Replacing old expansion tank

jgaudet

I'm replacing my old steel bladder less expansion tank with a new bladder style and I'm wonder if I can move the location of the new one to where I have the red mark in the pics? There is also an automatic air vent at that location that I will put on top of the expansion tank. One of the pictures is a diagram of how my system is set up.. thanks 

Jamie Hall

Probably a better location. What's wrong with the old tank?

STEVEusaPA

I'd use a bracket and strap it to the wall too. Or for better servicing, a Webstone expansion tank valve, and pipe the tank near the floor.

hot_rod

looks like the circulator is on the return, zone valves also? If you want to leave the circ there and pump away, the tank connection needs to be at the inlet to that circ.
You want a good air purger in the supply from the boiler, either up in the ceiling or get a vertical version.

EdTheHeaterMan

Are there 2 boilers? and 2 expansion tanks? Are they connected all the time or are they manually valved off when not in use?
Picture(s) of oil boiler to get a good idea of your situation.

jgaudet

@Jamie Hall well theres nothing wrong with the old tank but I have automatic air vents in my system and I'm pretty sure your not suppose to have the vents with the bladderless tanks! 

@STEVEusaPA yes I will be strapping it where ever i end up putting it! 

@hot_rod yes the circs and zone valves are both on the return line I was hoping to leave the circ where they are, that's how it was set up before I bought the house but I'm getting air in the system I'm thinking due to having air vents with a old bladdeless tank by the wood boiler? And I was planning on putting an air purger (separator) where my #97 automatic air vent is but that's on the return line!

@EdTheHeaterMan yes there is a wood boiler in my garage and an oil boiler in my basement they are connected together, after my fire goes out in my wood boiler the oil boiler will automatically take over when it gets to 150f and yes there is 2 expansion tanks the one beside my oil boiler is a #30 bladder type and the one beside my wood boiler is a 12"x36" old steel bladderless type! I have attached a few more pictures of my system.

Thanks for the great help so far everyone.

jgaudet

@hot_rod sorry just noticed your drawing now. I could get a vertical air purger and put it on my supply line like your drawing and I could also put my new bladder type expansion tank before my circulator like in your drawing on the return line!  Should I take the auto air vent #97 off of my return line? And also should my expansion tank by my oil boiler also be moved or would that one be fine where it's at? Or better yet could I just remove the one beside my oil boiler and just use 1 that is sized for my system. or do I need 2 because I have wood and oil boiler?   Thanks 

EdTheHeaterMan

You only need one expansion tank as long as you have it connected to the entire system. What I mean is that you don't turn off valves to isolate a section of the system, like shutting off both the supply and return of the oil boiler with manual valves isolating it from the expansion tank.

The one expansion tank needs to be able to handle the capacity of all the water in the system expanding when it is at the highest temperature the system would expect to be during normal operation. I believe that a #60 Extrol or equal will be sufficient for both boilers and all the pipes & radiation in your system. Replace the #30 with a #60 and eliminate the bladderless tank in the garage.

mattmia2

The conventional expansion tank needs to have an air fitting that directs the air that migrates out of the tank dissolved in the water or that gets in the system when water is replaced back in to the tank. if that part of the system only circulates intermittently that may not happen very well. the fact that the line to the tank pitches downhill from the tank also probably doesn't help. Converting it to a bladder tank with automatic air vents is one solution.

EdTheHeaterMan

But you still need only one tank for the entire system. So don't replace the tank, eliminate it. then see if the existing #30 is enough. If not then replace the #30 with a #60 in its place.

mattmia2

I meant follow what is said above about the tank and the air elimination. i was just explaining why they were likely having an air problem.

jgaudet

@EdTheHeaterMan that would be perfect if I could just eliminate the old expansion tank in the garage! When I moved in there was some valves isolated so that must be why they had 2 tanks! But I have every valve open I use the entire system all the time, only shut off valves to work on something.  Could I just shut the ball valve that goes to my old tank to test if the #30 is going to work for me?  and how do I tell if it's going to work if the psi don't go up or down after a burn cycle? 

WMno57

jgaudet said:

Could I just shut the ball valve that goes to my old tank to test if the #30 is going to work for me?

Yes.

jgaudet said:

How do I tell if it's going to work? PSI don't go up or down after a burn cycle?

Correct. If the PSI goes up and down a little, you are OK. If the PSI raises a lot from the starting point, and/or you get close to 30 psi and water comes out (hopefully) the Pressure Relief Valves, then further thought is required.

