Increasingly wild pressure fluctuations as hydronic system increases temperature

hot_rod

A long shot, but has the y strainer ever been pulled apart for a cleaning. They can add a lot of pressure drop to the circuit
might be time to replace the upper part of that Spirotnerm sep?🤔

np_mdbr

@mattmia2 Yes, there is a circulator dedicated to DHW as you observed. There is another circulator that is for the floor zones. That one is over near where the expansion tank tie-in happens.

@neilc I think you're right about that vent above the suction circ. I will check for other places where the vent could be pulling in air due to suction.

I know I'm late on it, but still pulling together a schematic of the system as pictures are hard to decipher. Just curious, are there icon collections for these systems that I could draw from? If not, I'll try to make up my own and be as descriptive as possible.

neilc

np_mdbr said:

neilc I think you're right about that vent above the suction circ. I will check for other places where the vent could be pulling in air due to suction.

look for any vent before, or on the suction side, of any circ,
except for the one at the PONPC

np_mdbr

hot_rod said:

A long shot, but has the y strainer ever been pulled apart for a cleaning. They can add a lot of pressure drop to the circuit
might be time to replace the upper part of that Spirotnerm sep?🤔

Which component are you referring to? I can say that I have never pulled apart a strainer on this system since we have lived here (4 years).

mattmia2

I believe there are 2 circulators for domestic space heating, one by the mixing valve and another near the boiler near where the feeder tank connects. is the one near the boiler running and free enough of air to circulate? I think it is what makes flow through the boiler on a DH call. I think there are separate boiler circulators for DH and DHW and the DH one isn't working, stuck rotor or is air bound (or has a clogged strainer as @hot_rod suggested) so that there is little flow in the boiler and water is actually boiling in the boiler.

np_mdbr

mattmia2 said:

I believe there are 2 circulators for domestic space heating, one by the mixing valve and another near the boiler near where the feeder tank connects. is the one near the boiler running and free enough of air to circulate? I think it is what makes flow through the boiler on a DH call. I think there are separate boiler circulators for DH and DHW and the DH one isn't working, stuck rotor or is air bound (or has a clogged strainer as @hot_rod suggested) so that there is little flow in the boiler and water is actually boiling in the boiler.

Just listening to the system as it reaches temp and the DH circ is the only thing running, this makes the most sense. I am going to try to run this circ from the boiler with no heat and see what happens. It might take me a bit, I have some work deadlines coming up!

I have to say this forum is amazing. I wish I could put a beef brisket in the smoker for all of you as a thank offering for all of the help thus far.

np_mdbr

I am up and running with videos on youtube. Here's the first video I took, where the pressure was becoming "increasingly wild"... I called to have the main heat shut off and that's when the relief valve blew.

https://www.youtube.com/watch?v=xlm2IS9Y8W8

hot_rod

This is a y strainer. You need to take it apart on the hex remove the strainer, maybe wire brush it if it is plugged.

Even brand new clean ones add a couple feet of head. When plugged or partially they can really reduce flow, starve the boiler and it overheats

To be honest I’d leave the strainer out. They are good for initial start up and cleaning, but can be problematic if not serviced every year or so.

np_mdbr

Thanks @hot_rod , this echoes what the local heat guy said. He suspected this Y strainer was a potential issue as well.

Here's a walkthrough video of the entire system. Let me know if you need me to go into more detail...

https://youtu.be/8FU5Fmdc_pA

pecmsg

np_mdbr said:

@hot_rod Thank you for that detailed explanation, I'll need to take some time to ingest all of the data there. @mattmia2 Yes, the oxidation on the pipes is due to the AC creating condensation on them during the summertime. Attaching more pics of the system, and hopefully this gives a better idea where the pipes go. This is the expansion tank connection going into the zone lines. I'm not sure what the component is there, it seems like an air separator that got "decommissioned"? Here is how the tank is connected to the system. I do not see an air separator anywhere in the line that leads up to the tank. Here's behind the water tank - the bare copper is for DHW, the insulated lines go to and from the floor zones. Some more detail of the boiler piping... One more boiler piping detail pic...

how does the A/C cause condensation on those pipes?

hot_rod

Looks like it may have a chilled water component if those are refrigerant lines to the plate HX? So all exposed metal will sweat

Ironman

Please note that the instructions require the secondary (system) loop to move more water than the primary (boiler) loop.

