Installing a new hot water system myself

Shemp

Can anyone recommend a book on installing a hot water system using pex pipe?

Or am I crazy doing this myself?



The reason I'm not so sure about hiring someone is because I went through quite an ordeal about 10 years back, having my old steam boiler replaced. No one near me, and I mean no one, had any clue as to how to do the near boiler piping. I ended up getting a ton of help through this forum and through books from here and fixing it myself.



Any suggestions would be appreciated.



Thanks.

CMadatMe

Hot Water

Heating system of domestic hot water system? Suggest you educate yourself with a lot of reading but still hire a professional to at a minimum consult and fire off all equipment.

Paul48

Start

at Taco FloPro University. It's a free site, with tutorials that  contain fantastic information.

JStar

Boiler

I will always say no to DIY'ing a boiler. Too many safety concerns.



There is no one magical book that will teach you everything you need to know. The best course is to follow the instructions exactly as described. Even the instructions leave out a lot of important information.



Where are you located? We may know somebody that is willing to help.

Bobbito

Go For It!

I'm doing the same thing.  Its simple and not simple, I know that's not much of an answer but you CAN do it.

First you need to know your BTU requirement for each room.  There are tons of free online calculators out there, just Google it and you'll come up with dozens.  For a BTU calculation, you need to know the square footage of the room and height of the ceilings.  Knowing the R-Value of your insulation (if any exists) is great, but if you don't know, don't sweat it.  Play around with the figures, make the room smaller, bigger, taller, calculate more windows than are actually there, and you'll get a sense for the range of BTUs you need to provide.  Houses lose heat a few ways:  (1) through the walls, a north facing wall loses more heat than a south facing wall (2) windows.  There are other more complex ways but for now, knowing that is sufficient.  Once you have an idea of how many BTUs you need, its time to search for baseboards or radiators.



I am doing baseboards.  To me, it makes more sense to go with a high efficiency unit, yes you pay more per linear foot but because you need fewer, you come out paying less.  I decided to go with Slant/Fin Multipak 80, they put out 730 btuh / lin. ft.  This option, versus the cheaper models Slant/Fin offer, saved me about $600.



Now that you've got BTU figures for each room and the baseboards, its time to pick a boiler that can put out the required BTUs for your house.  When you size a boiler, its important not to go too far over the BTU requirement.  Why?  An overpowered boiler will cycle on/off more frequently and shorten its lifespan.  Same thing if you go too small.  My house required 160k BTUs, I picked the Navien CH-210-NG tankless combi boiler which does 180BTUs @ 91% efficiency, so in effect, 163,800BTU's, only 3,800 over my requirement!



From here, its up to how you design the piping.  You can go with a few different layouts.  The three basic types are:

1.  Two Pipe

2.  One Pipe

3.  Series Loop



I haven't really been able to find info on one version being overwhelmingly more efficient than the other.  A two-pipe layout will be the most expensive and complicated.  A one-pipe layout is not as expensive, not as complicated, but requires expensive "Venturi" tees.  A Series Loop is the most simple, and what I decided to use. 

You'll also need to figure out the layout of this plumbing.  You can have different zones and loops.  What is that?  Let me ue my house as an example.

My home is 3 floors.  Each floor is heated independently of the other.  That means each floor has its own thermostat, and can call for heat independently.  So if my family is in our bedrooms, we can heat only that level of the house if we want.  Or we can heat the entire house, its totally controllable.  So for this, each floor is its own ZONE.

But to keep the heating lengths at controllable sizes, we broke each floor up into 2 loops.  My bedroom floor is 4 beds, 2 baths and a hallway.  2 bedrooms and 1 bath or on one loop, 2 bedrooms and the other bath are on a separate loop.  This way, the heat is more consistent and I can actually shut off the heat to the kids rooms and the hallway bath when they move out, saving more money!

