Burnam boiler pressure issue?

1075NH

Hello all, At a loss on this issue. 16 year old oil fired Burnham hot water boiler with tankless coil. Two Zones with circulators on return side, no zone valves. Aquastat set to HI: 180 and LOW: 160. Split level home with baseboard radiators. Highest radiator less then 6' above boiler.

The system had a dripping relief valve and gauge was showing at 30 psi. So i changed that, the Expansion tank and the Hy-Vent since all of it was original. Purged both zones. Things looked good except system pressure was still hovering around 28psi based on the Tridicator. Temp around 200-205. Pressure drops 5-10 PSI when the boiler is resting around 180 but would climb up to almost 30 when it would reach 200-205 degrees. Thinking i have a bad Taco Pressure reducing valve (it too is original to install) i lowered that pressure down to 12. For about two days things seemed ok. Pressure would rest around 14 and go up to about 20 when it was at 205 degrees. Then i checked it the next day and pressure was up around 30 again. Convinced its a bad Pressure Reducer i shut off the water supply (New Pressure reducer on order) and bled the boiler down to 15psi. Things seemed stable for a day. 15psi when at 180. 20psi when at 205.

But then yesterday morning i checked it and pressure was 0psi at 180 degrees. I opened the feeder to get it to 15psi then shut the valve. Check it again last night, back at 0psi. Opened it again to bring it up to 15psi. Just checked it again this AM, zero. Absolutely no signs of a leak anywhere. Checked all the radiators and visible piping.

What am i missing? Is the brand new Hy-Vent defective? But if the Hy-Vent was stuck wouldn't it be leaking water? I didn't have a tire pressure gauge handy but maybe the new expansion tank is not charged properly? Would that cause the system pressure to drop when the heat wasn't calling? I noticed last night the expansion tank was cool from top to bottom with the boiler at 180. Turned the thermostat up and the boiler kicked on and then the top of the expansion tank got hot.

I'm putting the new Pressure Reducing Valve in Wednesday and I'm certainly hoping that will solve the issue of the overpressure condition since clearly the current PRV is leaking through. Also bringing a tire pressure gauge and compressor to bring up the pressure (if needed) on the Expansion tank. BUT... Why is the system not holding pressure?

Jamie Hall

Serious expansion tank problems. May not be large enough; almost certainly not properly precharged. Or... may have failed completely.

STEVEusaPA

Has to be leaking somewhere, maybe back feeding, assuming your pressure gauge is correct.
You'll have to check the expansion tank with no pressure on the system.
It's also possible your system is not completely purged of all air.
Some pictures of all the near boiler piping may be helpful.

1075NH

Jamie Hall said:

Serious expansion tank problems. May not be large enough; almost certainly not properly precharged. Or... may have failed completely.

Well i don't think it's a size issue. I replaced the original one with the same size. But i agree, leaning towards maybe a charge issue. Will check it when i'm back on site wednesday.

1075NH

STEVEusaPA said:

Has to be leaking somewhere, maybe back feeding, assuming your pressure gauge is correct.
You'll have to check the expansion tank with no pressure on the system.
It's also possible your system is not completely purged of all air.
Some pictures of all the near boiler piping may be helpful.

I too was wondering if perhaps this is an issue with trapped air? But i'm surprised it has gotten worse as the days went by and not better. I would think the air scoop/Hy-Vent would have been improving a trapped air issue. And i bled both zones for a good amount of time. No bubbles at all for several minutes.

On the subject of bleeding the zones. The feeder/PRV is tied in at the return side of the boiler below the circulators.

EdTheHeaterMan

With the feed valve off and the system at 15 psi going up slightly when heated, that is normal. A few hours or days of operation the pressure is to 0 psi on the lower temperature, there is a place where "something" is leaving the closed system. If there are no water leaks, the only place left is the HyVent. It is designed to let out air. Air is "something".

Say all the air is not purged, and there is a little left in the loops. As the air becomes entrained by the moving water, small amounts find their way to the HyVent and leave the system over time. You don't see it while you are watching it because it is very small amounts.

When you return and find the low pressure, you add water, the pressure rises and you get the system to operate properly only to return later to see low pressure. More air left. The auto-feed will keep the pressure from falling so the problem is solved for now. After the system operates for some time all the air should eventually leave (in theory) and you should be able to leave the feed valve closed manually after a few weeks of operation.

