System Layout/Modifications

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Old 12-03-07, 12:11 PM
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System Layout/Modifications

Hi all-

This is my first post as I’m new to hydronic heating. We recently purchased a 3200 sq. foot 1920s 2-story home with a converted gravity system (now closed). The boiler is approximately 10 years old and has been able to keep the house at 68 degrees (Milwaukee, WI temps), but the boiler rarely got above 110 – 130 degrees (cold starts & takes awhile to get hot). I recently added a simple bypass loop with ball valve to get the boiler temps up and would appreciate any suggestions if minor modifications to the piping/setup would be beneficial. With our current weather (30 degrees), the boiler still has never reached the 180 degree high set point. My biggest priority is fuel savings and boiler life.

Current Setup (See picture):
Utica MGB Series 175,000 BTU Boiler (84.1% Efficiency)
TACO 007-F4 Circulator – ON RETURN SIDE
Effikal Auto Damper
Honeywell L8148E Auquastat – (Soon to be Tekmar Outdoor Reset)
B&G Flo Control Val – Part of the conversion??
Old B&G 18-Gallon Expansion Tank
B&G Pressure Reducing Fill Valve

What would you do if this was your setup? Are there any changes that would help reduce fuel costs (i.e. move and/or different circulator on supply side, better bypass loop, exp tank, etc.)? Thanks!

 

Last edited by jborders5; 12-03-07 at 12:58 PM.
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Old 12-03-07, 12:33 PM
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1) can you post some pictures of the rest of the basement piping?

2) what's the building heat loss, what kind of radiation do you have (standing cast iron rads, I assume), and what is it's output at various supply water temperatures relative to your design heat loss?

3) how deep do you want to get into this?

2 and 3 would help inform some suggestions on how you might improve efficiency and comfort within your budget and skills.
 
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Old 12-03-07, 12:56 PM
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1) Thanks for the reply. I'll take a couple of pictures of the rest of the piping tonight. It is the orginal large asbestos wrapped (cast iron?) piping after the supply and return ball valves on the top of the picture.

The radiators are orginal free standing cast iron.

2) I have not calculated heat loss yet, but wil start to take the measurements soon.

3) Since the pipes are asbestos wrapped I'd probably like to limit work to the copper supply and return sections, but also feel comfortable working with the old expansion tank line.
 
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Old 12-03-07, 01:10 PM
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Pump belongs at point of no pressure change, i.e. right after the expansion tank.

I assume you installed the bypass shunt around the boiler because of the condensation stains on the wall? Did it work?

Pete
 
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Old 12-03-07, 01:25 PM
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Yes, I installed the bypass after reading about the negatives of low boiler temperatures and in hopes of getting the boiler temps up faster. The condensation stains appear to be old and were there when we purchased the home. Even with the loop it still takes 1- 2 hours to get the temps up around 130 from a cool start (70 – 90), but it may still need adjustment as it’s only been on for a day. Currently the return is about 15 – 20 degrees cooler than the supply as the boiler heats up (with the bypass loop). The hottest I’ve seen the boiler is 160 degrees this morning. The house thermostat is at a constant 67.

The circulation pump placement is one of the reasons for the post since I’ve read numerous websites recommending it on the supply side after the tank. It would not be too difficult to move the expansion tank location and pump if it would help with efficiency and save gas.
 

Last edited by jborders5; 12-03-07 at 01:26 PM. Reason: spelling
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Old 12-03-07, 01:49 PM
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One zone? You might consider adding a Danfoss TV valve right above that circulator, piping it would be very easy the way your system is laid out!! It would stop that extended period with cool return temps, it can't be good for the boiler. Here's my TV bypass on the back of my Biasi.



The big silver beast to the left is a backup multifuel unit.

Pete
 
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Old 12-03-07, 02:14 PM
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Originally Posted by jborders5 View Post
The circulation pump placement is one of the reasons for the post since I’ve read numerous websites recommending it on the supply side after the tank. It would not be too difficult to move the expansion tank location and pump if it would help with efficiency and save gas.
It looks as though you've got the bypass throttled back a bit... why not run with it wide open for a few days and see how it goes ?

