what is the advantage of a danfoss valve over an adjustable thermostatic mixing valve?

[Garth B]

I installed an adjustable thermostatic mixing valve for boiler protection and it seems to be working fine, why does it seem everyone is using the danfoss mixing valve? I have found it nice to be able to adjust the return temp when I am messing about with my delta-T across the boiler and flow rates ect. Is this type of valve prone to failure or some other shortcoming?

 

[ewdudley]

I installed an adjustable thermostatic mixing valve for boiler protection and it seems to be working fine, why does it seem everyone is using the danfoss mixing valve? I have found it nice to be able to adjust the return temp when I am messing about with my delta-T across the boiler and flow rates ect. Is this type of valve prone to failure or some other shortcoming?

I suppose the main problem would be finding an affordable adjustable mixing valve with a large enough Cv to avoid idling when return temperatures get high. The common adjustable mixing valves have a Cv of 3 or 4, while the Danfoss is like 15 or 20 IIRC.

And the common adjustable mixing valves only go up to 150 degF or so since they tend to be for DHW, so the adjustability doesn't do much good since 150 degF is about as low as you'd want to go to begin with.

Nonetheless I put a Taco 5000 on my coal boiler, which works great because the max BTU output is about 75000 btu per hour, so it flows plenty with a 007 and maintains at least 150 degF return temperature.

Do you know of an affordable adjustable mixer with a bigger Cv and a higher range? It would make nice option for a lot of systems.

 

[Garth B]

I used a 1" honeywell mix valve that has a cv of 3.9 and max mix temp of 180deg it is 95$ from pex supply.

http://www.forwardthinking.honeywell.com/related_links/water/mixing_valve/install/62_3106.pdf

The 1" danfoss has a cv of 10.5 so it definitly flows better on its own and the 1.25" danfoss has a cv around 16.5 like you said.

But when recircing the cv would be higher due to the balancing valve, and it looks like it recircs through the balancing valve even when its up to temp? not sure, i am not familiar with them just assuming thats why they need the balancing valve. In the end when comparing them is the danfoss anymore efficient after the cv of the additional balancing valve and the continuous recircing?

 

[ewdudley]

I used a 1" honeywell mix valve that has a cv of 3.9 and max mix temp of 180deg it is 95$ from pex supply.
http://www.forwardthinking.honeywell.com/related_links/water/mixing_valve/install/62_3106.pdf

And it does diverting as well. Looks like a nice alternative to the Taco 5000, wish I had found it earlier.

But when recircing the cv would be higher due to the balancing valve, and it looks like it recircs through the balancing valve even when its up to temp? not sure, i am not familiar with them just assuming thats why they need the balancing valve. In the end when comparing them is the danfoss anymore efficient after the cv of the additional balancing valve and the continuous recircing?

When recircing I'd say you're right, the danfoss apparently needs balancing valve restriction to work correctly anyways, so what can some additional Cv matter?

When system return temperature increases above the mixing valve setpoint you can only pull less than 6 gpm with a 007 or 8 gpm with a 008. 8 gpm works out to 25 degF temperature rise through the boiler at 100000 btu per hour, sounds quite workable for most systems. But if you need more flow, then the smaller valve won't do.

I don't think 'efficiency' much matters. The pump is going to draw about the same current with high or low Cv, so if you're happy with the deltaT and the overall performance it definitely sounds like a valid alternative to the Danfo$$. As I've said the Taco 5000 is working well for return temperature protection on a 80000 btu per hour boiler for me.

 

[goosegunner]

I used a 1" honeywell mix valve that has a cv of 3.9 and max mix temp of 180deg it is 95$ from pex supply.

http://www.forwardthinking.honeywell.com/related_links/water/mixing_valve/install/62_3106.pdf

The 1" danfoss has a cv of 10.5 so it definitly flows better on its own and the 1.25" danfoss has a cv around 16.5 like you said.

But when recircing the cv would be higher due to the balancing valve, and it looks like it recircs through the balancing valve even when its up to temp? not sure, i am not familiar with them just assuming thats why they need the balancing valve. In the end when comparing them is the danfoss anymore efficient after the cv of the additional balancing valve and the continuous recircing?

The new VTC model apparently closes the hot port completely once return is up to temp. From the description from the Danfoss tech it seems like a nice upgrade from the model I have.

gg

 

[infinitymike]

I don't know anything about mixing valves, as you can tell by one of my threads. I was all set to buy the Danfoss (if I can even find it locally).
With the adjustable you have the obvious adjustment and with the Danfoss you are stuck with what you got. And speaking of that what should thermostat should one buy from danfoss? they offer 122*, 131*, 140*, 149*, 158*, 176* the first three they say are for return line boiler protection and the last three are for boiler output,storage tank feed. I was thinking for my system to go with the 149* but Wallace Eannace( a Danfoss wholesaler) doesn't even have that in stock so my supply house can't even get it. so my thinking is bump it up to the 158* so if I do storage at some point at least I'll be set up.
Here is a link to the new style danfoss (thanks gg)

Any comments. Garth If you want I will make my own thread so I dont take yours hostage.

 

[goosegunner]

Check the data sheet that I sent you, I believe they recommend the 140 if it is return mounted.


I would ask Danfoss if higher temp is ok.

gg

 

[ewdudley]

With the adjustable you have the obvious adjustment and with the Danfoss you are stuck with what you got.

Any comments?

Tough call. My system is set up with a return temperature controller, so I have the luxury of trying different return temperatures. My particular boiler seems to gasify more reliably, maintains a better coal bed, and never bridges with a supply temperature of at least 175 degF and a return temperature of at least 160 degF.

But that's my boiler, which doesn't have much refractory skirting the main combustion chamber. One of the WG boilers's strong points is supposed to be a nice hot primary combustion chamber. Go ahead and use the standard 140 degF unit and if later on you don't think that's hot enough you can swap in hotter thermostat guts into the existing housing.

 

[infinitymike]

Thanks guys. Cant find it locally.
New Horizon has what looks like and older style but the only have the 140* in 1.25"
I only have 1".
Is it ok to bush up?

 

[rkusek]

Thanks guys. Cant find it locally.
New Horizon has what looks like and older style but the only have the 140* in 1.25"
I only have 1".
Is it ok to bush up?

That should be better actually. I bought mine from them (old style) and Zenon only sold the 1.5" telling everyone to bush it down to 1.25". The higher capacity is why he only carried that size he claimed. Looks like the new version may have changed that philosophy.