Head Loss Cumulative?

knotgrumpy

In a multi zone Mono Flow system, is the head loss cumulative?



If I decide on removing five circulators and replacing w zone valves, do I size pump by highest head loss zone and then total gpm or do I add all head loss together? I'm thinking if pump can overcome highest HL it can handle the lower ones, but I'm not sure of that.



Highest head loss both measured and calculated came out very close. 7.9'



Total BTU load for all radiation is right at 113k



Also considering manifolds and home run piping.



Thanks,



Mark

Zman

Not cumulative.

The gpm is cumulative but not the head . When you are looking at the pump curve make sure it looks good with both the max head and max gpm as well as the max head and min gpm.That is what is so nice about ECM circulators.

Carl

Gordan

When you say multi-zone monoflo

How is the zoning accomplished? Multiple monoflo circuits piped in parallel, each with a zone valve?

knotgrumpy

Yes, that is how it would be...

Now each zone has its own pump of various heritage.

Gordan

So...

The head loss is calculated by adding up along the path the head loss of each section calculated for the design flow that THAT section would see. (So: for head loss in common piping add up the flow through all the branches that use the common piping.)



As Carl said, once you have the head loss for each branch, you size the system circulator using total design system flow, and the head loss of the "longest" branch.

knotgrumpy

Thank you both and while I have you...

I think you suggested the idea to me of a home run setup a while back.





I have 12 separate 'emitters' All cast iron save for 1 1/4" steel fin tube in two separate rooms.  All but a few emitters require less than one gpm.





If I swap this over to a direct run to each radiator, I think I can use 1/2" pex.  Longest run one way is 60'.





I picked up 10 brand new White Rodgers 1361-102 zone valves in their boxes for a song.  Not supposed to discuss pricing here so I won't.  Are they decent valves?





I was considering a 12 outlet supply manifold with 10 of the zone valves collecting the return.  They are 3/4" valves so I'd consolidate the 1/2" return from 2 radiators in each of two separate rooms on a 3/4" return.

If I figure it right a single ALPHA would run it. 



 

OR, I just make up a new supply and return manifold for my monoflo system and put five of the zone valves in it with an ALPHA which it looks like it will handle.





Downside I see to my current system with 1 1/4" BIP is that there is 7.9 gallons of water in each 100' of pipe.  That is probably more water than my boiler holds.  Yes, it is nice having hot pipes in the basement on coldest days, but not in fall and spring.  I'm heating a lot of water that is not that useful and is sitting in hundreds of feet of pipe.  A home run system would actually seem more energy efficient, though I know a lot of work to install.





Sorry for the ramble. Any comments, criticisms welcome.





Mark

Pughie1

jpughe@roadrunner.com

How about TRV's on your heat emitters with a homerun system using

the Alpha circ. Much simplier wiring. You could get a manifold with flow meters to monitor whats

going on. I'll bet 3/8" might work on some of your runs. I would also suggest

Pex-Al-Pex over Pex - It expands much less than pex & I think it is easier to

work with.



     John

Gordan

I'll second the recommendation of Pex-Al-Pex

A side benefit is that most of it (but not FostaPEX) is actually larger than same nominal size PEX so you'll have less pressure drop.



More thermal mass (read: water volume) is not a bad thing as it helps reduce cycling, but as you've noticed, if not insulated it can lose quite a bit of heat where you don't want it. Control is everything.

knotgrumpy

I've considered TRV's...

But I have these zone valves available.



If they are junk, I'd like to know but they seem to be regarded well by some.



What brand of PEX-AL-PEX have you used or recommend? I've looked at Multi Cor from Wirsbo and I sort of liked the FostaPex.



Mark

icesailor

Junk or not:

40+ years ago, those were my first exposure to zone valves. I even used those W/R 3-wire valves in my house. I'm not saying that they were junk but the weak link was the O-ring that seals the plug stem to the body. Water starts leaking past the O-ring seal and evaporates. Water fouls the contacts. With the 3-wire ones, they would either open and not close or not open but if you advanced them, they would turn off. The 1361's are two wire. They leaked too. If I hadn't been introduced to Taco 572 wax motor valves, I would have never used zone valves ever.

Gordan

Both those are very good

Multicor uses the QS-style compression fittings OR press fittings, and Fostapex uses press fittings and a special tool that strips away the outer PE and AL layers. I like compression fittings, personally. Disassembly and reassembly is a non-event with them.



1/2" Multicor is .490" I.D. and 1/2" Fostapex is .475" I.D. So, Multicor would have somewhat lower pressure drop but you wouldn't know it from Viega's charts which have to be overly optimistic (and on top of that, don't indicate at what water temp the pressure drop applies.)

knotgrumpy

So they are old school valves

Perhaps I'll post them on eBay and start fresh? Could you head off issues by just swapping the o-ring when you do your yearly boiler maintenance? They pull out easy enough.



Ack.  Too old to worry about another maintenance item.

Gordan

If you think about it...

Once you're done buying thermostats and zone controllers and wiring everything up, you'll easily have spent more than the TRVs. And you'll still be stuck with on-off operation, rather than proportional.



As I see it, the only disadvantage of the TRVs that are commonly available here (as opposed to programmable ones that you can get overseas) is that you can't do automatic setbacks but, like a lot of things (ahem, zoning :-)) these tend to work better in theory than in practice.

icesailor

Zone valve repair:

Last week, I replaced a power head on a Taco 572 zone valve. It had a green head and was stamped 1987. The valve wasn't leaking, just the power head was bad.

I haven't seen a White Rogers zone valve in years and know of no one installing them in the area where I work.

They may work for some, they just never worked for me.

knotgrumpy

What works better in theory than in practice...

"...but, like a lot of things (ahem, zoning :-)) these tend to work better in theory than in practice. "



The fancy TRV controllers?

Gordan

Setbacks

Setbacks is what I was thinking.

knotgrumpy

Repairs

I am sure they should be in demand for a homeowner or contractor doing repairs on installed systems.  The price will be right.  We'll see how it goes. 

I trust your experience on this.

Mark

PS - Back to the drawing board now...