Water temp in boiler


  #41  
Old 09-16-10, 07:11 PM
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Originally Posted by Mike Speed 30 View Post
Adding a boiler bypass will allow the boiler to run at a higher temperature - which will reduce the hazard of flue-gas condenstation. That's a good thing.

But, a boiler bypass won't cause more heat to go to the heat emitters, which seems to be the problem here. Actually, a bypass will cause a bit less heat to go to the heat emitters because boiler efficiency will decline a little when flue gas temps increase.
but constant circulation will cause warmer rads to heat the cooler room.

A boiler bypass is not designed to correct distribution problems, if you think it will then you have no idea what a boiler bypass is.
 
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Old 09-16-10, 07:44 PM
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Originally Posted by Mike Speed 30 View Post
Nice pix.

Since your system is now drained, this would be a good time to fix all the radiator valves. I would go ahead and replace them all with new valves - there is a union fitting between the valve and the radiator.

Otherwise, you could disassmble each valve and fix what needs to be fixed. Chances are the stem packings are shot - if you get the stem to move off its backseat, it'll probably start leaking.

Getting the valves working is a high priority - they will help you balance the system so that you can get more heat to the upper floors.

If your system was originally steam, the radiator valves might be gate valves? (That might explain why they are all stuck.) You'll want angled globe valves for hot water service.
Is it possible to tell from the rad pics if was originally steam or water??
 
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Old 09-16-10, 07:53 PM
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Originally Posted by drooplug View Post
Uhm. I can't tell exactly what is going on with your pipe work, but answer me this: Do the supply and return pipes for the 2nd floor rads go straight into the basement to tie into the rest of the system? What about the attic, do they do the same thing?

If they do, then you can zone those floors out with separate t-stats. That will be far easier than replacing all those radiator valves and trying to balance the system. The fourth picture down seems to indicate that this may be the case. I think you could even forgo the zone valves and running wire to your upper floors to simply things for now and just put in valves that allow you to restrict flow on a zone basis.
Yes, all rads are homeruns to basement, even the attic.
 
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Old 09-16-10, 08:09 PM
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Originally Posted by xiphias View Post
Without a heat loss we're just guessing. Might be the boiler's maxed out. But then it should be running A LOT. Might be the aquastat's messed up and the boiler never does get to high limit. Might be the room thermostat is too close to a radiator and the whole system never really has a chance to get up to temp. Might be the flow is sluggish (though it shouldn't be with all that large-diameter piping). Might be there's a lot of air in the top of the system.

One or more of these, perhaps?
How do I do the heat loss calc?
 
  #45  
Old 09-17-10, 03:45 AM
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Grab the slantfin heat loss calculator here
Contact Us - P.V. Sullivan Supply Co., Inc.

It does a real ASHRAE Manual J heat loss calc.

One can also do this by hand using the old written sheets, or there is low-cost software such as HVAC-Calc that also comes with tech support.

Doing a heat loss is really starting at square one. Might not be totally essential to solving your specific problem. But... it is very good info to have and helps understand the overall context of the problem. In this case it will give an idea of how many BTUs are needed to keep the house at a certain temperature.

Where roughly in upstate NY? There are tables of outdoor design temperatures that will give you that bit of essential info. e.g., Utica is -6F. Ithaca is 0. Buffalo is +6.
 
  #46  
Old 09-17-10, 06:15 AM
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Originally Posted by t56tr View Post
Yes, all rads are homeruns to basement, even the attic.
Ah. Each rad is a home run. That will make it a larger project to complete. I highly suggest separating the floors out into their own zones at some point.
 
  #47  
Old 09-19-10, 09:07 PM
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heat loss

I did the slant fin heat loss calc, but there were alot of variables etc that i did not understand orknow about. For example, it asked the outdoor temp, which I put as 20 deg because I thought that might be an average for albany NY

However I later found that it should be zero for the calc.

Anyway, the slant fin with an outdoor tewmp of 20 and indoor of 70 came out to 55,000 btu hr loss. I have no idea if thats accurate though cause of all the stuff I may have left out.