There are charts to size the expansion tank based on total system volume.

jgaudet

@WMno57 ok thanks, im going to test it now with the ball valve closed on the old expansion tank. also would it be better if i remove my #97 auto vent from the return line and put it on the supply line? thanks again

WMno57

jgaudet said:

would it be better if i remove my #97 auto vent from the return line and put it on the supply line?

I have no idea. Someone else will have to answer that.

jgaudet

Ok someone will probably let me know after. Thanks anyways

Jamie Hall

Since you have air vents and what not on your system, the old steel expansion tank probably isn't doing anything at all. Completely waterlogged, or very nearly so.

It's an either/or thing. If you are using the steel compression tank, it is completely dependent (in residential sizes) on any air in the system migrating to the tank, to maintain the air cushion in the tank. There are fittings and piping arrangements to do that, and the old timers knew all about it (shades of steam heat dead men...) and they worked, and continued to work, forever (one place I maintain has one which is almost 100 years old now, still going strong -- try that with a bladder). However, as soon as other air vents of the modern sort are put on to "improve" things, they will stop working rather quickly, and you have to use a bladder style tank. No options.

jgaudet

@Jamie Hall I have already decided I am removing my old expansion tank and I'm only going to use 1 bladder style tank in my system, I just tried my #30 tank and it's not big enough for my system so I'm going to remove my old steel tank and replace my #30 with a #60 and I just need to know now if I should put the new tank on my supply line like it is now or put it on the return side with my circulating pumps? And also should my auto air vent still be on the return side or move it to the supply line? 

mattmia2

Check that the tank is charged properly before condemning it. With no pressure on the system the air pressure should be set to the cold fill pressure of the system.

If the math from a volume estimate and the temp swing of the system says it isn't even close, don't bother checking the charge, but if the math say it is close, it is worth a try.

jgaudet

@mattmia2 I actually checked the charge yesterday and it was 12 psi I have to much volume of water in my system for just a #30 tank 

EdTheHeaterMan

The best place does not exist on your system. The best place is between the boiler and the circulator on the supply (hottest pipe) of the boiler. The second best place is on the supply pipe (hottest pipe) in the system. Place the expansion tank on an air separator (microbubble type) between the boiler(s) and the radiation, with room to place the circulator(s) just past the expansion tank in the future.

jgaudet

@EdTheHeaterMan ok thanks.  Well I think I decided I am going to leave my circs where they are and I'm just going to remove my old expansion tank beside my wood boiler and replace my #30 bladder type with a #60 beside my oil boiler and only have the one tank in the system!   Just wondering now if I should leave my #97 auto vent where it is or put it on my supply line that comes out of my wood boiler would it work better there? 

EdTheHeaterMan

Here is a slightly better piping design.

This will put the boiler supply piping in parallel. the next step is to put the return piping in parallel. this will also give you the proper place to install the air separator and the expansion tank.

there will still be some pressure issues with this design and with changing the tank size only. But changing the tank size only is a start for now since it is cold out and you don't want to do a major repipe in the middle of winter.

and yes leave the 97 vent in there for now also.

hot_rod

You can install tee together multiple expansion tanks, 2 #30=60. Pre charge them to the same pressure before installing.

jgaudet

@EdTheHeaterMan ok I'm starting to see how you want me to do it, so should I move my circulating pump that is beside my wood boiler also? Or leave that one alone? And in your drawing you want me to put the circulating pump by my oil boiler to where you said future on right? 

EdTheHeaterMan

That is for "future" because you need to make other piping changes to make the whole thing work properly. I would use a primary-secondary piping design to attach the boilers separately as secondary loops with each boiler having its own circulator. A project for another day.

jgaudet

Is that not how its set up now with each boiler having its own circulator? 

jgaudet

When the stove is going in my wood boiler the circulator will run but when the temp drops to 150f the circulator shuts off and then the oil boiler takes over for heating and the circulator pump beside the oil boiler starts running and the one by my wood boiler is off

mattmia2

jgaudet said:

Is that not how its set up now with each boiler having its own circulator? 

There would be 3 circulators. Each boiler has its own circulator and the heating loop has a 3rd circulator for the loop. When a boiler is heating, its circulator runs and injects its heat in to the heating loop.

jgaudet

Ahh ok gotcha

EdTheHeaterMan

THIS IS YOUR GOAL.

With this design, each boiler is independent and will not heat the other boiler when it is not in use. Any extra heat in the unused boiler is wasted heat going up an unused chimney.

