Boiler conversion from steam to hot water?


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Old 02-01-17, 09:31 PM
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Boiler conversion from steam to hot water?

Hi,

Have a steam boiler thats only 10 years old. Have 6 single piped radiators I'd like to change to hot water. I'm wondering if anyone has done this and is it worth it? More efficient? I'm wondering if I can use the steam pipes for the supply or return and just add another line. How much would this run to have done? Thanks
 
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Old 02-01-17, 10:43 PM
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M,
It can be done but it is a lot of work. The first thing to check is your rads. Some can handle both steam and hot water and some just steam. You have to look at the top of the rad's end section for a small screw or plug. This would be your new location for your air vent and you would plug where the steam vent is now. If you do not have that top plug you cannot use those rads. Then you're going to have to remove the plug on each rad to bring back a return from each rad to the boiler.

Obviously the entire boiler will have to be repiped for hot water. You can use the main probably for the supply and bring your additional returns to a new line and make it a 2 pipe system so you're not cutting into the BI pipe.

As far as efficiency goes it all depends on the boiler or if you are going to zone the system. If you're using the same boiler you'll get the same efficiency. You will have a lower water temp going to the units so it should save you something. Basically you can run the boiler temp at 150 to the rads. They do heat up a lot better than baseboards. instead of 212 for steam.

As far as price goes I don't have a clue not seeing your system. You would have to get estimates for that.

Hope this helps a little.
 
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Old 02-03-17, 09:06 AM
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S,

I checked all my rads and they all have the plug and screw on the top. Yes the boiler needs re piping and lose the site glass and low water cut off, etc. I'm sure..I have like 150 deg temp going to the hot water loop in the basement rads and that's fine. The hot water keeps the rads warm for much longer time compared to upstairs steam rads. I might get some estimates or attempt the conversion in the summer off season time. Have you ever used that pex composite plumbing for heating like here?

>>>https://youtu.be/5jfzmIOUSzA
 
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Old 02-03-17, 10:33 AM
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I have used pex but not that composite type. You might want to keep that LWCO since you have it already installed as a safety.
 
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Old 02-03-17, 01:58 PM
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IMO, steam is better than a hot water system.
 
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Old 02-04-17, 04:54 PM
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The most important thing about a steam to water conversion would be to do an accurate Manual J heat loss. Next determine the heat output fro the rads @ 150f if that is the temp you are planning on using. Going from steam to water you will lose around 50% output from the radiation. For instance a steam radiator gives off 240 btu's per sq ft of radiation, converted to hot water the same radiator will give 110 btu's per sq ft of radiation. At 170f the output per sq ft is 150 btus per sq ft of radiation.
After that if your returns are dray(above the boiler water level) they may be re-used if large enough. Any wet retu rns (below the boiler water level)must be replaced as they have been the garbage dump of the system and are very dirty.
If you can't get the plug out of the opposite side of the radiator for the return don't fret. There is a device sold that the supply and return go into the same side of the radiator that works very well.
Staying with steam.
Steam can operate fairly efficient. The conversion is normally very expensive and may ne be recovered. To make your decision harder I will throw in how to make your steam system more efficient.
1. Make sure all basement piping is insulated with a minimum of 1" insulation
2. If one pipe steam each main must have a good operating main line vent. Some mains may require more than one. This is dependent on how much air must be eliminated.
3. Good operating radiator vents
4. Do not have steam pressure set too high. The boiler should never be shutting down on pressure above 2 psi. Lower pressure is better.
5. Boiler should not fire back on until pressure drops down to 0.5 psi.
6. The hardest thing is the near boiler piping is correct.
 
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Old 02-04-17, 07:57 PM
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I was just thinking about the conversion. I'm pretty sure I'd have more even heating in the house. Since the rads would be warmer longer. But I'm gonna see if my steam system is running correctly. I don't think I have a main vents. I have ones that look like radiator ones. That could be why takes long to hit the rads. The pressure is set like low 0.5. The pressure gage on the boiler reads 0 always. That normal? Heres a pic of boiler and the NBP. Sorry cant rotate for whatever reason.

I didn't know they sold like a dual port device that acts as a supply n return? That would of came in handy on my basement hot water loop I couldn't get the top plug off so I had to go from the other end of the rad. Those plugs are very hard to come off being on 50-60+ years.

