Manual or automatic mixing valve?

[Der Fuirmeister]

I'm installing the piping for a SS140 Wood Gun and wondering whether to use a manual or automatic mixing valve? If manual, can I get by with a ball valve? Seems to me that if I need 9.4 gpm to get the 140,000 btu a ball valve throttled to provide the 160* return would be easier and much cheaper than a manual mixing valve. Ball valve - $12. Manual mixing valve - $85. Also, what's the benefit of using an automatic valve at ~$350?

Any thoughts?

 

[Nofossil]

The problem is that the amount of return (bypass) flow that you need varies continuously depending on how hat the fire is and how cold the return water is. Most systems use an active mixing approach that adjusts continuously and automatically. Econoburn uses a bypass circulator. Danfos and others make thermostatic mixing valves that do a nice job.

 

[in hot water]

A dumb valve or a smart valve is what they are called.

Manual valves are considered dumb valves because the cannot sense and react to changing temperature conditions. Not the best choice for critical temperature regulation.

Smart valves include thermostatic, or motorized with sensors to watch temperatures and adjust accordingly. 3 way thermostatic are the least expensive option. Motorized 3 way with a control, or a variable speed pump with a modulating speed control are a few other common options.

hr

 

[Der Fuirmeister]

Thanks. The more I've read, the more I realize that the manual valves are probably not the best way to go. I looked at the Danfoss thermostatic valve that nofossil mentioned and also another by Fluid Power Energy, made right here in WI. http://www.fpevalves.com/productsThermostaticControlValves.asp

I'll check out the cost on these on Monday. With the SS140 Wood Gun I'm concerned more about shock cooling than condensation.

How does using a 3-way thermostatic valve compare to using a circ. pump with an aquastat? Will the pump / aquastat control the temps better / more accurately than a thermostatic valve? From what I've read, the pump may have other advantages

My system has a flat plate HX between the boiler and storage tank. The boiler is a closed loop, and the storage tank is open. All loads draw from the storage tank. The boiler merely acts like a system btu charger.

On the boiler return side, the boiler should see pretty consistent temps once the boiler is up to operating temp. The boiler control is set for 190* with 160* as the desired return. The HX should exchange more btus than the boiler output. I have three speed pumps on both sides of the HX to help fine tune. Again, it's the start up that concerns me.

If I can figure out how to post a drawing I'll show what I believe are the two options that would work depending on whether I use a thermostatic mixing valve or circ. pump controlled by an aquastat.

Again, thank you and nofossil for your reply.

 

[Singed Eyebrows]

As I have been told the Laddomat loading unit is maxed out around the size of your boiler & the Termovar loading unit has more capacity, just pricy(I know you didn't mention these). You can get the Danfoss & this is what Zenon recommends at New Horizons as well as the 2 posters above with light years more experience than I. I posted just in case you contemplated getting a loading unit in the future, Randy

 

[flyingcow]

I just used what was recommended, termovar loading unit. This has the 3 speed grund0-fas(sp?) From when i throw the match on the kindlin', I have 165 degree water shipping to my house and storage, in 40-45 minutes. And it just climbs to max from there very shortly. And i have this rolling thru my baseboard in about the same time, via a termovar valve in the house. The damn valve is pricey, but it works good.

 

[Der Fuirmeister]

Hopefully these drawings will post and you can read them.........

It shows the two options at the boiler...

Unless the mixing valves are problematic or high priced that probably makes more sense than the circulation pump.

 

[rkusek]

http://www.cozyheat.net/Miscellaneous-_c_58.html

Cozyheat has the 1 1/4" Danfoss on sale for $165 now....Zenon at New Horizon sells only the 1 1/2", I got mine there. Think he charged like 200-240. He claimed should use the 1 1/2" for volume reasons even if you immediately reduced it down with bushings which I did since my close boiler piping was 1 1/4". You do need the manual balancing valve between the boiler output and the bypass portion of the valve. I made this line only 1" requiring just a 1" valve. You wouldn't think it should be necessary but most people run this valve 1/2 way close if not more. The instructions in the Danfoss also show all of this. I just used a standard ball valve instead of a balancing valve. The circ setup is definitely a more elegant and efficient setup but these mixing valves do the job as far as protecting the boiler which sounds like your main concern. Thermovar & Danfoss work identically from what I can tell.

 

[Nofossil]

The only drawback that I can see with using a thermostatic mixing valve is that you can't easily adjust the operating temperature. They use an automotive-style thermostat cartridge that has a fixed open/close profile at a fixed temperature. If you decided that you wanted 10 degrees hotter or colder, you'd have to find a different cartridge and open the valve to replace it.

That's probably more of an issue for compulsive tinkerers - not that I know of anyone like that ;-)

 

[jebatty]

This is only partially correct with respect to the Termovar. The setting of the balancing valve has a major impact on the temp of the return water. If I have "cold" return water (say 100F or less), I need to open the balancing valve considerably so that a large portion of the boiler output is directed to the return line. As return water temp from system rises, I need to close down the balancing valve considerably to limit boiler output to the return line. This is where an automatic valve would be useful, especially if your system experiences wide fluctuations in return water temp.

But, if system return water is typically at any relatively stable temperature, or is for example typically 140F or above, the balancing valve can be on a "set it and forget" setting once it is set to achieve the desired boiler return water temp. What is really useful here is a digital temp meter with the sensor on the boiler return line after the mixing valve. A quick glace at the meter will reveal whether the balancing valve needs to be opened or closed more. I usually aim for 145-150F minimum return water temp, although I believe keeping return water closer to 160F does result in better boiler operation.

My balancing valve is a gate valve, mainly because that's what I had when I put my system together. An advantage of the gate vale is the I can easily make fine adjustments. Usually, my adjustments are in 1/4 turns of the handle. With "cold" system return water, the setting from fully closed is open 10/4 turns. With system return at about 140F and above, the setting from fully closed is 4/4 turns; and when system (storage) return is 160F or above, I close the valve completely.

 

[Donl]

My balancing valve is a gate valve, mainly because that's what I had when I put my system together. An advantage of the gate vale is the I can easily make fine adjustments. Usually, my adjustments are in 1/4 turns of the handle. With "cold" system return water, the setting from fully closed is open 10/4 turns. With system return at about 140F and above, the setting from fully closed is 4/4 turns; and when system (storage) return is 160F or above, I close the valve completely.

With respect to the above, I would suggest that using a Termover or similar mixing valve should be considered as semi-automatic setup as manual intervention is sometimes required.

 

[btuser]

Thermostatic is the way to go if you don't want an actuator

 

[Donl]

Thermostatic is the way to go if you don't want an actuator

Another alternative if you have a Primary/Secondary design is to just control the flow on the Primary Loop. Monitor the return to the boiler with some kind of temperature sensor and throttle the primary pump either on/off or if you use a variable speed pump low/high. I have changed my system to this from a actuator/ 4way valve controlled by a tekmar setpoint controller. So far I am pleased with the change.