The logic of the control system can be set up so when the wood stove can not produce the minimum 150° temperature, the oil boiler will take over and the wood stove will not be heated by the oil boiler.
Likewise, the woodstove will not waste any heat warming up the oil boiler as long as the woodstove is operational.

jgaudet

I'm pretty sure it's sort of like that now, when the wood boiler temp goes under 150 the oil takes over and o don't think it's heating up the wood boiler because the pipes going to the wood boiler are not hot, they are only hot when the wood boiler has a fire and the circulator pump by the wood boiler is on

jgaudet

Another question. when I have to bleed my system again I have a utility pump now and would like to use that so I don't have to introduce new water to my system! Can I hook a hose to the outlet side of the pump to where I indicate in the picture it's the return line by my zone valves then put the other end into a 5 gallon bucket, then hook a hose to the input side of the pump and the other end into the same 5 gallon bucket, then hook another short hose to the boiler drain where do indicate in the pic and place the other end also in the same 5 gallon bucket! Will this work or do I need to hook the hose somewhere else? 

epmiller

jgaudet said:

Can I hook a hose to the outlet side of the pump to where I indicate in the picture it's the return line by my zone valves then put the other end into a 5 gallon bucket, then hook a hose to the input side of the pump and the other end into the same 5 gallon bucket, then hook another short hose to the boiler drain where do indicate in the pic and place the other end also in the same 5 gallon bucket! Will this work or do I need to hook the hose somewhere else? 

I can't quite follow your explanation, it implies more hoses than connections. You don't want to try to push any air thru the boiler, it's going to be difficult to purge that water jacket. You want a hose from the 5 gallon bucket TO the INLET of the pump. A hose from the OUTLET of the pump to the LOWER boiler drain. Then you want another hose from the upper boiler drain (the one right below the zone valves) down INTO the water in the 5 gallon bucket. Shut the system circulator isolation valve and pump away a zone at a time. Any air in the zone loops will bubble out in the 5 gallon bucket and won't get caught in the boiler. Purge from the outer zones to the inner in sequence or you may have problems with air getting caught below another zone valve above the header. Hopefully your pony pump can move enough water that the air doesn't want to do that. I recommend opening the system circulator isolation valve when you are finished (don't ask).

jgaudet

@epmiller ahh ok I just had it a little backwards and that's why I wanted to ask before I do it lol.  And my pony pump is a 1/10 HP with a flowrate of 360 GPH from princess auto!  And the only thing when you say purge from the outer to inner is it like this in my picture that you mean if I go 1 2 3 4 but in the order I have it?

ch4man

that'll work but you also must close the ball valve below the circulator otherwise the purge will just bypass the system and short circuit on that short vertical pipe

jgaudet

Ya I know I have to shut that ball valve off below the circulator! Should I also shut any other ball valves like the ones by my other circulator by my wood boiler? 

jgaudet

@epmiller I forgot to ask should I fill the 5 gallon bucket with water before I start? because at first there will be no water in the bucket and the pump will run dry for a minute! 

jgaudet

Just wondering instead of changing a bunch of things right while it's cold out maybe it's best to wait till spring!  I was just thinking I can shut the ball valve to my #30 bladder expansion tank and I can close the caps on my automatic air vents then just use my big bladder less expansion tank for now and with the caps closed on the air vents it might fix my air in the system problem for now? 

epmiller

jgaudet said:

@epmiller I forgot to ask should I fill the 5 gallon bucket with water before I start? because at first there will be no water in the bucket and the pump will run dry for a minute! 

Yes definitely start with plenty of water in the bucket. Frankly I’d wait until after the heating season. I would even be tempted to just replace that expansion tank with a #30 bladder tank and see how things work. I’ve been told you can have problems with expansion tanks at two different places in a system but I’d like to try it and find out why for myself. Don’t do it unless you can troubleshoot it yourself. 

Edit: after studying the picture again, the purge order you drew on the pic would be better done  just right to left, 2-4-3-1 (from the pic) because of that odd branch below the left zone valve which I hadn’t seen on my phone
screen. Just think about where the air can go when it is pushed out and make certain it can’t hide somewhere before getting to the 5 gallon bucket. 

EdTheHeaterMan

jgaudet said:

I'm pretty sure it's sort of like that now, when the wood boiler temp goes under 150 the oil takes over and o don't think it's heating up the wood boiler because the pipes going to the wood boiler are not hot, they are only hot when the wood boiler has a fire and the circulator pump by the wood boiler is on

OK, that works because the path of least resistance for the oil boiler is thru the radiators and not the wood boiler.

BUT

Is the oil boiler HOT when the wood stove is operational? I think YES with the current piping design... and that boiler becomes a big radiator connected to an outdoor vent... for the wood boiler.

Think about it... What is that big radiator in the basement heating? The chimney?... and the rest of the county? Not really helping the rest of the county that much when it is really cold out

Respectfully submitted,
Mr.Ed