Caleffi 940 Rad Adaptors

James340

Caleffi Rad adaptors are listed as having a 1/2 M Straight thread on one end. But 1/2M Straight is not as far as I know an official thread designation. There is an old designation of 1/2 BSPM - Which is now the G 1/2 or 1/2 BSPP same thread. Can anyone identify this thread ? I assume that it is the G 1/2 but without the product in hand I am only guessing, and that wont work. Thanks.

DCContrarian

Could "M" stand for male?

mattmia2

Definitely a @hot_rod question.

hot_rod

There are a lot of different versions of BSP British Pipe thread designation. This site explains them well. Some, as you discovered are no longer used or identified by just BSP. Good info at machingdoctor website shown below.

Straight thread is one way of identifying a pipe thread that does not have a taper. It will require an O- ring, hemp, or an adhesive to make the seal. Caleffi uses both o-ring or conical seals, and Loctite thread adhesive in some cases. Sometimes both.

1/2 and 3/4 BSP has a similar pitch to the NPT. But without taper they generally will not seal without some "work" Some of the Caleffi BSP male tailpieces have hemp threads to help grab and hold the hemp in place.

Male BSP do not go into female NPT fittings very well. You only catch a thread or two.

Male NPT will sort of go into female BSP fittings but will not tighten as there is no taper. I've used Loctite 272 or 545 to assemble this combination.

Ideally use the fittings that match and are designed to work together.

Caleffi makes many fittings for transitioning from one thread to another if you let me know what you are trying to accomplish.

James340

Thanks for your help Bob i appreciate your input. I have panel rads (Sanica 4 hole) with the G 1/2 (1/2BSPP) Straight threads. i would like to use Califfe 682 universal fittings to connect 1/2 pex- al directly to the rads. If the 940 Rad adaptors fit my rads it sure would make things easy and also then I would have the same compression fittings thru the whole system.

I am in Canada. And the male NPT into a female BSPP with a thread sealer is what people are doing. They seem to think that all BSP threads are tapered, of coarse they are not. Being a Machinist I could never do some thing like that. I will machine my own fittings for the rads long before putting a tapered thread into a straight thread. Although i know that at the low pressures they will see it would work, you and many others have done it.

Hemp to seal a thread I have never seen that before, thats cool. Old school i would think, I wonder how long thats been used.

Thanks

James

DCContrarian

While there are all kinds of standards for tapered pipe, there's only two that I know of that would be described as 1/2" straight — US and UK, NPT and BSP. Generally hydronics use BSP.

Straight pipe doesn't rely on the threads to seal, it uses a rubber washer or other mechanical seal. NPT straight is commonly used in shower heads and sinks, it uses a rubber washer that fits inside the female fitting and the tip of the male fitting snugs into it. BSP uses two different sealing methods. Some fittings seal like NPT fittings with the washer inside the female fitting. Some fittings use a larger washer that fits over the male fitting and sits on a shoulder. The female fitting also has a shoulder and the washer is squeezed between the two shoulders. This is s a shoulder-type male BSP fitting:

The two standards are very similar, the underlying pipe diameter is the same and both have the same thread count per inch in 1/2" and 3/4" sizes. The thread shape is slightly different. NPT male will easily go into BSP female, BSP male is reluctant about going into NPT female.

If BSP male is run through a NPT tap it will go into NPT female. Since the threads are very close the tap only needs to take a tiny bit off. Since the threads aren't relied upon for sealing they only have to fit closely enough that the joint is mechanically sound. Or you can use a BSP female to NPT male adapter like this:

https://www.amazon.com/gp/product/B0BHDNDH9K/?th=1

For the type of BSP fittings where the rubber washer goes into the female fitting, regular NPT shower head rubber washers fit perfectly. They can be found in any hardware store.

