pex pipe..what size copper to mate with?

[barkeatr]

does one inch pex diameter or flow volume match 3/4 copper?

Im hooking up a new empyre pro 200 but using my existing one inch pex lines from my previous central boiler unit. I allways thought 3/4 copper equals one inch pex in volume?

 

[DaveBP]

Using the same pump, an equal length of 3/4" copper M pipe will allow 15% less flow through than an equal length of 1" PEX according to Siegenthaler's software.

 

[barkeatr]

thank you. Looks like i go back to the plumbing store !.... I dont want to loose that fifteen percent. I assume that is due to a small difference in diameter of the pipe...not the drag of the material itself?

 

[jebatty]

How many BTU's do you need/want to move? 3/4" normally is rated at only 40,000 BTUh, and 1" at 80,000 BTUh.

 

[SteveJ]

Jim,

Thanks for posting the ratings.
Where are the BTU/hr numbers found?
Do you know where they can be found for pex?

Back to the thread - where do you find the friction of the various pipe types - black, pex, pex-al-pex, copper M, L, etc.?

Seems like the BTU/hr would be the major concern for everyone on this forum...

Thanks,
Steve

 

[flyingcow]

I've found that PEX ID's vary from company to company. Get the tape measure out, don't read the package.

 

[jebatty]

Seems like the BTU/hr would be the major concern for everyone on this forum

BTUh, or heat load, is where everyone ought to start. Then move backwards to select pipe type and size that can meet the load, calculate pump head for the selected pipe, identify a circulator that can provide the required flow in the middle of the curve (delta-T x 500 x gpm = BTUh) at the calculated pump head, then select the boiler size. Wood boiler output over a burn may average 75-80% of boiler rating, but you've got to watch that rating. Some mfr's rate conservative, some liberal, some state a "burn rate" or input and not output, some state confusing efficiency numbers (burn efficiency vs efficiency in converting input wood energy to output hot water), etc.

BTUh, or heat load, is not the same as the rating of an existing oil/gas boiler, which usually you have no way of knowing how the contractor determined the rating for the boiler you have.

Useful to calculate pump head: Friction Loss.
Cheat sheet follows, simple but useful.

 

[barkeatr]

Ok I think im starting to understand the errors i made in my first Central boiler install besides the first one listening to Central boiler tell me what line size to use. IM past that now though the old CB paid for itself and put quite a few thousands in my pocket.

HEAT load in my case would be impossible to figure out, i have a very custom experimental house with extreme amounts of mass. Im an architect by trade and experimented to high degree on myself. House well insulated but too much glass. Could we throw a number at it like design it for a peak load of 120,000 btuh an hour? Or maybe we can use the output of the boiler to tie down this unknown as you mention. Alternative ENergy solutions just dropped of the empyer pro 200 that I belive is rated for 200,000 btuh an hour

I have 150 feet one inch central boiler pex in the ground and it rises 8 feet to a second floor mechanical room. It runs through a flat plate heat exchanger, with 3/4" ports. oops. Im assuming my HX ports are my most limiting limiting choke point in the line, second is the buried pex. Im not quite seeing why you cant use powerfull pump to drive the water through faster..All this said, im not afriad of pulling up the pex if I cannot work around its limiters.

WIth the central boiler using my one inch pex and all my limiting factors..I did keep the house warm in the coldest of times..although i had to really crank things at 35 below. i think the large amounts of mass helped me in this regard. but i went through sick amounts of wood.

jeez Jim i wonder if i could hire you for a consult?

 

[jebatty]

I have 150 feet one inch central boiler pex in the ground and it rises 8 feet to a second floor mechanical room. It runs through a flat plate heat exchanger, with 3/4†ports. oops. Im assuming my HX ports are my most limiting limiting choke point in the line, second is the buried pex. Im not quite seeing why you cant use powerfull pump to drive the water through faster.

I'm not in the business, just a user like lots of others, and willing to help as able - so I don't hire out. I see the Empyre Pro 200 is advertised as a gasification boiler, open system, not pressurized, 230,000 BTUh peak, 110,000 BTUh over an 8 hour burn. I have no knowledge/experience with this boiler. My direct experience is based mostly on the Tarm, which is closed system, pressurized. There are a number of other gasification boilers that operate on the same principles as the Tarm. I have a bias that favors boilers designed from the start to be gasification boilers, like the Tarm, and with a history of success, and I am a bit skeptical of outdoor wood boilers (OWB) that the mfrs now have redesigned to be gasification boilers. From what I have read, results have been mixed on these redesigned boilers. I'm not dissing your choice, you may have a great boiler -- just be aware of this bias of mine.

Is your house side of the HX also an open system? or is it a closed system and pressurized?

