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friolator

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We've had an ongoing issue that I think I've finally narrowed down a bit. Every once in a while, our Buderus GB142 reports water pressure that's too low, and won't come on. Thus, we come home to a cold house, or like this past weekend when we were away, I get an email from the thermostat that it's 55 degrees inside, and have to have a friend with a key run over to the house to reset it.

When the water pressure is too low, it's reporting values along the lines of 3PSI. ("P03" flashing on the control panel)

The solution to this problem has always been simple: power cycle the boiler. As the boiler initializes, you can watch the pressure rise a bit, usually by 1-2 PSI, then when the circulator pump comes on momentarily, it spikes up again, and will eventually return to around 15PSI. It can stay like this for weeks or months before dropping again.

What I have noticed is that there's a pattern: the pressure only drops when the outside temperature rises for a couple of days. There are fewer calls for heat in this case, and the pressure seems to slowly drop until it's so low the boiler won't fire. Power cycling it always seems to reset it as described above.

The system is pretty simple: single zone, heat only (no domestic hot water). There's a single circulator pump and a small expansion tank (which may have been re-used by the installer 12 years ago, when the old system was upgraded, I suspect).

The house itself is on Boston city water, and I would argue the overall system pressure is actually too high (we blow through a lot of sink gaskets because of it), and more than once I've had the kitchen faucet in just the wrong spot and the water bounced off a pot right into my face. I've been considering adding a pressure reducing valve for the whole house because of those issues, but have held off until this heating pressure thing is dealt with.

So, any ideas? Where should I start looking? Could an old expansion tank be the culprit?

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Reach4

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So, any ideas? Where should I start looking? Could an old expansion tank be the culprit?
I don't know these systems. But I would say that the expansion tank should be empty of water when the system is cool. Knock on it to see if it sounds empty.
 

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If the ET is precharged to your normal operating system pressure, very little water will enter since it won't be able to push back on the bladder. When the boiler turns on and heats the water, it expands, and the water will enter the tank. So, it depends somewhat on when you check it, and what the temperature of the water is at the time.

Note, to precharge the tank properly, you have to turn off the autofill (if you have one), open a drain valve to let all pressure out of the system, keep that valve open, then check and adjust the pressure. Only then can you close the drain valve and refill and pressurize the system. I have that boiler, and it works well. Worst case, the pressure transducer, the main computer board, or the connection to the circuit board is defective, loose, or corroded. It sounds like there may be a problem with the transducer or the connection. But, if the ET is defective or it has lost its precharge (the cap loose?), just redoing that may solve your problem.

You can download the full service manual of that boiler (it's huge - several hundred pages), and it will give you some troubleshooting help even if you don't want to or feel comfortable doing it yourself, it may help you figure out what's wrong.

You can also get some weird symptoms if there's air in the lines...it may need to be purged. Air expands and contracts LOTS more than the water, so that can cause the system pressure to change more than if it is properly filled with water.
 

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I don't know these systems. But I would say that the expansion tank should be empty of water when the system is cool. Knock on it to see if it sounds empty.

Ok, so we haven't been around much for the past week or so, but this morning we woke up and it was 5 degrees below where we normally keep it. The thermostat was calling for heat but the boiler was off because the pressure was down to 4.

I went downstairs and tapped on the expansion tank, which seemed to be empty on the bottom half, but full on the top half. Roughly around the seam across the middle of the tank is where the sound changed, when tapping.

Cycled the power on the boiler and within 30 seconds it was reporting pressure of 15PSI, and pumping out heat.
 

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Worst case, the pressure transducer, the main computer board, or the connection to the circuit board is defective, loose, or corroded. It sounds like there may be a problem with the transducer or the connection. But, if the ET is defective or it has lost its precharge (the cap loose?), just redoing that may solve your problem.

the cap on the tank doesn't appear to be loose.

You can download the full service manual of that boiler (it's huge - several hundred pages), and it will give you some troubleshooting help even if you don't want to or feel comfortable doing it yourself, it may help you figure out what's wrong.

I've got a copy of that, and have done a fair bit of work on the boiler myself (replaced the fan unit this past fall after it died, etc). I'll dig through it again but last time I looked it wasn't particularly helpful on this issue.

You can also get some weird symptoms if there's air in the lines...it may need to be purged. Air expands and contracts LOTS more than the water, so that can cause the system pressure to change more than if it is properly filled with water.

Every fall I bleed the air out of the system. Our apartment is on the 2nd floor, and the boiler is in the basement. There are two bleeders in the apartment, and I check both. This past Fall when I did it, no air came out at all, just water. Not even a sputter. One bleeder is at the absolute highest point in the system, the other is slightly lower. Same result in both.
 

