Boiler Temp & Gravity Conversion

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Old 01-01-15, 10:43 PM
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Boiler Temp & Gravity Conversion

Hey all,

First and foremost thank you to all the contributors & mods on this website. It's been a tremendous resource over the years and it's my first stop for resolving issues around the house.

I have a recently installed Burnham Series 2 P205 & an indirect hot water heater for a gravity conversion in a 1900sf old house with all cast iron rads. It replaced a "slightly larger" vintage American Standard boiler & leaky hot water heater. Manual J says a total heat loss of 81k. Volume calculations for the system comes in at 70 gallons, and I think that's where the problem starts. But I've been wrong before!

Everything works wonderfully and the house is a comfy 70 degrees on another 5 degree night right now, but as you may have suspected there's a flue condensation issue. I can say that with confidence not just because the system temp typically doesn't rise above 130 when the boiler is running, but also because there's been a visible trickle of water where the pipe vents to the chimney (which is lined with a 6" steel pipe if that's of any consequence).

When the DHW circulator runs the boiler temp quickly rises to 160 or 170 and seems to act like it should. It's only when the system circulator is running and the large volume of rad water is introduced that it struggles. Both are Taco 007's and the system circ has a flow check.

After many hours researching the symptoms and through insight i've gained from NJ Trooper and others replying to similar posts, it would seem that a thermic valve on the supply side of the bypass would help the boiler climb to the appropriate temp range while allowing the cooler water to satisfy the radiators/thermostat. I've tried throttling the existing bypass valves and there is a noticeable improvement in the delta between supply & return temp, but still not enough to get above 130 consistently. There is room to add a third circulator for a system bypass but it seems that just slowing the release with the thermic valve would be a good start. ANY advice or suggestions otherwise would be appreciated! And thanks in advance for taking the time to read through this.

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Old 01-01-15, 10:53 PM
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boiler bypass

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Old 01-02-15, 07:34 AM
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You knew your nickname would get my attention, diddinya?

the chimney (which is lined with a 6" steel pipe
Stainless? say yes please...
 
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Old 01-02-15, 07:41 AM
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Both are Taco 007's and the system circ has a flow check
The DHW circ does NOT have a flow check? I think it needs one. When the system is pumping, it will pull through the DHW in reverse flow.

There are two main loops in the system it appears? (trying to decipher the pics... kinda hard to make out where the pipes all go.)
 
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Old 01-02-15, 09:50 AM
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Fraid not. It appears to be a standard steel pipe they bricked around when they built it. It has a metal elbow at the basement and extends to the roof. I removed the old boiler and it seems quite smooth and rust free.
 
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Old 01-02-15, 10:05 AM
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Correct on the DHW circ. I have another Taco 007 with flow check that I was going to swap out in addition to adding a flow check below the system return line because it when the indirect aqua stat was messed up** it caused the DHW circ to run 24/7 and some heat convection was happening in the returns.

**that model of Weil McLain Aqua plus has a faulty aqua stat which, after some digging, was evident thanks to other posters on this site. They shipped a replacement brand for free and a 2 minute fix solved that little setback!
 
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Old 01-02-15, 10:13 AM
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"There are two main loops in the system it appears? (trying to decipher the pics... kinda hard to make out where the pipes all go.)"
Correct. It's a 2 pipe system with 2 loops coupled for a single supply and single return. I can post other angles if needed and thanks! Or color code a photo?
 

Last edited by NJT; 01-02-15 at 03:47 PM.
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Old 01-06-15, 11:56 AM
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Bump.

Any other recommendations for or against a thermic valve on the system return to help temperature gain at the boiler? Convert to primary/secondary? Get quotes on a full blown ODR addition?

And is it even possible (or necessary) to line a 6" schedule 40 steel pipe without restricting the vent size beyond what the manufacturer allows? I think it would require a complete chimney rebuild otherwise because it's a steel lined flue that appears to be original to the 1917 addition back when it was a coal fired boiler. Only "upside" to that is it's an exterior chimney and easy to access...
 
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Old 01-06-15, 03:51 PM
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If I were going to do a gravity conversion such as yours I would strongly consider a setup such as this:



Don't pay exact attention to the piping sizes noted, as this was drawn for another post a while back.

