Boiler Return Water Temperature Protection

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Old 08-21-14, 08:04 AM
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Boiler Return Water Temperature Protection

Hi, Iím in the process of installing my boiler. My plumber is assisting me but I will be designing and installing everything. The boiler is Cast Iron-Gas Fired-Hot Water-Weil-Mc Lain CGA-3 (IBR 51,000). Iím installing a total of 6 zones; 3 Slant/Fin Baseboard zones and 3 radiant (concrete floor) zones. With help from others I have the following piping arrangement, please see below.

How do I protect the boilerís return water temperature so its always above 130 Deg.?

On this website I read the following;
Comfort Calc

1. I can pipe in a boiler by pass but I want something that operates automatically.

2. I can install a 3-way or 4-way valve, like the Tekmar 710 3-way valve with the Tekmar 741 Actuator.

But am I on the right track?

Thank you all for your help.

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Old 08-21-14, 12:00 PM
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Read an article by John Siegenthaler in the March 2014 HPAC magazine intitled Do not go unprotected , page 32 .
 
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Old 08-21-14, 06:12 PM
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Normally the boiler manufacture's installation instructions will have recommended system configurations. Do you really want to automatically control the return temp to exactly 130 deg? Why? Assuming that this is a cold-start boiler, I'm thinking that the return temp may run quite a bit cooler for many hours.

A small 51K boiler with six zones seems a bit unusual.
 
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Old 08-22-14, 04:32 PM
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Why is a small 51k boiler with six zones a bit unusual ?
 
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Old 08-22-14, 04:40 PM
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Seems over-zoned. I'm visualizing a small 5- or maybe 6-room house, on a slab. But the O.P. may correct us.
 
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Old 08-22-14, 04:42 PM
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In most cases it just doesn't make sense.

If one can use a 51K boiler to heat the entire home, then six zones probably enters into the realm of 'micro zoning' with little (if anything) to gain by doing so.

A home that size would do just fine with two, maybe three tops.
 
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Old 08-23-14, 12:32 PM
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The layout is as follows
Baseboard Zone 1: 1st Fl Studio Apt
Baseboard Zone 2: 1st Fl Kitchen, dining & living
Baseboard Zone 3: 2nd &3rd Fl Bedrooms
Radiant Zone 1: Basement concrete Slab
Radiant Zone 2: Future Driveway/Sidewalk concrete slab
Radiant Zone 3: Future Garage a Concrete Slab
 
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Old 08-23-14, 02:12 PM
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Radiant Zone 2: Future Driveway/Sidewalk concrete slab
Ummmm...

NO.

Just forget about SNOW MELTING right now. At least with that boiler. It's a losing battle.
 
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Old 08-24-14, 07:18 AM
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The radiant driveway/sidewalk slab is really a long shot and I doubt I will be able to afford that anytime soon. But for the radiant basement slab that will definitely be installed next year

1. I'm still a little baffled on why the system pump is needed? This is a relatively small system, can the baseboard pump serve as the system pump too?

2. And can the system pump be placed on the return side of the diagrams?

3. Lastly right now for this coming heating season. I will only be running the baseboard zones, no radiant. Do I need primary and secondary piping or should I just pipe it anyway; so do I need to tie in the baseboard supply with the baseboard return?

Thank you everyone for your help. I'm literally working on this as I type.
NJ Trooper thank you for your feedback
 
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Old 08-24-14, 03:34 PM
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Rick, was a heat loss estimate done on the home?

You said " 2nd & 3rd " floor bedrooms... makes me wonder?

How many square feet is the home?

I'm thinking that a 51K boiler might be too small.

Your diagram only shows ONE baseboard zone.

What you've drawn shows a primary/secondary system piping setup, and YES, the boiler pump is needed in ADDITION to the 'system' pumps.

I think you need to step back, take a deep breath, and draw up a COMPLETE design and post the diagram. I'm afraid you're going to make some expensive mistakes.
 
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Old 08-24-14, 03:36 PM
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2. And can the system pump be placed on the return side of the diagrams?
Google the term: " PUMPING AWAY " and read and understand what those articles are talking about.

What are those " HYDRO-CON " things in your diagram?
 
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Old 08-26-14, 12:34 PM
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Diagram

The home is total of 1200 sq. ft.;1st fl., 2nd fl. & Attic and the basement is a total of 530 sq. ft. A heat load calculation was done and the boiler was appropriately sized. The house is newly renovated and well insulated inside and outside as well.

Please kindly review my diagram. I’m only installing the baseboard zones this season but I am planning the installation of my basement radiant zone next year. I used the Weil Mclain piping diagrams that came with the boiler as my guide.

Here are some questions I have regarding my diagram

1. From what I understand the Air Separator (#9) should be right after the supply pipe comes out of the boiler on the suction side of the pump. In my case I have it in-between the system pump and the baseboard pump but on the suction side of the baseboard pump. Which position is best and does it really matter?

2. Do I need the by pass shown (#26) ? If I certainly use the Taco I Series R mixing valve it will have a boiler senor and supply sensor to monitor the temperature to prevent boiler condensation.