Another possibility is an air leak in the system that is so small that the water evaporates off the hot pipe before it can form a puddle anywhere. Are any of the pipe joints covered in white or green crust near any valve packing nuts or connections?

1075NH

Thank you for the explanation Ed. That makes a lot of sense. I looked over every pipe joint i could see in the unfinished basement and see no evidence at all of even old leaks. Which leads me to believe it's the issue you describe. With the supply to the feeder shut off while i await the replacement that must be why i'm getting the pressure drop. My friend (who's house the issue is at) said it was at 0 again before she left for work an hour agi. So i told her to leave the water supply on while she's at work. Hoping that between now and 9 PM the feeder behaves and it doesn't go above 30.

STEVEusaPA

Air scoop/hy vent, even if piped correctly, is ancient technology and not your best option.

1075NH

STEVEusaPA said:

Air scoop/hy vent, even if piped correctly, is ancient technology and not your best option.

Ok, so what do you suggest? Although i don't think the technology of my air eliminator is the issue here. System worked with zero issues for 16 years.

Ironman

How About some pics of the boiler, its near piping and the expansion tank?

JUGHNE

I see you have the high limit at 180, but you talk about 205 temp when pressure rises.
Did you try setting the limit down to maybe 170?

JohnNY

I got ten bucks says the problem has to do with where the connection to the water feed is in relation to the pump.

1075NH

1075NH

JUGHNE said:

I see you have the high limit at 180, but you talk about 205 temp when pressure rises.
Did you try setting the limit down to maybe 170?

I was considering that. Not sure why it runs so much hotter than the control is set for. But i did set it for 170/150 and it's still running up to 200-205.

Could the Tridicator be that far off temp wise? Do they go bad?

1075NH

JohnNY said:

I got ten bucks says the problem has to do with where the connection to the water feed is in relation to the pump.

The make up water enters in the return below the pumps and Iso valves. Just ahead of the boiler drain. When i install the new PRV i'm going to re-pipe it so it's horizonal. I had thought of re-piping it and have it feed between the expansion tank and air scoop but i have had quite a few people tell me it's not worth the re-piping and where it enters now is actually better?

I should have taken a pic where you can see higher up. But the supply pipe coming off the top has a 90 and then a short piece into the air scoop and expansion tank. It's just out of view in the picture.

JohnNY

So, you're pumping into the connection point to your makeup water feed?

1075NH

JohnNY said:

So, you're pumping into the connection point to your makeup water feed?

Yes. Has a pipe manifold going to the boiler return. Piped as Boiler drain, feeder, zone 1 return, zone 2 return, then into boiler. If you look at the picture i posted where you can see the circulators and water enters just past the feeder on the right.

Ironman

Pics of the x tank and its connection to the system?

EBEBRATT-Ed

Could just be the new expansion tank is bad

1075NH

Ironman said:

Pics of the x tank and its connection to the system?  It’s attached below the air scoop just out of view above the boiler standard air scoop/Hy-Vent/expansion tank setup 

EdTheHeaterMan

Look at the tankless water heater. #1 the "well adaptor" has the white/green build-up I spoke of. #2 when was the last time anyone snugged up on the flange bolts? I'll bet is was maybe NEVER. If they are not seised up (you can tell if they come loose easily, but be careful not to snap off the bolt heads) then try to give then a 1/6 or 1/4 turn.

Most techs don't know this but after about 500 hours of running the gasket shrinks and the bolts are hand tight in many cases. A 1/2 turn 6 months into operation will usually take up the slack and that gasket will never leak. I like to just loosen them 1/6 turn then put them back to that 1/6 to 1/4 turn every annual tune-up to keep them from getting seized up after I install a boiler with a tankless heater. But I don't try it on an old boiler that has been around for 10 years or more.

Use your good judgment on the bolts for your friend/customer. You don't want to create a bigger problem/leak. You should be able to snug up on the well adaptor since it is a brass fitting in steel.

l

BDR529

Pull top jacket off. Rear left corner tends to be the place. It'll be nice and crusty. Evaporating before any visible puddling

Riello on a Burnham.. Good example of hubcaps on a tractor.