Lastly, you'll need to decide if you want zone valves or zone circulators.  Zone valves = a cheaper install, but you have to replace them ever so-often.  Zone circulators = slightly more expensive, but will last you much longer.  I decided to do zone circulators, and to make that installation easy, I used a zone relay. 



If you haven't found them already, pexsupply.com has most of what you need, good luck.

CMadatMe

Perfect Example of Why Not To

That Navien output is it's capability for DOMESTIC HOT WATER NOT HEATING! The max flow rate through the heat exchanger for heating is ONLY 5GPM!! If piped direct it only has the capability to produce 50,000 btu/hr based on the standard 20 degree delta-t for heating. Now, piped with a low loss header or pri/sec and you may get 120,000 btu/hr out of it for heating.



See it isn't fudge with a heat loss, just pick any piece of equipment that has ratings. You still need to know what you are doing and how the piece of equipment actually works.



Best of luck with that install.

SWEI

went for it

Sounds like a typical American system design from the 1990's.  Zone pumps pretty much guarantee overpumping, and unless they're setup for variable speed injection your boiler will almost certainly be short cycling most of the time.

Gordy

I wanna see

In 10- 15 years how these all work out for everyone.....maybe less in some cases.



I'd rather spend more money with a company that has a proven track record with appliances dedicated to boiler technology. If I could not afford the high eff. Then you can step down to an 85% cast iron, and pretty much get 25-30 years of trouble free operation maybe even more.



As far as zoning if your sub 3000 sf I think it's over kill. Especially in an open floor plan.



As for the DIY in the boiler room. Better do some serious education. With respect to your own family, and others that may own your home down the road. And see how the homeowners works out in an event involving the appliance.

Bobbito

Dont Hate the Player, Hate the Game BRO!

"That Navien output is it's capability for DOMESTIC HOT WATER NOT HEATING! The max flow rate through the heat exchanger for heating is ONLY 5GPM!! If piped direct it only has the capability to produce 50,000 btu/hr based on the standard 20 degree delta-t for heating. Now, piped with a low loss header or pri/sec and you may get 120,000 btu/hr out of it for heating."



Is that so? Well, young padawan (Star Wars lingo here), I refer you to the manufacturer's website and manual here:



http://www.navienamerica.com/__DATA/ProductDocument/2012/11/30/[1]_4.%20Installation%20Manual_CH-180_210_240ASME_120307.pdf





Page 5:

Heat Capacity MIN = 20k Btuh

Heat Capacity MAX = 175k Btuh



Flow Rate DHW: 3.8 - 8.3 GPM

Flow Rate Heat: 5.1 - 11 GPM



I hear you already "yeah, but what about the DELTA-T?" For that my good man, I refer you here to a slightly older manual for a near-identical unit:



http://ecomfort.com/PDF_files/Navien/Combi/Navien_CH_Combi_Boiler_Installation_Manual.pdf



Page 5:



At a 35 degree temperature rise it can maintain output at 10GPM. At a 77 degree temperature rise, the unit can maintain output at 4.6GPM.



So ... what was that you were saying? Furthermore, where is your proof to back that up?



Beyond that, my heating is sized such that it could be cozy even at 2GPM, which means my system could tolerate a delta-t greater than 77 degrees. This is going to prolong the life of my pumps, and my boiler. I'm awesome, this, I already know.



----------------------------------------------------

"Zone pumps pretty much guarantee overpumping, and unless they're setup for variable speed injection your boiler will almost certainly be short cycling most of the time."



Well, to me, this is really a matter of opinion. We've all heard the saying, which is true, that if you ask 100 preachers their interpretation of a verse, you'll get 100 different answers. Just FYI, I'm using the Taco Bumblebee pumps so, yeah, its variable speed. Back to the point, I got the idea to do zone circulators from this forum:



http://nepacrossroads.com/about19084.html



My reasoning is (1) durability, (2) control, (3) I'd rather spend more money putting in a better system than to save a few bucks and have to constantly replace zone valves. The fact is that Zone Valves do fail, its unavoidable. Its also true that a properly sized pump, a Taco 007 on the cheap end, a Taco Bumblebee on the high end, will serve you pretty well for a long time. But I don't knock folks who opt to go with zone-valves, to each his own, right?



