3-Way mixing valve recommendation

[mpilihp]

Ive been looking around for a 3-way mixing valve to be used to temper the return water into the wood boiler and I can only find ones with one inch connections. Im piping with 1 1/4 and woud prefer to stay with that size. Im not a flow expert and would think I would need to keep all the same. I do see some but they are very expensive, im looking for something resonable.

If it doesnt matter I will go with a 1 in unit.

Thanks

~ Phil

 

[Eric Johnson]

I'm sure the pros will correct me if I'm wrong, but I don't think it makes a huge amount of difference.

 

[mpilihp]

I dont understand the dynamics of water flow but I would think putting in a 1" section in a 1 1/4' piping system would create a restriction and limit the flow, cause a pressue difference??? Granted the flow level is very low compared to a garden hose with a nozzel at the end making a spray.

THe fittings for 1 1/4 are almost double that of 1" so im wondering if I doesnt matter that much that I could run 1" instead and save alot of $$

~ Phil

 

[Bob Rohr]

When you size valves or mixing devices what you need to look at is the Cv number. That tells you how many GPM will flow through the valve with a 1 psi pressure drop. Often times the valve can be a pipe size smaller and actually in case of a mixing valve they will track and control more accuratly when sized to the actual flow rate, not the pipe size.

But they do look odd and require reducing fittings often times.

Here is a flow chart for a 3 way thermostatic valve. Notice at 3 gpm flow you have a 1 psi pressure drop.

hr

 

[mpilihp]

Hi thanks for demystifying it for me. I have and was planning on re-using the pumps I have, they are Taco 007-F5 which are rated at Flow Range: 0 - 20 GPM
Head Range: 0 - 11 FT, it will be on 1 1/4 in pipe.

So, how do I tell what GPM this pump will be running at??

~ Phil

 

[steam man]

Hi thanks for demystifying it for me. I have and was planning on re-using the pumps I have, they are Taco 007-F5 which are rated at Flow Range: 0 - 20 GPM
Head Range: 0 - 11 FT, it will be on 1 1/4 in pipe.

So, how do I tell what GPM this pump will be running at??

~ Phil

I am not a hydronic specialist but here's my take:

Basically you have to figure the head loss for the total system by using the flow rate (in gpm) you want to achieve-then adding up all the friction losses for each part of the system. In hydronic systems I think you would want to limit the flow velocity (as opposed to flow rate) to 4-6 ft/minute flow rate keeps noise down and minimizes potential erosion problems. To a certain point you can force a lot of water through a small pipe but you shouldn't. Once you know the gpm you want to achieve and have figured the right size pipe to keep the velocity down, you then figure the total head loss. Using that information is how you select the right pump for the job. I am currently installing a couple of 1" three-way valves in a solar system piping and maybe wished I went to an oversized valve because of the pressure drop. I'll probably be OK as I have a 3 speed pump ready to help me out to fine tune everything. It isn't as efficient to use to big a pump for the job. You can check the flow rate of the 007 pump you have once you know the head loss. There are online pipe/flow calculators that can help you out.


Mike

 

[mpilihp]

Hi Mike thanks, again i know nothing about this, how do i calculate the head loss? Is that to say for the loop going up to the 1st floor its the distance from the boiler out let to the highset point of the loop on the first floor??

Thanks

 

[steam man]

I hope the hydronic guys help out here but here's my take:

Every straight length of pipe, elbow, tee, valve-basically all components in the flow path have a certain head loss if ft/water. You have to add up the head loss for the complete loop. The flow rate you want to achieve is determined by the boiler output. Say the boiler output is 120,000 btu/hr. Normally you design for a 20 deg F drop from 180 deg F to 160 deg F from the output back to the boiler input. 1 gallon of water is 8.34 lbs. Each lb of water can carry 1 btu/deg rise. So, 8.34 x 20 = 166.8 btu's. Multiply that by 60 minutes and that gallon of water can carry 10008 btu's/hr. Take 120,000 btu/hr and divide it by 10008 btu's and that gives you about 12 gpm you have to be able to move through the boiler at design rating. Go to http://www.gearhob.com/eng/design/calculators/calculator-Fluid_Flow.htm. This calculator is only good for straight pipe but you can find one to add up all the fittings. Enter 12 gpm for 1" copper pipe at 180 deg F flowing through 100 ft and you'll find the flow velocity is 4.7 ft/sec. Their recommendation is no more than 4 ft/sec for 2" and under pipe. If you put in 1 1/4" pipe it ends up around 3.0 ft/sec-which is within spec. Knowing the total head loss allows you to pick the right pump according to the example chart above to achieve the desired gpm.

To calculate the head loss through the valve, Use the required flow rate to find the drop in PSI. Each lb/in sq is equal to 27.5" water or 2.3 ft. Basically you want a valve that offers little resistance.

And that's flow 101.

I hope I got that right. Hopefully I am not missing anything.

