14 branch manifold for boiler system

zman11

I have a new cast iron boiler that replaced a gravity boiler. The boiler heats roughly 6500 square feet. The boiler has 1.25” outlets for supply and return with 1 pump. I have 14 cast iron radiators that it supplies. Most the rads are pretty large. Biggest is a column radiator 38” tall 12” wide, 18 rungs. Most are around 9” wide, 38” tall and 18 rungs. What id like to do is redo all the piping to oxygen barrier pex home runs. I’d like to keep it all zoned together. From my calculations, the rads should have 3/4” pex connections to flow. Correct? I’d also have to make a 14 branch manifold to supply the run since I can’t find any that big with a 1.25” inlet. Would I have any issues doing this? The farthest rad is about 70’ away. Which I would put first on the manifold and last on the return side. Any advice would be really helpful thank you

Karl Reynolds

A company called PHP makes them in 1-1/4" trunk with (18) 3/4" branches. Part number PHP1250187504. Alberta Tee is another option for the same.

hot_rod

Get an 8 and 7 port do you have a spare port

Caleffi can build inverted versions also, branches pointing up

zman11

thank you Karl, I will check into these

zman11

would I run into issues with flow using 2 manifolds on a single pump? Thanks

Alan (California Radiant) Forbes

No - You just have to size the pump for the proper gpm and resistance.
Let’s say you need to flow 16gpm at 8 feet of head. A Taco 0010 would work fine.

hot_rod

You need heat load numbers to know what flow you need to each radiator. 1/2” may be enough to all if them. It is much easier to work with 1/2” pex, good for 10- 15,000 btu/hr

zman11

how can I calculate heat load number per rad? I have been researching for hours trying to make my system most efficient and flow nicely but the pex piping size i can’t find a good link to direct me to the most efficient pex size per rad. The sites I have find, when I do the math, the biggest rad I have comes to about 21000btuh. I just don’t know if that’s correct. Thank you

hot_rod

You want to know the btu/hr load of the space the radiator is in. there is no knowing if the radiator was sized correctly on day one?

a wild guess at heat loss, call it 22 btu/ sq. ft X 6500 =143,000 btu load.

If the radiators were all the same you need 1 gpm per radiator to move 140,000.

So some will need .5 gpm or less maybe the big ones 1.5 gpm.

You need one solid number to start with, the heat load, ideally room by room.

A free simple load calc program demo at hydronicpros.com

Without that we are just spitballing.

Info on radiator derates here.

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_25_NA_Lowering%20water%20temperature%20in%20existing%20hydronic%20heating%20systems.pdf

zman11

thank you hot rod. This is great info, I will review.
Unfortunately the information on knowing if the radiators were sized correctly to begin with is unobtainable. The house was built in 1850. It had a giant dinosaur gravity boiler that went to hell last year.

Alan (California Radiant) Forbes

Since 1850, have there been any improvements? Double glazed windows, attic insulation, outside wall insulation, floor over unheated basement insulation? If so, those radiators are oversized.

Before you begin any work, you will save a lot of money to learn about the characteristics of your house; room by room. You want to know how the existing radiators relate to the actual heat loss of each room. Either you or someone qualified should do a heat loss calculation.

Get comfortable being confused. It's the first step to learning.

zman11

all of those upgrades are on my list to do, this is my primary project house and it’s 9500 square feet total, the other portion is heated by other means. I can only do so much with the money I have and have to go in a specific order so I don’t bury the upgrades I need to do. Windows are on my list, the attic has some insulation but not enough, I need to rewire the upstairs before I cover the electrical with insulation. The exterior is 2 feet thick stone. Not sure if it’s insulated, basement does have heat, electric, but I still am going to insulate the joists

leonz

Hello zman11,

I am a homeowner that has a hot water baseboard-which I hate that is heated with a coal stoker boiler.

About your home, is the riser and return piping for your gravity hot water heating system in your home already gone??? I hope not as the system as designed provides a continuous flow of heat and hot water with the piping as it was installed.

If your system is a bottom fed gravity hot water system there should be orifice discs in the radiators the control the speed of the water heating your home by diverting the hot water to the upper floors first and heating the first floor and basement last as hot water is lazy and will go to the first floor radiators first if there are no orifice discs in the first floor radiators.

Was your home set up with a bottom fed gravity hot water heating method or a top fed gravity hot water heating method???? Do you know which type of gravity heating method was used to heat your home?

Was there an open to air expansion tank with a vent pipe exiting the roof?

If there was no open to air expansion tank in the attic your radiators were partially filled with water leaving an air charge in them to allow expansion in your heating system.

Lest get this out of the way first and foremost; how are your beautiful radiators piped? The various designs piping methods are described in CLASSIC HYDRONICS starting on page 11 in Chapter 4 titled CLASSIC GRAVITY and continuing to page 40.