Pipe sizes MIGHT be correct though... you need to use what's appropriate for YOUR system.
 
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Old 01-06-15, 04:00 PM
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Why in the picture is the boiler bypass closed?
 
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Old 01-06-15, 04:02 PM
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What size expansion tank have you used? Can't see it in the pics.

I'm guessing it must be a 90 ?
 
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Old 01-06-15, 04:03 PM
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Your pics show two mains on the left, and two on the right.

Is this a supply and return on each side, from each side of the house?
 
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Old 01-06-15, 04:24 PM
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Looks like he has a boiler bypass troop.

I say open that bypass valve all the way.

Also set the t stat to one temp and leave it there.

I assume get the check on the indirect then run the boiler and post back boiler temps on call for heat...

(There should have been a valve at the boiler return inlet to restrict flow through the boiler...)

If its new install why isnt the company making these changes? You paid them right?

 
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Old 01-06-15, 04:40 PM
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From what I can see in the pics, it appears that you are feeding and returning from the 'bull' of tees that are connecting the two sets of pipes together. This isn't good practice. It creates lots of turbulence and the flow may not split evenly.

The graphic below is a modified one that I previously posted.

Note that the two 'halves' of the system are joined into manifolds, and they are piped in 'reverse return' so that the flow will more evenly split between the two loops.



I don't know if you've got room to do like this, but it's worth some thought...
 
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Old 01-06-15, 04:45 PM
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And is it even possible (or necessary) to line a 6" schedule 40 steel pipe without restricting the vent size beyond what the manufacturer allows?
It may be allowable to go down one size to 5". Check local codes.
 
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Old 01-06-15, 04:47 PM
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Mike, I don't think the boiler bypass will be enough protection for the boiler.

TONS of cold water coming back...

I was under impression that Beer did the work... am I mistooken?
 
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Old 01-06-15, 04:49 PM
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Individual pumps on each half might be advisable.

That 007 might be a little on the wimpy side to move all that water.

But an individual 007 on each half would probably be fine.
 
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Old 01-06-15, 04:49 PM
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it appears that you are feeding and returning from the 'bull' of tees
Good eye troop... IMO again it should not be his reponsibility..

But I would think if he breaks a union at the boiler supply or return and adds a valve there it may be the easiest solution and may fix his temp issue..

Just speculation of course...

Its what I would try anyway because should take 30 minutes or so to do...
 
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Old 01-06-15, 04:51 PM
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Also, without a check valve on the indirect loop, there is in a sense, more boiler bypass there.

When the system pump runs, it will suck through the indirect in reverse somewhat, and will pull some of the return before it hits the boiler.

The net effect is that it will tend to suck heat out of the indirect.
 
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Old 01-06-15, 04:51 PM
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I was under impression that Beer did the work... am I mistooken?
You may be right... Well he better make a phone call to himself then...LOL...
 
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Old 01-06-15, 06:34 PM
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If I were going to do a gravity conversion such as yours I would strongly consider a setup such as this:
Yes it's "close" to what i have and was what I considered doing initially (saw that in another post here and other places a while back) but ended up following Burnham's instructions instead. Their recommendation is just for standard valved bypass in a high volume condition but it's looking more and more like you seasoned veterans know a thing or two . It wouldn't be terribly hard to make that switch.
 

Last edited by BeerM3; 01-06-15 at 06:56 PM.
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Old 01-06-15, 06:38 PM
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Why in the picture is the boiler bypass closed?
I was fiddling with the valves prior to taking the picture. Burnham recommends starting with it half closed and going from there. Lately it's just been left wide open like lawrosa suggested.
 
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Old 01-06-15, 06:54 PM
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What size expansion tank have you used? Can't see it in the pics.
Watts ETX-30 and from their online calculator i now think it's a size too small even though it's holds a steady 12-20psi when heating.

Your pics show two mains on the left, and two on the right.

Is this a supply and return on each side, from each side of the house?
Correct. Both 2-1/2" supply & returns on each side. Returns are the outer pipes.
 
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Old 01-06-15, 07:02 PM
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From what I can see in the pics, it appears that you are feeding and returning from the 'bull' of tees that are connecting the two sets of pipes together. This isn't good practice. It creates lots of turbulence and the flow may not split evenly.

