Location of expansion tank moved for the better?

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Old 07-11-15, 10:29 AM
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Location of expansion tank moved for the better?

Hello all! So I recently had a boiler tech come out and clean and service my boiler. I mentioned to him that I was having an issue with increasing boiler pressure to 26psi when all 3 zones were running. Sure enough he sounded concerned, tested it, and found out I was not lying. After the service he told me to change the location of my expansion tank, as well as get a larger one. Both things I did. You can see in the pictures that It is now installed between zone 1 and the other 2 flow checks for the other zones. I also went with a larger tank. Unfortunately, the pressure issue is still apparent. The smaller expansion tank WAS mounted off of the old Thrush valve check that I am showing in the pic. I also had to do some 're-piping' in order for this tank to be moved to I really hope the new location is better.

As you can see in the pictures as well I have 3 circulators on their respected return pipe which merge and head into the boiler. I'm wondering if the circulator (Taco 0010 3 speed variable) in the front of the picture, may be causing some of this headache. The reason being, as soon as it clicks on, the pressure jumps 3psi. I have verified the boiler gauge with a home made job on the boiler drain valve and the boiler gauge is over reading +1-1.5psi from the drain gauge I made. None of the other circs make an sort of pressure change.....??? This is my last go at this, and if not solved, I will be either replacing the boiler, or running it at a high psi all winter. I have also recently replaced the pressure reducing auto fill valve, and just for now, have the gate valve before it turned off....
 
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Old 07-11-15, 10:36 AM
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Pictures to support above text
 
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Old 07-11-15, 10:46 AM
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another picture and I think I have one more, but before I do that, how do I make them not come out on its side?!?!?!?!?
 
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Old 07-11-15, 01:23 PM
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I don't understand the location of the tank previously.

Cell phone pics do that. I wish there was a way the forum could know it's a CP pic and upright it automatically. Unless you have a way to upright it on your computer before uploading, you're stuck.
 
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Old 07-11-15, 02:23 PM
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So, in regards to your question, the tank was located off of a 1/2" black iron pipe and then a 90* elbow which the tank was screwed into. The 1/2" black iron pipe was coming out of that thrush flow check in picture #2 (where the hole is in the picture with my hand in it). I guess my question is, When my Taco 007 and Grundofs 15-42 FR both kick on and circulate water to my bedroom zones (which are copper finned baseboard), the pressure gauge acts as its supposed to. 12 cold and 18 hot. Throw in the Taco 0010 on setting 2 to feed my main house (cast iron radiators) and as soon as the circ clicks on, it jumps 2 psi. Which obviously raises the top end of the hot pressure reading. ...

NJT, if you look at the picture of the expansion tank by turning your head lol, does that look like a 'workable' location? The main house zone is the zone that goes straight up the piping, and the two bedroom zones are on the other side of the Tee the expansion tank is hanging from.
 
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Old 07-11-15, 02:29 PM
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Maybe I should be asking, should 1 of 3 circulator pumps on the return side of my system bump my pressure up 2psi just by turning on?
 
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Old 07-12-15, 09:54 AM
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I don't see the advantage of having moved the expansion tank a few inches on the supply side... if I'm reading you correctly.

The idea of moving an expansion tank would be to install it at the SUCTION SIDE of the system pumps.

The expansion tank is what is known as the "Point Of No Pressure Change" (PONPC) in modern school of design.

The idea is to have the pumps located so that they PUMP AWAY from the PONPC.

Google the term "PUMPING AWAY" and read some of the papers on this for better understanding.

The fact that one of your pumps increases the pressure in the boiler is not unbelievable, because you are pumping toward the tank, through the boiler. Part of the pump's pressure differential is appearing in the boiler.

Why the other two don't do it... could be a few reasons. Those loops are less restrictive maybe? Those pumps are not pumping as much as the Taco.

Bottom line is that what was done is basically not a 'cure', but if the system was air free (no gurgling noises) then it wasn't necessary at all.

As long as your system pressure stays below say 25-27 PSI, you are good to go.
 
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Old 07-12-15, 01:35 PM
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I agree with Trooper that moving the expansion tank accomplished nothing beyond you buying some fittings and getting your hands dirty.

Assuming the 26 psi you see is the uncorrected pressure showing on the known high reading boiler gauge your real pressure is closer to 24 or 25 psi. This is a perfectly acceptable pressure. Depending on the particular boiler you may be able to swap out the existing safety valve for one with a higher pressure rating; look at the nameplate on the boiler and see what the MAWP (Maximum Allowable Working Pressure) is stamped. If it is higher than 30 psi then you may use a higher rated safety valve, up to the MAWP rating of the boiler.

Have you tried the Taco 010 at lower speeds to see if (a) the pressure increase when running is less, and (b) if the system still heats that zone in an acceptable manner?
 
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Old 07-12-15, 04:11 PM
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After reading into both your replies I feel your both right. I did a lot of research on the ponpc and actually just finished up a informational pamphlet from B&G on all the systems in hydronics. That being said, I feel my plumber sold me a bill of goods by telling me it would be better to move the tank. I fee he just didn't like it off of that old thrush flow check.
The 0010 is probably showing some of that pressure differential in the boiler since it's so close. And it appears to be determined by speed of pump too. I.E. Speed 3 bumps up the gauge 3psi, speed bumps up the psi by 2 or so and speed 1 bumps it up a psi or so. I guess I can live with that. I just wonder how after having large diameter iron pipes and cast iron radiators it would be more constructive. Probably because of the fittings right? I guess in a high mass system like mine it's expected to have higher pressures.
My question for you Furd, you said lower the pump to 1 and see if all the radiators get hot. Well they do. However, that heating tech/plumber that gave me that faulty information before told me not to do that. He said, if I decrease the speed of the circulator, that A. colder water will returning to the boiler, and force longer burn times to heat that water back up (delta T would be wider) reducing efficiency B. The slower the water velocity is flowing through the radiators, the less BTUs it's giving off- and trying to sound smart said, many installers believe differently- that the faster water wouldn't have time to jump off the water and onto the radiator piping. He said to keep it as high as you can to not hear turbulence or a hissing sound in the pipes. I will trust what you tell me over him obviously.
 