This extremely detailed well written chapter describes how you heating system works from the basement to the top floor by showing you the piping designs for the bottom fed and top fed gravity hot water systems that may use the EUREKA fitting invented by Mr. Mark Honeywell as well as the 2 pipe systems using the O.S. Fitting designed and patented by Mr. Oliver Schlemer.

With the very large amount of thermal mass already in your system and the thick foundation in your home why do you want to rip out all the pipe which is probably schedule 80 pipe which in itself creates a great deal of thermal mass?

The gravity hot water heating method provides the user with slow even heating in the entire home or building.

Insulating the ceiling joists in the basement defeats the ability of the boiler to heat the first floors wooden planks.

Mr. Holohan also explains in detail why your new boiler will run a great deal more than the old boiler because it has less thermal mass too.

Adding a hot water storage tank like the New Horizons 490 gallon insulated hot water storage tank piped to the sump of the new boiler would add a great deal of thermal mass that the new boiler would benefit from as it would provide a great deal more hot water to the boiler sump requiring less energy to heat the water used to heat your home.

Please visit the Heating Help Bookstore and Purchase at least these two books on hot water heating, CLASSIC HYDRONICS and PUMPING AWAY and you will benefit from Mr. Holohan's many decades of work experience in the heating industry as well as the combined knowledge of all the dead men that created these heating systems like David Honeywell and many others and the scientists before them that created all the formulae creating the formulas for thermodynamics and gas law and many others that gave the dead men this ability to build heating systems.

Please tell us more and provide pictures of your system in its entirety if possible as we are on the outside looking in.

new horizons 490 gallon storage tank 0000244_300.jpg

zman11

Thank you for all of the information. No all the original piping is still there. I live in Minnesota and the old boiler went out and needed to be replaced in the middle of winter. So a new one was retrofitted using the existing old pipes. It worked good last year, heating the home well but inconsistent room by room with the way the old piping was configured. The main supply run tees off in the basement for a 4” iron pipe and a 3” iron pipe. The rads on the 3” line didn’t get as hot as the 4”.

As far as I know, there aren’t any orifice discs on any rad but there are radiator valves on each one.

I am not sure if the system is bottom or top fed. Unless I can figure that out with the rads. The main level supply feeds and returns on the bottom of the rads and the top level supply feeds the top of the rads and returns on the bottom. The boiler is in the basement. All the pipes are accessible from the basement and none are ran inside a wall cavity. I can take some pictures when I get home later.

the system does have an expansion tank in the system but it’s not open to air and it did always have exhaust vented through the chimney. There is nothing connecting to the system in the attic.

since the new boiler is already installed, I just want to make it efficient now. I don’t see how new home runs wouldn’t do that but that is why I am here getting more educated. Thank you for the information. I will post pics later after work

hot_rod

maybe consider getting a complete energy audit

Heating and cooling load calc, infrared scan, blower door test, etc

Then you can determine where best to spend energy upgrade $$

leonz

Hello zman11,

Now that have been made aware of this I/we can move forward.

Was the original hand fired or coal stoker boiler that was converted to the new fuel?

Mr. Holohan would know whether new home runs with replacement piping will save you money but I think part of your answer will be adding orifice discs to all the radiators on the first floor and adding a hot water storage tank like the New Horizons 490 gallon insulated hot water storage tank connected to the boiler sump/return piping to replace the thermal mass you lost when the old boiler was lost.

I am glad the piping has not been ripped out as you can still use it to its full advantage for thermal mass and still make your system more efficient and keep the first floor warm without adding insulation to the ceiling joists.

Please take pictures of ALL the basement plumbing, every radiator and its piping and the "expansion tank" as it sounds like some whoodo voodoo was done that should not have been done to the "expansion" tank.

If you have pictures of the old boiler and it's plumbing it would help us a great deal and help us to help you.

zman11

I believe it was a coal fired converted to natural gas. This is the only pic of the old boiler without its abestos insulation around it and the only couple of the new boiler. You can kinda see the large expansion tank connected with 1/2 copper line in the upper right of the 3rd pic

leonz

Would you mind taking more pictures of the steel compression tank at both ends and under it as it should be connected to the boilers hot water flow to absorb air bubbles as it is pumping away to the radiators to heat the home if they did not reconnect it you do not have a useable air management method and that explains a great deal and is part of the reason the system is not working well.

By what you have described you have a balancing problem not an air problem.

Where is the low water cut off switch? is it plumbed into a pipe to sweat copper Tee or in a boiler tapping that we cannot see in the pictures?

About the bell end fitting with the 2 tappings and 2 copper pipes connected to the 4 inch pipe; what is this pipe? A cool water common return header?

Ask your plumber if he or she has cold and hot water flow direction tape that they can apply to the new piping PLEASE or at least use permanent tags that label each pipe as hot water feed or cool water return PLEASE.

zman11

I can take more pics later on. The expansion tank has no connection on either side but does have the 1/2” copper connection on the under side that is connected to the boilers hot supply line.

