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Air in the hot water rad every couple of days - any ideas why?

MilanD
MilanD Member Posts: 1,160
edited December 2016 in THE MAIN WALL
Hello again to the board. While I'm dealing with how to down fire our LGB Steam boiler, I have a question about my rental unit and the, what looks like, a converted gravity hw system (?)

I don't have pics of the rad, but it's one of those convector in-wall fin tube with a metal door. A few of them went cold a few days ago. I checked all pipes in the basement first and all were nice and hot. Part of the loop is in the basement garage, and someone had left the garage door up which got the garage extra chilly, so not sure if this was a culprit to cold rad... thinking probably not.

Anyhow, I let a little bit of air from them and they went hot right away and stayed warm until today (so, some 5 days). Then, I got a call this am that one of the same radiator is again cold (only one of the 2 cold before).

Before I start on a weekly pilgrimage to this radiator, I am wondering why this is happening in the first place, and how to alleviate the problem. I understand that sometimes air can get in with make-up water and this is what it is. I also don't think there are any leaks, so there shouldn't be any make-up. I think also that this is the last or second to last radiator on this particular loop/zone so air congregating there also makes sense, but not why or where's it coming from. I am going to go and take a look one more time today for what this is exactly, but it's one of those one-pipe water systems with diverter tees on a rad riser intake (pointing against the flow), and on the outlet pointing with the flow. At any rate, it's all heating fine and has been since I fired-up the system, other than this rad that went cold 5 days ago and then again today.

So where's the air coming from if there isn't a leak? I will check for them today too, btw, and report back. Noone has called me with a wet floor (which may not mean there isn't any - only that noone called me).

There aren't any air scrubbers by the boiler, and I haven't explored if there are air vents on any rads, but I'm going to venture to guess there aren't.

It's a Smith CI, model GB100, and appears to be a newer one. As you can see Tacco 007 pump is on the return side (pumps into the boiler), and it has an air expansion tank piped just outside the boiler riser. System otherwise works fine. I have it set on A350R outdoor reset, 140 F min temp (pic is from before it was set to 140), and 2.5:1 ratio on the A350R. Seems to keep the building nice and warm.

The op. PSI is at about 17.

Being new to this hot water, I am not sure how to exactly do much of anything other than check the electric circuitry.

Any tips to get this to scrub air out would be super-helpful. Where to place it, should I move the circulator on the outlet side (vs. intake) and after the expansion tank, and where to place air vents. Should I even bother with it and just accept a once in a while pilgrimage call to the rad?

Thanks again!


Comments

  • Brewbeer
    Brewbeer Member Posts: 616
    edited December 2016
    It sounds like the radiator that is air bound is the air elimination device. With the recent cold weather, the system may be as hot now as it has been all season. The hotter water can't hold as much dissolved air, so it can come out of solution and end up in the radiator. If the expansion tank doesn't have a bladder, air can be coming from there. Consider bleeding the radiator a few more times to see if the problem goes away. If not, you may consider making some modifications.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
    MilanD
  • MilanD
    MilanD Member Posts: 1,160
    edited December 2016
    Thanks @Brewbeer! I'm at the building right now. Bled the rad. Didn't take a lot to get it opened up and hot again. I checked psi on boiler gauge and it was at 15, temp at about 160. So I raised the pressure regulator on the intake and manually added the water to about 18 psi. Higher psi should also hold those air bubbles smaller, I hope.

    So you also answered where the air may have come from. I am still wondering if some rads are slowly dripping and will check that another time as it's getting late. I remember being at 17 psi the last time I looked (it was months tho).

    Thanks again! I'm hoping only this doesn't turn into a weekly pilgrimage, although I do like people living here. Hehe.

    Will keep everyone posted as to the final outcome.

    Cheers!
  • MilanD
    MilanD Member Posts: 1,160
    Here are two pics. Gauge and the vent, or whatever that thing is called.
  • MilanD
    MilanD Member Posts: 1,160
    And this was the gauge before I started. Clearly below 15.
  • MilanD
    MilanD Member Posts: 1,160
    edited December 2016
    After the last heat cycle.
  • Brewbeer
    Brewbeer Member Posts: 616
    Higher system pressures will allow more of the air in the expansion tank to dissolve into the water. An expansion tank with a bladder would prevent that from occurring.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
    MilanD
  • MilanD
    MilanD Member Posts: 1,160
    I'll watch it. I suppose I can always let some water out and lower the psi that way. I mean, that is the way to do it, right?

    Thanks again!
  • MilanD
    MilanD Member Posts: 1,160
    Well, it's been a couple of weeks since the last pilgrimage. Looks like some air was bled then and all is now well