----------------------------------------------------

As far as Navien durability goes, I must admit I was a little skeptical about them. A relatively new company, its foreign at that, VERY competitively priced units ... I was unsure. But I read around the net and found a lot of people have come to appreciate Navien units, I figured, heck, I'll give it a try. But like everyone else, I'll have to see how this plays out over the next 15 years.



That said, Navien units are VERY sensitive to scale. So I recommend using a water softener and whole house water filter to ensure that your domestic and heating water is as clean as possible to prevent scale buildup. I also used pex tubing throughout with the crimp connection system, this means there is no solder flux running through the system or gumming up my air vents. You could drink my heating water... that is, if you COULD drink 180 degree water.



I was also considering a Takagi unit, but they're very similar to Navien and twice the price. If you were looking at a Chevy Impala or a Mercedes E class which would you want? Sure, you might WANT the E class, but the Impala will get you from A to Z just as well. Mercedes' are better built, better engineered, probably will last longer than a Chevy, but the Chevy will do you right for as long as you ... TAKE CARE OF IT. I'm taking care of my Navien by performing the scheduled maintenance and giving it super clean water. I hope it will last me just as long as the Takagi but only time will tell.

JStar

Bobbito

Let me quote your very first post on this website...



"I'm 100% new to hydronic heating, "



There is a lot of experience, and hard earned skill here. It would be very wise to at least listen to it without getting defensive.

Bobbito

Wow

That was not a defensive post, it was a jovial retort of certain falsehoods regarding my chosen setup.

Yes, I was new ... still consider myself to be new.  Anyone NOT continually learning is just living in the past.  I'm not discounting anyone's skill, hard earned or not, but if this really is a scholarly exchange of ideas and experience then let it be that ... when you go after someone "blah blah blah, 50,000 Btuh blah blah blah" you should have something to back it up -- else it looks like an attack.



I don't need to get defensive because I know what my system is, after long 10 hour days at work I would spend hours pouring over installation manuals, plumbing diagrams, etc, so my experience and knowledge is hard earned as well and doesn't deserve to be downplayed or have someone push some false ideas on it. 



The bottom line is the guy who started this post wants to do it himself.  Period.  So we can either help him, or get out of his way IMHO. 

Paul48

Funny

Since you mentioned it, I thought about adding that to my original response. Don't even think about the details of how yet. You have to do the homework.It's not about 1 pipe at a time. You will probably draw it up 50 times, and change and refine it many times.Consider it a late summer job. Start Crammin!

CMadatMe

The Proof

Is the installed pump on the unit. It can only move 4gpm and it is a fixed speed pump so it's always moving 4gpm. So why don't you educate us on how your unit can only move 4gpm and yet overcome your heat loss? No, the answer isn't a 79 degree rise or delta-t because we all know that is impossible.

Paul48

Chris

The manual calls for primary/secondary.Why is a 77* DT impossible on the primary side? It would seem that if you put enough btus to a given(fixed) flow of water, it is possible? It seems as though the chart is written in a different way than most mod/con manuals.I think they believe those DT's(primary) could be maintained at the given flow rates(secondary) within the firing rates of the units.Something just doesn't jive with the belief that the units only put out 50000 btus. There are folks that have come here with heat losses of 150k, and their 199k combis heat their home just fine. You could argue they're over-sized. Something doesn't jive.I'm not arguing for, or against.

SWEI

77F ∆T for heating

Would require a supply temp of 180F and a return temp of 103F.  How often do you think that will happen?

CMadatMe

Down Stream Mix Formula

See the attached. I can't attach a spreadsheet so I had to turn it into a PDF. I'm willing to bet those heat losses are not accurate and you know as well as I that a heat loss is for a design day with everything needing heat at the same time. Not real world.



