Should I use a Bypass Valve?

Hey_Obie

I currently have an oil fired hot water system.  I will be replacing the boiler this summer and I want to address the fact that my system is only one zone.  I will be breaking it into 4 zones and I will be adding a DHW tank.

I read that it a Bypass Valve can help to smooth out the flow of water in the system as the various zone valves close.  Here is the valve I was going to buy: 

<a href="http://www.pexsupply.com/Taco-3196-1-3-4-Bypass-Valve-4424000-p">http://www.pexsupply.com/Taco-3196-1-3-4-Bypass-Valve-4424000-p</a>

What I was going to do was put the Bypass Valve between the new Supply and Return manifolds that I will be making.  In other words, it will be like a very very short zone (without a zone valve of course). 

Am I doing the right thing?  I think it makes a lot of sense.

Obie

Mark Eatherton

Options...

What you are looking at is a fixed speed pump, sized based on all zones calling at the same time. A rare but necessary event indeed. So basically, your circulator is technically oversized (as are all components of your heating system) for 95% of the time.



So, in an effort to avoid over flowing zones, we incorporate a pressure relief valve between the supply and return, OR around the inlet and outlet of the pump.



I equate this to driving your car with one foot on the gas, and the other on the brakes, while slipping the clutch. Not a wise use of energy.



At the time that the pressure activated bypass valve was introduced, ECM circulators were not yet prevalent on the open market. Now, there are numerous manufacturers of extremely efficient and intelligent DC, ECM variable speed circulators that are reasonably priced, and can be justified in lessened wear and tear of the piping system, and significant reductions in parasitic power consumption.



For ECM circulators, google Wilo (pronounced VEElo) Ecos, or Grundfos (pronounced GRUNDfuss) Alpha. Hopefully, a North American favorite manufacturer will be out with their ECM version in the near future so those who want to "BUY AMERICAN" can satisfy their need.



Now, you have options. BTW, when employing ECM technology, you do NOT want to incorporate a bypass, because it will confuse the living crap out of your circulator. It will continually be trying to fill the hole that it see's in the system...



ECM circulators are becoming more and more common for the ultimate in efficient systems.



ME

djthx

Zoning 101

Found this book very helpful:  http://www.bellgossett.com/literature/files/809.pdf

Mark Eatherton

I wonder who wrote that...

Great stuff there, even today!



ME

Big Ed_4

Bypass

I think your over engineering from what you described as a simple system .… I personally would only use zone valves for set of short loops radiation and use the proper circulator for each loop or set of loops ...



I would use a bypass on a constant circulation system with TRV 's installed where you might dead end a pump ... Your zone valves will control the pump .…



Keep it simple but do it right …

Unknown

As Mark says,,,,

An ECM pump is the way to go!, if you want zone valves,,, but Big Ed has a good point too.

Hey_Obie

Big Ed - I was trying to keep it simple

What started this whole enderver was that I wanted to replace my 30 year old boiler and I wanted to add a zone to place a heat exchanger into my heat pump.  I wanted to get away from using electric heat as the backup when the heat pump couldn't handle the cold. I also had the problem that my 1st floor was too cold in the winter. 

So here I am learning my brains out trying to make this work  I have had to learn my old system first.  Steal pipe, venturi tees, flo control valves, mixing valves, air seperators, expansion tanks.

I have had to learn about Federal tax credits (oil doesn't cut it unless you put in a rocket ship_, DHW, circulator pumps, zone valves, ball valves, Pex versus copper, copper to steel, tankless hot water, thermostats, baseboards, water to air exchangers and now bypass valves that I don't need.

I also have to learn how to size what boiler I need because apparently what has been recommended to me is to large.  So I need to figure out how much heat my house is loosing.

While I am not trying to over engineer, I feel like I have earned my degree in engineering.  I just want to end up with 3 house zones and 1 heat exchanger for my heat pump all working one circulating pump and possibly DHW (I prefer my tankless hot water because it is simple).

But the whole process has been very educational and I actually have enjoyed every minute of it.  Thank you for Zoning 101.  I will read it tonight.

If I am over engineering, please let me know where I am making it too complex.

Thanks and keep teaching me.

Hey_Obie

Circulator Pump

ME,

Do you think it is safe to say that a new oil boiler that includes a circulator pump will be an ECM pump?