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Old 02-05-17, 09:25 AM
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I'm pretty sure I'd have more even heating in the house. Since the rads would be warmer longer.
How would that make the heat more even? Why do you think that the heat is uneven, in the first place?
I've lived in places with steam, hot water & forced air. Nothing beats steam. Correct whatever problems that the steam has & don't waste your money on the conversion.
 
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Old 02-05-17, 09:52 AM
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The problem with the near boiler piping I see quickly is the piping to the system risers from what I can tell. It looks like there are two system risers in the upper left hand corner if it was rotated properly.
They should have been cut apart and both run down to the near boilers piping separately.
A steam system balanced properly will heat evenly again providing good venting practices.
You can probably update your current system and it will work much better and even save some money.
I have done these types of jobs for maybe 1/4 of the cost to convert to water.
Main line vents usually vent 15+ times faster then radiator vents. The purpose of a good main line vent is to vent the main quickly to get steam to the end. The radiator vents vent the vertical pipes and radiators. All radiator vents should be the same style and manufacturer.
When balancing the system most believe the farther from the boiler the radiator is the faster you vent it. This could not be farther from the truth. With good main vents you balance dependent on the size of the radiator. Larger means faster. If the radiator is over 25 sq ft it may be best to add a second radiator vent.
I'm pretty sure I'd have more even heating in the house. Since the rads would be warmer longer
Not really accurate. Steam at 0 pressure moves very quickly, about 50 to 60 ft second and water moves 2-4 ft a second. Moving water will heat slower to a given temp than still water. The radiator will get hotter with steam and take longer to cool off.
A good operating steam boiler/system will operate evenly, quietly and efficiently.
 
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Old 02-05-17, 11:07 AM
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I with the others... keep the steam heat... I wish I had steam...
 
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Old 02-05-17, 08:49 PM
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Not actually sure what you mean ? Do you have a diagram or picture..?(if not its fine).My old boiler had a single riser pipe..But read it would be better to have 2 risers to slow the steam.

The problem with the near boiler piping I see quickly is the piping to the system risers from what I can tell. It looks like there are two system risers in the upper left hand corner if it was rotated properly.
They should have been cut apart and both run down to the near boilers piping separately.
 
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Old 02-05-17, 09:02 PM
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I with the others... keep the steam heat... I wish I had steam...
Yes I'm gonna keep the steam! You guys talked me into it. Never figured steam was still so popular. Thought it was considered like old technology. I started wrapping the NBP and noticed the difference of the pipes staying warmer longer. I have replaced all the rad vents not to long ago. These are straight vents I found at home depot. I have 3 installed. These fine to use as main vents or do I need strictly main vents?

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Old 02-06-17, 04:50 AM
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As a Real Estate Broker, I can say that a lot of people around here like "Steam" because you needn't be so concerned about frozen pipes in the periphery of your building.

That issue is avoided by having FHA; but that comes with the issue of air quality and many people won't even look at a house with Forced Hot Air, especially those with asthmatic children because of the suspended particulate matter.

Steam heat can be a happy medium for many buyers . . . . IF they understand it.
 

Last edited by Vermont; 02-06-17 at 06:17 AM.
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Old 02-06-17, 10:01 AM
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M,
Off your riser it looks like you go into a tee that may feed 2 mains. Ideally you should have each main fed separately off the header. As for your main line vents you should use main line vents and not rad vents. Main vents have larger openings to vent faster and the faster you remove the air the quicker steam gets to the rads.

As for rad vents that is how you balance the system so they all heat up together. Rad vents come with different size openings or adjustable varivalves.

As was previously mentioned the larger the rad the larger the vent opening for faster removal. That way the large and smaller rads heat at the same pace for even heating through out the house.

Varivalve Quick Vent | supplyhouse.com
 
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Old 02-06-17, 10:53 AM
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Spott,

Oh I think I know what you mean now. I'm not sure if that's an easy change or not. I started to wrap the pipes near boiler as shown in the pic and better pic of the mains. That might be a job for after the heating seasons over. I know those mains will not be easy to remove they been on for like 60 years..That was the original main supply off the boiler..


I'll have to look into getting main line vents...I picked up a couple swing checks today for hot water loop an looks like those have to be installed horizontally? They have a plastic washer I'd probably take the cap off to sweat it because know that will be ruined from the heat.

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Old 02-06-17, 11:24 AM
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I worked in steam power plants, commercial and industrial sized, along with a short stint in an electrical generating station for over thirty years. I LOVE steam power but I wouldn't have a steam heating system in my single-family house to save my life.
 
