Converting Steam Boilers to Hot Water

Tony Conner

... of "drainage problem"?

James Wernicke

Converting Steam Boilers to Hot Water

A client wants to convert his Sellers steam boiler to hot water to eliminate drainage problems associated with the blowdown. The manufacturer says no problem. I'm concerned there may be hidden issues. Has anyone done this before and had problems?

James Wernicke

The drain system has an extensive number of leaks and must be shutdown. The drain pipe goes a very long way so replacement is not economical.

Tony Conner

How Much...

... blowdown water is there to deal with? Switching the system to hot water isn't necessarily going to be either cheap or troublefree. If all or most of the condensate is returned, there shouldn't be much blowdown.

James Wernicke

Replacing the drain just isn't an option. The ES&H folks have decreed it so. So I either install new hot water boilers or convert the steam boilers. I'm concerned about acid gas in the flue if I convert but maybe I'm irrational.

Tony Conner_2

So...

... if (when?) the hot water boiler needs to be drained for service or repair, what then - bucket brigade?

How big is this steam system? How much is that going to cost to convert to hot water? I'm thinking that the condensing flue gas issue is going to be nowhere near the top of the "potential problems" list.

Christian Egli

Converting, a matter of religion?

The systems I have seen being converted provided nothing but dissapointments and problems.

A steam system with its larger pipes is not well suited for water. There are pressure problems too, steam only calls for at most 1 or 2 PSI, your water system will easily be cranked up to 40 PSI, even just momentarily. Leaks will pop up somewhere, that's for sure. Think of the valve stems and the vent holes.

Good luck and happy steaming.

But you won't have your drain problem! Yipee.

The bigger problem is with the condensate lines. Those are too small and too dirty for pumped water. You'll have losts of pump and strainer problems. Unless you install new return lines.

That, I see as a more expensive proposition than the new drain line you are considering.

I haven't mentionned the cost of the new controls you'll need.

Plus, you will find your deleted steam system was performing much better than the converted water system. After the cost, that will be a huge dissapointment.

There are all sorts of ways to deal with the blowdown water. You could easily collect it and sump-pump it away. You can also add a pipe your blowdown valve so as to raise the level at which it pours out, thus allowing you to reach a drain line maybe 2 feet above the floor.

Steamhead (in transit)

Why

is this "not an option?"

And who is ES&H?

Dave Yates (PAH)

conversion

It really depends on the system, but the first and most important step is to measure the entire home, room-by-room, to determine the actual heat loss. Once that's completed, the radiators must each be measured to obtain the square footage of equivalent direct radiation. (They also need to be surveyed to ensure they're convertable & not all steam rads can be conveted, although many were built for either use.) That will show the BTU capacity for steam or hot water and will also allow you to see what temperature water must be supplied in order to meet a design day's load.

If you continue beyond that point, the next consideration is the actual conversion of each radiator. If there's a trap, it either must be replaced or have its guts removed. In all likelyhood, the valve will need to be replaced and you'll need to drill and tap the rad (the hot water threaded plug often found will not turn out - it's long since gaulded fast), which can be a dicey affair.

You'll want to closely survey system distribution piping and look very closely for marks left behind from minute steam leaks.

The boiler's near-boiler-piping will need to be reworked and the control package replaced with hot water controls as per factory specs.

Your concern regarding sustained flue gas condensation in either the boiler or chimney may well be a possibility & that'll require a chimney liner to CYA.

Lots of work, but, like anything else, there's a time & place for everything. If your customer is willing to spend this kind of money and is willing to take the risk that there may well be leaks that develop in the older piping and/or radiators, I'd suggest they seriously consider changing out the boiler and install a high efficiency condensing modulating boiler.

Case in point: we gained a customer due to the previous mechanical contractor deciding (without asking the owners) they needed a new steam boiler! By the time they returned home, it was in pieces scattered across the basement floor. They fired him on the spot. Next, they went on-line to discuss their dilemma with fellow engineers. The husband is an engineer who owns a company that manufactures a very popular compionent in hydronic systems & the wife a big wheel with a major HVAC manufacturer. Both have lots of contacts & decided they were going to go to hot water, install radiant in select areas, zone off multiple rooms and incorporate hydro-air into one A/C air handler serving a great room that was always too cold in winter. He also had picked out a condensing modulating boiler. By the time they contacted me, the system was essentially designed & they knew what they wanted. The old steamer had been fairly new (about 20 years young) and an atmospheric burner type. They shaved 70% off of their actual fuel usage the first season & he, being an engineer, calcuated that by degree-day comparison between the two years to be as accurate as possible. That was four years ago & since the conversion only one tiny leak developed in an old return line at floor level.

On the other hand, we had a similar situation in another older home with cast iron baseboard in every room. Following the conversion, every section waas a leaker! Turned out there were hairline cracks at almost every oval casting on the back-side of the sections. All new cast iron BB had to be installed and there were leaks in hidden distribution lines behind basement walls - one was a piece of 2" copper that had been jammed into the black iron piping to "patch" a bad section! That's how far sounth one of these conversions can go.

In both cases the owners drove the decision & in both cases, we forwarned them of the potential problems and included that in writing in our proposals.

Zoeller makes a high-temp sump pump if you need to have a sump pit for blow-down. Might be a whole lot cheaper to add.

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