The house is an approx 2600 sq ft center hall colonial circa 1929. There is no insulation in the walls, except a 1/2 layer of some type of cardboard/fiberboard against the brick.

The windows are the original 8 over 8 wood. There are modern storms on the house though.

I did another calc for a boiler size estimate, and it came in at a recommended size of approx 100k btu, which I think is what I have....
 
  #48  
Old 09-19-10, 09:10 PM
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Fill valve

Another question... the system has a pretty standard watts 1156 feed valve/ pressure reg that comes right off my domestic cold. Does that style unit have a built in back flow preventer, and or do I need one? Can the boiler water back flow into the domestic?
 
  #49  
Old 09-20-10, 04:10 AM
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Albany should be 0F for outdoor temp.

In slantfin, just try to find the wall construction that best approximates yours.

Particularly for older homes, a blower door and thermal IR energy audit, followed by insulation and air sealing can cut the heat loss in half or more. See dsireusa.org for NY programs/rebates/credits for energy improvements. There's a bunch.

You want to insulate and air seal to reduce the heat load and thus size of boiler you need. Smaller boilers cost less, and cost less to run.

As a guess, your heat loss might be 90,000 BTU/hr. Imagine cutting that in half with some insulation and air sealing work. If you're going to be in the home for more than a few years, it's a worthwhile first step.
 
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Old 09-20-10, 01:36 PM
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So far...

Thank you for all of the great advice so far.

I fired the boiler for the first time this season (after I filled the system and bled it).


Outside/inside temp was 66.

The water temp in boiler was approx 60 according to gauge.

I set the thermostat for 80.

It took the boiler 25+ min for the water temp to get to approx 120 (due to high water volume perhaps).

By the 35 min mark the water temp was closing in on 130 and the stat was up to approx 68 and climbing.

At 45-50 min (yes 50 min of the boiler running), the water temp peaked at 140 and stayed there - would not climb any more. The stat/temp was still climing at approx 71-72.

At that point I turned the stat off. I was just curious to see if the water temp would go higher given the opportunity...it peaked at 140.

All of the rads in the house, even the attic, were hot. The hottest I have ever felt them. Then again, I have never run the boiler for an hour before.

Keep in mind, it has always heated the house - Usually in the winter, it turns on, runs and runs,and the water temp never makes it over 125-130 before the stat is satisifed and it shuts down (stat is usually locked at 65 all winter night and day).

Not trying to beat a dead horse, Just tryin to hone in on the low water temp issue.

(edited)

On a side note I discovered a couple new things. The flame(s) coming out of the burners are all consistant in size and color - blue/orange with more of an orange look (?).

The air shutters are all adjusted back (and screwed tight) as far as possible wide open....acccording to the mc-05 manual the flame shouldnt be burning like that...
 

Last edited by t56tr; 09-20-10 at 02:39 PM.
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Old 09-20-10, 02:46 PM
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I m on my day off so please excuse all the posts.

I adjusted the air shutters. Closing them back seemed as if it produced a taller blue flame, but I am not experienced enough to really tell.

I did notice that with them closed back the over all sound of the fire was more of a hiss. With them all open (the way it has been) its more of a roar like a fire place. I am not talking night and day, I a mean if you get close and listen.

Also, the tops of the burners were all covered in crust and rust debris that had fallen on them. I removed each one and cleaned them prior to all of the above.

With them closed shut I redid my test as in my last post with the same results. Water temp wouldnt go over 140.

For now i put the shutters back to the way they have been (Ill get a pro in to look at/adjust them)....
 
  #52  
Old 09-20-10, 03:38 PM
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Yeah, that flame color ain't right... could be a few causes.

First, would be a lack of adequate combustion air.

If there was a lot of rust and crud that was sitting on the burners, it is possible that some of the flue passages in the boiler are plugged up with rusty scale also.

Definitely have that checked out.

Do you have operational CO detectors in your home?

If you've got the T'stats cranked all the way up, as long as that burner is firing, the water should (and I bet WOULD) be getting hotter, all the way up (eventually) to the high limit setting of the aquastat. Maybe 2 hours is what it takes with all the water in your system?