I assume you have not had any elevation issue with the boiler lower than the house. This can cause a problem. What circulator have you been using (make, model)?

I see a possible red flag in the 3/4" ports plate HX. What are the dimensions and number of plates in your HX? Dimensions, port size, and number of plates determine what a plate HX is able to do at various gpm flow rates.

When you say 150' of 1" pex in the ground, is that round trip (150' total) or one way (300' total)?

Can you post a diagram of your system?

Do you plan to add any hot water storage to aid your boiler in delivering peak output, which may be more than you need, and then draw from storage to supplement your boiler to meet demand as the boiler fire goes out or to cover demand until the next time you fire your boiler?

It certainly is possible to design a system to deliver a specific BTU load. Perhaps since you already have bought a new boiler, it might not be unreasonable to design the system around the capability of your boiler to enable you to use it most efficiently. In doing this though, there is no guaranty that you will get the heat you need or want for your house.

I'm not experienced at all in using pumps in hot water systems, so any question into that area is beyond me. My experience is limited to using circulators, which are not literally pumps but instead just move water (circulate) in a closed loop.

 

[barkeatr]

thanks Jim, i sure will post a diagram. Might take me a day to draw it.
I looked at the house side of the operation (yes its pressureized on the house side of the HX) and its all 3/4" I think at the time i was told that Central Boiler 1" pex matched 3/4" copper I.D. or flow rate and I made all decisions from there. the ports on my retired CB are all 3/4" threaded so I guess I thought that was the case. Does anyone know the i.d. or flow rate of central boiler themopex.. One felllow said there is a fifteen percent increse in flow between 1 inch pex and 3/4 copper but IM not sure if that is true with Central boilers thermopex. If it is true i certainly want to get rid of all the 3/4 copper connections.

I will post my diagram soon so i can poach more help sizing my circulator!

I appreciate the help.

 

[rowerwet]

the hookups on my CB Maxim are also 3/4 or 1 1/4, I used the 3/4 but everything else in my system is 1", If your HX is 3/4" bungs you are loosing flow there, however the square footage of plate in the HX will make a difference, from what I remember my dealer only stocked one size of HX, for my system it was massive overkill, for most houses it would be marginal from the info I found online.
I bought mine off Ebay, freeheat4U is the dealer name, according to the chart they post in the listings I needed less than I got at 5.03 square feet of HX.

 

[barkeatr]

i cant seem to get a drawing scanned and downloaded..so i will describe the system below.

before i explain, plumbing store did a quick calculation and sold me a 350 dollar taco 013. Its a monster. Im worried about the cavitation you spoke of.

here is a text version:

All pipes at boiler are one inch copper. They transition to 150 feet of one inch central boiler thermopex for the main run to the house. that run rises 8 feet to a second floor mechancial room. there it switches to 3/4 pipe, and three HX, (one sixteen flat plate and two hot rods...all 3/4" ports.) it then runs 8 feet back to the pex and then the 150 run in pex to the boiler.

my heat exchangers are set up in a sidearm set up on a hot water heater that heats our domestic and radiant floors.

Thanks

 

[jebatty]

As an approximation only, the 316' of piping between the boiler and the house, not including the hx or other piping, shows head loss at 9-10 gpm in the range of 23-28'. The pump curve for 013 shows that at a head loss of about 27', the 013 will circulate about 10 gpm. This performance is on the top side of the pump curve for the 013, which is not ideal but will handle the flow indicated. At a delta-T of 20F, 10 gpm is 100,000 BTUh. This probably is a pretty good estimate of the maximum performance that you will get to your heat exchangers from your current install setup. The rest depends on the ability of your heat exchangers to extract the available BTU's and transfer the heat to your system hot water supply. This is about as far as I can go on the info provided. Hope it all works satisfactorily.

 

[barkeatr]

hi Jim,

you said "This performance is on the top side of the pump curve for the 013, which is not ideal but will handle the flow indicated" what would be ideal (with my pipe constraints)? a larger circulator?

obviously my HX and piping will add head and worsen performance. thanks for looking at this Jim.

 

[jebatty]

Based on the approximations in my post the 013 will work OK. I think you need to consider a more complete analysis of your system and heat demand needs before giving more thought to a circulator. Your 1" lines and their length are choke points in your system, other choke points are the heat exchangers. I don't know what your usable system delta-T is either, nor your minimum usable hot water temperature, nor your heat load. There is lot more going on than what has been posted. And it is very difficult to make too may suggestions from afar due to the gaps in knowledge. You would do well to hire someone who can actually examine your system and provide you with more fact and data based suggestions.

 

[barkeatr]

THANKS Jim happy spring!