The graphic below is a modified one that I previously posted.

Note that the two 'halves' of the system are joined into manifolds, and they are piped in 'reverse return' so that the flow will more evenly split between the two loops.

I don't know if you've got room to do like this, but it's worth some thought...
There is room and it's a tweak that could be easily made. Thanks for suggesting that. You're correct that right now the "bull" T's into the middle of the supply horns. There's a pressure gauge on each one to monitor any kind of substantial difference between sides, and there isn't, but the returns are manifolded as that diagram shows so what you're suggesting makes sense.
 
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Old 01-06-15, 07:10 PM
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Watts ETX-30 and from their online calculator i now think it's a size too small even though it's holds a steady 12-20psi when heating.
Holding the pressure probably because the water never gets over 130F-ish. Not as much expansion. If you're hitting 20PSI at 130F you'll be up to 30 EASY at 180F.

Yes, at LEAST one size too small, maybe even two!

BUT... your SYSTEM might never need to get to 180F ... with the setup I posted, the BOILER can run at proper temp, but the system will go where it needs to go. If you've got enough emitters in the home to cover the heat loss at 130F water, then that's as high as the system will go.

Both 2-1/2" supply & returns on each side. Returns are the outer pipes.
Good, I guessed right... I downloaded and blew up your pic and saw the 2 ball valves...

I would say that 1-1/2" interconnecting pipes are probably a good size. What's there now?

And I'm certain that 1-1/4" will be fine for the boiler up to the CSTs.
 
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Old 01-06-15, 07:12 PM
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But I would think if he breaks a union at the boiler supply or return and adds a valve there it may be the easiest solution and may fix his temp issue..

Just speculation of course...
Of course . Free advice is worth exactly what you pay for it, right! Lol. And that does seem like a logical starting point the more digging i do. Failing that the system loop with the close T's that Trooper suggested is workable as well.
 
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Old 01-06-15, 07:17 PM
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the returns are manifolded as that diagram shows
Are they? as my diagram shows?

I don't see that...



Isn't that return pipe running straight up into the bull of a tee? Or is the angle of the pic deceiving me?
 
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Old 01-06-15, 07:21 PM
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You may be right... Well he better make a phone call to himself then...LOL...
Ring ring. BeerM3, Reality is on line one.

But in all honesty I'm not a "screw them that stuff ain't hard" kind of persona, rather i'm in a very small town where of the 3 plumbers i had come by for quotes, only one followed back up and even he was admittedly not very familiar with hydronic heat. There's not much of it left in this area. And who doesn't love learning a new trade? Plus i didn't want to give up my wonderful old cast iron radiators. (we did get permit approval for those wondering)
 
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Old 01-06-15, 07:30 PM
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Isn't that return pipe running straight up into the bull of a tee? Or is the angle of the pic deceiving me?
Ah I see what you're saying. You're correct, the returns meet at that T, not as that diagram you posted shows. Makes sense with the turbulence issue you described. If it's happening it's not very audible (but it's probably happening...)
 
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Old 01-06-15, 07:34 PM
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Also, without a check valve on the indirect loop, there is in a sense, more boiler bypass there.
Yep. Changed the circulator out for a spare 007 with a flow check last weekend. A step in the right direction hopefully.
 
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Old 01-06-15, 07:53 PM
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Im not so sure changing those tees will make a world of difference...

So you changed the pump to the indirect with a check valve??

And opening the bypass fully and t stat cranked up for test purposes whats the max boiler temps?

So your saying the boiler never shuts off on a call for heat until the t stat is satisfied?


(Valve already there.... Wrong advice here)

If still low I would just add a valve at the inlet or outlet of boiler and throttle it down some. The boiler will come up to temp more.. Its an easy mod . This I stated before..
Just my suggestion rather then go through a lot of repiping now in the winter months...
 

Last edited by lawrosa; 01-06-15 at 08:11 PM.
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Old 01-06-15, 07:55 PM
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Two unions right thar'''... Pic one and add a valve...

Probably the shorter one as you may get a nipple the right size off the shelf...

