3 way mixing valve

John Mills_3

There's little room for repiping and customer doesn't want the expensive of 2 mixing valves, etc. How about doing something like this with the baseboard loops coming off the primary piping (not shown) and the radiant off the mixing valve?

John Mills_3

Which one?

We have an older house with several baseboard zones and 1 floor zone. There's an old Taco 3 way mixing valve on the floor zone now but it's plugged up. Trying to come up with a 3 way replacement as much repiping would be murder. Would be nice to go to a simple 4 way but with working conditions prefer not try. 2 of our suppliers say use a Taco 5003-C1 but that appears to be 2 inputs and 1 output. If you can read my drawing below, we have hot in and output to return & floor tubing. Any ideas or are we stuck with major repipe? Thanks

J.S

Here is a pic

Here is a picture of that Taco valve you spoke of. included are the dimensions also. Hope this helps for you.

John Mills_3

That's it BUT...

Ours is piped with 2 outs and 1 in. We have 2 pumps on the system too. Is this gonna work? We're confused!

Mark J Strawcutter

something's funny

Unless I'm missing something, it looks like the floor return and boiler supply are mixing before the 3-way.

Are you sure the drawing is right?

Mark

Eric

Impossible

Something is missing from your drawing. Please double check. No water can mix or divert the way you have drawn in the valve.

Art Pittaway

Something is drawn wrong....

the way it is drawn you will starve the suction of the circulators and stop flow in the system. Go back to the pumps, look at the volute and determine the direction of flow, then track down the direction of flow. 2" masking tape and a marking pen is a lot of help in sorting out a messy piping system. If it is drawn correct, it is installed wrong, you should never just starve a pump.

John Mills_3

We give up

and are going to use a 4 way valve. The one we're familiar with isn't available. Not much hot water stuff locally. We used before the Enerjee HY3420S. Anybody know of a substitute?

Steve Eayrs

I would think piping in the new 3-way would be easier to retrofit then installing a 4-way valve.
I agree with others that you existing 3-way look like it is not piped right. Maybe it should have been piped like the new valve drawing, and somehow managed to get enough flow to keep things going, on this small zone.


Steve

John Mills_3

More help?

We have 2 pumps, the main one and the one just for the floor. How would we pipe using this 3 way thermostatic valve?

Earthfire

is existing

3-way valve being (attempting to be) used as a boiler protection valve? Check the pump direction and your system temps. This does not look like it is the optimum way to operate the system. Just about any manufacturers adjustable 3-way valve would be retrofitable, as long as you match the Cv and temp range.

Art Pittaway

First understand what they do

Lots of boilers are installed primary/secondary with a separate pump to keep flow going through the boiler and a thermostatic valve used to maintain a minimum return temp to the boiler. Copper Fin Tube boilers are often piped this way because the HX will overheat if flow is lost or low. Before you jump in with a wrench use a pencil and paper to figure out exactly what was going on. Thermostatic mixing valves are not diverting valves, they take hot and cold and make it warm. Once again, if the pump is pumping into or out of the A or B port of a 3-way with no bypass, it's wrong. If the pump is pulling from the common it's ok.

John Mills_3

The purpose

is to provide cooler water to the floor loop while maintaining the boiler at 180 for the baseboard.

Can I ask a big favor! Someone who knows how we can use the 3 way valve with 2 pumps, the main one for the baseboard and the 2nd one for the floor, draw a simple drawing for us. Thanks.

hr

Better yet

I agree this looks like an attempt at boiler protection, not radiant mix down.

Paste this link, for some 3 way knowledge. Thanks to PM mag and Siggy!

hot rod

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,96144,00.html

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Steve Whitbeck

The piping diagram JS posted is correct and I have used it many times. The difference is that you have a high temp loop also. All you need to do is at the boiler taps put tees so that you can tap in your high temp loop and you will need a seperate pump just for that loop also. Add check valves to each of the hot feed lines so that you can't get a reverse flow problem.

Steve Eayrs

The drawing is similar to what we do, but we always pipe a bypass between the supply and return of the boiler, just before they reach the 3-way valve, and put the boiler pump on the supply. That way there is no pressure put on the 3-way, and it can decide oon its own which side of the 3-way it pulls the mix from. Without the bypass, the only flow the boiler pump has is what it forces through the 3-way.
This is a problem when you want lower temps. on the mix side of things.

Steve

John Mills_3

would could we do...

to keep it as simple as possible? Would my drawing work? We have little room to work in the closet and an overstuffed tech. The customer doesn't want to put any money in it (sound familiar) as the house may not be there that long.

Steve Eayrs

John,


I'm sure it would work your way, but not as well, and all your talking about adding are two tee's, a couple feet of pipe. Not a big difference in price or space needed to pipe.


My experience is with the higher flow rates being forced through the 3-way, you not only will not be able to keep the slab temp. down as low as you might like, but the 3-way itself may wear out faster too.


to put it another way........ 100% of the flow from both pumps has to go through the 3-way, the way you have it piped. The by-pass gives another option for flow.

John Mills_3

The pmmag

drawing shows 2 mixing valves. Can we get by with that drawing but 1 valve?

Remember on our project, most of the house is baseboard so only a small portion of the water would go through the mixing valve, most would go through the baseboard - if that makes a difference.

Steve Eayrs

John,

Sorry if I mislead you. I was under the impression that you were just doing a radiant floor heat zone with the 3-way.

And no you don't need two mixing valves to do both radiant and baseboards/high temp. zones/etc., BUT I would only use the 3-way mixed down temp. for the radiant floors, and take run the higher temp. zones, (baseboards,etc.), directly off the boiler.

Based on what I think you are doing, I can't understand why you would want to mix down the temp. of the higher temp zones. There are various ways I would do this, depending on the flow rates needed to the zones.

Steve

Art Pittaway

No, that won't work

as drawn without a bypass. The boiler flow would be restricted or stopped when the mix temp is satisfied. Full flow for the boiler needs to be maintained, a bypass from the boiler outlet to the boiler pump suction with a balance valve and the baseboard loop could be another loop off the boiler pump. Art

John Mills_3

how about this

Thanks guys, especially Steve.

Here's a solution that would be relatively easy to pipe. Would this work?

John Mills_3

how about this

Thanks guys, especially Steve.

Here's a solution that would be relatively easy to pipe. Would this work?

mph

Latest drawing

I'd add a globe valve after your closely spaced tees to help convince the water to flow through the high-temp zones. You'll also need to wire the primary pump to come on when the secondary pump runs, but not vice versa. I use Honeywell R832A relays.

Jeff

Steve Whitbeck

If this is a cast iron boiler then you don't need the boiler pump.
Like I said I have done this many times.
Put the pump after the mixing valve - pulling the water through the valve. Pumps push better than they pull so putting the pump on the return side of the floor loop will put more of a restriction on the pump.
pipe off the supply side of the boiler to the mix valve and tee to another pump for the baseboard loops.
You don't need any bypass with a cast iron boiler.
You will not need any pumps other than for the baseboard loops and after the mix valve.