Viessmann mixing valve threads I.D. too large
We bought a 3-Way mixing valve for a job. My installer said the threaded connections keep leaking. I had him bring the valve back to the shop. I tested a 1-1/4" black plug in the ports. I fits way too loose. I can tightening the plug until bottoming out WITH MY FINGERS! Has anyone else ran into this? My vendor says he's been selling these for 20 years and never heard of any issues. Any sealant you can think of that would work? Maybe Expando? Or some automotive sealant like RTV or Hylomar?
Comments
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Sounds like a BSP straight thread version made it through.
If it isn't too sloppy and you can get it clean, with acetone, we use Loctite on all our BSP connections.
#545 or 272 high strength.
For BSP nipple to BSP female fitting hemp or Loctite 55 Sealing Cord will work.
BSP and NPT is always a work around.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
This usually occurs when you attempt to put an NPT fitting into a straight fitting that seals with an O-ring…………as Viessman is likely to have done. Some people attempt to do it with tape and dope but it usually doesn't go well for them in the end.
@hot_rod will know the suitable adapter from Caleffi.
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I installed a Viessmann indirect/ solar tank recently it came with BSP to NPT adapters in the box, up to 1-1/2” size. So somewhere in their catalog must be adapter fittings?
Some connections depend on a fiber washer on the face to seal. Piping for boilers and fuel piping is generally done with hemp.
Caleffi machines hemp specific brass fittings. The threads get knurled so the hemp doesn’t roll off so easily.
When German boilers first started arriving in mass, they came with a fist full of hemp.
You know what that means to a young thrill seeking installer🫣
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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I remember the hemp days, almost 30 years ago or so. I was baffled. Paul Ross the rep had to come make up the joints.
Doesn’t the Loctite string do a good job?
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It is much easier to use, you don't need to seperate it and hold it in place.
It looks like a siliconized dental floss.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
yes the dental floss stuff. I have some tucked away
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Hello everyone and thanks for your replies. Hotrod great to see you are still on here sharing wisdom.
To address the comments about a sealing washer, I thought the same thing but if you look inside the F.M. fitting there is not a nice flat surface in there. It is a welded bead so not uniform at all.
This is what I have on hand currently for sealants-
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I just ordered the Loctite 55 incase that is the way to go. I will tell you what. We learned one very valuable lesson. DO NOT install one of these valves without UNIONS piped in on all ports!
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get the threads good and clean, maybe sacrifice a fitting brush.
Are you heading back to the future soon?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Why won't your supplier just warranty the thing? I had a couple of these leaky "out of the box" a year or two ago and it was no trouble to just warranty them with Viessmann
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Heading back to the 80s! The vendor is sending a new valve. I'll test fit the plug in the new one. If it is loose then we will use Loctite then.
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They are saying they will warranty it "As long as something is wrong with it" (the valve we currently have).
They ordered another valve, and it is supposed to be here any day now. Actually they said that they direct shipped it and it was supposed to be here last Friday the 24th.
I was just asking for advice in advance in case the second valve has the same issue and the vendor didn't have any answers.
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Update- We received the other replacement valve. It was exactly the same so I sent it back. I bought some of the Loctite "dental floss" type pipe sealer. I cleaned the threads my tech went and put everything together with the loctite floss. It still leaks…..😔
If I could go Back in Time,…I would have disassembled the valve, welded screwed three close or space nipples into the body (dry), then MIG welded them in. Then we could have piped from that with FM adapters. A whole bunch of repiping would have to be done for that though.
My only other thought is to use a pipe bonding fluid like Copper Lock which when I remove the cover, looks like red loctite fluid to me.
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If they use a gasket I think it seals on the outer face and a shoulder on the fitting, not at the bottom of the fitting.
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I had no luck with Viessmann tech support. I was on hold for——e-v-e-r. I finally picked the option to recieve a call back. They eventually called,..of course it was while I was on an important phone call. I finally spoke to someone there. They basically just told me to put more wraps of sealant on it and more pipe dope and tht "should work". 🙄
I continued to bug Matt Anderson, the local Viessmann rep. for Maine. He figured out the issue and called me back later in the day. It turns out a bunch of valves got messed up at the factory or they have EU straight threads but got sent to the US. He said that this valve has been pulled off the shelves in the US (not sure why Viessmann themselves didn't know this). It's been a long day so I may not have all my facts straight but something like that.
He said he located some valves that may be the correct thread in another location and he is having them shipped to my local dist. I am having them check them with a 1-1/4" plug when they come in. If they are good they'll send me one.
Very frustrating situation. Especially when you get the impression from your vendor that there is nothing wrong with the part, we are just installing it incorrectly. And when you keep hearing how great Viessmann stuff is.
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didn't viessmann recently get bought by someone?
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I've got 3 1-1/4" viessmann mixing valves in michigan, npt plugs thread into them. Hopefully your supplier takes care of you on it, I know the regional rep in my are would. This is not a common occurrence in my experience
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Plugs will thread in fine,….they are just way too loose. Can you screw yours all the way in by hand. If you can then yours have the same issue. If it gets tight after 1 turn then they'd probably work.
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Male NPT will go into female BSP ir G thread. But male BSP, G thread will not go into a female NPT, maybe 1 or two threads.
Usually you can Loctite a male NPT into a female BSP, G thread. You basically "superglue" the connection.
272 or 545 is what we assemble with at the factory.
But it is always best to use compatible threads or adapters.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Yeah this is my next step if the "new" mixing valve body has the same issue.
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When I watch your video I wouldn't really describe that as threading in fine. Without putting tape or dope on my valves they seem to thread just like any other NPT thread. I have a message out to my internal contacts at Viessmann to see if there is any way to identify these BSP valves by the packaging, or if they are aware of an issue.
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I hate it when this happens. A big void in the female threads from European fittings have been a thorn I my side for years.
Was happy when blue monster came out with that blue type teflon. The direction on that stuff say three wraps around the pipe thread. Not in this case.Ssix to eight wraps should do the trick with some pipe dope on the wraps. This is a pain in the neck but it can work. I have found that the Loctite stuff doesn't always fill that void.
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