Steam boiler with indirect water heater

Paul Mitchell

I would probably install a strainer in line also to keep any crud from the old pipes getting into the tank,coil.


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jim sokolovic

Steam boiler with indirect water heater

I recommended an indirect water heater as the best source of domestic water to use on a replacement boiler job for a friend. The indirect I recommended has a stainless steel tank and a cupronickel coil (I'd like to stay away from brand names for this discussion, since that has been covered alot here). Is this advisable with an oil-fired, cast iron steam boiler, as far as possible problems with the condition of the water going through the pump and coil? My 2 "experts" are divided on this idea.

Unknown

Pumps

Most pump bearings and seals are rated to 230 degrees F. In low pressure steam boilers, boiler water rarely reaches 220 degrees F. So a circ pump will have no problem there.

If you use a pump on domestic water you need to use a non ferrous pump with non ferrous trim.

I am not recommending a brass or stainless steel pum[ as I do not know what your domestic water chemistry is.

The pump that circulates the water through the coils can be the same metal that you use for a water heating system, typically that is a cast iron pump.

What you need to do is locate the suction pipning for the circ pump away from any location that can pick up boiler sludge or rust particles. In so doing you will legnthen the life of the pump.


Jake

jim sokolovic

Good points on the piping...

A strainer on the piping and locating the piping away from sludge accumulation areas sounds logical. Now, what typically provided tappings that are on residential steam boilers would you use for the flow to and from the indirect water heater coil? The return tapping(s) are at the lowest point. The rest (skimmer, LWCO) are near the top of the water line. And the supply is at the top of the boiler, and only delivers steam.

Unknown

I'd use the tapping...

The one for the probe-type LWCO for the supply, and return into a tee on the Hartford loop piping.

This means using the float type Low Water Cut Off, which mounts on the gauge glass ports.

I'd surely use a bypass around the boiler to keep the pump impeller from cavitating, as it starts out at about 1 PSI, and drops in pressure as the pump comes on. 210 degree water in a vacuum flashes to vapor quickly as it hits the impeller.

For the same reason, I'd not use a strainer before the pump. The mud is at the bottom of the boiler, and the feed tapping is at the top. The stuff that wears out the impeller is pretty fine stuff and is present throughout the boiler water, so use a nice big voluted pump, like a B&G 100. It'll hold up a long time. I'd not worry about the grit, much.

Noel

jim sokolovic

Noel, you're the...

Man! It all makes sense, the way you explain it. Good "free agent" signing by Slant/Fin.