Thanks,

Obie

Hey_Obie

Thank you ME.

Heating 101 is printed

Unknown

No Bypass With ECM Because...

Interesting post...  Here's the deal.



Constant speed circs build pressure as flow goes down, causing the requirement for the by-pass.  Without the by-pass valve (assuming it's set correctly) the constant speed circ could overheat under low flow conditions and cause the last zone "calling" control problems - the last zone sees almost the highest head constant speed circs produce.



ECM circs decrease head as the flow goes down (opposite what a constant speed circ does).  Almost tracks a system friction loss curve believe it or not.  Because of this a by-pass is not required (minimal differential pressure and power at zero flow demand).



As an example of power, our Stratos ECO has a max wattage of 58 and a minimum wattage at zero flow of 5.8 (point of reference - a door bell transformer is 10 watts).  It will never overheat or overpressure the system.

Unknown

Kudos Steve,,,,

I have a Stratos ECO on my monoflow 3 zone system(after trying 2 Taco VDT`s),,,, I love-it!

Mark Eatherton

Wishful thinking Obie...

Maybe SOME day, but not right now. The technology is more expensive than waht is available, and most boiler makers are looking for ways to decrease installed costs, not increase it.



Eventually, it will be mandatory, but for the time being, don't hold your breath.



ME

Hey_Obie

Wilo Stratus ECO

Thanks guys, this clears up a lot of concerns that I have about noise and strained pipes.   While they are a little pricey, the extra $100 bucks is well worth the benefits and will be part of my system.

I am getting there.

Thanks,

Obie

Big Ed_4

Mono Flow

You mentioned Venturi tees , and iron pipe ? Sounds like a mono-flow system ...Up flow or down flow system ?(main over head radiation or underneath ) That is one system you may want an independent circulator ... An indirect hot water tank is another ... Now you want to add one hydro air coil , What size coil fits into your heat pump ? Most work out to be over size .... Which is not a bad thing



Why do you only what to run one pump ?



The over engineered remark was not a jab , just hate to see you go in the wrong direction ...



P.S. That bypass you posted was only 3/4" , a bypass should be full port ... My guess your mains would be larger ..

Hey_Obie

Monoflo System

I think Monoflo is a B&G terminology if I am not mistaken.  The Venturi tee's are made by Taco.  The boiler is in the basement as is all the iron 1 1/4" piping.  There are 1/2 and 3/4 inch venturi tees running off of the main.  The  1/2" lines go directly to baseboards on the first floor.  The 3/4" inch venturi's feed risers which go to the 2nd Floor and feed a couple baseboards off of each line.  Each baseboard has it's own control to regulate flow and a bleeder valve.

The exchanger that I have inserted in the heat pump (the heat pump services an addition that was put on 20 years ago) is 18 by 18 by 3.

My plan is to break the current system into three zones with three programmable thermostats. The West side of my house very cold in winter.  Especially the first floor which is two rooms (zone 1). The West side upstairs would be a second zone (zone 2).  The rest of the piping would be the third zone (zone 3).  The heat exchanger would be Zone 4.

I have read and understand that you do not cap off venturi tees. Piping must be added if you are removing a baseboard/radiator.

You asked why only one circulator?  From what I have read, circulators or zone valves are both acceptable designs.  I chose zone valves because I thought it was simpler  and zone valves are less expensive.  I currently have one circulator and it moves the heat around just fine.  I just can't control my zones very well for day use and sleeping.  A separate circulator for the heat exchanger may be better, I just wanted to keep it simple.

Ed, I appreciate your interest in making sure that I do not make a major mistake.  Beleive me, I am not trying to over engineer.  I want to make it simple, but I just can't seem to get there.  I thought zone valves would be the simplest way to go.

Any thoughts are welcome.

rcevan

a follow-up, unrelated, question

Thank you for the link to the "Zoning Made Easy"

On page 25 of the booklet, the first paragraph, it talks of outdoor reset with a 3-way valve and says "this is not a good way to do it, however, if you have a tankless coil or a side-arm heater."



I am thinking of using a 3-way w/ outdoor reset w/ the radiant heat source being a flat plate exchanger. BUT I don't have a boiler, so I think the booklet's caution may not apply. My heat source is a water heater. Given I've got a reservoir, I think I'm OK? right? Thanks.