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Old 07-12-15, 04:26 PM
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High mass systems really should have a bypass to allow the boiler to heat up and to limit the time that really cold water is returning to the boiler. Your plumber is dead wrong when it comes to wanting higher velocity as it is higher velocity that causes noises in the system. BTUs released will not change significantly unless you are making really wide excursions from a very high velocity to a very low velocity. I suspect that the speed one will be more than adequate.

Longer burn times are often much more efficient than shorter because it is the initial warming of the combustion chamber from a standby mode that really decreases the efficiency. Further, the close you can come to continuous circulation by lowering the water temperature but going with longer burns the higher will be your comfort.
 
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Old 07-14-15, 09:03 AM
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O.k., I figured as much (that he was a dink). I will run the circ at setting 1 and just watch what's happening. In the future I do want to 'pump away' however I have some interesting piping to overcome and figure out first. So for now it will remain, return, circulator, boiler, supply, tank, flow check. That being said I am going to tear into it and had a boiler bypass. I have hear that it will DECREASE the Delta T, and reduce the possibility of flue gas condensation, correct? Is that the only purpose to have it?
Also, while I have you here, I have a Taco HYVENT attatched directly to the boiler. There are 3 holes in the top of the boiler.... water feed, supply piping, and a port for the HYVENT. I don't want to jinx myself but will that little vent do a job of removing air? I see a lot of people on here either have the scoop, or spirovent (where I only have a regular old Tee for my tank). I imagine that having more protection against air is better, but is the technology between the both of them that much different?
 
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Old 07-14-15, 09:13 AM
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I guess another reason I'm asking about the air vent, is everybody is saying it is best installed at the hottest, lowest pressure point. However, obviously my HYVENT being near the feed and supply piping, would be probably at one of the higher pressure points....
 
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Old 07-14-15, 09:18 AM
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I have hear that it will DECREASE the Delta T
Actually, a BOILER bypass will INCREASE the Delta T.

Since you are diverting flow from the boiler, less flow through the boiler will INCREASE dT.

The return remains at the same temp, but the supply gets hotter, faster.

The AVERAGE temp in the boiler is increased, which is what provides some boiler protection.

Regarding the air venting...

Your boiler may be of the type that basically uses the entire boiler as an 'air scoop'.

If you don't have problems with air now, never hear gurgling and such, then there's really no reason to do anything at all.
 
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Old 07-14-15, 11:06 AM
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How old you figure that boiler to be?

Is there any point of adding a bypass now? After all, it's been living this long without one.
 
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Old 07-14-15, 04:29 PM
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Your boiler may be of the type that basically uses the entire boiler as an 'air scoop'.
That's the way mine is set up. There is a 2-1/2" Bell & Gossett Airtrol boiler fitting on the supply from the boiler. There is a dip tube from the fitting into the boiler for water, and an annular space inside the Airtrol fitting for air to collect. The annular space tees off to a conventional expansion tank. Air is continuously separated and returned to the expansion tank. My circulator pump is on the supply to the boiler.

All very obsolete and not one plumber in a hundred would probably understand it. But, it has worked fine for 60 years.

How old you figure that boiler to be? Is there any point of adding a bypass now?
My gas-fired system is over-radiated with cast iron emitters. The conventional wisdom is that a boiler bypass would be essential to protect the system from damaging condensation in the flue. But it hasn't ever had a bypass and there has been no condensation or corrosion problem. It is set up for warm start, which may help.
 
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Old 07-14-15, 06:29 PM
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The boiler is approx 30 years old. So 1985ish manufacture date.... I figure a bypass would be good to have just for efficiency and the delta T increase.....???

BTW, I solved all my pressure problems... THANK GOD! I've been obsessed for 8 months about boiler pressure and all it needed was a ETX 90 (which is HUGE) thermal expansion tank. Didn't realize I had that much water in the system that it would expand that much.... THAT MUCH...........
 
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Old 07-14-15, 07:11 PM
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I figure a bypass would be good to have just for efficiency and the delta T increase.....???
I can't see why a bypass would increase boiler efficiency. It would cause the boiler to run at a higher temperature, which would reduce efficiency.

There may or may not be a reason for a boiler bypass, but this isn't one.

So that boiler has been operating for 30 years without a bypass? Without condensation problems? Forget it, and spend your money elsewhere, or just put it in the bank. Why are you hung up on adding a bypass?
 
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Old 07-14-15, 07:34 PM
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...all it needed was a ETX 90 (which is HUGE)...
Nah, that's just a baby expansion tank.

Trooper likes this picture, the expansion tank is the white horizontal tank in the upper right quadrant. It's capacity here is about 5,000 gallons and it was added to when the system was expanded. Only two boilers in this picture but later expanded to five, total BTU input around 100 million per hour.

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Old 07-15-15, 06:17 AM
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Didn't realize I had that much water in the system that it would expand that much.... THAT MUCH...........
From room temp to about 180F water will expand in volume by nearly 4%.

So, if you've got say 50 gallons in your system (you have standing radiators I believe) when the water is hot you would need room for about 2 more gallons.

It's not THAT MUCH, but if there's no room in a closed system for the extra water, then there's no room, and the pressure will rise ... a lot ... 52 gallons in a 50 gallon can.
 
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