If you ultimately need to get to PEX, I'm not aware of any BSP to PEX adapters. So you'll have to go BSP to NPT and NPT to PEX.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1803357#Comment_1803357

You still see hemp at plumbing and hardware stores in Europe, I bought that clump at a hardware store in Italy. Threaded gas line piping is still commonly sealed with hemp on straight threads over there, as are many boiler block connections.

When Buderus first came to the US the boilers and indirects had hemp installed fittings. Or included a small piece of hemp in a plastic bag!

One advantage of a straight pipe thread is the make up distance always works out. With a tapered pipe thread you don't always end up at the exact length you want based on how the taper was cut into the fitting or onto the pipe.

I think BSPF is still used on some hydraulic hose connections, instead of a flare.

The C, or conical connection you see on radiant manifolds and some TRVs has been standardized in Europe, but there are still some odd OEM versions out there.

The 940 is the transition fitting, BSP to conical, that will accept the 681 pex, 682 PAP, or NA 102 copper sweat, NA 103 1/2 npt union adapters.

If you want to pipe radiators with copper tube, compression fitting, use the 437 nut, onto the 940, H valve, etc.

Unless it has an odd OEM thread on that radiator, the 940 is a pretty universal adapter.

James340

Thanks for all your help DCContrarian & Hot Rod.

Hemp must work well if its still being used in gas lines. That will be a fun fact around the machinists I have worked with. We all spent most of our time machining oil field threads and i am sure none of them has heard of Hemp to seal a thread.

THANKS Hot Rod for confirming that the 1/2 straight thread on the 940 is BSPP. Since my rads are definitely 1/2 BSPP the 940 adaptor- BSP to conical - will allow for every possible piping combination a person would need . Very much appreciated.

James

hot_rod

https://forum.heatinghelp.com/discussion/comment/1803429#Comment_1803429

We supply products, fittings and components to 97 countries. The only market that uses NPT is the US. Luckily it is large enough market that the factory cuts NPT on parts for just us :)

We we first asked Italy for NPT threads they started sending NPTF threads. That did not work out so well. There was a bit of a learning curve getting the NPT that we work with.

NPTF is another thread used in the hydraulic and fuel pipe industry, it eliminates the spiral leakage path.

Loctite 55 is a sealing thread, looks like floss that is used instead of hemp. Or a product like Loctite thread sealer.

But Europe is using mostly press these days for copper, stainless, and steel pipe. Hemp wrapping is a dying art. along the lines of a wiped lead joint :)

ChrisJ

NPT and NPTF cannot be used interchangeably?

That's a new one on me.

jumper

With modern chemistry why isn't there stuff to seal straight threads?

hot_rod

https://forum.heatinghelp.com/discussion/comment/1803465#Comment_1803465

I mentioned the two Loctite products above that are used to “glue” together straight threads.

if you heat most ball valves hot enough you can un screw the assembly joint, that too is put together with an anerobic sealant. Perhaps a different brand or version as it appears green, where the Loctite is red.

jumper

https://forum.heatinghelp.com/discussion/comment/1803471#Comment_1803471

So tapered threads are obsolete? Old methods continue for from inertia?

James340

Hot Rod you truly are a source of diverse knowledge. I admit as a machinist I have not heard of the National Pipe Thread Fuel . I have seen multiple times where NPT was difficult to seal the pressures that were being used. The NPTF would have been a better option.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1803500#Comment_1803500

I doubt that NPT threads disappear in the US, anymore than we will convert to the metric system like most of the rest of the world. And the automotive industry.

Flanged circulator pumps are mostly an American product also. Union bodies are more common globally.

hot_rod

The bigger issue I see with NPT is the poor quality of the nipples and fittings you see on the shelfs. Out of spec, ripped threads. Same with the pipe you try and thread on the jobsite, it's tough to get a perfect thread on todays steel pipe, import or domestic. Most pipefitters hide that with gobs of thread tape, I suspect.

A lot of the straight thread connections on tailpieces, valves, etc, depend on a gasket, fiber washer, o-ring to make the seal, like the radiator valves for instance.

