whenever you raise the temp setting son the boiler you will get a bit of water that comes out of the overflow tube as water expands when it is heated. Again, this is why i keep a tight differential settings most of the year. set at 175-180 your stove will bubble a bit out the first time gettting up to that temp, but from there on it should stay at the same level as long as you keep her full of good hardwood and dont let the temps drop on you
I'm building a homemade boiler
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maple1
Minister of Fire
I am thinking an expansion chamber type of thing on top of or above (but connected to) the air vent would help. An open expansion tank, if you will. The rise & fall of water would be confined to the tank/chamber, and the boiler would be constantly immersed with no air spaces in the boiler itself - which should also help some in preventing corrosion. The higher the expansion tank, the better.
Fred61
Minister of Fire
That was kind of the idea behind my access opening being almost 10 inches above my boiler top. I was hoping the water would expand up into that, pushing all the air out the vent tube. Which it does, but since I didn't pitch my top toward the opening, like I thought about doing, the air gets traped where it can until the expansion pushes it to the opening.
Fred61
Minister of Fire
Trapped air is something to be expected when first filling a boiler. Even one with a low capacity such as yours. I would wait a while before making any changes if it isn't continuing to blow out.
I fired it back up after work today, hopefully for good this time. Nights are supposed to be in the 30s and days in the high 40s. A few warmer days next week with cold nights. So fingers crossed I won't be shutting it down again.
Since I have had it at 180 the last few times I fired it to keep the water warm it hasn't spilled any more out. I'll keep an eye on it if it continues to burp out the vent line I'll be looking into something for sure.
I am a little concerned about the loud bang noise I heard when I turned off my pump at shut down. I was asking our maintenance guy at work about it and he described, what lead me to believe, this loud noise was water hammer in the system. I'm wondering if I cut my pex line at the highest point and install an expansion chamber, like used in house plumbing, if that would help with the loud bang noise. Can anyone give me any insight on this?
I am a little concerned about the loud bang noise I heard when I turned off my pump at shut down. I was asking our maintenance guy at work about it and he described, what lead me to believe, this loud noise was water hammer in the system. I'm wondering if I cut my pex line at the highest point and install an expansion chamber, like used in house plumbing, if that would help with the loud bang noise. Can anyone give me any insight on this?
maple1
Minister of Fire
It does sound like water hammer.
Does that zone also have a zone valve? If the zone valve is installed backwards it will close with the flow rather than against it which can cause hammer. Might also be bigger potential for hammer with some valves vs. others.
Is there any copper piping in the circuit? I had a banging start here once on one of my zones, turned out to be a hanger had loosened over the year & the piping would bang in the hanger when a valve closed. I think it would need to be a long section of piping for that to happen though.
If everything is solid, and doesn't have any movement potential, a water hammer arrestor like you mention might do the trick.
What do you have for a circ pump pumping that zone? Sometimes if a zone is being over pumped, that could maybe cause something also - larger water flow coming to a sudden stop. Since I swapped my 15-58 3 speed for an Alpha, things are very quiet & gentle here.
Does that zone also have a zone valve? If the zone valve is installed backwards it will close with the flow rather than against it which can cause hammer. Might also be bigger potential for hammer with some valves vs. others.
Is there any copper piping in the circuit? I had a banging start here once on one of my zones, turned out to be a hanger had loosened over the year & the piping would bang in the hanger when a valve closed. I think it would need to be a long section of piping for that to happen though.
If everything is solid, and doesn't have any movement potential, a water hammer arrestor like you mention might do the trick.
What do you have for a circ pump pumping that zone? Sometimes if a zone is being over pumped, that could maybe cause something also - larger water flow coming to a sudden stop. Since I swapped my 15-58 3 speed for an Alpha, things are very quiet & gentle here.
All my lines are 1" pex and The pump runs 24/7 so no zone valves, it was when I shut the pump down manually that I heard the noise. My pump is over sized for this system. It's a Bell and Gossett NRF-36 3 speed. But I got a really good deal on it so I couldn't pass it up. I think I will try to install a water hammer arrestor and see if that helps.
Fred61
Minister of Fire
If you still have air in the system which I suspect caused your burp, you already have, in effect, a water hammer arrestor. Does your circ have a check valve?