Mike

 

[Miner3]

I was dissapointed with the Termovar valve supplied with our Tarm boiler. The gaskets leaked so I changed from paper to Viton rubber better for a while. Also the Termovar was supplied for 1-1/4" pipe but the internals are reduced to about 1/2". I selected a 3 way thermostatic valve from Fluid Power Energy http://www.fpevalves.com/ I chose the temperature that I wanted and added Taco flanges to all three ports. You can pick the size ports that you want as well as temperature. Also no metric threads to deal with.

 

[mpilihp]

Hi Mike thanks sounds alot more complicated than I figured. Putting into account that my zones use individual zone pumps.... Im planning on for just this year to have my wood boiler be in parallel with the oil boiler and when its hot it will cycle water through the oil boiler keeping it hot and preventing the oil burner from kicking on. I know its not the most efficient method but its quick, cheap and does the #1 thing im trying to do, stop the oil burner from kicking on. Ill work up the loop going from the wood boiler to the oil boiler and try to do the math and see what it comes out at, Thanks.

Hi Mark thanks for the link so you have to pick a temperature that they set at the factory for you... Ive been told and read several different values for return boiler tempertures either 130 or 140, what is yours set at?

~ Phil

 

[steam man]

Hi Mike thanks sounds alot more complicated than I figured. Putting into account that my zones use individual zone pumps.... Im planning on for just this year to have my wood boiler be in parallel with the oil boiler and when its hot it will cycle water through the oil boiler keeping it hot and preventing the oil burner from kicking on. I know its not the most efficient method but its quick, cheap and does the #1 thing im trying to do, stop the oil burner from kicking on. Ill work up the loop going from the wood boiler to the oil boiler and try to do the math and see what it comes out at, Thanks.

Hi Mark thanks for the link so you have to pick a temperature that they set at the factory for you... Ive been told and read several different values for return boiler tempertures either 130 or 140, what is yours set at?

~ Phil

It can be involved designing a heating system-good heating guys earn their money. I am not sure what your piping layout is but if it is short and simple just go with the 007 and use a 1 1/4" mixing valve. The 007 will probably work OK, maybe just not optimum. The trick is to be energy efficient by not oversizing a pump and getting all the heat moving when you need it. My current project is a nightmare to figure the flow rate so I am going with a high head 3 speed Grundfos pump. Hopefully I can fine tune the flow rate to get what I need. I feel like I am almost cheating.

Mike

 

[mpilihp]

Good luck with that Mike, Ive got new questions about the 3-way valve, My assumption was there were two in ports and one out MIXed port and that it did not matter what temp water was coming into the IN ports. But upon reading about the ones in the link Mark posted from www.fpevalves.com/ it appears there is a HOT in and a COLD in correct? I am also brain storming the simplest way to supply DHW with automatic backup in a setup with storage. I can see how to easily have my Oil boiler kick on when the storage temp is down but how do you swap over your supply for DHW? NOTE the plan is to have the DHW coil in the storage tank, eliminating the cost of a boilermate tank and pump/zone valve for DHW. I was thinking of feeding a 3 way valve with supply from the Oil boilers DHW coil and from the DHW coil in the storage tank. Under normal conditions the storage tank temp would be up and it would be feeding the hotest water, the oil boiler burner would be disabled from coming on because the storage tank temp is up and it would be providing cold water to temper the DHW coming out of the 3way valve.

When the temp in the storage tank drops, an aquastat would enable the oil boiler's burner and it would come up to temp, then in the threeway the hot water supply would switch to be from the oil boiler and the storage feed would be tempering the water. I might need a second 3-way to provide further tempering afterward for during the time that the storage DHW is still too hot to adequately cool the DHW out of the 3way.

But if a 3way valve has a set HOT in and COLD in that would work. Would have to do it with zone valves on the HOT feed, one normally closed and one normally open and then they switch when the temp in the storage drops....

~ Phil

 

[steam man]

I had to read your post a few times to understand what you want to achieve. We like pictures on this site. I guess its so we don't have to think so hard. LOL.

Your first post indicated you wanted boiler return protection. That would be achieved by using a fixed set point mixing valve in the return line or a diverting valve in the discharge line. They both maintain temp through the wood boiler for protection. Be aware that the mixing or diverting are different as mixing is two in one out and diverting is one in two out. Select the correct one from the manufacturer according to their instructions. Termovar (Tarm sells them) Danfoss ( newhorizoncorp.com?) AMOT(not sure sure where for consumers), and fpevalves as above. The last two seem to be more industrial. I use a number of AMOT valves for critical applications and they work flawless for years. I think Tarm recommends the 140 deg model. You have to check the start opening temp and fully open temp to see if it meets your needs. They don't switch at one temp but modulate over a narrow range.