James340

Hot Rod - You are right abought about the bigger issue with NPT - being the poor quality nipples & fittings. I had originally planed to use a BSPP to 1/2 NPT adaptor from the panel rads to 1/2 NPT fittings and nipples . So I could run pipe down to the floor - then pex from there.

Until I realized that I could not find even an average quality fittings or nipples. The quality of fittings and nipples I was able to source were close to useless are far as I am concerned. Maybe my standards are to high, but I decided it wasnt worth it.

Much easier , cheaper and reliable just to use the 940 adaptors - with the 682 universal pex fitting.

jumper

Sometimes I'd be stuck using straight threads + goop when doing plumbing repairs. I worried needlessly that time & pressure would eventually thwart my MickeyMouse work. If I ever have to do steel pipe work again…..

Hilly

These caleffi adapters would be excellent for me on an upcoming project. I’d seen them in the catalog before but didn’t remember / realize how they converted. They’re much smaller profile that the option that shipped with the heaters.

hot_rod

just be aware, some radiators do have odd, proprietary connections. I think Buderus panel rads have a unique thread or size. Always best to check, or get the thread spec from the man.

DCContrarian

Just for the sake of adding to the conversation, here is a picture of a 1/2" BSP type G (parallel thread) female fitting. The brass outer ring spins around the center, the copper-colored inner is the seat where it seals. A rubber washer sits on that seat and the threads draw the male piece against the washer.

DCContrarian

For illustrative purposes, this is the same fitting with a 1/2" NPT tapered street elbow screwed in. It screws in easily until it bottoms out. A showerhead washer, which you can get at any hardware store, completes the seal.

DCContrarian

This is a 1/2" NPT female straight thread swivel fitting — basically the same thing as the fitting above, but for NPT rather than BSP. It would most commonly be used in American plumbing to hook up a sink with 1/2" straight thread connectors. It also seals with a rubber washer.

https://www.amazon.com/gp/product/B09WQPJ4WN?th=1

A 1/2" BSP male fitting will not go into this easily, the thread will be slightly too big. You'd need to either put on a BSP to NPT adapter, or run a NPT rethreading die over the threads:

https://www.amazon.com/gp/product/B00FXKK0W0

DCContrarian

The T in NPT stands for tapered —National Pipe Tapered. So I shouldn't be saying "NPT straight," I should be saying NPS — National Pipe Straight

The die I linked to above is NPT What you really want is NPS, no taper. Like this:

https://www.amazon.com/14-NPS-Straight-Pipe-Die/dp/B008FHCNB4

hot_rod

If you seal a NPT nipple or fitting against a washer, belt sand or file the end to get a nice flat sealing surface.

Schedule 80 fittings or nipples give you more sealing surface, like this PCV jumper nipple.

jumper

» get a nice flat sealing surface.«

Yes. I've tried O rings and they don't work. Why?

hot_rod

https://forum.heatinghelp.com/discussion/comment/1803634#Comment_1803634

You don't have much wiggle room with an o-ring sealing against a flat surface. It needs to be in the exact correct spot.

This is the PosiStop that Caleffi is switching all products to. The o-ring is held in place "captive" and it has a large smooth, flat surface area to mate up to.

Whereas a nipple, or the end of a fitting has a small seating surface.

Also critical with an o ring used this way is the compression amount.

The brass groove is machined so the two brass surfaces touch as the o ring is compressed to the ideal amount. You can actually feel that when you hand tighten the union nut. This is an o ring in a static application. An o ring face seal.

Different o rings are used in dynamic applications like pneumatic or hydraulic cylinders, faucet stems, or a pump seal for example where there is a moving surface to seals against. O rings are manufactured to a specific use. The material and hardness, durometer, of the ring are other considerations, as you will see with press fittings also.

Square cut o rings, like many circulators use, with 4 flat edges, cover more surface, so they work better against a "thin" sealing area. And a high sealing force, application, like` a garden hose washer.