Caleffi ThermoMix Thermostatic mixing valve

cutter

I want to buy a ThermoMix Thermostatic mixing valve but can not find the pump to go with it. The valve calls for a pump with a 10 GPM flow. I assume that to be maximum flow.I have to buy all or most all of my stuff from supply house. I have looked at all of their variable speed pumps and unless I have missed something all of them pump a lot more than 10 GPM. Or would the valve just restrict any flow to 10 GPM? Any suggestions?

unclejohn

I suggest you ask Hot Rod.

SWEI

What is the application? Do you have a sketch or a photo of the intended installation piping?

cutter

unclejohn said:

I suggest you ask Hot Rod.

I thought Hot Rod would chime in being it is a Caleffi product.. Thats why I mentioned Caleffi in the title. He most likely still will.

Ironman

The gpm of the pump is dependent upon the head of all the components and piping in the circuit. Most of the small wet-rotor circs (Grunfos ups15-58, Taco 0010, B&G nrf22,etc.) will pump about 10gpm @ 10' of head.

cutter

SWEI said:

What is the application? Do you have a sketch or a photo of the intended installation piping?

I have wanted to build this for awhile now but did not know much about hot water heating. I have learned a lot since then.
The picture is what I intend to build. I got the idea from this site and had to learn a lot reading Caleffi's trade journals. I could buy the thermoBloc pump from Supply house for the wood boiler but they don't have it listed on their site any more that I can see. The pump on the oil boiler does not need the Thermobloc feature so i am trying to find a pump for that boiler. And am tempted to use the same on the wood boiler.

The pump on the therm bloc is a Wilo Star S-16 U15, When I google it the Supply House site says it has been discontinued. Ideally I would like to find a pump from a different manufacturer with roughly the same pump curve and a simple two wire connection with ground.

SWEI from past posts of yours it appears you do a little wood boiler,or combination wood boiler, conventional boiler work. What have you found that works with that ThermoMix valve?

The pump curve is for the Wilo Star S-16 U15 pump that is on the Caleffi ThermoBloc valve.

cutter

Ironman said:

The gpm of the pump is dependent upon the head of all the components and piping in the circuit. Most of the small wet-rotor circs (Grunfos ups15-58, Taco 0010, B&G nrf22,etc.) will pump about 10gpm @ 10' of head.

I have looked at the Grunfos 3 speed ups 15-58. That pumps slowest speed pump curve is close to the Wilo Stars fastest speed pump curve. would the ThermoMix valve still do it's job properly with a higher GPM pump?

Harvey Ramer

The thermomix, or any mixing valve does not require a certain gpm. They work best within a certain range of flow. The boiler protection valve is far less critical to have sized to a specific flow rate then for example, a DHW mixing valve. The reason for that is response time of the mixing function. If the thermomix responds a bit slow or over compensates due to incorrect flow, it won't hurt a thing.

So in a nutshell, buy the valve to fit your piping. (As long as you size the piping correctly) They have a very high cv rating but make sure you include it in the piping calcs.

Bob Bona_4

I suspect HR is tied up in Orlando/ARI event . He'll emerge soon!

cutter

Harvey Ramer said:

The thermomix, or any mixing valve does not require a certain gpm. They work best within a certain range of flow. The boiler protection valve is far less critical to have sized to a specific flow rate then for example, a DHW mixing valve. The reason for that is response time of the mixing function. If the thermomix responds a bit slow or over compensates due to incorrect flow, it won't hurt a thing.



So in a nutshell, buy the valve to fit your piping. (As long as you size the piping correctly) They have a very high cv rating but make sure you include it in the piping calcs.

The thermoMix valve says use 10 GPM and the Wilo Pump on their ThermoBloc valve and pump puts out 10 GPM with 17 feet of head on the highest speed and 5 GPM at 8 feet of head on the slowest speed. That is why I thought I needed a pump with the same characteristics.

I am planning on using the 1- 1/4" thermomix. The piping from the pump to the boiler I was planning on using 1-1/2" steel pipe and from the boiler to the manifold I was planning on using 1-1/2" steel pipe. On the suction side of the pump I am planning on using 1-1/4" steel pipe.

I used the on-line friction piping loss-free calc. to do a head loss on the steel pipe and fittings. Their number was .3 feet of head loss.

Would that Grunfos UPS 15-58 FC work with that head loss or would I need a smaller pump?

Harvey Ramer

Just because the boiler tapping are 1-1/2" does not mean that's the size pipe you should use. What is the btu output of the boiler?

You want the result of head/gpm of the piping to fall as close to the center of the pump curve as possible. If you have a very low head loss, you can start dropping pipe sizes to accomplish that goal. Also pumps come in all flavors. You can pick a pump with a flatter curve in a low head situation.

cutter

Harvey Ramer said:

Just because the boiler tapping are 1-1/2" does not mean that's the size pipe you should use. What is the btu output of the boiler?



You want the result of head/gpm of the piping to fall as close to the center of the pump curve as possible. If you have a very low head loss, you can start dropping pipe sizes to accomplish that goal. Also pumps come in all flavors. You can pick a pump with a flatter curve in a low head situation.

In my first post I show a picture of what I want to build. So this pump is not a zone pump. This pump will pump from the boiler to the manifold. So it may not need the flatter curve. On the manifold will be another pump that will supply water to individual zones.