Where you've got the thermometer stuck in... try adding some more of the pipe insulation up and downstream of that point. You will never get a "true" reading with an external like that, but you can get close, and more insul around it will help. I also believe you will get truer readings on steel pipe than copper. I've done some experiments with an IR gun type thermometer. If I take the temp of my cast iron air scoop on the supply side, it reads within 1-2 deg of the well type thermometer about 12" upstream. If I read the copper pipe going in and out of the air scoop, it's like 30* LESS.

Try putting some insulation around that elbow below the circulator and put the thermometer there... I bet you see a big difference!

About moving the pump and expansion tank... that won't really _save_ anything... what that will do is assist in removing air from the system. I wouldn't worry about that for now...

You might like these thermometers
 
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Old 12-20-07, 03:44 PM
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Update

Update after a bit of researchÖ The boiler still rarely gets past 160 degrees after hours of condensing temps from a cold start. Iím currently looking at a Danfoss/ESBE thermic valve with P/S piping as recommended by the manufacture since it will be used in a converted gravity system. Iím on my second reading of Danís P/S pumping made easy, but need some help with circulator sizing. I believe the secondary circuit feeding all radiators will require approximately a 24 GPM circulator due to the conversion, but am at a loss on how to calculate the primary boiler circuit circulator size. Any help is greatly appreciated. Below are all of the current specs of the system with heat loss and EDR calculations.

Utica MGB Series 175,000 BTU Boiler
DOE 143,000
1=B=R 124,000 BTU/HR

Taco 007-F4 (currently pumping from the return into the boiler and expansion tank)

Total Heat Loss - 112,594 BTU/HR (Slant/Fin Program)
Total Sq Ft EDR Ė 964.5

Let me know if you need any other information. Thanks for your assistance.
 
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Old 12-20-07, 04:02 PM
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Primary loop : I'm pretty sure it would be based off the BTU of the boiler. I think you'd wanna use the IBR number ? (not sure), but figure 1 GPM per 10,000 BTU if that's indeed the way it works. So, you would need like 12 GPM or so ... I think ...
 

Last edited by NJT; 12-21-07 at 03:30 PM. Reason: anyone?
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Old 12-20-07, 07:12 PM
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24 gpm? Wow. What does the distribution piping look like? What pipe diameters?
 
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Old 12-20-07, 07:50 PM
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The largest distribution pipes are 3" OD. I calculated 24 GPM using a chart from an article regarding circulator size and gravity conversion. The chart uses total EDR or MBH (can I post links to other sites?). If I'm way off, please point me in the right direction.

 
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Old 12-21-07, 08:21 AM
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My argument has always been with a boiler bypass. I have installed many boilers with cast iron radiation and used a boiler bypass. Reduce the flow in the boiler and the supply water gets hotter. Stops condensation, flow in the system not affected and supply water gets hotter. I have not had a problem with boiler bypasses doing the job if they are adjusted to about a 40ļ delta T. Condensation stops and boiler gets above condensing with in 5-10 minutes. This is not to say using a thermal bypass or variable speed circís is not better. I do not want to affect flow to the system so if I do a system bypass I always use p/s. Boiler bypass no need if all zones are the same temperature.
 
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Old 12-21-07, 03:32 PM
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Anybody else take a stab at the question on the primary pump sizing ? I'm pretty sure it would be correct to size for BTU's, but not sure... rbeck ?
 
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Old 12-21-07, 03:45 PM
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I'm always perplexed at which circuit is primary - I consider my heating loop primary -- it was there first, and it has the supervent!!

If we're talking the boiler loop, ΔT seems appropriate. That's ultimately the limitation I would think.
 
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Old 12-21-07, 03:55 PM
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The primary pump / loop is the boiler loop.

At the plant I worked in for 19 years the primary pumps were rated at 900 gallons-per-minute. Of course the boilers were rated at 16 and 25 million BTU / hour.
 
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Old 12-21-07, 04:33 PM
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Thanks guys for the continued input. If we assume I’m on the right track with a 24 GPM on the radiator circuit and 12 GPM on the boiler circuit, wouldn’t I also have a pseudo boiler bypass with the p/s piping arrangement? With the secondary loop operating at twice the flow rate of the primary, half of the cooler return water from the secondary loop will mix back into it’s own supply (backwards via the common piping between the Ts). I’ve been using a Delta T of 20 on both circuits, but that’s when things start to get fuzzy. Using a 180 degree supply temp from the boiler and applying it to the heat equation for the secondary loop, I come up with a 170 degree supply temp for the secondary loop. Using a Delta T of 20 for the return temp of the secondary, wouldn’t I have a Delta T of 30 on the boiler loop return temp? Would I be better off just installing a full size boiler bypass with a 3-way mixing valve? This would eliminate the Danfoss valve and additional circulator, but would still allow me to control the flow and raise the boiler temps.
 