1075NH

I replaced the feeder and bled the zones again thoroughly. The feeder was just a bit clogged. And I did confirm the temp gauge is pretty accurate. The new expansion tank only had 3psi in it which probably explains the pressure issue. In any event, recharged it and so far 24 hours later the boiler seems perfect. Pressure stays consistently between 14-16psi.  Thank you to all who responded with helpful insight.

Ironman

215* is way too high! Set the limit to 180*.

1075NH

Ironman said:

215* is way too high! Set the limit to 180*.

The limit is set for 180 and that’s where the boiler stays normally. All summer too. It only gets that hot (above 200) when theirs a call for heat and the temp slowly creeps up. Then the heat call is satisfied and burner shuts down and the temp drops down.   

Ironman

It should not get above 180*, no matter what.
 You probably have a bad aquastat and a potentially dangerous situation.

1075NH

Ironman said:

It should not get above 180*, no matter what.
 You probably have a bad aquastat and a potentially dangerous situation. 

    I mentioned it to them that it should be changed out. That fact that I have it set at 150/170 and it shuts off at 180 leads me to believe the temp on the control is not accurate. Do they degrade over time??  It is odd that it has that occasional swing up that high. 

neilc

and not to pile on, but,
that tridicator is also showing 24, 25#,
not the 12 - 16 you mentioned above.
or is this only as the 215* shows?

EBEBRATT-Ed

As @neilc mentioned could be a bad tridicator showing false pressure and temperature....there both reading high

neilc

actually,
I'm more of a gage is correct guy,
both temp and pressure is discussed above us,
and I don't think OP is done chasing his issues.

EdTheHeaterMan

Sometimes, depending on the call for heat, then DHW then back to Heat, stacking can overheat the water near the temperature gauge but still be within the acceptable range of the Aquastat.

Now that you have diagnosed the air pressure in the expansion tank as the most likely cause of your problem, I would let it be for a while.

Many on this site would have you spend $$$ for unnecessary repairs, new gauge, new aquastat, new boiler... "it's not my money so I think you should spend it" seems to be an intrinsic phobia for some.

I still like to say If you replace that expensive part and it does the same thing, what will you check next? If the answer is a lot less expensive, then do that first!

1075NH

neilc said:

and not to pile on, but, that tridicator is also showing 24, 25#, not the 12 - 16 you mentioned above. or is this only as the 215* shows?

  Sorry about that. The temp test I did was before the new feeder went in. So far 2 days since the new feeder and pressure is great. 12-14 when boiler sitting at 180. At most creeps up to 16-18. 

1075NH

So it’s been about 48 hours since I did the new feeder and another really good purge of both zones as well as lowered the Aquastat to 160/140. Expansion tank is showing 14psi with 0 system pressure. 

 Since then water pressure is good. Sits at 12-14psi normal and no higher than 16-18psi hot. 

Temp is staying at 175-ish when the boiler is just sitting. Gets up to around 185-ish when calling for heat for awhile. 

  So I think (and hope!) the issues are over for now. Definitely something wrong with the accuracy of the control and she said maybe next month she will have the $$ for a new one. In the interim just lowering the High/Low settings by 20 degrees has compensated for the inaccuracy.  Is it uncommon for an almost 20 year old control to slowly lose its accuracy? 

  Thank you to all who helped out with some great insight. Very much appreciated. 

EdTheHeaterMan

20 YO control to be inaccurate is common, and not a real problem. You could leave it that way for years as on as you check it annually to see if it gets any worse. Only then would I replace it.

If you do decide to replace, consider this one. https://www.supplyhouse.com/Honeywell-L7224U1002-120-Vac-Oil-Electronic-Aquastat?gclid=Cj0KCQiAhZT9BRDmARIsAN2E-J2lOj0HwB_5BuWE8-yferBCXlmXz_Wn_4hpWloeeuIN_p4De_VipI8aAnpOEALw_wcB

it is more accurate, uses an electronic sensor, and is less expensive.

1075NH

The current control is a L8124A1007.  The one you linked is basically the same thing except it’s electronic vs the older relay style?  Would be a direct replacement and install the same way? 

SuperTech

The L7224U is a direct replacement for your original control. It would be a big upgrade over your malfunctioning aquastat.