Having a problem filling the system, pressure getting to high?

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Old 12-26-11, 12:06 PM
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Having a problem filling the system, pressure getting to high?

Hello all,

I have a WeilMcLain WGO 5 series 3, 152,000 buts hot water boiler hooked up to two cirulator run zones both have their separate loops (old gravity system but piping loops changes to 1 1/4" copper)

I just install this boiler, it was used about five years old. I installed the piping exactly as the old one a WeilMcLain P68 which petered-out.

I have an old home with three floors and radiators (lots of water in the system). At set-up I filled the boiler to 12 PSI cold but to get water to all the third floor radiators I had to go higher. The old system had to be filled to about 20 psi to get the third floor radiators to bleed, so I filled this system to 20 PSI but that only gave me water to just above the second floor. As I filled more while bleeding the air out on the third floor, the pressure just got too high for me, 25 PSI. So, I've been running the boiler just on the first and second floor with all the third floor radiators closed. I figure it may take a little time for the pressure to equal out as all the radiators have there own feed and return directly back to the boiler (loop for each zone, two zones-first flr one, second and third the other).

After a week or so running, I "slowly" added water to try to get the third floor radiators filled but the pressure keeps going up passed 25 PSI with system hot, still can't get the third floor filled...? The other boiler had no problem filling all the radiators and the press was around 20 PSI and never got higher than 25 when all three floors were hot. Same piping as this new boiler too.

I have an expansion tank (same one as the old system) above the boiler in the basement, it's a relatively large galvanize holding tank about 30 gallons. I notice that it's about a third to half full of water when first and second floors rads are full and hot, seems to be correct. The expansion tank is piped off a tap at the top of the boiler, 1/2" iron, the fill comes into that pipe and then the pipe now changed to 3/4" copper goes the expansion tank close to and right above the boiler.

One other note, I had some problems with the temperature/pressure gauge not reading correctly so I replace it with a WeilMcLain replacement gauge, brand new. Seems they were having problems and changed gauge style. The pressure reading on the new gauge goes form 0 to 360 (very wide range for max 30psi) so reading at 20 to 25 PSI it hardly moves a 1/16" if that, for five lbs reading difference. Wish I had a gauge that went form 0-50 for more accuracy.

Could it be that the gauge is reading five lbs heavy than actual pressure? Should I just fill the system to get water on the third floor and let the gauge go to higher? I guess I could watch the pressure relief valve on the boiler and if that doesn't blow or weep as I fill just enough to get water on third floor..?

Any advice appreciated.

Thanks in advanced,

al
 
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Old 12-26-11, 12:42 PM
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Hi Al,

I would first suspect the gauge.

You should be able to get water up to the third floor with around 17 PSI or so.

You can piece together a gauge with an adapter to screw onto a drain valve if you don't want to drain and replace the gauge on the boiler.
 
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Old 12-26-11, 12:43 PM
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Originally Posted by dadalee View Post
One other note, I had some problems with the temperature/pressure gauge not reading correctly so I replace it with a WeilMcLain replacement gauge, brand new. Seems they were having problems and changed gauge style. The pressure reading on the new gauge goes form 0 to 360 (very wide range for max 30psi) so reading at 20 to 25 PSI it hardly moves a 1/16" if that, for five lbs reading difference.
You're sure that you are reading psi, not kPa?(50 psi approx = 360 kPa).

If in fact the range of your gauge is 0-380 psi, ditch it and replace it with a Winters Tridicator, 0-75 psi range.
 
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Old 12-26-11, 12:45 PM
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Good catch Doug... I didn't even notice that!
 
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Old 12-26-11, 01:14 PM
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Originally Posted by gilmorrie View Post
You're sure that you are reading psi, not kPa?(50 psi approx = 360 kPa).

If in fact the range of your gauge is 0-380 psi, ditch it and replace it with a Winters Tridicator, 0-75 psi range.
Ha, thanks a lot, I feel like an idiot. There are two scales on the pressure side, not kPa but "feet H2O" on the outer dial and the inter is pressure from 0 to 60 psi. I was reading the feet H2O side, I actually had only 8/10 psi filled cold should be like Trooper says 17psi for three flr.

OK, I'll just slowly fill till around 20psi when warn/hot. I would assume running between 19 and 23 at the hottest would be OK? that's were the old one ran.

My dad an engineer would tell me the higher the pressure the faster the flow rate..

I've been freaking out trying to figure out why I had high pressure... and I'm reading "Feet H2O" BTW, what is Feet H2O? It goes from 0 to 300...?

al
 
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Old 12-26-11, 01:26 PM
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Glad you found the problem - and you're now on the 0-60 psi scale. But "ft of H2O" makes no sense to me. 300' water column is about 150 psi. If you post a good photo of the gauge dial face, maybe we can understand better.
 
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Old 12-26-11, 02:15 PM
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Pressure has nothing to do with amount of flow only vertical height. I hope you followed the new piping ideas and not the old boiler piping. You can get the I&O from the new boiler on line.
 
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Old 12-26-11, 02:37 PM
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Originally Posted by rbeck View Post
Pressure has nothing to do with amount of flow only vertical height. I hope you followed the new piping ideas and not the old boiler piping. You can get the I&O from the new boiler on line.
I downloaded the manual for the boiler and piped according, thanks. There were several ways and I picked the one similar to the old piping.

A far as the "Feet H2O", I think that represents the height of water the set pressure will produce...? At about 40 feet H2O the pressure reads about 20 PSI...?

al
 
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Old 12-26-11, 02:48 PM
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A far as the "Feet H2O", I think that represents the height of water the set pressure will produce...? At about 40 feet H2O the pressure reads about 20 PSI...?
Close enough for Gummint Work...

The exact numbers are:

0.431 PSI per FOOT

or inversely,

2.31 FEET per 1 PSI

So, to raise water to a height of say 30 feet, you would need 0.431 X 30 = 12.93 PSI (say 13).

Then, we always add 3-4 PSI as 'headroom' to make sure the top of the system always stays nominally pressurized. That's where the 17 PSI for a 3 story home comes in.

I would assume running between 19 and 23 at the hottest would be OK? that's were the old one ran.
Yes, that's fine. If it approaches 27 you need to start thinking about why.
It usually means the expansion tank is waterlogged or kaput.
 
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