Not trying to beat a dead horse, Just tryin to hone in on the low water temp issue.
You really do already have the answer! The fact is that your home only needs 130░ water to satisfy the thermostat. Once the thermostat is happy, that water ain't gonna get any hotter because the boiler will shut down. As previously explained, with your high volume system, you now have about 50K BTU stored up in the pipes and rads.
 
  #53  
Old 09-20-10, 04:13 PM
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Another possibility... the temp gauge on the boiler is broke.

Try the OUCH! test. Grab a hold of the supply line out of the boiler when the gauge says 130 and see how long you can hold it. Don't be a maniac of course, I don't want you to hurt yourself! If you can hold 130 for more than say 2 or 3 seconds, then it ain't 130.

Or, measure the actual temp with a thermometer...
 
  #54  
Old 09-20-10, 04:32 PM
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Rerun the slantfin calc with 0 degree design temp. The idea of this is to design your system to be at maximum output on the coldest day of the year. That's what that 0 degree temp is for.

My personal opinion is that you need a lot more than 55k BTU for your home. I calculated that my house would need 100k BTU if it had no insulation, and my house is 1600 sq feet.
 
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Old 09-20-10, 06:49 PM
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Originally Posted by t56tr View Post
Keep in mind, it has always heated the house - Usually in the winter, it turns on, runs and runs,and the water temp never makes it over 125-130 before the stat is satisifed and it shuts down (stat is usually locked at 65 all winter night and day).

Not trying to beat a dead horse, Just tryin to hone in on the low water temp issue.
OK,

Think of it this way,

You have a pickup truck full of stone, and you come across a 25 % incline, so you mash the gas pedal and go.

You have a v6 and put out about 150 HP.
Based on the weight in the truck and the available power the calculations say you need 150 HP to maintain 30 MPH going up that hill...
So what happens... you hit 30 MPH and stay there.

Your heating system is the same.

The rads are sized to transfer a certain amount of energy at a specific water temperature and flow rate. Understand too that btu/hr is based on temperature difference between what you send out and get back, and how fast you move the liquid.

So, like the pick up, the rads are sized to raise the temp of the air around them the same as the truck has the gearing to pull the load.

The boiler puts out power the same as an engine does, just that its rated in BTU/HR not horsepower. Actually 1 Hp is equal to about 2500 BTU/hr. So that is your energy input the same as your engine.

The load is the incline of the hill, and equates to your home heatloss.

Simply put, your rads are sized to heat your home to a certain temp, at a specific outdoor temperature as long as your energy input is big enough. It's all about equilibrium. the boiler will put energy into the water until such appoint in time where the rads equal that inout in their output. Once you reach that equilibrium, the water temp stops climbing unless the input changes or the load changes. the water temp will change until it reaches equilibrium again.

So, the rads are working fine as it satisfies the thermostat at 130 F, and the boiler is making the water get to 130. Really the question now is, how fast does it hit 130. That will tell you how oversized the boiler actually is, given of course the load on the building from the outdoor temp... Once again things run to equilibrium.

Sound fair ?
 
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Old 09-20-10, 07:20 PM
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Let's not re-invent the wheel. It seems to be true the house only needs 130f to heat the home. Cast iron rads heat well at 130f and even cooler temps. I have afriend that heats his rads to 115f and heats a four unit apartment house @ 0f.
The problem is the length of time it takes to get the water to 130f. Too much flow through the boiler. A boiler has a certain range of gpm flow that it can heat the water and raise the temperature. The boiler will input the same btu's but the temp rise is dependent on flow. Low temp rise excess flow, excess temp rise too little flow.
A boiler bypass will help the boiler get hotter to add higher temp water to the system and balance out system temps. A boiler can work well between a 20f to 40f rise. Your delta-T is low, below 20f.
A boiler bypass will keep the flow in the system up and the flow in the boiler lower.
I probably would not change the valves on the rads unless you want to shut them off but a home run system should be able to do it in the basement at the manifold. If you add all those globe valves you may need to check pump sizing as a globe valve is equal to about 30 ft of pipe.
Pressure is calculated by determining the height the water must be. The lowest point to the highest point. Divide the height by 2.31 than add 4psi.
Example;
32ft/2.31 = 14 psi + 4psi = 18psi.
Your system needs 4 psi at the high point at all times. This is why we pump away from the point of no pressure change with wet rotor pumps. Your pump will add pressure to the system.
 
