Help! Difference of opinion need adivce

Jamie Hall

I have designed a revision to a vapour steam system, and have two contractors working on it. One says my concept will work, the other says I am bats and proposes something quite different. I need your opinions and reasons...

The application has two quite distinct zones (with existing radiation and piping in each): one is to be maintained at 'normal' room temperature, and the other at about 40F (except now and then, for only a few days at a time). There is an existing Peerless boiler which feeds, quite adequately, the 'normal' room temperature system. No problem so far. The other system is valved off, at the present time, with a single large gate valve on the steam main (no other valves). My proposal is to add another, smaller, boiler (keep the water levels the same, second Hartford, etc.) piped to the same main header (an old header from a H.B. Smith boiler, long since gone) sized to handle the additional load from the 'other' system (based on equivalent radiation, allowance for pickup and so on). This boiler will also be controlled by a Vapostat, but set slightly higher than the existing one so the new boiler runs by preference (since it is more efficient). The 'other' zone would be turned on or off by motorizing the gate valve splitting the two sections, and controlling that valve with a low temperature thermostat in the 'low temperature' zone.

One contractor says that's a little unusual, but why not?

The other contractor says that a) there is no way that the two boilers can be different size; you must use two boilers of exactly the same size and rating (which would mean two new boilers, both sized for the larger 'normal' zone -- which will result in a serious oversize condition when both zones are on, in my opinion) and b) that the single valve won't work, the only way is to go around and turn all the radiators on or off by hand (about 16 of them!) when you want to vary the temperature in the 'other' section.

I fail to see the difference between turning all of the radiators on and off by hand with individual valves and turning them on and off automatically with a single valve, and the contractor can't explain why a single valve won't work.

I fail to see why two boilers of different ratings can't be used together (assuming equal water levels), and the contractor can't explain why they won't.

HELP!

Thanks--
Jamie Hall

Mike T., Swampeast MO

Proving

Can't comment on the concept as not familar with steam but, I believe it would be utterly imperative that the 2nd boiler be wired through proving contacts in the motorized valve. i.e. IMPOSSIBLE to fire unless the valve is FULLY open.