Caleffi/ Zilmet Solar expansion tank weird thread?

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

pybyr

Minister of Fire
Hearth Supporter
Jun 3, 2008
2,300
Adamant, VT 05640
Hello all--

based on prior discussions 'round here about how modern-made expansion tanks seem shorter-lived than the ones in past decades, but that the solar-rated ones seem to be longer-lived, even though more expensive, I picked up a Caleffi/ Zilmet solar-rated 18 liter tank from Houseneeds.com, which is about a half hour from me

(I should say, too, that Houseneeds in general, especially Gil there in sales, were very patient and helpful with me and that they stock a lot of interesting stuff like Caleffi, Laing DC pumps, and other things that are still a bit off the beaten track in much of the US plumbing industry).

but tonight as I was doing some more preliminary layout and trial fit-up of parts of my system, I found that the Caleffi tank has a male thread that _looks_ a whole lot like a male 3/4 NPT, but won't seem to thread into a female NPT beyond the first 2/3 of a turn. On closer examination, it looks like a straight-taper thread, not the taper that goes with the norm of NPT. The instructions and specs, printed in a panoply of languages, say nothing about the thread type or size.

part # is Caleffi Solar 259018
and it's described here-
http://www.houseneeds.com/Shop/solar/caleffiexpansiontankbuy.asp

now that I bumped into this "issue," I do see that they describe it as "3/4 inch straight thread connection" When I read that before, I thought that they meant straight as in "not elbow" but now I am scratching my head in thinking that they meant "non-tapered"

I am most familiar with NPT, but have heard of BPT, Whitworth, AN/ O-ring, and what not, although I forget a lot of the distinctions. I'm not too familiar with any un-tapered pipe thread.

Anyone know if the pitch of this is likely the same as NPT so that I might find a friendly person with a 3/4 NPT die to re-cut it to a taper thread without mangling it?

Can anyone shed any light on what thread this critter has and how to adapt it, or, if I have to return it if it is too complicated to make it fit, other makes and sources of solar-rated expansion tanks that won't send me to the poorhouse? I am going to try to contact Houseneeds and maybe Caleffi tomorrow, but knowing the reservoir of knowledge here, if someone else can clue me in first, that'll save me some wild-goose chasing.

while I am asking annoying questions, is an 18 liter/ 5 gallon tank hopefully in line with a 32 gallon boiler and a compact/ not-too-high-volume primary/ secondary system? I've been sweating so many other details that I decided to take a knowing careless fly-er on the sizing of the expansion tank, but now that it looks like I may need to hack with it in a way that'd make it non-returnable, I'd rather return it sooner rather than later if I really need something bigger



Thanks, as always
 
Trevor, It's probably British Straight Pipe (BSP).If you snuggle a male NPT nipple onto its threads you might find they don't quite match in the distance form thread to thread. If it is BSP it's also not 60 degreee thread form but 55. Best to get the definitive answer from the distributor.
If they don't have an adapter to get you to NPT, try searching on the term "Steel Conversion Adapters" at

www.mscdirect.com

One of the bigger industrial suppliers, they sell to any credit card off their website. Not the cheapest but terribly convenient and quick delivery.
 
BrownianHeatingTech said:
Caleffi solar tanks are, indeed, straight thread.

They do have a connection kit, and it looks like Houseneeds does stock it...

It's a nice CSST pipe, with a fitting with the tank at one end (complete with service check valve and wall bracket), and a fitting with a washer at the other.

Joe

thanks- except that the kit is almost as expensive as the tank was, and this is one detail I'd rather keep simpler if I ccan
 
BrownianHeatingTech said:
pybyr said:
thanks- except that the kit is almost as expensive as the tank was, and this is one detail I'd rather keep simpler if I ccan

Yeah, it's not cheap.

You can get straight x NPT adapters, though.

Joe

Hmm- last night I spent quite a bit of time looking around on the web sites of places like McMaster, MSC, and various fitting supply places, and to my surprise and frustration (I'm usually both stubbornly persistent and usually successful at unearthing things via multiple ways of phrasing google searches), did not find anything to go from 3/4 female straight thread to some form of NPT.

any chance anyone knows of a place/way where I can zero in on a fitting?

Any other nominations for good makes/ models of solar-rated expansion tanks that have an easier to use thread?

thanks
 
pybyr said:
Hmm- last night I spent quite a bit of time looking around on the web sites of places like McMaster, MSC, and various fitting supply places, and to my surprise and frustration (I'm usually both stubbornly persistent and usually successful at unearthing things via multiple ways of phrasing google searches), did not find anything to go from 3/4 female straight thread to some form of NPT.

It does look like the MSC book has some candidates on page 4065.

Joe
 
Trevor, as Joe says there is a busload of candidates at MSC, but you need to know what thread is on your tank. BSPP (British Standard Pipe Parallel) straight threads are common in imported stuff, even in chinese and japanese machinery. Metric straight threads are used sometimes for liquid lines against a shoulder with a gasket. You need to know what you've got there. This sort of uncertainty can drive you nuts, I'm proof of that.
 
DaveBP said:
This sort of uncertainty can drive you nuts, I'm proof of that.

yeah, some would say I'm already 'round that bend too...

speaking of which, I'm thinking more and more of returning the Caleffi tank IF someone can PLEASE point me to a solar-rated tank at a non-crushing price that has a normal US pipe thread

I have too many other details to get working on my system to futz with this set of variables
 
Somewhere there's a quote about the perfect being the enemy of the good - Voltaire, perhaps?

It might be time to stick in a used hot water tank, connected only at the bottom, as an expansion tank and get on with the system. Plan on replacing it next year - give yourself time to relax and plan, rather than driving yourself crazy trying to achieve perfection on the first iteration.

Just a thought....
 
I got a 3 gal solar exp tank, extrol, from the solar store in Waterbury Ctr when mine crapped. They are a bit more "hands on" than Houseneeds.com, so even though I like them, I'd say pass over them for true connection issues. No need for converting a Euro product when US stuff is available.

Or Granite Group, on Barre-Mont. road. Good guys there, with many years of experience. They are very patient with my "dumb questions" assuming I have some clue, and they will tell me what I'm attempting is beyond the non-pro status, then reccommend a pro.

Al
 
Vtgent49 said:
I got a 3 gal solar exp tank, extrol, from the solar store in Waterbury Ctr when mine crapped. They are a bit more "hands on" than Houseneeds.com, so even though I like them, I'd say pass over them for true connection issues. No need for converting a Euro product when US stuff is available.

Or Granite Group, on Barre-Mont. road. Good guys there, with many years of experience. They are very patient with my "dumb questions" assuming I have some clue, and they will tell me what I'm attempting is beyond the non-pro status, then reccommend a pro.

Al

Thanks Al- agreed- I've been on a first name basis at Granite there for a while, and finally opened an account with them for this project. They've always been helpful to me, including sending me other places that they think will be helpful (like EJ Prescott) when I've needed something outside of their product range)
 
I have the same caleffi solar expansion tank. It has a BSPP thread-British straight parallel pipe thread. It is a pain in the ass but I got the brass conversion fitting to go from 3/4" female Bspp to 1/2" male NPT from McMaster-Carr. The bad part is those conversion fittings are expensive anywhere you find them. Mine was about $35.00.

Mike
 
Status
Not open for further replies.