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Old 02-06-17, 02:21 PM
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I have replaced all the rad vents not to long ago
That could the reason why you have uneven heat. All radiators don't take the same vent. The distance from the boiler determines which vent goes where. I hope that you calculated it correctly.
 
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Old 02-06-17, 06:23 PM
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Hello Furd, been a long time. You have always said that and I ask why?
I am from PA and there is a ton of steam heated homes around her. Even more in DC, Baltimore and Philly areas.
They were installed with milli-volt so everyone had heat even if no power.

mikk1
Don't buy anything else as far as vents until there is some homework done. This is not a buy and use situation as all vents are different. You need the right ones. The last thing you want is too waste money in this project.
You are right ...... re-piping is a summertime project.
In your case not two risers but three.
 
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Old 02-06-17, 08:54 PM
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Don't buy anything else as far as vents until there is some homework done. This is not a buy and use situation as all vents are different. You need the right ones. The last thing you want is too waste money in this project.
I still have some of my old radiator vents think 2 or 3 had a dial 1-8 setting. Which ones do I need ? Which ones are good for the main vents? I think the system works well way its piped not sure if it will make a Noticeable difference if I re-pipe. Will I have to move my boiler and re pipe hot water loop and gas line? Maybe proper venting will suffice. I start getting heat to the rads after like 15 mins. I have only a single story house.
 
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Old 02-07-17, 03:19 AM
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I know that one of the vent manufacturers provide a chart as to what vent goes where. I don't remember their name.
 
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Old 02-07-17, 05:48 AM
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I know that one of the vent manufacturers provide a chart as to what vent goes where. I don't remember their name.
Oh ok... possibly Vent Rite? I'll have to look into this more.
 
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Old 02-07-17, 06:03 AM
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Hello Furd, been a long time. You have always said that and I ask why?
I am from PA and there is a ton of steam heated homes around her. Even more in DC, Baltimore and Philly areas.
They were installed with milli-volt so everyone had heat even if no power.
I'll wager the vast majority of steam-heated homes were built more than 75 years ago, when any kind of "central heat" was considered innovative. Back then homes were also built to allow a fair amount of air exchange as it was thought that making homes tight was a contributing factor in sicknesses.

Because of these factors the steam heating systems were made vastly oversize and rather than basing the heat input (to the boiler) by the heat loss of the structure instead various "rules of thumb" were used to determine the requisite number and size of radiators to install. From the number of radiators the size of the necessary boiler was deduced.

Also, because the heat was radiant, there were often drafts, sometimes severe drafts, along with areas that would be cold while other areas would be hot. Individual control of any radiator to a specific temperature was problematic and the response time of the entire system was fairly slow.

Now in the decades since there HAVE been some improvements but for the most part the technology is simply stalled. It is necessary to heat the water to the boiling point, which pretty much precludes getting anything better than maybe 85% overall system efficiency and that figure is probably only achieved on an infrequent basis. Utilizing "temperature set back" for energy savings is all but impossible with any degree of repeatability or true savings. Cast iron radiators are butt ugly in a modern house and the high temperatures they operate at are a burn hazard. The ability to run a milli-volt system without utility power is a VERY minor positive.

Either modern hot water or a well-designed and installed force air system has far better response time along with much better control while also offering substantial fuel savings.


Now you might ask me if I think there IS a place for using steam for space heating and indeed, I do think there is. In historical buildings where the decor is important to be maintained as built, in large office buildings, in facilities where the controls can be quite sophisticated to overcome the general lack of controls and in many industrial heating situations steam DOES make sense. Just not in single family residences.

Just my opinion.
 
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Old 02-07-17, 10:06 AM
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Steam vents are made by VENT RITE, HOFFMAN, GROTON, WATTS. Depending what brand they have different size ID'S. Some letters and others numbers.

To get a sense of the size you will need you can remove the vent and start up your system. Watch the amount of time it takes for that pipe to remove the air and deliver steam. Now you get a vent or maybe 2 if need be to vent the air at the same rate.

So if it takes you 3 minutes to get steam to that point you want a vent or vents to do the same thing. There is no sense in overkill because the line will never vent any faster than an open hole.

Hope this helps.
 
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Old 02-08-17, 06:43 AM
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Spott,

I have installed back my old 3 dial radiator vents on the furthest rads on supply run. Opened from half to fully and is much better already. Heating of the rads 5-10 mins much quicker more even through out and boiler runs less time.
 

Last edited by mikk1; 02-08-17 at 07:16 AM.
 

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