The reason the loads can be satisfied is what goes into a tee must leave a tee. The question becomes can that supply water temp to the emitter provide the emitter what it needs to produce btu/hr to overcome the loss.



Your moving x btu/hr, the emitter is taking x btu/hr and returning x btu/hr back. I'm recycling that return btu/hr and giving it a jolt of btu/hr from the boiler. Basically what goes into a tee must leave a tee. The boiler is a tee, the LLH in this case is a tee.

Paul48

May Be Wrong

I believe those figures are meant to reflect the capabilities of the boiler at a given flow rate(seconday). Not an expectation that the system would operate at that those DTs for any length of time.

CMadatMe

This Is True

But we can only look at one snapshot in time. Generally worse case. No matter pri/sec or a LLH your always going to have a boiler with a higher water temp then the system side. I wish more mfgs would put supply water temp logic via a system side sensor on their boilers.



That built in pump on that Navien is going to move 4gpm across it's HX. Now the burner may back off but that 4gpm is constant. If the system side takes it all away great because my boiler return is going to see the coolest water. Which in the case I posted before a 30 degree delta. As the system side delta starts to decrease because a zone or all zones are satisfied then that delta will begin to shrink, the boiler will mod down and eventually make limit.



The on board pump is a constant flow. The only change is boiler delta and burner mod rate. Even at the min of 21,0000 btu/hr I'm still moving 4gpm except my delta should be shrinking to 10. Alla, short cycle if I can't scrub out the flow to the system side.



The entire key to all of this is the emitters. Better have enough. In most replacement jobs homes are 35% over radiated so DYI's and plumbers installing these get away with it without knowing the math and the real system water temp they are moving.



All just my opinion..I'm also not going to waste my time on replying to the foolishness. I think I've made my point, oh, facts...I'd like to see Navien publish the actual flow rate and pressure drop across the hx in the manual but they don't even have it for the CH to even email you. Best I could get out of them was that the on board pump will move between 3-1/2 and 4-1/2gpm.

Bobbito

Chris!

We had a rough start but I appreciate what you're saying on this board, just want to understand more of what you're saying. Are you saying that the internal pump is operating even when there is no call for heat?



I spoke with Navien and they said the internal pump is "continuous" in certain situations. If connected to an air handler, then yes, the pump is operating almost 100% of the time. However, if the system is hydronic-only (as mine is), the internal pump only operates when the boiler is firing. Isn't this pretty much identical to a typical cast-iron boiler?



I'm not being combative or trying to offend you, I just want to learn more and you're a pro so...

JohnHenry_2

dood,

you do understand that the 11 GPM flow rates are through the DHW heat exchanger at a 90 psi pressure drop, right?



The heating system side will not flow any more than 5 GPM through the primary (combustion) side.



I know this to be true because Navien sent me their pressure curves and pressure drop test spreadsheets.



If you truly do need 163k BTU of heat out of that unit, the only way you'll get it with that unit is with a metric crapload of radiation (1 metric crapload = 1.15 standard craploads).



The CH-240 unit won't do you any better as it only burns more fuel than the CH-210. All of the other parts (pump, heat exchangers etc. are the same part numbers).



I seriously hope you haven't started to put this together yet as it just plain will not heat your house properly on a design day unless you have enough radiation that you can heat your house at design temperature with an average emitter temperature of 110*. That pretty much means you'll need to have VERY well designed in floor radiation.



The emitters you've chosen output 740 BTU/hr/ft at a 180* avg temperature. There is no way on God's green earth that the Navien CH-210 will do that for you. Those emitters put out 200 BTU/hr/ft at 110* average temp. Do you have enough space for 4 times the radiation you planned on?



This isn't religion, it's physics. It's not subject to interpretation.



With the system you describe, you'll be sleeping alone in a very a very cold house...



