a question regarding danfoss valves

jonny88

i came across a hot water heating system.it had tremendous water hammer,which we discovered was the danfoss valve,it was baseboard heating and every room had a danfoss valve.should there be a bypass before each valve which there wasnt.if the tennant closes the valve in the first room,how does the water get through.i take it danfoss valves do close 100%

Mark Eatherton

Bass Ackwards valve...

If the valve is installed in the wrong direction of flow, when the valve gets close to closing, the needle gets sucked into the seat, and it sounds like a jack hammer going off. BANG,BANG, BANG, BANG, until you open the valve a little, and clear the needle from the seat, then it quiets down.



Has somebody replaced the system pump recently? Maybe installed it backwards?



Is it just one valve hammering, or all of them? Did it use to do it before, or is it a new problem?



Regarding bypasses, if it is a series loop, and the rooms are seeing different exposures, then yes, it requires a bypass, otherwise, closing one off will close all emitters in that circuit off. Oventrop makes a 3 way valve that is designed for this application, and automatically bypasses the convector when the valve closes, which keeps flow moving to the subsequent emitters.



And yes, all non electric TRV's close 100%.



ME

jonny88

danfoss

thanks for getting back to me,the valve was pointing in the right direction and was the last valve on the loop.we changed the valve,and even with the new one as you would close it slowly it would start to hammer.no problem if it is closed or fully open.we have to do some more investigating tomorrow,the people have been living with the noise for 5 years.it is a 5 story apartment building and every apartment is set ip the same way,i just dont understand how if the first valve is shut how does the heat transfer to the next rooms,definitly no bypass there either.again i really appreciate you getting back to me,

jonny88

oventrop

i will talk to my boss tomorrow and mention the oventrop valve,

Mark Eatherton

Also....

And there's an Also in every crowd, ain't there :-)



Forgot to mention, if you don't have a pressure activated bypass around the pump serving the TRV's you can expect HISSSSSSSSS when the needle approaches the seat face.



Better yet, switch to a DC ECM motored pump and be done with it :-)



Once set up correctly, you will have the most comfortable space they've ever had. They will want to do TRV's everywhere :-)



PS, double triple check that valve. It sounds like one thats installed backwards....



ME

World Plumber

Sounds like the flow is going the wrong way through the valve

I got the lines twisted around on one somehow, You could hear it 3 stories away.

Check to see if they aren't coming up from a loop into each valve. The one that is hammering might be connected to the return line. They can get noisy it took me the better part of a day to figure it out. If there is no bypass and others heat when one valve closes that is probably how it is set up going around bends and through walls they may have got one backwards.

MC

croydoncorgi

Bi-Di TRVs

There are (at least in UK) bi-directional TRVs which will fit either way round with no hammer risk in normal situations.  Fitting one of this type might be quicker / easier/ cheaper than pipe-surgery.  BUT even a bi-di valve will hammer if the flow is backwards and excessive......