valves used in hydronic boiler systems

bob eck

Drive with caution this morning getting snow & frezzing rain in Eastern Pa.

Question when installing boiler hydronic systems and if you need to slow the water down going to baseboard zones, cast iron radiators ect to balance the system what type of vales do you use. Ball valves, gate valves or globe valves? Thanks

kcopp

For most all...

residential situations a ball valve is fine. Gate valves should never be used to throttle.... that will wear them out in no time.

Mark Eatherton

Shouldn't have to balance if it is done right...

If there is a BIG difference in required head pressure, you should use either a pressure activated bypass, or a constant pressure variable speed pump. And IF you MUST balance, throw in a Thrift Balancing valve.



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The use of ball valves as balancing valves is difficult because the valve has to be about 9% closed before it even begins throttling. If left in this position for a long period of time, hydraulic erosion will cause the ball and seat to fail and the valve will never fully seat again after that.



If you can keep your minimum to maximum length within 10% of each other, and the proper pump is applied, you should not have to balance anything out.



The old adage of "If a little pump does a little good, then a BIGGER pump will do a LOT of good" couldn't be further from the truth.



ME

Jean-David Beyer

Balancing hydronic systems.

"If you can keep your minimum to maximum length within 10% of each other,

and the proper pump is applied, you should not have to balance anything

out."



My upstairs is two rooms with baseboard and these are just piped in series, so the only way to balance them is to adjust the amount of baseboard. Fortunately, their load is about the same, and the flow rate of the water is high enough that they heat about the same, close enough.



The problem I have is in the radiant heating downstairs. The tubing is in the slab already. I have no idea the lengths. I have a ball valve for each of the five circuits, and I have five rooms, so I assume one circuit per room. I have pretty much figured out which valve goes to which room, and three of these valves are full open. The others are closed down a lot.



Not only is the problem in turning down the ball valves to adjust the flow something to be concerned with, but also, changing the flow rate does not seem to make that much difference in the heat delivered until you get it very low. When I looked at Slant/Fin's documentation, they give heat output with 1 gallon per minute and 4 gallons per minute. You get a little more heat at 4gpm, but no where near 4x the heat. I imagine the same applies to radiant in slab. I.e., if I cut the flow 75%, maybe the heat will go down 10%. If I want a larger reduction, I have to cut the flow even more.



In one room, I do not need much heat because I have two computers, one of which runs over 400 watts, so it produces a lot of heat. The valve for that room is almost off: I can hear the water going through that valve. I wonder how long it will last. There are special valves for balancing that are shown in John Siegenthaler's book, but I do not have them.

Tim McElwain

Mark have you ever

used a Honeywell D146 differential pressure valve, if so how did you apply it?

bob eck

valves used in hydronic boiler systems

I asked the question because I have a condensing TT PE110 boiler and cast iron radiators with one zone and large 2" supply and return and next heating season I want to get rid of the 2" pipe and build a supply and return header and run 1/2" viega fostapex supply out and back to each radiator and want to have valves on each supply so if one radiator gets hotter than the others I can balance the system. I will do reverse return on the sypply and return. There will be a few new radiators added to the system and I will not be able to keep all runs with in 10% of each other. I was told to use globe valves to balance the system. thanks

Mark Eatherton

Use a manifold with flow meters and balance valves on the returns..

This way, you can fine tune the flows to the individual loads based on actual calculations instead of by guess and by golly.



Uponor, Viega, Watts and many others make them. More expensive than a DIY site built manifold for sure, but well worth the money in knowing what is going on.



ME

Mark Eatherton

Tim...

No, not that specific valve, but they are all essentially the same. I would pipe it between either the supply and return lines, if flow through the heat source is critical. If not, then I'd pipe it between the pumps inlet and outlet. (European way)



Set it for the maximum required feet of head and anything in excess is bypassed.



I usually use either Oventrop or Danfoss.



ME