adding zone valves

nytech28

I need add zone valves to an existing hot water boiler, feeding 2 airhandlers with hot water coils , 2nd & 3rd floor with radiators,currently the system is not zoned , & working inefficiently ,over heating space that dont need  heat, the supply & return piping is about 1-1/2 dia, do you guys recommend installing 3way zone valve for each zone to get return water back to boiler when zone not calling for heat or 2way valves are good.any recommendation would be apreciated.

hot_rod

A two way should wok fine. With a 3 way you would need to run the circ all the time.

Are the coils in an area where they could freeze, attic for example?

nytech28

no the coils in basement ,no risk of freezing

mattmia2

Another option would be to add a relay and thermostat such that the blower only runs when both the aquastat is hot and the thermostat calls for heat, use a double pole relay and use one contact on each in parallel with each other to fire the boiler if either one is calling for heat.

nytech28

it's a 3 phase evap motor, aquastate  may not work. unless some other controller is installed that delays energizing the contactor to turn the fan, when water temp get hot.

mattmia2

What controls the blower now? I was thinking the boiler fires on the thermostat then when the coil gets hot an aquastat in the air handler turns the blower on(possibly through a low voltage control circuit and triggering a contactor in the air handler)

pecmsg

Is this a commercial building ?

EdTheHeaterMan

From your original post, it appears that you have possibly 4 zones. You will need to determine how many BTUh is needed for each zone. If each air handler is fed by 3/4" pipes and each radiator zone is fed by 3/4" piping, the job becomes very easy.

If however your air handlers are much larger, then using a Taco 1-1/4" zone valve on a zone, may reduce the GPM flow thru the coil. A more expensive motor actuated full port valve might be in order.

Capacity of the boiler in NET I=B=R or NET AHRI capacity will help in the design, also the model number of the air handler or at least the pipe size feeding the duct coil. Any info where we can determine the CFM capacity, coil size, and temperature rise through the coil will help. follow that with the total radiation capacity of the radiator loops. Are they baseboard radiators, or cast iron radiators, or convectors?

Finally is each zone easily isolated in order to place zone valves where needed to zone the system properly?

Is the existing single circulator able to handle reduced flow if all but 1 valve on the smallest zone is operating? and what @pecmsg said

EdTheHeaterMan

You may find this booklet helpful. https://www.xylem.com/siteassets/brand/bell-amp-gossett/resources/technical-brochure/fh-z100b-bg-zoning-made-easy-2.pdf. You will want to start with the first 5 paragraphs on page 4. this will get you interested in the rest of the book. Especially the part about "they didn't have that problem before you got involved"

Then go back and start form the beginning. The author is a great story teller and will make learning the correct way to add zone valves, more interesting.

nytech28

theres no equastat or controller to turn on blower when water temp gets hot at this time, the radiators are cast iron, & theres a ball valves to isolate coils to add isolation valves, I have made a  diagram of the boiler & the system, to help understand the piping & I also got model & serial numbers for the Air handler any info would help.

EdTheHeaterMan

The air handler seems to be able to handle 10 tons of cooling capacity. This is a commercial application, Im guessing... or at least a really big home
The piping that feeds the duct coils for the air handlers might be able to have a flow rate of 10 to 15 GPM. that translates to 100,000 to 150,000 BTUh assuming a 20° temperature drop across the supply and return pipes of the coil(s). By using the only residential zone valve with a 1-3/8" OD copper solder connection that I know of (Taco 573) You risk reducing the GPM capacity slightly. So if you need the full 15 GPM, you may find that there is a reduction in the amount of heat you actually get. If, However, you only need 10 GPM then you should see little difference.

To use the 3/4" zone valve (7/8" OD copper) on the baseboard loops, you should be just fine.

The next thing is to look at the model number of the circulator to see if you are going to get any velocity noise if you have only one of the 3/4" zones calling.

nytech28

appreciate looking into this I didn't mention before, it's a commercial bldg , i.ll get pump info to find out , but that's the system

EdTheHeaterMan

Here are 2 options to consider.
You will need to take into consideration what your GPM flow rate is on each separate zone. You may need to add a bypass with a differential bypass valve, (old School) or consider a new ECM pump that will adjust to the changing GPM flow requirements, based on the number of zone valves open at any given time.

Do you know why you need 2 pumps? There is on on the supply and one on the return. That is unusual.

EdTheHeaterMan

One other thing. where is the expansion tank and water feed pipes located? Please add them to the diagram.

EdTheHeaterMan

Another Query
Since you indicate 1=5/8" OD pipe for the supply and return to and from the boiler, The maximum capacity of that pipe based on a 20° temperature drop from the supply to the return we are looking at about 22 GPM to keep noise to a minimum. (A commercial system may vary) so based on 22 GPM leaving the boiler, you may expect to find the following flow rates to each zone. This is only an educated guess, your actual flow rates may vary.

Also what is the boiler rating in BTUs
And double check that check valve, the flow may be backwards. That is possibly a bypass pipe that will short circuit the supply water to the return water for some reason. (Reasons for a bypass are on Pages 18 thru 20 of that booklet link above.)

nytech28

little update on the diagram for the boiler , there is acually 2 circulating pumps on the return, only 1 pump is used, dont know  who designed the system, but it's over  heating  the place for years , I want to add zones vavles in simple way & not cause any noise issues.i apreciate the help

nytech28

I was able to get boiler info