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I just went downstairs and took some pictures of the whole system, in case that helps to figure this out. Below the boiler is a styrofoam box, where the circulator pump and pressure/temperature gauges are located. To be honest, I had forgotten the pressure/temp gauges were there, and never checked them against the value reported by the Buderus control panel. If this happens again, I'll check them both to see if they corroborate.

Also, there's a fair bit of corrosion on the pipes in there. I'm not sure what that's all about, but I imagine it's not good. My guess is that the condensate drain from the system, which ends above the black funnel that the condensate fluid drops into, has been splashing onto the pipes. I've seen it splash onto the foam box, but not the pipes, and have meant to extend it by another couple inches to prevent this from happening. But now I'm wondering if just enough of that slightly acidic condensate was splashing onto the exposed pipe and dripping down. Because it looks ugly.

Let me know what you think. I suspect this is going to cost a bit to fix...

Full System:
31683212870_0f82ddcd00_b.jpg



Backflow Preventer, Pressure Valve, Condensate pump:
32019083546_93fb327473_b.jpg


Corrosion inside the foam box:
31940278011_7f12021975_b.jpg
 

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Also - on that corrosion, can I just brush that with some baking soda and water to try to neutralize it, or do I need to be thinking about getting all of this replaced?
 

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I went downstairs and tapped on the expansion tank, which seemed to be empty on the bottom half, but full on the top half. Roughly around the seam across the middle of the tank is where the sound changed, when tapping.

Cycled the power on the boiler and within 30 seconds it was reporting pressure of 15PSI, and pumping out heat.
If there is water up top but not on the bottom, that says that expansion tank has not failed.

When your water pressure is minimum, that tank should be empty of water. So I would think the precharge (measured with zero water pressure) should be at least 4 PSI. Maybe it should be higher; I don't know.. As water expands with temperature, there should be maximum available room for the water to expand into. Is there an automatic refill in this system?
 

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The ET precharge pressure should be your system normal working pressure. That boiler will not work if it is at 4psi. I'd have to verify, but I think the low-pressure cutout switch on that boiler opens up at less than 6psi, and 12psi is more of a normal range. The safety valve, unless changed because you have to pump multiple stories, is probably a 30psi version. If your ET has failed or not setup properly, that could be opening.

You could try a little bit of baking soda mixed with water...the corrosion may not effervesce as, if it is caused by leaks from the condensate system, the acid may be neutralized in the process of creating the corrosion. You could just clean it off. If the pipes aren't pitted, it should be fine. If it dripped on any electrical bits, the resulting corrosion is more likely to be a source of problems.

If the ET is not properly precharged...during a heating cycle, things could get to overpressure, dumping a bit of water out the safety valve, then, when it cools, your pressure will be lower since you lost some water.
 

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If the ET is not properly precharged...during a heating cycle, things could get to overpressure, dumping a bit of water out the safety valve, then, when it cools, your pressure will be lower since you lost some water.

I've seen no evidence of this happening. That is, when it fails, there's no sign of a puddle on the floor below the pressure valve. In terms of overpressure, I've never seen it go up above 18PSI. It typically operates in the 12-15 range when it's running normally.
 

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Another update. Yesterday we woke up to a cold house: 5 degrees below where we normally keep it at night. Went downstairs and checked the pressure gauge on the boiler control panel as well as the dial gauge on the hot water output from the boiler. Both matched: about 4PSI.

I saw a little water on the floor (not much, just a few drops), so I took the foam cover off the section below the boiler where those corroded pipes are, and found that there was a very small amount of water pooled below a cross-brace that connects the hot and cold lines. See below. There doesn't seem to be any water above that. when I felt it it was totally dry.

Power cycle returned pressure to normal, heat was back on in a matter of seconds.

32022924501_7b9ac70515_c.jpg


At this point I'm starting to think that the problem might be in these corroded pipes - and this is a bit more soldering than I'm comfortable with, so I'm guessing it's time to call a plumber to come redo this section of the system? ugh. this isn't going to be cheap...
 
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What I'd try is first to remove those threaded devices where you can, clean things up, get a quality pipe dope, and reinstall. IT really looks to me that things are leaking at the threaded joints - just look at the pressure relief valve and the pipe below it. Unless the pipe is severely pitted, it's only cosmetic, but if it continued onto any electrical connection or (an interlock, or sensor), you'd need to clean up the contacts and maybe replace the sensor(s).

Does the mechanical gauge move when you tap on it? They sometimes get sticky and do not read properly. Depending on the type of pressure sensor that is used for low-pressure cutout, that may be suspect or the contacts to it. If there is a buildup of debris to the inlet of the pressure sensor, it may not reliably read a correct value.

