Conversion of old Hydronic Heating System

ClayR

I bought a 1955 house with oil fired hydronic Heating baseboards. It has the traditional expansion steel tank after the boiler but the 2 zone circulating pumps are before the boiler. What a loud winter it was last year! I tried to purge air all winter and did not get any additional air out of system. From my research this system is design wise a dinosaur but all parts work. Can I eliminate the old steel expansion tank after the boiler, add two small diaphragm expansion tanks with air eliminators before the circulating pumps to get it as close to modern design with out major overhaul? Or is this building a bomb in that as water is heated in the boiler there is not enough expansion room around the flow back or circulator pump?

HVACNUT

Pics would be better and more than likely, just one #30 extrol will do.

ClayR

Thank you for your help. Here is a picture of the system.

HVACNUT

Is replacing everything out of the question rather than re piping and then having something else fail?
I dont think that's the original boiler. Peerless JOT?
Looks like a block swap.

ClayR

Good eye, Peerless TW-4! My guess is that it was installed around 1983-1987 range. I'm pretty sure the piping is however older. I could afford to replace the whole but right now it would put a huge pinch on the budget. If I could just do a simple cut and solder job and get another three years I would be happy.

hot_rod

More than anything I would add a good air purger, and a single expansion tank, in either location you show. use the micro bubble type, many good brands out there, although none as good as Caleffi

Ideally a new system would involve some repiping, ECM pump technology, etc to bring it into the modern hydronics world.

ClayR

If I could get away with only one tank, that would be even easier as that would be an easy choice to cut into the blue circulator line! Would it be okay to have only one air purger/micro bubble eliminator in that same spot that the tank attaches to since it would be the lowest pressure spot?

hot_rod

The very best place to remove air is at the hottest point in the system, next the lowest pressure spot which would be the highest point in the piping.

Soma micro bubble sep at the boiler, float or manual vents at any high points near emitters, etc.

SeanBeans

@hot rod what’s the advantage to having the compression tank where it is in your attachment rather than coming off the bottom of he air separator?

mikeg2015

Suction side of the return pump has less normal variation. If you put it after the pump, the pump itself will introduce some pressure variation and you would have to set/adjust the tank pressure with the pump running. On the suction side you cna set it while not running. the autfoeed is often located at the expansion tank. Suction side of the pump is also a good spot for air and dirt separators.

hot_rod

SeanBeans said:

@hot rod what’s the advantage to having the compression tank where it is in your attachment rather than coming off the bottom of he air separator?

Either location with a low pressure drop boiler is fine, cast iron, electric, any wide open passageway boiler.

Ken D.

Hard to tell, Is that exp. tank piped to the riser?