pressure /temp issues

Old 12-20-09, 01:28 PM
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pressure /temp issues

I was able to solve my ghost flow problem but wanted to ask about some system pressure issues
MY aquastat setting is 170 degrees on my Galaxy gg-75 during heating I get about 200 degrees and 30 psi on the pressure/ temp guage there is no release from the PRV. After shutting down the system and waiting a few hours my temp gauge went down to 90 degrees and 8 psi's . the pressure regulating valve is a 12 psi one . Does this temp / pressure sound normal I know that 12-15 is the standard . I am wondering if maybe the gauge is bad . Do thes e slant fin gauges lose accuracy the system is about 8 years old . thanks vavso

for system photos please see my thread below regarding ghost flow Its a two story home with 2 zones .y
Old 12-20-09, 03:14 PM
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No, it doesn't sound normal. Your symptoms suggest that your expansion tank has lost some of its air cushion.
Old 12-20-09, 04:11 PM
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Newbie suggestions that might just help

Hi Vavso,

As a disclaimer, I'm certainly a newbie when it comes to boiler troubleshooting...

However, I did just "solve" a very similar problem with my Slant/Fin.

I knew my pressure and temp gauges were accurate, as my pressure relief valve is a 30psi one, and just after reaching 30psi it would open... It would open after the boiler reached a bit over 200deg F (even though HI was set to 180), and just over 30psi...

I fixed it by:
  1. Replacing the expansion tank (may not have been necessary)
  2. Lowering the HI setting to 160, which translated to an actual high temp of ~180

I would guess that you may be able to solve the problem by lowering your HI so that the true high is closer to where you'd want it, and also:
  1. removing your expansion tank
  2. emptying any water
  3. hooking up a bike pump to it's fill valve and pumping it (while not connected) to whatever your boiler's stable temperature is (usually 8-15psi)
  4. Re-attaching the properly pressurized expansion tank

If you need it (or find it easier), IIRC, a new expansion tank is ~$60...

Good luck!

Last edited by ADaubman; 12-20-09 at 04:12 PM. Reason: spelling error
Old 12-20-09, 05:35 PM
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I drained the system recharged the expansion tank and boosted the aquastat up to 180 now the temp hits 205 then lowers down the psi's are showing 25 max. These are actually lower than when i was setting the aquastat to 170 . My only concern is as i start to bleed buildup air that the pressure will rise .

I am suspecting the gauge may be faulty i never jhave any release on the prv . If i wind up getting a new gauge I may get a new expansion tank at the same time .

BTW the pressure in the expansion tank was under 10 psi but i did the thumbnail water mist test the other day so may have released some pressure .

i was wondering if anyone would know the part # for a slant fin galaxy gg-75 boiler trhe part # slant fin shows does not show up anywhere on the net . i believe it may have a superseded #

Would there be any benefit to going up in size larger than the 2 gallon I have now ? If I get one ? I really appreciate your help thanks Vavso

Last edited by Vavso; 12-20-09 at 05:58 PM.

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