Abondoned F&T traps a problem?

Tim_33

for which I will be conducting the pre-bid meeting the afternoon for the Boiler replacment work, has old F&T traps left in the system from its early days as a steam system. Can these pose a problem in it as a HW system?

School building, late 1950's era steam boiler, converted to hot water, I'm guessing sometime in the 70's. Old traps left in the system in the classroom unit vents, and few other places. At the end of the season, had a fire box failure, so time to replace. We're going with some Patterson-Kelly condensing/modulating replacements and upgrading the pumping system for variable flow primary pumping. Local controls at the unit/classroom level is vial 2-way zone valves and/or aquastats. Nothing outside of the boiler room gets replaced this summer.

The next phase of this project will replace the poorly maintained and oversized steam piping as well as an addition and some renovations and controls upgrades at the unit/classroom level. At that point, the traps will be removed, until then, they will stay.

What's the worst that could happen?

Christian Egli_2

Ah ha, busted

Conversions from steam to hot water are never as easy as promised by those who come up with the idea in the first place.

Obviously, since the seventies, your system has been limping along to the point now where everyone realizes the piping is no good for anything but steam and in need of more costly repair.

F&T traps work great on steam, inserted in a hot water system, they just flush hot water through to utter waste. How nice, for more than thirty years now, imagine how much uselessness you got out of that. Is it taxpayer's money? They'll also cause short circuiting and poor water distribution.

The only problem with your steam system is the water in it. I have seen many problems such as yours and I ran out of sympathy for them. Sorry. Going back to steam will be the only way for you to achieve efficient operation again - which, it seems, you are not getting right now, it's not surprising either.

You will need to get the hot water out of the F&T trap...

Thanks for bringing up your problems on the wall.

Tim_33

That doen't help

I understand your sentiment on the conversion. I didn't convert it, nor would I have advocated the same. On the other hand, it would be impractical for this private religious organization to convert back. I'm simply trying to help them avoid any future problems due to the HA conversion.

Christian Egli_2

Oh, but rubbing it in helps

I don't know how much else to say all of this with more compassion: steam heating systems are great, hot water systems are great, but the middle road between the two in the form of a conversion are total junk (which your case is demonstrating). I feel sorry for your system owners falling pray to this con(version) thirty years ago. Mind you, it used to be a very common occurrence, and your system has at least remained viable, which is great, because many other grand old buildings have simply been left behind once its owners became overwhelmed by constant repairs while waiting for the promised savings.

Steam heating systems work with great economy, there is no doubting that. Steam also has great advantages in applications such as schools that only need heat part time during classes, plus steam comes with great delivery flexibility that bends itself backwards to make a difference between occupied and unoccupied rooms. That's a little fluff about steam without talking about its drawbacks, which it has of course, like every other heating system imaginable.

It seems to me your laundry list of repairs in this particular school include replacing the boilers and the pumps and changing the near boiler primary-secondary piping. This all to be done now, and to be done later, the list includes replacing the old converted steam mains that are wildly sized and replacing the control valve. Seems to me like a whole new system broken down into two phases.

This would be an opportunity to redesign the whole thing from scratch and get a fully functional system. Whatever it may be along with new insulation.

It seems you plan on operating with condensing boilers that can provide "cold" hot water, but this may not be of any benefit because you're still using radiators and convectors in your classroom that were sized for hot steam. They won't be putting out a lot of heat when fed with low temperatures. Heat loss calculations would be highly useful.

The system will work, but not in low temperature mode, thus without the condensing boiler mode of which the owners are probably expecting great savings - as brochures imply. Remember what happened to them in the seventies, the water scheme was promising great savings, which never showed up. Fool me once, fool me twice.

I don't know of a good way to proceed in phases here. This would probably call for written disclaimers on your part about expected savings (not) and expected system problems. At the very least, protect yourself and your boiler by installing filters for the system dirt. Once your boiler is in there, you own the system...

Converting from hot water to steam only requires draining the water!

Then changing all the traps is very simple too, it's no more work than the labor to check that all traps are removed for proper hot water operation - no major cost change here. The F&T traps, you've got already, repairing them is nothing. Assuming the boiler room is downstairs, you won't need any pumps with steam. And the boilers, you're changing them anyways. The new classroom controls can always come later, and you won't have to solve the steam main sizing issue and you won't have to try another water pumping mode because the current one doesn't work and you won't be thinking of changing all the convectors in phase three (which will come).

I'm imagining a Jetson age sprawling school, all one floor with big crawl tunnel underground. Unit air convectors in each classroom and perhaps some radiators. Is there the ghost of a vacuum pump in the boiler room?