I am unsure if the boiler has a low water cut off switch. I’m the only operator of the boiler so I check it weekly to make sure the water pressure is up to par.

Those 2 4” lines is a supply and return that does most of the rads in the house. Supply and return line is labeled, but can’t see in the pics. The supply line is the closest to the expansion tank

HomerJSmith

Off hand, calculating pressure losses may be a challenge, so I would use an ECM pump that is oversized (even tho rudimentary calculations are better than guesstimates) and use balancing valves on each loop, especially so, if the manifolds do not have them. Not all zones operate at the same time, but you should plan for that 2% when temps drop precipitously.

Flow is the determining factor at a given water temp at each heat emitter in thermal transfer.

leonz

How are you checking the water level in the system if there is no sight glass gauge?? You may be waterlogging the system by adding water and pushing it out of balance.

Is there a drain valve with a hose bib in the base of the tank? If there is it may be a Drain-O-Tank valve.

The Drain-O-tank valve like the Airtrol valve has a copper dip tube that regulates the air to water ratio in the compression tank.

If there is too much water in the compression tank it is waterlogged and you have no point of pressure change that allows the circulator to work correctly.

If there is a shut off valve on the copper line to this tank you should close it and open the vent on the airtrol or drain-o-tank valve to see if there is too much water in the tank. if water does come out of the air vent you need to let the water drain out until you see air sputtering out of the tank and then close it. Open the valve up to the boiler and the system will be balanced.

Once you have the compression tank drained of excess water if there is too much water in the compression you close the vent and you are done with the system and balance is restored and no more water is required to operate it. The only time you add water is if there is a leak in your system after it is repaired.

Once the system has been filled or refilled and the steel compression tank is drained to the proper ratio of 1/3 air 2/3's water you are done.

zman11

I guess I just make sure the boiler has adequate pressure inside the system.
However, there is a drain valve with a hose bib on the bottom of the tank but no dip tube valve to regulate air to water ratio. Which one do you recommend? Last night, the tank felt more empty than full. Definitely not 2/3 full of water. Could that be an issue as well? Thank you

leonz

If the tank has too little water in it or if it is flooded your circulator will not work well.

That valve may very well be a Drain-o-Tank valve- if it is it should have a metal tag surrounding the base of the globe valve handle stem or a tag in the center of the handle, the Drain-O-Tank valve has the dip tube as well.

drain o tank valve.jpg

bell-&-gossett-air-trol-tank-fitting-installation-manual.pdf

If your steel compression tank has 2 tapping's in it, you can use one of them for the Drain-O-Tank valve other wise you will need to use the Bell and Gossett air-trol-tank fitting.

As long as you measure the tank diameter you will know which air-trol-tank fitting you need based on the submittal sheet listing.

bburd

That new boiler came with a modern, wet rotor, relatively high head and low flow circulator. Those work well with systems designed for forced circulation, with smaller pipes. It probably doesn't move enough flow for an older system piped in parallel and designed for gravity circulation. The uneven heating is most likely due to the change in flow dynamics.

You probably need a pump with a higher flow rate, as well as some rebalancing. That would eliminate the the need to re-pipe what is there. Most gravity conversion jobs work well on the original piping with a traditional three-piece circulator like the B&G 100 that was designed for that application.

What is the make and model number of the circulator? And what is the boiler nameplate rating?

zman11

I’m looking at balancing valves. Any idea which ones I should look at? Also looking into updating the expansion tank. As well as possibly the circulator. The circulator is on the return side and here is the model of the circulator. The highest point of a rad is about 30’ above the boiler. Does that mean I have 30’ of head?

zman11

my boiler says 145,000 btu with a 125,000 btu/hr. When I got the boiler, this is the size the “experts” said I needed.

Is this the circulator your recommending?

bburd

Yes, that is the circulator I meant. I had a house with a converted gravity system of about that same heating capacity, 13 big cast iron radiators on three stories, and that circulator pump, that heated evenly.

No, you do not have 30 feet of head. When selecting a circulator rather than, say, a well pump, head refers to friction from the connected pipe and fittings, not to the height of the column of water above the boiler which is what reads on the pressure gauge. That does not matter to the circulator, because whatever water it moves out will come right back into it; the system is a closed loop

You might be able to keep your existing expansion tank. The tank is sized based on the water volume of the system, and old gravity systems hold many times more water than modern systems with small pipes and fin tube or steel panel radiators.

Regarding balancing and how to do these conversions, the best reference I have seen is Dan Holohan's book "How Come?", available from the bookstore on this site.

Is there a pattern to the balancing problems? A particular floor that is too warm or cold, or trouble getting heat to the radiators furthest from the boiler?

leonz

Hello Bburd,

Zman11's even heating issue leads me to think he does not have orifice valves in the radiators. I agree with you that he needs a copy of HOW COME along with CLASSIC HYDRONICS and PUMPING AWAY to help him.