typical of old systems (think gravity, coal, then

oil, then pellets and gas)?  

We were leaning toward using a hydraulic separator.  Now we’re wondering if we should

provide true mechanical isolation with something such as an indirect tank with

the domestic side supplying the radiator zones.  We don't want to compromise the efficiency or functionality

of the new system.  Any thoughts on

what the old oily residues will do to the heat source heat exchanger in the

boiler, or to the mixing valve for the radiant, or to any other new

component?  We're planning home

runs for the radiators.  Any good

ideas for flushing the radiators out?





 

Wyrm

heat exchanger?

why not just use a heat exchanger so you're not fouling up the new boilers.  It might cost a little more up front but a heat exchanger is cheaper than replacing a damaged boiler.

Use the heat exchangers between the boiler and the old radiators.



The DHW should be clean, as would the new radiant pex

Paul Pollets

New system tips

I'd recommend you consider using a cleaning chemical before commisioning the new boiler. Purge valves on the returns will allow flushing of the sludge.  You may have problems withg the system if you don't clean it.  Rhomar makes an excellent product.  I'd be using a hydraulic separator and changing all of the existing radiator valves to TRV's.  A system using the new variable speed pumps will really perform!