Now, also notice that the secondary loop is also chocked down at least two pipe diameters at the 3 way motorized valve in your video. It appears to be 1-1/4” reduced to 3/4”. A 1-1/4” pipe carries 4 times what a 3/4” does. This means that the flow is reduced to one forth of what it should be at that point.

If the valve switches to divert flow to the AHU, the restriction becomes greater because then all of the flow must go through the 3/4” piping to the AHU AND its coil. This may not be the main or only issue, but it should be corrected.

Ill post a diagram following.

Another thing to realize is that these cheap boiler gauges can be inaccurate. The fact that you have two of them reading a very different static pressure is proof of that.

Also, because the boiler circulator is pumping into the boiler (as per the manual), it’s adding its pressure to the boiler when running.

What’s the black substance running down from under the air vent?

np_mdbr

hot_rod said:

Looks like it may have a chilled water component if those are refrigerant lines to the plate HX? So all exposed metal will sweat

Yep, the system uses the same hydronic fluid in the summer, cools it down at those plate exchangers, and circulates it between the blower and the floor zone. At the same time, DHW can call for heat and the circulator pressures are supposed to keep the two different fluid temperatures separated from each other.

np_mdbr

@Ironman thanks for that schematic. This looks pretty similar to my setup minus a few things. I will take some time to study it.
The black substance started appearing when the local heat guy replaced that air seperator. I don't think he put any tape around the connection. I'm pretty sure it's just the slow seepage of hydronic fluid from that connection. I have been meaning to put some tape on there but haven't yet.

Do you have a recommendation for good quality gauges? I'd be interested in picking some up and installing them.

hot_rod

Chilled water piping needs to be insulated and vapor sealed, even an exposed ball valve handle will sweat.

Chilled water holds air / o2 better, that why fish die when water gets too warm. So if that spiro is no longer working, you could have a corrosion building monster. Plugging that Y strainer as it tries to work. It could even have that spiro mesh plugged, Yank it apart.

The fact that you indicated this problem has increased, again, suggests a plugged filter. It is an easy thing to check, start with the low hanging fruit😆

Ironman

Here’s a simplified drawing of what needs to be done at the piping going to the AHU.

Remove the motorized valve and install two closely spaced tees with a small circulator (007 or equivalent) pumping the AHU.

The tees should be 1-1/4” straight through with 3/4” bulls feeding the AHU.

hot_rod

Ironman said:

Here’s a simplified drawing of what needs to be done at the piping going to the AHU.

Remove the motorized valve and install two closely spaced tees with a small circulator (007 or equivalent) pumping the AHU.

The tees should be 1-1/4” straight through with 3/4” bulls feeding the AHU.

I wonder though if that motorized valve is intended to modulate? I see a Johnson control 350P which can spit out a 0-12 VDC signal which the damper motor actuator could accept. With chilled water application you need to keep a pretty tight delta T to avoid dew point operation. I’d observe how that valve operates, or see how that 350P is configured, before removing it

I don’t suppose there is a wiring schematic or sequence of operation essay anywhere?

mattmia2

Isn't it also controlling the temp to the radiant heating?

Ironman

hot_rod said:

Here’s a simplified drawing of what needs to be done at the piping going to the AHU.

Remove the motorized valve and install two closely spaced tees with a small circulator (007 or equivalent) pumping the AHU.

The tees should be 1-1/4” straight through with 3/4” bulls feeding the AHU.

I wonder though if that motorized valve is intended to modulate? I see a Johnson control 350P which can spit out a 0-12 VDC signal which the damper motor actuator could accept. With chilled water application you need to keep a pretty tight delta T to avoid dew point operation. I’d observe how that valve operates, or see how that 350P is configured, before removing it I don’t suppose there is a wiring schematic or sequence of operation essay anywhere?

That’s a valid point. I assumed that the 350 was controlling the mixing valve for the floor. Still, a 3/4” valve would seem to restrictive for a 1-1/4” line. Do you know the cv rating?

hot_rod

Ironman said:

hot_rod said:

Ironman said:

Here’s a simplified drawing of what needs to be done at the piping going to the AHU.

Remove the motorized valve and install two closely spaced tees with a small circulator (007 or equivalent) pumping the AHU.

The tees should be 1-1/4” straight through with 3/4” bulls feeding the AHU.