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Old 09-20-10, 08:39 PM
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Originally Posted by NJ Trooper View Post
Another possibility... the temp gauge on the boiler is broke.

Try the OUCH! test. Grab a hold of the supply line out of the boiler when the gauge says 130 and see how long you can hold it. Don't be a maniac of course, I don't want you to hurt yourself! If you can hold 130 for more than say 2 or 3 seconds, then it ain't 130.

Or, measure the actual temp with a thermometer...
Yes...did the ouch test. You can grab the feed at anytime and just hold it - even at 130...

yes have the CO;s thanks!
 
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Old 09-20-10, 08:48 PM
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Originally Posted by TOHeating View Post
OK,

Think of it this way,

You have a pickup truck full of stone, and you come across a 25 % incline, so you mash the gas pedal and go.

You have a v6 and put out about 150 HP.
Based on the weight in the truck and the available power the calculations say you need 150 HP to maintain 30 MPH going up that hill...
So what happens... you hit 30 MPH and stay there.

Your heating system is the same.

The rads are sized to transfer a certain amount of energy at a specific water temperature and flow rate. Understand too that btu/hr is based on temperature difference between what you send out and get back, and how fast you move the liquid.

So, like the pick up, the rads are sized to raise the temp of the air around them the same as the truck has the gearing to pull the load.

The boiler puts out power the same as an engine does, just that its rated in BTU/HR not horsepower. Actually 1 Hp is equal to about 2500 BTU/hr. So that is your energy input the same as your engine.

The load is the incline of the hill, and equates to your home heatloss.

Simply put, your rads are sized to heat your home to a certain temp, at a specific outdoor temperature as long as your energy input is big enough. It's all about equilibrium. the boiler will put energy into the water until such appoint in time where the rads equal that inout in their output. Once you reach that equilibrium, the water temp stops climbing unless the input changes or the load changes. the water temp will change until it reaches equilibrium again.

So, the rads are working fine as it satisfies the thermostat at 130 F, and the boiler is making the water get to 130. Really the question now is, how fast does it hit 130. That will tell you how oversized the boiler actually is, given of course the load on the building from the outdoor temp... Once again things run to equilibrium.

Sound fair ?
Yup.... sounds good! Im cool with the 130 if thats what its gonna be
 
  #59  
Old 09-20-10, 09:07 PM
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Originally Posted by rbeck View Post
A boiler bypass will help the boiler get hotter to add higher temp water to the system and balance out system temps. A boiler can work well between a 20f to 40f rise. Your delta-T is low, below 20f.
A boiler bypass will keep the flow in the system up and the flow in the boiler lower.
This is what you need to do. Somebody else probably has a link to Danfoss or similar bypass valve manufacturer that shows how and what to pipe. Or just do it with piping and a high-quality globe valve.
 
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Old 09-20-10, 09:29 PM
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Originally Posted by drooplug View Post
Rerun the slantfin calc with 0 degree design temp. The idea of this is to design your system to be at maximum output on the coldest day of the year. That's what that 0 degree temp is for.

My personal opinion is that you need a lot more than 55k BTU for your home. I calculated that my house would need 100k BTU if it had no insulation, and my house is 1600 sq feet.
I redid I best I could with the new outdoor temp of 0 deg (originally I put 20 ).

The numbers did go up alot, but the calculator is asking too many questions that I do not know the answer to.

I got it up to 125k btu this time.

The house is a center hall colonial - a 30x40 rectangle. Its brick with no insulation, with a staircase up the middle to floor two, then again to floor three.

