Steam to Hot Water

Jamie Hall

This comment is correct -- for hot water. It is absolutely incorrect for steam, which MUST be sized for radiation.

While I completely agree with nbc -- and would continue to do so, even if the pipes were truly seriously corroded! -- it may be possible to convert to hot water. However, I would be prepared, if I were doing it, to replace every single pipe in the system -- and to replace most, if not all, of the radiators. Even if they are sized for hot water, and even if they are flow through (and many steam systems are not), and even if you can successfully tap them for the required vents... they're going to leak as soon as you put 15 times as much pressure on them as they're used to.

I'd be very very inclined to get the steam system working right. It's not that hard...

Michael_17

Steam to Hot water

I am looking at a church project that wants to replace their steam system with hot water. I have all the radiator sizes and all piping is accessible. I am having trouble getting calcs for these old radiators in order to size the boiler. Any help and or tips I can get from you folks would be great.

nicholas bonham-carter

making hot water from steam

as i understand it, steam radiators may be under sized, when they are used for hot water heating--that is if they can even work with water, [some are not flow-through].

as far as sizing the boiler for hot water, calculate the building heating load, and pick a new boiler and rads, based on that output.

why not make their present steam system work right, so they can cut their fuel bills down? i am sure with a vaporstat, and a case of gorton #2 vents, you will seem like a boiler angel, who arrived, and made the system work like new!--nbc

scrook_2

I=B=R derate for temperature

Burnham has a derating table for CI radiators for temperatures lower than the standard 215° for steam.

See http://www.burnham.com/PDF/Baseray.pdf

(page 5, top), note 2000 lb/hr water = 4 gal/min, 500 lb/hr = 1 gal/min.

If you can find the steam SF or the radiation then you can de-rate for your design water temperature.

Getting everything to work (including having the right type of radiators) without leaking at the higher pressures is a whole 'nother trick!

TK03

Do the heat loss and than multiply the sq ft of steam radiator times 150 and see if the output of the radiation will at least match the heat loss.
Never size any boiler by the amount of radiation.The connected load has absolutely nothing to do with boiler sizing.

Michael_17

I use wrightsoft almost daily and am aware that I need to do the load calc. See if you can read this post from another site.
http://hvac-talk.com/vbb/showthread.php?t=255322

I read as much as I could on the subject and the radiators are suspect as to being flow through. Problem is I'm 110 miles away. I figure I would ask as much as I could before my next trip. They have allot of corroding pipes etc, so the piping was going to be changed anyway.

Michael_17

This system is pretty thrashed, and I agree about replacing all the piping, it is all accessible. Anyone have a good resource for cast radiators? This is an amazing church and I would not put anything else in it.

Steamhead (in transit)

Unless you like living dangerously

don't convert it. You might end up as a liability lawyer's dream.

Jamie's right. That system might not be able to take the extra pressure. I've seen the results of this and it's not pretty. The water damage looked like Satan himself had broken into the church and.... well, you get the idea.

How tall is the building? If it has radiation in more than three stories, the static pressure of hot water in the system may be enough to lift the safety valve on a regular basis.

If you replace all the radiation, you will have to find more room for the additional amount needed for enough output to heat the building with hot water. This will not be anywhere near as easy as it sounds- no one wants you to take up more wall space.

Where are the corroded pipes? If the corrosion is confined to the wet returns, simply replacing them will be a lot easier and less complicated. I'll bet the steam lines are fine- as long as they continue to carry steam instead of water.

That looks like an American-Standard PFA-5 series boiler. If I'm right, it dates back to the 1960s or so. There are more-efficient steamers out there now.

Why were you thinking of converting? It has never been proven that transporting BTUs by steam is less efficient than doing so by hot-water. There are those who compare steam systems on the brink of total failure with brand-new hot-water systems, and expect us to take this as a fair comparison. It is not, never was and never will be.

Our company does not recommend or perform this type of conversion, and will not work on a system someone else has converted.

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Michael_17

The steam system is only in the rectory, single floor with all pipes on the first floor ceiling (all accessible). As far as corrosion, they have had radiators rust through as well as piping. The system is old obviously. I am not scared of rebuilding the steam system, the customer generated the call for going to hot water (not sure who or why they wanted this conversion). I definitely don't want to turn this into a call back nightmare, and can't thank you all enough for the replies. Michael

scrook_3

If...

you're completely re-piping and replacing radiation anyway, then hot water's the way to go, lower temperatures than steam. Should be sweet once it's done. Post before and after pictures.

Michael_17

http://i9.photobucket.com/albums/a54/ifish4fud/img_0421.jpg

This is the layout, hopefully you can see it.

Steamhead (in transit)

Rectory?

That looks like the layout for the main sanctuary.....

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Michael_17

It is. As I said earlier, this is a single floor level that is being heated.

Steamhead (in transit)

Hmmmmmm

do they have water quality issues? Steam pipes and rads don't usually rust out like that on their own. What heats the rest of the church facilities? Are they having these issues there?

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Albert Huntermark

I agree!

Same thing happened at our church a couple of years ago, (I didn't do it though! and was only involved after it was finished!,) a rotted pipe turned into a completely new system. Let me just say that they missed the steam!

nicholas bonham-carter

wayer quality

i see in the pictures some sort of chemical solution setup, piped into the return tank, so someone must have thought they had a water quality issue [or excess money].

i hope acidic boiler cleaner is not in one of those buckets of garrat callahan.

is it really certain the radiators were rusty? if the sexton had been "misadjusting" the pressure, he could have caused radiator leaks, which might go away when the pressure was set down again.--nbc

P.S. i see this information on the chemical treatment use, so it could have introduced harmful ingredients such as citric and phosphoric acid. what is the latest theory on chemical additives? i always thought, in this type of system, if you can't drink it, don't put it your boiler.

http://www.g-c.com/solutions/boilers.shtml