does the danfoss 3-way TV valve block all the flow to the system or does it mix? i have read that it is a mixing valve but want to be sure. i don't want something that will stop the flow to my system just mix the water to get it to temp. thanks for any reply.
danfoss question please help
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A danfoss valve is a thermic valve. It will block flow 100% from one of the ports when the water is below it's temp rating (usually 140 degrees). Once the temp of the flow approaches 140 degrees the thermostat in it will begin to open. My understanding is that the flow will be full open shortly after temps reach 140, and the "other port" will then be closed.
thanks for the reply. what I'm afraid of with the danfoss is when the temp is below 140 no heat is going to the house and the other pumps of off the main line will kick on and have no flow to them with the danfoss shutting the flow off.does anyone know of a mixing valve that will work to prevent cold water return? all the mixing valves I've seen cool the water down.
You might want to check out the post "simplest storage" at the top of this forum. The danfoss valve should only be directing water between bypass and "the rest of the system". If the boiler is off and cold then yes, you're other pumps should get no flow through the boiler. If the boiler is on and hot, the circ pump will be running and the danfoss valve will stay open. If you're running a system with no storage you really should be okay since the danfoss will only be closed when the water is "cold" and you wouldn't want it being pumped into your zones at that point....
my boiler is in the main loop that is on 24/7 and the temp to heat in radiant floor heat can be below 140 and work, this is my problem. if the floor pump turns on in the house will it hurt the pump trying to push water into the floors and back to the boiler and being stopped by the danfoss? if that happens and it doesn't harm anything until the temp gets to 140 and everything opens up and flowing then all is well and ill install a danfoss. if its going to burn up pumps than i need to do something else.
I think you should probably post up a schematic of your system if you can. You need to protect the boiler from cold water return. And you surely don't want pumps trying to push through a closed valve...
stee6043 said:
So that's a good question that would be worth getting a definitive answer for: Is it harmful for any circulator to be run dead-headed for periods of a few minutes?
I can say from first-hand experience that at least some Taco 007 circulators can survive this with no apparent ill effects.
I can imagine that there might be some circumstances (very high temps and higher power circulators) where this might cause flash boiling and cavitation, but is this always a bad thing? We know from Taco that pumping backwards through an inactive circulator is OK. We should get a real answer for this one too.
I already got that answer from Taco a while back:
"If EBV valve opens before, or at the same time as the pump, that's a good thing. If the valve opens slightly after the pump energizes, it will dead head the pump for that amount of time, but with no detriment to the pump."
I hope that helps.
"If EBV valve opens before, or at the same time as the pump, that's a good thing. If the valve opens slightly after the pump energizes, it will dead head the pump for that amount of time, but with no detriment to the pump."
I hope that helps.
WoodNotOil said:
That does help - thanks.
However, I can imagine that there might be a difference (heat buildup, for instance) between operating dead headed for 15 seconds while a valve opens vs. operating that way for 15 minutes while waiting for the boiler to get up to temperature. This is an area where I just don't know the answer yet. My suspicion is that smaller circulators operating with cool water could run dead-headed indefinitely. At some point, a more powerful circulator might be able to raise the water temperature to the point where it might be problematic. I'm hesitant to suggest plumbing schemes that involve dead head operation, although there are many cases where that would be the simplest solution.
i think I've figured it out. after looking at my system layout i dont think the pumps will dead head just recirc the water in the system. thanks for the input but i think the danfoss will work for my system. i do think the small pumps like stated by nofos could hold up but a large pump could build to much heat and burn up.
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