As a backup check, you could buy a screw-on pressure gauge and connect it to one of the drain valves to double-check the built-in one after you open that valve. Water nor corrosion do not help electrical connections or electronics.

FWIW, an ET that is actually leaking is way past failing...the bladder goes first (almost always), then getting water where it shouldn't, if left long enough, will then start to cause it to rust out from the inside. But, you'd normally notice problems as soon as the bladder fails...rusting out could take quite awhile after that has occurred.
 

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Email from the thermostat just as I was leaving for home tonight that the temp dropped yet again. The frequency is increasing. So, I guess my afternoon tomorrow is going to be cleaning those pipes, draining the whole system and applying fresh pipe dope to those threaded connections.

When I got home today and went downstairs to reset the boiler, I noticed that there was some water pooled on the pump seen in that picture as well (that's on the return side of the loop). So I'll be doing both of those threaded connections, just to be sure. Far as I can tell there's nothing on the electrics for the pump, so that's good.

The mechanical gauge seems to be working properly, and it seems is purely informational - that is, it's not connected back to anything else in the system, it's just a combo temp/pressure gauge.

As an aside, do you know if there's any way to interface with the control panel on these things? I see the small plug (covered with a plastic cap) with a stethoscope icon, and that looks like it may be a 1/8" mini jack or similar connection. If there's a way to connect that up to, say, an Arduino or Raspberry Pi, I'd be interested in getting more information off the boiler that way. I didn't see anything in the manual about that, so I'm guessing it might just be for factory service use?
 

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As I understand it, it is for diagnostics, and they only give the program to trained personnel. Their US headquarters is only about 15-miles from my house. I've been thinking about trying to see if I could sit in on one of their training sessions, but have never called them to see if that is possible, or if so, what it might cost.

When it fails due to the low-pressure cutout...does the digital readout match the mechanical gauge? If not, you'd have to check to see the state of the electrical connections that go to the pressure transducer and clean them up if corroded. Sometimes, all it may take is to remove then reinstall the connector. I do not know the voltage or resistance across the sensor, but it may be in the service manual. You'd need a decent DMM that could read accurately into the millivolt range, but it should match what is called out in the manual. There may be a physical low-pressure switch as well as the pressure sensor, but you should be able to sequence the readout to view what pressure the computer thinks is in the system...that's the critical one, and if it drops too low, will force the computer to shut it down and flash the error message. Are you certain that the primary loop pump is turning on?
 
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So yesterday I drained the whole system, cleaned the threaded fittings and as much of the corrosion on the pipes as I could (with a wire brush, mostly), and attempted to loosen the large nuts on the output and return sides of the boiler. No luck moving them. Tried tapping them, applying heat, liquid wrench, but none of it worked. So I filled it back up, purged it, and powered it on. I did see some dribbling out of both of the large threaded fittings, so I'm pretty convinced this is the culprit. I'm probably going to have to have someone come in here to deal with this, because it just wasn't happening for me.

On the pressure question: the mechanical gauge and the Buderus control panel are always the same. So I think the issue is a slow leak causing the cold pressure to drop below the boiler's cutoff threshold.

Below the boiler, on the return side, is a circulator pump. When you power on the boiler, as long as there's sufficient pressure, this pump is always running. On the output side, past the expansion tank, is a Taco circulator pump. When I was testing this yesterday, I couldn't tell if it was running or not. I never really paid much attention to how loud it normally is, but I couldn't really hear anything from it. My understanding is that the pump below the boiler is not supposed to cycle the water through the whole system, so if the Taco pump is dead, could that also lead to pressure issues?
 

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Hi, this just started today with my GB142 - that is how i found this thread. Did you ever find a solution? Thx!
 

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With a working water regulating valve and fill valve open the water pressure should never drop unless the a leak is more that than the makeup. Ex tank even if bad it doesn't matter. With a cool boiler 100° or less pumps and boiler off. System pressure 12-14 lbs ex tank should be the same pressure water comes out ex tank valve tanks bad.tire hand pump to adjust pressure. Turn system back on.
 

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Fitter30, I was surprised to see there was a low-pressure cutout. What is wrong with turning on the heat when the water pressure is zero? I guess you would want pressure before the water hit near 200F. Maybe that is the deal-- simpler to require pressure regardless of temperature
 

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Fitter30, I was surprised to see there was a low-pressure cutout. What is wrong with turning on the heat when the water pressure is zero? I guess you would want pressure before the water hit near 200F. Maybe that is the deal-- simpler to require pressure regardless of temperature
What if your gone for the weekend or middle of the night. Pressure going somewhere and has to be check out.
 
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