The windows are original wood 16 pane approx 60x36 , but have newer storms. There are approx 14 windows on 1st floor, 14 on second. The attic has 4 little 1/4 rounds. The attic was finished into living space in late spring and is got super insulated during that period.

As I stated in an earlier post, the attic burnt at one time. When the fire restoration was done they put very thick insulation in the attic floor (in the ceilings) of all of the upstairs rooms (2nd floor).

Bottom line is that its seems I am lucky that I can heat with 130 deg water, but its not healthy for my boiler, flue, or chimney I guess.
 
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Old 09-21-10, 07:35 PM
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Originally Posted by xiphias View Post
This is what you need to do. Somebody else probably has a link to Danfoss or similar bypass valve manufacturer that shows how and what to pipe. Or just do it with piping and a high-quality globe valve.
This?

Bell & Gossett - The Ins and Outs of Boiler Bypass Lines
 
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Old 09-21-10, 07:39 PM
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wow... from that article

"......Now, why would you want to raise the temperature of the water returning to the boiler? Well, suppose you had a high-volume system and a low-volume boiler, like an old gravity system. If the returning water were cool (less than 140 degrees for a cast iron boiler), the flue gases would condense inside the boiler and cause corrosion. Thereĺs also the possibility of thermal shock, although this is usually less of a concern than condensation....."

Some people on this board really know their stuff!!
 
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Old 09-21-10, 07:59 PM
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This

Bypass_Piping_Explaination

is also worth a read.
 
  #64  
Old 09-22-10, 05:24 AM
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One of the important things to understand concerning bypass piping is the difference between a BOILER bypass, and a SYSTEM bypass.

One of the easiest ways to tell the difference is where the bypass pipe is in relation to the circulator pump.

A BOILER bypass is on the BOILER side of the circ pump, and a SYSTEM bypass is on the SYSTEM side of the circ pump.

For your application, a boiler bypass would be recommended, and it doesn't appear that it would be a heckuva lot of work to set one up on your system.
 
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Old 09-22-10, 02:29 PM
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Originally Posted by NJ Trooper View Post
One of the important things to understand concerning bypass piping is the difference between a BOILER bypass, and a SYSTEM bypass.

One of the easiest ways to tell the difference is where the bypass pipe is in relation to the circulator pump.

A BOILER bypass is on the BOILER side of the circ pump, and a SYSTEM bypass is on the SYSTEM side of the circ pump.

For your application, a boiler bypass would be recommended, and it doesn't appear that it would be a heckuva lot of work to set one up on your system.
Troop -

So if I piped a bypass, I would:

a) have a higher water temp in the boiler and to the rads

b)shorter run time

Can you give one example how it might be done on my system?

Thanks

PS My hot water tank is a 16 year old ao smith gas 40 gal..(might be visable in pic next to boiler). Belive it or not its still working fine. I would like to replace it with an indirect tank someday (preferably before it does quit and strand us).

Would piping a bypass now not be wise if I plan on changing the piping in the near future for an indirect? How would the piping methods for each effect each other?

If I wanted to pipe the bypass now, could I just stubb out with valves as part of the pipe job for the future indirect?
 
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Old 09-22-10, 09:36 PM
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a) have a higher water temp in the boiler and to the rads
Yes, and No. The boiler bypass would allow the boiler to run at a higher average temperature, alleviating some of the condensation concerns. But no, the water temp to the system won't necessarily be changed... it _might_ change some, but it's not like it's gonna be red hot... that's a whole 'nother issue. And besides, you don't need the water to be hotter, it satiates the thermostat just fine as it is... you DO have a balance issue, but again, a whole 'nother issue.

b)shorter run time
Sort of... you will get 'cycles' instead. The boiler will get hot, and the burners will shut down while the water is still circulating. When the boiler cools again, the burners will fire in another 'cycle', and this will repeat until the t'stat is happy.

Can you give one example how it might be done on my system?
I can, but right now gotta hit the sack... laterz!
 
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Old 09-23-10, 03:19 PM
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Originally Posted by NJ Trooper View Post
the water temp to the system won't necessarily be changed... it _might_ change some, but it's not like it's gonna be red hot...
Ah, but it should change, quite a bit. As rbeck perceives -- and I agree -- the problem is the dT through the boiler is too low. Jack up the dT through the boiler. System temps will go up.
 
