Boiler pressure too high, replaced several parts already

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  #41  
Old 02-03-18, 02:07 PM
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Originally Posted by AllanJ View Post
Can you get the cold system pressure to be 10 PSI instead of 15 and stay that way?

I am led to believe that if the system now runs between 15 and 30 then after you drained some water out to lower the pressure to 10 then the maximum high temperature would also be double, namely 20.

The significance of the 180 degree temperature limit you gave is that, to me that means the water is not producing steam that would make the relationship between minimum pressure and maximum pressure less predictable.

At 10 PSI there may be difficulty keeping second or third floor radiators working so a cool pressure of 10 might not be realistic to live with.
A,
I may be able to, at least while the manual water valve is closed. When the valve is open the cold system pressure seems to be moderated at about 15 by the pressure reducing valve. I have turned the screw to try to lower the pressure in the pressure reducing valve (when one of the working ideas was that the water pressure in the house was too high and somehow causing the pressure to go up by water continually be let into the expansion tank -- however given the pressure is still going to 30 with the manual water valve closed I think that theory is now officially debunked) and it is possible I could put it at the minimum pressure position and get it close to 10 but not sure..when I turned it too far it basically went to 0 when cold.

All that said, it still seems like I shouldn't have such a big swing in pressure? But perhaps what you're saying is as long as it doesn't keep going up to 30 and potentially tripping the pressure relief valve/stressing the system then it isn't that big of a deal? I will say that the 10 degree difference between high and low is more based on the temperature I am trying to go to/from -- said differently if I wanted the house to be warmer and say go from 62 to say 67 or 68 in the morning (vs just 64/65), I definitely think the pressure swing would be higher than 10 psi. It had been in the past and I've now tried to minimize the temperature swing to put less stress on the system while I troubleshoot this.
 
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  #42  
Old 02-03-18, 02:57 PM
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B,
Not to be unduly harsh but please disregard any and all info about lowering your pressure to 10 psi. It is too low for any hot water system and you'll have nothing but problems.

First of all these come factory set at 12 psi for a reason and that is the minimum.

Taco recommends 20 psi to eliminate possible cavitation in the pump.

Enough said.
 
  #43  
Old 02-03-18, 09:59 PM
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"enough said."

Okay, scratch my suggestion of trying to run the system at 10 PSI cold.
 
  #44  
Old 02-09-18, 06:31 AM
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Over the last week I had the manual water valve closed and the pressure seemed to consistently stay between a low of about 15 psi and a high of about 25 psi when the boiler was hot. I opened the manual water valve yesterday just to see if it had any effect and it now seems that the high psi is about 30 (it went to around 30 psi twice now, yesterday afternoon and this morning). I don't think there has been a change to the low/cold psi.

It doesn't appear that in either case, with manual valve closed or open, that the relief valve has needed to release any water.

I'm about to decide on trying a #90 expansion tank, but wondering if this may indicate my problem is more than just the tank.
 
  #45  
Old 02-09-18, 09:15 AM
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B,
15 to 25 psi, although a safe range is a wide span and to me says the tank is too small for the system.

If you wanted to run your system at 20 you would be in trouble.

The fact you opened the manual valve should have no effect on the boiler pressure going to 30 psi unless water is getting by the feed valve. With the manual valve open over a period of time check your cold pressure to see if it is still at 15 or if it climbed. It may just be dripping in and may take some time.

Your system, if it has proper expansion, should climb no more than a couple of pounds if any at all.

I would do whatever you feel comfortable with.
 
  #46  
Old 02-09-18, 02:19 PM
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Thanks Spott, I appreciate the insight
 
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