No check valve on my pump. It seems the my heat exchangers are causing cavitation in my system. My water comes from the boiler with no air then on the return side it has air in it. I can hear one of the HX gurgling with pump running.
brenndatomu
Minister of Fire
Pump is on the return side of the HE? If there is more restriction on the suction side of the pump as compared to the pressure side then there will be cavitation at the restriction, which in this case sounds like it is the HE. If you can slow down the pump (?) that would work...or throttle the discharge side down a little.
Pump is running the slowest setting right now. I could close my HX isolation valve slightly to see if that helps. The thing I find weird is the problem seems to come and go. I had air in the return lines when I got home from work. As I was working in the garage for a little bit the air was gone, then by the time I went inside the air was back.
maple1
Minister of Fire
That's a pretty big pump. Really big to me, but my perspective might be off. Its pumping a lot even on 1. Have you figured out the head its seeing? Have you measured temps in & out of the hx?
I tried measuring the temps in and out but the infrared gun I had wasn't working right and I haven't found another one to test with yet.
I haven't figured the exact head number but both my HX combined are about 8 ft and I have about 90 feet of 1" pex line total. There is one 45 degree 1" black iron elbow on the boiler.
I haven't figured the exact head number but both my HX combined are about 8 ft and I have about 90 feet of 1" pex line total. There is one 45 degree 1" black iron elbow on the boiler.
brenndatomu
Minister of Fire
You need to throttle on the discharge side of the pump. If you throttle the HX isolation valve and it is still on the suction side of the pump all you are doing is moving the restriction (cavitation point)
Are you sure that ALL the air is out of the system from startup? I know when we take our 600K BTU boiler down for maintenance at work, it can take a number of days of intermittent bleeding at various points to get all the air back out
EDIT: The more I think about this the more I think you are just gonna chase your tail trying to balance things out with this oversized pump
Ok I have a isolation valve on that side of the pump as well. I will try closing it slightly to see if that helps the cavitation.
On this subject, is it possible for a system to start creating air bubbles simply from turbulence in the lines? My heat exchangers have what we, my work, calls a "h" leg header design, I'm wondering if that type of fitting is causing so much turbulence that it's causing this to happen.
On this subject, is it possible for a system to start creating air bubbles simply from turbulence in the lines? My heat exchangers have what we, my work, calls a "h" leg header design, I'm wondering if that type of fitting is causing so much turbulence that it's causing this to happen.
brenndatomu
Minister of Fire
Yeah, especially if the pump is pulling a "negative pressure" on the HX, turbulent spots are prone to "boil" under a neg pressure.
I was at a pump service class last year and they had a glass front pump. It was CRAZY being able to actually see what all was going on in there under various different "improper install" conditions!
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Well I guess I'll be choking back my post pump valve then. I planned on moving this pump to the house system next year and replacing it with a more appropriate pump. I Honestly didn't think it would be giving me fits like this.
maple1
Minister of Fire
I think I would get a smaller pump. A Grundfoss 15-58 3 speed is pretty robust & common, and not that expensive.
Fred61
Minister of Fire
It's difficult to control throttling with that type of valve. A regular globe valve works so much better. You're allowing more flow than you think you are.
On the "water hammer" noise --- I'm not qualified to determine but perhaps some of the "smart" guys here could tell us whether this pump could lower the pressure enough upstream to cause the water to boil when the temperature is at 180 at atmospheric pressure.
On the "water hammer" noise --- I'm not qualified to determine but perhaps some of the "smart" guys here could tell us whether this pump could lower the pressure enough upstream to cause the water to boil when the temperature is at 180 at atmospheric pressure.
brenndatomu
Minister of Fire
Whys that? Looks OK to me.
You'd be surprised how much water still flows past a 1/2 closed ball valve like that one.
Cutting back on the discharge side doesn't hurt anything on a centrifugal pump like that one, only if it is totally cut off for extended periods (more than a few minutes) would it be an issue (water would eventually heat up...could melt the impeller (plastic) or burn the seal up)
The valve just seems really close to closed to me being is about half way. I'm glad that I shouldn't have to worry about it like this. If this pump gets me through the season like this I'll be getting a smaller pump when I build next year's project.
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