adding hot water zone to steam system

gary lomp

I have read Dan's informative article on the subject of adding a zone to a steam system using hot water.

Hybrid Hydronics: How to add a hot-water zone to a steam-heating system—successfully! in Old House Journal and online at

http://www.oldhousejournal.com/magazine/2003/february/hybrid_hydronics.shtml

It answered questions I had - and some I didn't know I had. I like how the aquastat keeps the system below the steam generation temp when the steam system is not needed. Thus, the sudden water-to-steam expansion in the HW loop when the circulator shuts off is not an issue. But what if the steam system is at full throttle and the hot water system is running at the same time? Doesn't that mean that superhot water is circulating in the HW loop? (Not that I see a problem with that, per se). What happens if the circulator on the HW system shuts off with superhot water in the loop? That seemed to be considered a problem in Dan's article - solved with the switch and aquastat gear.

I could add a couple of new risers to the existing single-loop one-pipe system without too much trouble. I have already removed a couple of radiators years ago, so there is capacity available, and the boiler/burner is new, with space for additional burner elements if I need more BTUs. I think the pipes are in good condition, and can withstand a cutting and slicing operation. Is this a better way? I don't actually need the separate zones - except for one major place: I am adding to my basement. The existing basement is warmed by the main loop pipe which I leave uninsulated for that purpose. The extension will need some kind of heat source and HW would be great for that....

Thanks in advance!

Gary,
Centerport, NY

John Doll

By Pass Line

Gary - I am a homeowner with the same issue. We ended up adding a hot water loop to a 1 pipe steam boiler and had a lot of issues with water flashing to steam (even when the pump was on). The solution for that was adding a bypass line that mixes water from the loop with super hot boiler water.

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Add Steam Main or HW loop?

I have 2 alternnatives for an addition that was done around 1920. Both require doing work in a very tight crawl space.

Alternative 1: Add a hot water loop
Alternative 2: Redo a mucked up too small steam main in a tight crawl space that is connected to 3 radiators (EDR = 35+ 35+ 45 = 115 total)

John, does your solution require a mixing valve?

Anyone else have an opinion?

John Doll

There is a valve like the one described in Dan's article (attached). You can simple open it more or less to control the temperature of the water in the loop. If you open in more, less water goes through the boiler and the water in loop stays cooler.

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Thanks John

Thanks John.

Steve Garson_2

But doesn't using an Everhot heat exchanger offer a better long term solution since you keep the boiler crud out of your hot water loop?