Last edited by jborders5; 12-21-07 at 04:42 PM. Reason: Additional text
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Old 12-21-07, 05:13 PM
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I don't see any reason why you need to stick with the 20* delta in the boiler loop, as long as you insure that you stay out of condensing territory on the return temps. And when you ARE there, that you aren't there long...

If you're going P/S, I don't see any reason why not to include the boiler bypass line (or a thermic bypass). If you find you don't need it, then just close the valve. If you don't do it and find you need it, then what ?
 
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Old 12-21-07, 05:20 PM
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If it was my boiler... I'd ask the manufacturer what they recommend doing in your situation. Do they show a recommended bypass piping system in the installation manual? Most simply shunt some of the flow between the return and supply with a direct bypass pipe between those two ports, and a balancing valve to steady the return temperature. If you are dealing with only one zone, that be the easiest method to use.

On the other hand, the Danfoss TV valve is fully automatic, and foolproof. And you are dealing with a gravity feed system with a lot of water?

Pete
 
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Old 12-21-07, 06:33 PM
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I don't know enough about gravity conversions to know whether 24 gpm is outrageously high or just right. I agree that an email or call to Utica to ask for suggestions would be useful. Even better would be to call a local supply house and find out who the local Utica rep is. Get him over to the basement and see what he suggests. Also rbeck's suggestion for boiler bypass would definitely help solve the condensing problem.

[Nice door!]
 
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Old 12-21-07, 07:03 PM
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The Utica installation manual does recommend a bypass on large gravity systems and gives examples of the most common piping arrangements inclusing a P/S layout. I wish the original installer would have read the manual.

If I end up just re-piping to add the proper bypass, do you all recommend swapping the old steel expansion tank for a newer bladder type with a spirovent (or similar)? I definitely will configure the layout with the circulator on the supply side pumping away.

Thanks xiphias. The entire house is full of great doors including some beautiful leaded glass ones... All but 3 of the 18 radiators have custom covers.
 
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Old 12-21-07, 07:19 PM
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Any idea of the total water volume?
 
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Old 12-21-07, 07:32 PM
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I don't. Most of the piping is either still wrapped or hidden. The basement has a finished plaster ceiling. Is there is way to approximate using the radiator sizes and distance from the boiler?
 
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Old 12-21-07, 08:38 PM
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Well you'll need an idea of the volume if you are going to get a new expansion tank. What size is the one there now?
 
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Old 12-22-07, 06:33 AM
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The current tank is 18 gallons.

The only guidelines I've been able to find if the total capacity is unknown was from an article by Dan Holohan using the total EDR. His rule of thumb is to multiply the total EDR by .03 (for systems with an EDR less than 1000) to size a steel expansion tank. The article then states to multiply the steel tank volume by .55 (for a 2 story house) to calculate the diaphragm tank size (total volume).

Using my total EDR:
964 X .03 = 29 Gallon Steel Tank
29 X .55 = 16 Gallon Diaphragm Tank
 
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Old 12-22-07, 07:56 AM
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If 18 has been working, then 29 might be a a conservative overestimate. The only downside of too much expansion tank is initial cost (and cost of replacement should it fail).

You might do two Amtrol 60s or one 90. That might be enough.

A simple diagram for installation is at

http://amtrol.com/pdf/extrolbrochure.pdf

Regardless of what model air purger, pipe the water feed and tank as shown in that diagram.

A very useful modification is to put a butterfly or ball valve between the tank and the water feed. This makes removing the tank(s) a breeze. If you go with the big tanks, you can sit them on the floor. Make up a little "wok ring" for the tank(s) to sit in. Cutting a 5-gal bucket down would work, for example. Double tanks can be piped using a simple header (tees with nipples, etc.).

When you move the circ, use shutoff flanges. Makes replacing the pump a simple job.
 
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