I wonder though if that motorized valve is intended to modulate? I see a Johnson control 350P which can spit out a 0-12 VDC signal which the damper motor actuator could accept. With chilled water application you need to keep a pretty tight delta T to avoid dew point operation. I’d observe how that valve operates, or see how that 350P is configured, before removing it

I don’t suppose there is a wiring schematic or sequence of operation essay anywhere?

That’s a valid point. I assumed that the 350 was controlling the mixing valve for the floor. Still, a 3/4” valve would seem to restrictive for a 1-1/4” line. Do you know the cv rating?

It looks like a globe valve style, hard to tell but it could be a 1”, maybe 10-12cv. That label may tell. It just looks like a lot of actuator and control to be just a divert operation? Some time was spent putting that control box together. Seems like a control persons work more than a plumber.

Ironman

@hot_rod
Are we looking at two different things?
 I’m referring to the motorized valve that diverts flow to the AHU and only appears in his video, not in the pics. It looks like a common 3 way valve to me.

Also, are we maybe missing the obvious: could the expansion tank be under-sized or going bad?

A lot of complexity which brings a lot of possibilities and info was piecemeal by a HO doing his best to explain what’s there. The video does show things more completely. 

mattmia2

I dint' look at the video. I see a 3 way valve with a proportional control that looks like it it controlling the temp to the radiant about 4' or so up the wall near the radiant manifold.

mattmia2

*watches video*

There are a lot of circulators and somewhat questionable hydraulic separation between them, I can see where there might be a combination of operating conditions that brings one of the automatic vents in to vacuum and pulls air in.

Also looks like it was over engineered for what it is doing, was the previous owner some sort of control system engineer?

hot_rod

mattmia2 said:

I dint' look at the video. I see a 3 way valve with a proportional control that looks like it it controlling the temp to the radiant about 4' or so up the wall near the radiant manifold.

Possible it control temperature for the heating season, but it also sends chilled water from that plate heat exchanger. I believe those are refrigerant lines on the plate HX So it must have a summer/ winter mode

mattmia2

If the boiler is serving hydroair and radiant it has to be making high temp water for the hydroair and be mixing it down.

np_mdbr

I am back from a business trip and am ingesting all the replies. @hot_rod The first step I'm going to take is pulling apart that Y strainer and cleaning it. This will be documented in pictures and shared here. I'm a little apprehensive about how much air it'll introduce into to system but there are many air separators that will hopefully alleviate the issue.

I am so grateful for the help, and while we're still without "real" heat this problem and the discussion around is fascinating to me. Cheers.

np_mdbr

I cleaned the Y strainer last night, pics attached. I have not yet filled the system back up as I'm still planning out how to do it while trying to avoid pumping air farther into the system. I am sure it won't be perfect, but will try the refill tonight.

The strainer was quite dirty, as you can see. There is a lot of debris in this system and for a long time I have thought of using one of those in-line filtration systems with either a bag filter or a magnet filter. I would love some recommendations on those if you have any.

I really wish they had put some ball valves on both sides of that strainer!

Debris caught in the strainer:


Outside view of strainer before cleaning:


Strainer after cleaning:

hot_rod

Too fine of a mesh in that Y strainer, I'd lean towards leaving it out. Even brand new, clean, you have a some pressure drop. In that condition, a lot of pressure drop.
In chronically dirty systems you should really have gauges or PT ports across a strainer. Just like a swimming pool filter

What you need is a dirt separator. A separator removes particles and drops them to the bottom, out of the flow path, no flow reduction. Adding a magnetic function, DirtMagPro adds very fine metal particles removal, much smaller than then y strainer could trap.

I've tested a few different brands on this clear pipe panel in my shop and the Caleffi is the only one that has both particle and magnetite removal down to 5 micron size. It also has a composite media inside so aggressive water cannot harm it

You have enough room to press one in that pipe where the Y is now.


https://video.search.yahoo.com/yhs/search?fr=yhs-ima-st_mig&ei=UTF-8&hsimp=yhs-st_mig&hspart=ima&p=caleffi+dirtmag+pro&type=q3000_A1BWP_set_bcrq#id=1&vid=9ac0c841dc882bd70fea3161700a7231&action=click

np_mdbr

@hot_rod Wow, that DirtMag Pro looks awesome, thanks for the tip!