The BTU output of the wood boiler is 140,000 BTU if oak or coal is being burned. The BTU is lesser if soft woods are being burned. The OIL boiler is 132,000 BTU, and is a little over sized unless the garage is being heated also.

I had forgot about the Head/GPM being close to the center of the curve. The Wilo and Grundfos I mentioned above are within 2 GPM and head is real close.

I will look for steel pipe friction losses and do another head loss for 1 1/4 pipe. That on-line friction piping loss-free calc does not have 1-1/4" pipe listed.

SWEI

I've worked on a number of wood boilers over the years. Harvey does them on a semi-regular basis.

140,000 BTU/hr at a 30°F ΔT would come to 9.33 GPM. I'd size for that, but even 9 GPM should be OK as a design point.

Harvey Ramer

1-1/4" will likely work out to be the correct pipe size.

hot_rod

Is that the boiler input, 140,000? If so maybe 75- 80% efficiency so you only need to move about 11 gpm to transfer full output of the boiler.

1" copper could do that at just under 4 fps velocity, near perfect. The pressure drop in most wood boilers is very very low, you may see more than 10 gpm, but the pump is a 3 speed to dial in an exact flow, if desired.

The 281 ThermoBloc is still available and should be ideal for the boiler protection device. Maybe you are pumping into a buffer tank? Or a hydroseperator as shown? If so you have enough pump in the Star 16.

cutter

SWEI said:

I've worked on a number of wood boilers over the years. Harvey does them on a semi-regular basis.

140,000 BTU/hr at a 30°F ΔT would come to 9.33 GPM. I'd size for that, but even 9 GPM should be OK as a design point.

SWEI I decided to use your temperature drop and use 30 degrees. Instead of using that on-line friction piping loss-free calc, to get a head loss, I did it with a caculator.

Another post on this site I learned it was third and fifth grade math. I flunked those two grades.

Taco's and Caleffi's numbers give a head loss with about a foot and a half difference. Their calculation numbers are slightly different also. The numbers are for copper tube sizes. When I googled K values for steel pipe fittings, I got the same Taco chart as for copper tube sizes/equivalent length of pipe.

1 1/4" K=.000324 X C=.933 X L=55.2 X F=46.765 = .780345 Foot of Head loss
! 1/4 pipe K Value of K (water in system) C 180 degree average fluid temp. L Total equivalent length of circuit F= flow of 9 GPM Raised to 1.75 power.

Here is Caleffi numbers, They use A instead of K in formula

1 1/4" A=.045 X C=.0068082 X L= 44.1X F=46.765 =.631835 = Foot of head loss

Caleffi did say if threaded fittings are used to double the friction chart numbers That would give me a 1.263 head loss. And what is that 1/2 psi or so???

cutter

Harvey Ramer said:

1-1/4" will likely work out to be the correct pipe size.

Harvey, that 1-1/4 is what I will most likely use. I put my friction loss calculations in SWEI's post. That run from the boiler to the manifold is so short there is very little head loss. So I don't see what 1-1/2 pipe would hurt. But 1-1/4 will flow 8.2 gallons per minute based on 2 ft/sec and 16.3 GPM based on 4 ft/sec.

cutter

hot rod said:

Is that the boiler input, 140,000? If so maybe 75- 80% efficiency so you only need to move about 11 gpm to transfer full output of the boiler.

1" copper could do that at just under 4 fps velocity, near perfect. The pressure drop in most wood boilers is very very low, you may see more than 10 gpm, but the pump is a 3 speed to dial in an exact flow, if desired.

The 281 ThermoBloc is still available and should be ideal for the boiler protection device. Maybe you are pumping into a buffer tank? Or a hydroseperator as shown? If so you have enough pump in the Star 16.

Hot Rod, that one inch pipe is at or close to the minimum pipe size I could use. I am thinking 1-1/4 is what I will go with. I figure on using steel pipe.

SWEI

I use a 30°F ΔT for design conditions, meaning the boiler is at full fire and the bottom of the storage tank is cold enough to absorb a lot of BTUs. As the load begins to satisfy, the tank volume heats up and the RWT increases. Assuming you've sized the boiler, the load, and the tank correctly, this is the point where the boiler fuel load starts to burn down.

cutter

SWEI said:

I use a 30°F ΔT for design conditions, meaning the boiler is at full fire and the bottom of the storage tank is cold enough to absorb a lot of BTUs. As the load begins to satisfy, the tank volume heats up and the RWT increases. Assuming you've sized the boiler, the load, and the tank correctly, this is the point where the boiler fuel load starts to burn down.

SWEI, The boiler has a 140,00 BTU capacity but when burning soft wood or a half full fire box the BTU output is only a guess. I will use your 9 GPM flow. I do wonder though if it would really matter if I used 1-1/4" or 1-1/2" pipe with the head loss so low.

When I built this house back in 84 I wish I knew then what I know now. I would have put in a buffer tank then. The boiler room is too small for one. It looks like the architect knew even less than I back then. The boiler room should have been larger. I am at the wrong end of the tape measure of life to make big changes. I do not know how much longer I will be heating with wood the entire season. I would like most of all to have the conventional boiler plumbed in correctly and be able to run that boiler without problems when I am gone or run out of wood for the year. I feel I have all that just about figured out now. My wife just finished her 9th year of Alzheimer and now requires more attention so I don't know how much wood cutting/splitting I can do in the years ahead.
I do appreciate the help, suggestions, advice, you and others have given me. Thanks
.