  #68  
Old 09-23-10, 04:03 PM
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It's not gonna change that much... you are still inputting the same BTUs, just in 'cycles' instead of continuously. Yes, the BOILER will run at a higher average temp, and the supply side coming out will be hotter, but don't forget that with the bypass you have very significant flow of cool return water mixing with the hot supply out of the boiler. Net result, same temp water.

It is true that the water will get hotter the longer the system runs, which it should run longer in colder weather, which is why rbeck calls it the "Poor Man's Outdoor Reset" ...

Bypass or no, you still need to put the same BTUs to heat the water to the same temp, and that temp is going to be whatever point the t'stat satisfies.

Aside from the bypass issue and boiler protection, the issue isn't one of water temp, it's one of BALANCE... warm downstairs, cool upstairs.
 
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Old 09-23-10, 04:20 PM
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If a boiler bypass would increase the temp to the system, it will also increase the heat emitted by the system to the house. That won't happen. If it did, then let's all install boiler bypasses and get free energy.

If anything, the heat emitted will decrease because, with a higher boiler temp, the boiler efficiency will decline.
 
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Old 09-23-10, 04:58 PM
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Without drawing a picture, I will try to describe how you should pipe the byspass. It needs to go from the supply pipe to the return pipe. You will need a valve on the bypass and the return pipe. The one on the return needs to be between the boiler and the by pass. You do not want the hot water tank to have its return water to flow through the bypass. So you want it to come into the return piping after the valve that you install. Install a check valve on the return to stop the water from flowing backward into the bypass while water is heating. I also recommend have a temperature gauge on the return pipe and one on the supply after the bypass.
 
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Old 09-23-10, 05:21 PM
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That's gonna be a bit tough to pipe an indirect I think... I need to spend some time viewing the pics... the bypass line alone wouldn't be as much rework... perhaps the hardest part of the bypass part is the fact that it appears you will have to repostion the circulator pump in order to gain access to 'the boiler side of the pump'.

While you are at the task of repositioning the pump, why not go all the way and set the system up to 'pump away' from the expansion tank?
 
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Old 09-23-10, 08:21 PM
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Consider a candle burning steadily. It's putting out a constant amount of BTUs. Pass your palm quickly over the top of the flame. Now do it slowly. Which one raised the temperature of your palm more, moving fast or slow?

Now consider the distribution system. For a given load, water temperature, and flow rate, it will emit a certain amount of BTUs and the water temperature will drop a certain number of degrees from boiler supply to boiler return.

Now add hotter water for the same load and keep the same flow rate. What happens?
 
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Old 09-24-10, 03:50 PM
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Originally Posted by xiphias View Post
Now consider the distribution system. For a given load, water temperature, and flow rate, it will emit a certain amount of BTUs and the water temperature will drop a certain number of degrees from boiler supply to boiler return.

Now add hotter water for the same load and keep the same flow rate. What happens?
Nothing. The hotter water from the boiler is diluted by the cool bypass flow.

Actually, the net effect is less heat to the system. The net boiler output (Btu/hr) declines because the flue gas temp increases when the boiler runs hotter.
 
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Old 09-24-10, 06:27 PM
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The flow in the SYSTEM is unchanged. The flow in the BOILER will be decreased. The water from the boiler will average higher temps, but as Mike sed, once that hotter water mixes with the cooler return water from the bypass, you are right back where ya started.

The bypass is only about raising the average temp in the boiler, the system will run at the same temp.
 
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Old 09-26-10, 06:13 PM
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Uh, no. If you jack up the temperature at which the boiler is running from 130 to 180 or 190, there should be plenty left over to raise the system temp by 10-20F. Maybe more. A boiler bypass will also increase the flow rate in the system, and thus reduce the system dT.
 
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Old 09-27-10, 03:51 PM
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Great info and thank you for all of the help. I will be researching the bypass and possible plumbing it soon!
 
 

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