PS, I have a CH-210 and like it very much. It's just that my heat loss is round 60K and I have a metric crapload of cast iron radiation...

JohnHenry_2

The thing is,

With the type and amount of radiation you're speaking of, Chris is absolutely correct, you'll only get 50K BTU/hr out of the CH-210. He just didn't explain why. I've done that for you above. I think you owe him an apology...



I would encourage the original poster to start a new thread and ask the question again so that it may be answered by pros without the noise of this one.

CMadatMe

We Didn't Have Anything

I provided fact and you didn't like it because of what you read in the manual. Too bad the manual doesn't give fact as to the on board pump.



I also found your orignal post back a few weeks ago, don't think that heat loss you posted above of 160,000 is true either based on your original post. My advice to you would be to listen, read, and learn before you step into the game. We all share our knowledge and time to help others. We are not here to tell someone to do something wrong. I could care less what equipment you put in as long as it is rated and installed to do the job. Equipment choice is the end users not mine. My job is to explain, when asked, why "A" over "B" what are the benefits.



To answer your question. No, the pump is only going to run on a call for heat. It wouldn't run continuous on hydro either. Hydro is still hydronic and would still have to call the boiler for demand.

Paul48

How

many gpm would you send through a Vitodens 100 to get a 40* DT?

CMadatMe

Vitodens

On a WB1B10-26 4.2 on a 40 Rise

On a WB1B10-35 5.4 on a 40 Rise



The max flow rate through the HX is 6.2gpm. Without the LLH or pri/sec you'd never get the btu/hr the boiler is capable of making out.



4.2 x (40 x 500) = 84,000 Btu/hr

5.4 x (40 x 500) = 108,000 Btu/hr



Just so happens those btu/hr outputs are what the boiler is rated at. Boiler wouldn't have the same output on a 20 Rise you would have just turned it into a 60,000 btu/hr piece of equipment. Just like that little Navien except they don't tell you in the manual what the rise is nor what the on board pump is moving. Top secret stuff! That's why the down stream mix formula is critical to calculate design water temp. Have to make sure those emitters can over come the heat loss.

Paul48

Ahhh

I figured the Universal Hydronic Formula was in there somehow. I didn't know how to use it though. Thank You

CMadatMe

Yuppers

That simple little formula rules! Let's take that little CH-210



We know from them based on a phone call the pump will move about 4gpm and it's published heating capacity is 158,000 btu/hr



158,000/4/500 = 79 Degree Rise



Never came across a heating system in my life that did that. In the real world most of our systems are over pumped and run between 10 and 15.



4x10x500 = 20,000 btu/hr

4x15x500 = 30,000 btu/hr

4x20x500 = 40,000 btu/hr

4x25x500 = 50,000 btu/hr

4x30x500 = 60,000 btu/hr

4x35x500 = 70,000 btu/hr

4x40x500 = 80,000 btu/hr





The burner will make it's rated btu/hr output but it needs a reason to. Scrub off the btu/hr into the system and increase delta more btu's, don't scrub it off and decrease the delta, less btu/hr. That's why pri/sec or LLH is needed. The system flows on that coldest day of the year should be higher then boiler flow. In an ideal world you would always want system flow higher then boiler flow. That way I scrub out all the btu/hr and hopefully the emitters are scrubbing it out of the conveyor belt sending back the coldest water temp it can. Notice we are not even talking water temp just btu/hr production capability.



Look at my house. Typicall 1,800 sqft. R11 walls, R30 Attic, decent windows. Have an are with a crawl beneath. Heat loss is 36,000 btu/hr. The typical 3,000 sqft home heat loss is 50,000 or below and that is why these little creatures work, DYI's , homeowners and plumbers get away with them. They just get lucky because we both would be fooling ourselves if we thought they were doing the math.

RobG

Pex System

Hey Bobbito, could you post some pictures of your system? I am always interested in seeing heating systems piped in PEX only.

Rob