[ATTACH=CONFIG]44452[/ATTACH]
 
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Old 01-06-15, 08:05 PM
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BUT... your SYSTEM might never need to get to 180F ... with the setup I posted, the BOILER can run at proper temp, but the system will go where it needs to go. If you've got enough emitters in the home to cover the heat loss at 130F water, then that's as high as the system will go.
A mod-con with a makeshift mod (and hopefully without the con)? Long sustained runs of cooler circulated water not requiring the boiler to run? It makes sense to me in principal but let me see if that's actually the case: A 3rd party aquastat holds the boiler in the 160-180 range or whatever delta you dial it to and the boiler circulator is wired to the boiler itself. The stat & indirect DHW aquastat would be wired to an tekmar or similar controller directly to the circulators on the loop?
 
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Old 01-06-15, 08:06 PM
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But I see an issue maybe too.. Did you pipe the indirect off the system side and return it to the boiler side below the bypass????

And forget my previous comment about adding the valve. I see you have two there... I just put my glasses on... he he

Throttle the inlet side a bit when the boiler is running on a heat call.. see if the temp goes up. Leave supply side and bypass fully open...
 
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Old 01-06-15, 09:06 PM
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Im not so sure changing those tees will make a world of difference...
No, probably not, but if there's re-piping to be done, then would be the time to 'make it right'.

Did you pipe the indirect off the system side and return it to the boiler side below the bypass????
I was going to bring up the indirect also. I don't show it on my diagram, it must be piped directly off the boiler.
 
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Old 01-06-15, 09:25 PM
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I was going to bring up the indirect also. I don't show it on my diagram, it must be piped directly off the boiler.
It may work ok that way... very interesting and creative. As long as he has the indirect set as prioity. It just so happens the valve I want him to throttle is above that tie in from the indirect return.

So if he throttles flow through the boiler with the valve I suggest its only affecting the system return. The indirect will still get full flow..

Also a test would be, and I think he stated this, that the boiler comes up to temp when the indirect calls while in priority mode....
When the DHW circulator runs the boiler temp quickly rises to 160 or 170 and seems to act like it should.
Its kind of ingenious or madness...

I hope the op tests this out... the suspense is killing me....
 
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Old 01-07-15, 07:44 AM
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It may work ok that way... very interesting and creative. As long as he has the indirect set as prioity. It just so happens the valve I want him to throttle is above that tie in from the indirect return.
The indirect does run on priority and it hasn't had any trouble reaching the cutoff point. Unless someone is taking a long shower it's usually satisfied by the time it hits the 170 mark. The tank is set to approx. 140 degrees with a mixing valve for the house downstream. I'm not sure if Burnham was intentional with their piping schematic to have it return below the bypass but it does and here's their diagram
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AND some good news! As you suggested throttling the return by about half with the other 2 bypass valves wide open is allowing the boiler to reach the shutoff temp after about 7-10 minutes. I'd swear i tried that before but must've had my head stuck elsewhere and thought it wasn't doing the trick. It's highs in the single digits today and it takes about 4-5 minutes for the system water (about 120-130) to cool the boiler below the low set point of 140 before it fires back up.
 
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Old 01-07-15, 08:56 AM
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I'm not sure if Burnham was intentional with their piping schematic to have it return below the bypass
Most certainly it is intentional. Full power of boiler to the indirect.

As you suggested throttling the return by about half with the other 2 bypass valves wide open is allowing the boiler to reach the shutoff temp after about 7-10 minutes.
Be mindful of the delta T across the boiler when adjusting the bypass flow. You don't want more than a 40F DT across the boiler, and that's about the 'hairy edge'...
 
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Old 01-07-15, 04:25 PM
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I count 5 gauges. You only need 3 to set the valve properly.. Im looking for the proper procedure...

[ATTACH=CONFIG]44507[/ATTACH]
 
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I count 5 gauges. You only need 3 to set the valve properly.. Im looking for the proper procedure...
The top 2 are only pressure gauges on each side of the old gravity inlets. Think of them as a poor man's balancing valve. Or an idiot's attempt to balance pressure...my skin is pretty thick. As it stands they're never more than 1/2 psi different with both valves wide open when the circulator is running. The other 3 gauges are exactly what you'd expect - pressure/temp on the supply and temp on the mixed return. Although I've been checking the return temp below the bypass with infrared since it doesn't have a gauge.
 
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