I didn't even consider leaving the Y strainer out completely, but I will pull it out for now just so we can eliminate that part of the equation.

np_mdbr

@Ironman I am still looking at your schematics... they seem super useful and I'll get back to you on the motorized valve. That thing is unpredictable to say the least.

mattmia2

It looked like there were valves near the strainer, each was a couple feet away, but there were vales that would isolate it so you at least didn't have to drain the system, but it was hard for me to tell what connected where.

The fact that there was a hose hooked up to flush the strainer was also a clue that there had been issues.

np_mdbr

OK, I removed the mesh strainer from the Y junction completely and used my 1/2 HP pump to push hydronic fluid back into the system. It was convincing (at least to me) that most of the air had been purged. The air separators were singing a tune and doing their job. I was expelling bubbles from the bucket of hydronic fluid that was hooked up to the output and intake of the system.

I fired things up. DHW called for heat first. That went perfectly and finished. I let the system rest a bit. Then we called for heat via the floor systems. That fired up and was MUCH better than previous attempts. Just slight fluctuations on the pressure gauge that I've been using the most, and way way better flow through that bottom section where the Y strainer was removed, i.e. the temperature on the left matched the temperature on the right whereas before there was a large temperature differential.

I have had the system running now for about an hour and there hasn't been any insane pounding or pressure fluctuation. And the house is actually getting warmer, ha!

I will keep you all posted on how it goes overnight. Hopefully we have addressed the root cause (suppression of flow at the Y strainer)?

np_mdbr

Good morning all, good news. Woke up this morning and went into the area where I had the single zone running overnight. And it was toasty! The kids were even complaining that it was "too hot" (it was actually around 64 degrees, they've been used to waking up to 55 degrees, lol).

Went to check on the system and it was running nicely, aside from a pulsing effect on the main pressure gauge that I use. This is the "cheap" gauge and the pulse effect wasn't showing on any of the other gauges. I did take a video of that:
https://youtube.com/shorts/uaeiFWOpSK0?feature=share

I believe that I now need to make sure that the expansion tank is at the correct pressure. I pressurized the system to around 20 PSI which is probably a bit high.

Also, I need to order that Caleffi DirtMag Pro but am wondering about sizing and whether to do a press or sweat fit. The OD of the copper pipe that connects to either side of the existing Y strainer is 1 3/4". I am looking on supplyhouse.com and don't see any available at this size, but I assume this could be remedied by using an adapter of some kind. Any advice here would be appreciated.

I am crossing my fingers for now, but the difference overnight was so profound that it's hard not to be just a bit optimistic that we have found the root cause. Again, this forum is amazing and I am blown away by the interest shown in this and for all the help and advice offered. You guys rock.

Ironman

There’s no 1-3/4” pipe size. It’s probably 1-5/8” OD which means it’s 1-1/2” ID. 

mattmia2

Copper pipe is measured by id. 1.5 in copper pipe is 1 5/8 in od. I would use press if you have access to the tool, otherwise get the npt version and sweat adapters and a coupler. The body of that dirtmag is a lot to heat if you are inexperienced and is expensive if you screw it up. Sweat the adapters on, then screw them in withevteflon tape then use the coupler to reconnect the cut you made to screw it on, unless there is a flange or union nearby you can disconnect to screw it on.

hot_rod

You could leave one of the male adapters in place, saw just beyond the right side adapter. Screw off the old Y strainer
Get a male adapter and a slip (repair) coupling to install the new one. Unless the piping can move enough to slip in the new one. Might be best to have a plumber or hydronic person do the swap.

The break in 1/2 easy if you are tight to the wall. A 10" cresent just took this one apart.

np_mdbr

I went ahead and ordered this DirtMag Pro.

Wondering about the location - most guidance I've seen says to place these things close to boiler intake... is the Y strainer location OK, or would it be better to locate it closer to the boiler?

Yet another night of good heat. The system sounds pretty happy.

hot_rod

It will work fine where the strainer is now.

np_mdbr

Another question... is it advisable to add ball valves on both sides of the DirtMag, in addition to pressure gauges? Just thinking if I want to take apart the main housing for a deep clean at some point it would be nice to isolate this part of the system. And, pressure gauges might be a good helper to know when to drain the DirtMag?

hot_rod

No reason why not to add service components