Your second scenerio is somewhat different. You need logic to decide what heat source to use. Simply put an aquastat on the tank (as you mentioned) could change over a three way valve such as a Honeywell 3 way zone valve with an electric actuator, 110v or 24v. They can divert or mix. These are not self powered thermostatic valves as above. They can have end limit switches that could enable an oil burner. However, with the oil boiler it would take time to get up to temperature. My idea would be to use a aquastat that can switch the three way valve over when the storage tank is dropping close to the oil boiler. A second aquastat could be on the storage tank set at a slightly higher temp than the first to enable the oil burner. Experience would dictate the settings that would be optimum. This setup would have some overlap and the oil burner running at times unless you diligent in keeping the storage tank hot.

My setup will have a storage tank with a preheat coil for the DHW that feeds an indirect heated by the oil boiler. This setup has the logic done automatically without controls. The oil burner would only come on if the preheat coil does not supply hot water and to make up for standby losses. I have a switch on my indirect's aquatstat to manually shut the oil boiler off when I have preheat temp available to prevent any short cycling. Personally, I think if you got an indirect, maybe just a small 40 gallon or so it would be the simplest setup. If you got one with a dual coil you would have th option of adding solar eventually.

Good luck

Mike

 

[mpilihp]

HI Mike thanks, sorry for the confusion, yes two seperate situations, my wife says Im hard to follow sometimes!

140 is what Ive heard for the return temp and I think Ill try going with the pre-set 3-way so it is simplier on me anyhow to set up correctly, one less thing to worry about.

As for the DHW that is a future plan/idea for next summer. I doubt Id have time to get storage setup this summer. Ill be creating another thread on that idea so not to mix discussions!

~ Phil

 

[steam man]

HI Mike thanks, sorry for the confusion, yes two seperate situations, my wife says Im hard to follow sometimes!

140 is what Ive heard for the return temp and I think Ill try going with the pre-set 3-way so it is simplier on me anyhow to set up correctly, one less thing to worry about.

As for the DHW that is a future plan/idea for next summer. I doubt Id have time to get storage setup this summer. Ill be creating another thread on that idea so not to mix discussions!

~ Phil

We'll be here...........................

Mike

 

[Miner3]

Phil,
The valve that I have is set to open full at 170deg f. If memory serves me I think it begins to open 6-8 deg. below the full open temp. The laddomat site includes a thermostat that opens at 78C or 172F. I have included a picture of the 1530A 1-1/2" valve that I have.

 

[Miner3]

Also I mentioned in an earlier post that the Termovar valve supplied with the Tarm was reduced to aprox 1/2" and I have included a picture of a Termovar fitting next to a piece of 1-1/4" copper for purposes of clarity. I hope this serves to help others with their selection.

 

[mpilihp]

Hi Mark I like how you set up your valve using the Taco fittings so you can easily pull it out, gonna plan on doing that myself. I am confused now though by what your saying how it operates. My understanding was the MIX out port is what gets set to a certain temperature, IE Set it at 140 deg so the min temp it would put out is 140 deg, will take HOT water on the output of the wood boiler and use it to increase the temp of the returning cold water into the wood boiler to be 140 degrees. But the way your describing it is different, you are saying it will open which port full at 170 deg, the HOT Input?? So what temp is it trying to make come out at the MIX output??

Sorry to ask so many questions but your loosing me. Reallly like the Taco flange idea!

~ Phil

 

[steam man]

I seen where some pros suggest to oversize a mixing valve by one size to avoid the restriction they can cause. As long as the flow is kept on the low side it should be OK. Its when you start moving alot of water that the restriction is going really come into play.

Mike

 

[Miner3]

Phil,

You are correct in your understanding of the threeway valve operation. The diverting application scematic on this site demostrates the valve operation (broken link removed to http://www.fpevalves.com/applications.htm) The hot outlet (port C) is full open when the temperature that you order the valve is met. The hot outlet (port C) does start to open though a few degrees before the purchased max open temperature. This allows a little flow out of the hot outlet (port C) gradually this flow increases as the temp increases. When factory set temp is met or exceeded(port B) closes entirely and all hot water exits via (port C). The return water goes directly to the boiler. I hope that I have not been too confusing.

 

[mpilihp]

Hi Mark thanks, so your using a diverting valve, ensuring the temp headed to your heat exchanger/storage is at least 170deg, which is different than what I am trying to achieve (or ive come to understand I want to achieve, IE maintain return temp), im looking to ensure that the return temp is at least 140deg, which I would use a mixing valve.

~ Phil

 

[mpilihp]

Ive ordered one from Fluid Power ENergy, got the 1 1/2 3-way mix set to 140 deg for alittle more than I could get a TACO 3-way 1" unit in town. I like the idea of using the Taco flanges Ill be doing the same.

~ Phil

 

[Miner3]

Phil,
I think you will be satisfied with your choice. Also I think changing the thermostat is a simple process if you select another temp or need to service it in the distant future.

 

[mpilihp]

Thanks Mark Ill be ordering the rest of the supplies later this week I hope. Ive priced the parts out and most of the stuff is cheaper online than at local places.

~ Phil