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Last edited by rickr86; 08-26-14 at 01:15 PM.
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Old 08-26-14, 04:19 PM
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Well, that's a LOT different than the first diagram you posted!

What you've drawn I think is OK... I started to comment that the zones should be piped in 3/4" but then blew the drawing up and see that the longest zone is 22' of baseboard, so 1/2" should be fine.

At #16, where it says 12" MAX, you want to get those tees as close as possible. Only go to the max when there is no other choice.

Do you need the bypass? I would say no, probably not... in general fin-tube baseboard systems don't require bypass. It's the large water volume, cast iron radiator systems that do.

You may not even need it for the radiant zone, depending on the size of it.

BUT, look at it this way:

What if you find you DO need it for some reason? What then? cut up the piping to install it after the fact? What a PITA!

Better to install it, and if you DON'T need it, just close the valve!

And, once properly adjusted, there should be no reason to have to adjust it again, so there isn't really a need to consider an 'adjustable' bypass as I believe you mentioned early on.

Was the heat loss estimate done on a ROOM BY ROOM basis in order that you can select the correct amount of baseboard for each room?

I ask this because you are showing 22' in the bedrooms zone 1, and only 20' in the main living area zone 2. Maybe it's correct, but in general, the upper floor bedrooms generally require less baseboard than the main living area where doors will be opening and closing, with more windows, and usually there's more floor space. Was this taken into account?

I really think that $$$ I-series mixing valve is over kill for the radiant zones. I would just use a standard mixing valve there.

What's with all the P/T gauges? You certainly don't need all those. Gauges 15 and 7 are going to be what they're going to be, there's nothing to adjust there. If you like gauges and stuff, then by all means, do what you like, I'm just saying that you probably don't NEED all of them. I'm a 'gaugeaholic' and might install them myself... just saying.

You DO want to put a gauge after the mixing valve in order to be able to set the valve properly.

Also, you should have (move?) one to the boiler side of the bypass on the return so you can adjust the bypass valve.

BY THE WAY, that bypass valve should preferably be a GLOBE valve, and NOT a ball valve. Ball valves 5uck for throttling purposes. If anything, valve #3 will only need to be cracked open a bit to raise the return temp as needed. If you use a SYSTEM bypass (shown in diagram) versus a BOILER bypass, I don't think you'll need to throttle valve #4.

Is the location that you show the take-offs for the radiant subsystem what is shown in the WM piping diagram? If so, can you tell me what manual that's in, and provide a link if you have one? I'd like to look myself.
 

Last edited by NJT; 08-26-14 at 04:35 PM.
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Old 08-26-14, 04:34 PM
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By the way, you MIGHT want to consider a 'Differential Pressure Bypass Valve" installed between points 12 and 13.

If only one zone is calling for heat, it will likely be severely 'over pumped'. DPBV will compensate for this by opening more or less depending on how many zones are calling for heat. It's a one time, set it and forget it adjustment.
 
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Old 08-27-14, 12:50 PM
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Thanks for your awesome feedback.

I wish I would have used 3/4" PEX to run to the 3/4" baseboard but the plumber who ran the piping insisted on using 1/2" PEX. So I ended up increasing from 1/2" to 3/4" into the baseboard and reduced down from ĺĒ to 1/2" on the other end of the baseboard.

I understand what youíre saying about the bypass piping & globe valve for throttling and I think I will install it anyway to play it safe. Is it ok to have a 1Ē by pass line (the same size of my supply piping)?

The heat loss calculation was done on a room by room basis. The upper bedrooms (2nd & 3rd floors) have slightly more baseboard then in the living room because I wanted to cover the entire wall with baseboard in each room for aesthetics. I understand heat rises and I know I could of just used the dummy baseboard but I had extra heating fins so I equally added baseboard in each room.

Here is the link for the Weil Mclain piping diagrams. I referenced Page 19- Figure 12 & Page 21- Figure 14 http://s3.supplyhouse.com/product_fi...stallation.pdf

However, none of the diagram show where to tie in the radiant supply and return. Based on my the water temperature being the lowest on the return line I choose to tie the radiant supply and return at that point (#18 and #24 on the diagram). But other diagrams (see below) show the radiant system coming of the supply manifold for the baseboard system. What is the best design to tie my radiant supply and return into my system?
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Referenced From http://www.doityourself.com/forum/bo...ld-boiler.html

Now another thing thatís bothering me, every piping diagram I see shows the Air Separator (#9) being the first connection on the supply pipe from the boiler. In my case its in-between two pumps, #2 and #10. Itís correctly positioned on the suction side of the baseboard pump #10 but on the discharge side of pump #2? Should I rearrange my piping so the Air separator is the first connection from the boiler supply pipe and then the two pumps follow? OR Can I leave it as is?

Lastly Iím going to incorporate the Differential pressure Bypass and update my diagram. What size should the Piping & Differential Pressure Bypass Valve be? The Same size as the manifold supply, 1Ē? Taco has one but only ĺĒ
 
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