At this time, it might be interesting to look into steam again, install new boilers and new traps in one phase and be done with it. More than just replacing parts, you may be able to find a great solution that will please everyone. Wouldn't that be neat?

I don't know how much this all truly helps you, for sure, any scalding tone was not meant for you, it's just that steam is hot stuff. I rather appreciate the frankness with which you bring up your problems.

I still did not say what to do with the F&Ts, did I? Plugging the flow through them in hot water operation is necessary. There, I can't just say rip them out.

Where are you located?

Steamhead (in transit)

The damage is done

take the guts out of the traps if that hasn't been done already. I would want to convert that system back to steam too, but you'd have to get the school to admit it made a huge mistake- which will never happen.

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Al Letellier_20

convertion

I assme that you mean the system was converted from steam to hot water and the traps where left in place with the guts removed. As mentioned in other posts, a lousy way to do things. The only real problem could be restriction of flow as the orifice open in the trap is quite small compared to the pipe size, but the pressure drop may to insignificant in a large system. If the system works and heats the building, only efficiency is lost. As long as the comfort level is OK, the trap pose no serious problem. If the guts are still there ?????? sounds like you're taking an intelligent approach to the problem.

Tim_33

A lilttle more information

Gentlemen,

Thank you for responses so far. I can provide you some more information, for those interested.

I am located in Rockford, Illinois. The church/school is located 25 miles east of my office.

Thorough heat loss and gain calculations have been performed on the existing school, and the proposed two additions. The current heating needs for most of the season will be met with 140 degF supply temps and a 20 degree dt. Not ideal, but still condensing, most of the time. A great deal of flexibility is designed into this system, as it will accomodate present and future loads.

The owner decided what they wanted to do, and purchased the boilers. I engineered the installation and will engineer future controls and equipment upgrades/retrofits as necessary. Re-establishing a properly operating steam system, in this instance unfortunately, is not an option. I doubt I'm the first one to face fixing a hacked-up, half-a$$ed coversion mess.

The "radiator" traps (Illinois GTST type) have been left in the supply piping to each of the classroom unit ventilators. I don't know if they have been gutted or not. The F&T traps are plugged and gutted, I have since verified. The ventilators, with original steam coils (I assume), and mostly without fully operable controls, and no provisions for cooling, are scheduled for replacement in future phases. These will be sized for low temperature supply, will have DX coils for AC and the necessary controls/provisions to bring them into compliance with current ventilation standards.

When complete, the school will have a low temperature hot water heating system. The (2) boilers will be piped in parallel, primary/secondary arrangment, the secondary pumping is done via variable flow rate pumps, controlled based on HWS/HWR differential pressure. Boilers are modulated and staged to maintain and adjustable and variable supply temperature, with outdoor reset.

Tim_33

Just drain the water

"Converting from hot water to steam only requires draining the water!"

If only that were the case, we would not be discussin this. Without expanding too much, "volunteers" for the church have made modifications trying to make this work over the years.

The boiler/pumping replacement/correction is phase one.
The piping and unit level controls is phase two, in support of a building addition.

The boiler replacement work will include, for the existing piping; flushing, cleaning, passivating, flushing again, filling with treated (roughly demineralized) and treating the system water (never before done here), plus the addition a side stream filter, chemical pot feeder and strainers upsteam of each boiler and system pump.

"More than just replacing parts, you may be able to find a great solution that will please everyone. Wouldn't that be neat?" Yes, it would be neat. I like steam systems, fixing and correcting and restoring them. However, sometimes you have to make decisions based on something other than "neat". We are providing the owner with a complete and well designed solution, albeit hot water, as easily, quickley and economically as the situation allows. School starts in two weeks, boiler delivery in three, pumps in four. Heat by October 1st.

Tim_33

Thanks!

That is abolutley what I meant.

Only one area of problems with heat, but not due to old traps. Comfort levels are ok, sorta. They realize the problems in the classrooms will be addressed after a reliable source of heat is provided.

Christian Egli_2

Burnt by sarcasm

Whew, I'm glad you're located somewhere cold. If your school had been in say, Miami, or somewhere else hot, all the concerns I brought up would have looked way out of place.

Thanks, Tim, for giving more information, you did indeed cover everything to be concerned about. The school should have had somebody like you in charge a long time ago. We dream of what could have happened 30 years ago, but oh well.

Best of luck with your project and thanks more particularly for sharing all the upsetting troubles associated with this standard steam to hot water conversion.

I still didn't help, did I?

Good

Tim_33

I'll post pic's

of the installation in late September. Of course you helped. More than you intended.