loops of different lenth in one zone

Vad

Hello All

I would appreciate any advise 

        I am going to have multiple baseboard loops. The longest loop will be about 160-170' (baseboard only), the shortest - about 45-50'. Can it be a problem? Is there anything I can do in advance to prevent issues if any? Short loops for aluminium radiators (one in each loop), Long loops for baseboard.



 The other question I have. Longest loop (160-170') is going from the basement to the second floor. It is going to have about 13K BTU (about 27' baseboard calculated at 160 degree). I already ordered 5/8 PEX pipe for it, but now I am thinking that maybe 1/2 pipe will be sufficient. From the other side, I am thinking that it is going from the basement to the second floor and loop is quite long and that maybe I will not get enough flow rate. I do not know what the circulator is going to be and I calculated a baseboard based on 1GPM flow). What is your opinion?

      Also would you advise to have TRV at each loop with this setup? My radiators came with TRV on it. Any particular model of TRV you can recommend?

  

Thank you a lot

Vad

Alan (California Radiant) Forbes

Loops

Don't even think of using 1/2" PEX with that long of a run and that amount of heat output.  And 5/8" might do the job, but you'll have to install a high head pump to overcome 18 feet of pressure drop.



You should read John Siegenthaler's article on sizing baseboard before you do anything else:



http://www.pmmag.com/Archives/ed49328d24fc7010VgnVCM100000f932a8c0____



And if you insist on using PEX, do yourself a favor and install a high-limit aquastat on the supply line to prevent water over 180 degrees from entering the tubing.  The aquastat should be wired to disable the pump or the boiler on temperature rise over setpoint.  The attached picture shows what happens to PEX tubing with a runaway boiler.

Bob Bona_4

do you

and the system pump a favor and run 3/4 for the loop. Alan is right. From your apparent inexperience, and unknown flowrates, do the norm and run the 3/4". You should be safe. 

You are splitting hairs with the 1/2"/5/8" debate. Do the job in 3/4 copper or 3/4 Pex-Aluminum-Pex (avoid single layer pex). It cannot be cost preventing you from doing so.

Vad

Thank you

a lot for your advises. I am ordering 3/4 pipe for the second floor.

Vad

Related question, an urgent one since it is getting cold

        On my first floor, I am planning to put 3 aluminium radiators (3150BTU at 160 degree) together in one loop using 1/2 PEX (or PAP) pipe. The loop is going to be about 140-150 feet. Manifold is going to be at the basement close to the ceiling.

   Since supply and return for each radiator is only 1/2 inch anyway and the altitude difference is very small (about 4' max) is this a right or wrong to think that 1/2 inch pipe for the whole loop will do the job?

Thank you again

Vad

Brad White

Elevation

only matters in open systems and in the 45 minutes after you take a small blue pill.



In a closed system, dismiss that as a factor.



If your radiators total 3150 BTUH each, that is just under 1.0 gpm at a 20 degree drop. I do not know the pressure drop of the radiators (aluminum meaning fins or aluminum baseboard radiant such as Hydronic Alternatives?), but 1/2" ought to work.



Even so, I would stick with the advice of others and go 3/4", you are only going to do this once. The cost difference is not that great.



Flow rate is forgiving, it is true, but you also want your pump size to not be dominated by one circuit with four times the potential pressure drop of any other.



My $0.02 anyway.

Vad

Thanks Brad

   My last question was about the first floor. As for the second floor and long loop  (my initial question) I stick with the advises I got on this forum. I do not want to much pressure in some loops and a little in others.

   On the first floor I decided to use aluminium radiators (Baxi Euro) and not a baseboard. Looks like these radiators have 1/2 suply and return opening.

    My question is how bigger pipe (3/4) can help me to low the pressure if opening for each radiator in a loop is only 1/2?

 May be I am wrong and opening is bigger than 1/2 on the Baxi radiator?  I know that it accept 1/2 NPT fitting



Thanks a lot

Vadim

Brad White

Even if the connection size

is half-inch, there is no reason necessarily to run that size all the way from the pump.



True, economically speaking, you want to size your tubing based on flow and a consistent pressure drop rate, so there are some places where runs of "connection size" make sense. But what you are describing are mains, essentially and you are going to install it once, so being a bit generous for low cost is a prudent thing to do in my opinion.

Vad

It is not about the cost

 .1/2 pipe is just easier to install. I was reading a chapter written by John Siegenthaler (attached) about Modern radiators and the author suggest using 1/2 or even 3/8 pipes to individually connect each radiator.

In my case I do not really want to connect each one individually (to much work ), but combine them in a set of 2 or 3 in one loop.

 Thank you

Vad 

Bob Bona_4

I'm getting

a better picture here of what you are trying to do. My thinking before was along the lines of a loop type system.

That's a great article of Siggy's. Perhaps you should re-think not wanting to run individual home runs to each emmitter. The manifold system Siggy shows is one sweet set up. If you run individual lines, you now can control and balance if need be, and zone if you'd like very easily.

And in this case, if your biggest emmiter is under, say, 15K BTU, you are just fine with 1/2" pex. Pex-AL-Pex, that is

Vad

Bob,

If I can connect one 15K emitter with 1/2 pipe, I assume I can connect three emitters 3K each in one loop with 1/2 pipe. Since the openning is limited to 1/2 by the radiator supply/return valve diameter I feal that I do not gain anything from a bigger pipe.  This is my unprofessional feallings . I can connect TRV at the first radiator in a loop to follow the article.

    Am I still wrong?

    The only thing that bothers me is that loop is pretty long 140/150'

Regards,

Vad

icesailor

Loops/Loopy

Vad,

I've run a lot of pipes in my day and troubleshot and fixed quite a few. Your project sounds to me like the makings of an interesting troubleshooting project for someone.

I troubleshot a expensive waterfront home with a first floor zone that sounds similar to what you want to do. The loop was long, but 3/4" with 1/2" inlet aluminum radiators. The supply started in the kitchen and ended in the living room, after going through a dining room/sun room. The complaint was that the kitchen was too hot and the living room was too cold. The thermostat was in the living room. By the time the water got to the end of the living room, there wasn't enough BTU's in left in the water to heat the room.

The owner was PO when I showed him what was wrong. It couldn't be fixed due to construction.

I find that you can get away with a lot of stupid stuff with hydronics. But when you can't get away with it, you are screwed. If you don't know what you are doing, call a pro.

Vad

 Let's do not generalize.

IseSailor, with you example you confirm that pipe size for the mains does not matter as soon you have a bottleneck in the radiator. Agree?

   Most likely in you case person had too much BTU in one loop. In my case it is 9K BTU (three emitters) in one long 140/150' loop on the first floor and all three emitters are in one room.

Am I still wrong? Is this setup require a strong circulator (that I want to avoid)?

Regards,

Vad

Bob Bona_4

I feel

you are fighting convention. Not sure why.

You are saying you want to do a series loop of three radiators, 5K each, using 1/2" pipe and TRV'ing the first one? Bzzzt.

What is the adversion of running home runs like Sig's diagram show? THAT is the norm, it's proven, and it works like a champ.



 

Vad

Bob,

It is loop of 3 rads, 3K each at 160 degree. It is an old house and to run pipes from each Rad will be much more painfull because of lack of access.

You still think It is not going to work?

Regards,

Vad