COMMUNITY FORUM

pwclarkeVT

08:39AM | 04/26/06
Member Since: 04/25/06
2 lifetime posts
Bvplumbing
P & T valve on boiler was leaking (approx 1 gal/day). Valve replaced twice (in case first was faulty) STILL leaks, but now only 1/4 gal/day. Same problem 2 yrs ago, P & T replacement cured problem util now. Where do I go from here? or more info needed? must sell house in next 2-3 months (my job "evaporated"!). Thanks for any & all responses.

Peter C.

Sylvan

09:34AM | 04/26/06
Member Since: 01/24/06
1529 lifetime posts
Me_office1
1- There is NO T&P on a "boiler" What there are is a pressure relief valve (Hydronics) Or a SAFETY valve (POP SAFETY) Steam or vapor System

A Temperature and Pressure Valve is located with in the top 6" of a water heater.

If this is what your talking about

1- Check to make you do not have a check valve or back flow preventer on the water main

2- As water get s hot it expands thus the T&P is doing its job.... relieving pressure

3- If the water temperature is excessive NEAR 210 DEG F. the T&P will respond.

I would first find out as to what you have either a hot water yank Or a "boiler" Then find out if it is STEAM 15 PSI MAX or hot water .. Depending on system design what the relief valve is set at.

Sylvan

09:34AM | 04/26/06
Member Since: 01/24/06
1529 lifetime posts
Me_office1
1- There is NO T&P on a "boiler" What there are is a pressure relief valve (Hydronics) Or a SAFETY valve (POP SAFETY) Steam or vapor System

A Temperature and Pressure Valve is located with in the top 6" of a water heater.

If this is what your talking about

1- Check to make you do not have a check valve or back flow preventer on the water main

2- As water get s hot it expands thus the T&P is doing its job.... relieving pressure

3- If the water temperature is excessive NEAR 210 DEG F. the T&P will respond.

I would first find out as to what you have either a hot water yank Or a "boiler" Then find out if it is STEAM 15 PSI MAX or hot water .. Depending on system design what the relief valve is set at.

Sylvan

09:45AM | 04/26/06
Member Since: 01/24/06
1529 lifetime posts
Me_office1
Part 2

If this is a hot water system and the relief valve leaks the following are the possibilities

1- Automatic feeder is set to high (12 -15 PSI)

2- The tank less coil may have sprung a leak and your getting supply pressure in the system

3- the Expansion tank may be water logged

4- The diaphragm tank bladder may have lost its charge

5- A run away firing condition building up to much temperature thus you have a pressure temperature relationship where the pressure becomes excessive

6- Check the pressure /attitude / temperature gauge (tri gauge)

pwclarkeVT

10:16AM | 04/26/06
Member Since: 04/25/06
2 lifetime posts
WOW! that was fast response! Sorry for inaccuracies! It IS a boiler (hot water baseboard heating), so must be just PRESSURE, as you suggest (boiler ALSO does "feed" a water2water water-heater, but this is NOT any problem). New valve says it is 30 psi. There IS a backflow valve on the cold incoming water line, plus a pressure reducer valve with range 10-25 psi & "recommended" 12 psi, don't know ACTUAL. Also don't know ACTUAL temperature, but do know no-one has changed it for years! (thermostat could have "died" though). Diaphragm tank was replaced approx 2 yrs ago, but again, could have since "died". Part 2, point 5 -- I don't think I have a "runaway" as I have stood by it for some time, and it seems to cycle at what I (non-plumber that I am) might expect (i.e. not too long). Are'nt points 3 & 4 (Part 2) referring to the same tank? Looks like I need to measure pressure on "outlet" side of "automatic feeder", and temp of water exiting boiler. Will gather instruments & check 'em out tonight. Thankyou very much for your assistance.

G'day for now.

Sylvan

03:49PM | 04/26/06
Member Since: 01/24/06
1529 lifetime posts
Me_office1
OK Class is in

Now we know you have a hot water boiler as opposed to steam we have a better understanding of what the bloody heck is going on

The PRESSURE for a 30 # Relief valve should not have a feeder that is capable of 25 PSI

WHY? BECAUSE I said so!!!! and here is my reasoning

As the temperature rises so does the pressure

The thermostat is nothing more then an on and off switch and has nothng to do with the relief valve going off unless this device is constantly calling for heat and the controller on the burners stick in the on position firing away 24 - 7 which you stated was not the case.

So the problem most likely is as follows

Let start off with some theory so you can better understand the workings of pressure.

Figure an automatic feeder has a set point between 12- 15 PSI WHY these numbers and not 40 -80 PSI?

We know that 10 PSI will elevate water to a height of 23.10 feet (IN New York City not sure about the rest of the country)

Now we can measure the top of the boiler to the highest radiator/ baseboard and say ok we have X amount of feet HOW MUCH PRESSURE WILL WE NEED TO Get to the upper most location?

So we have two choices?

1- Measure it

2- Cold fill the boiler look at the altitude gauge and set the little arrow to this mark on the tri indicator gauge

(Pressure - temperature - Altitude)

Now we have a great starting point

We know from the cold fill that we have say 25 feet on the altitude measurement and we take this 25 feet and TIMES IT by .434 which equals 10.85 PSI which means water will possibly trickle out of the highest radiator / baseboard

NO GOOD to say the least.

SO We say ok we have 10.85 STATIC pressure means we have to increase the pressure of the feeder to over come friction losses and we do want positive pressure to keep air out.

So lets add a few pounds to say 12 PSI and times this by 2.31 = 27.72 PSI good BUT not quite enough as we like to have at least 4 PSI more to give us a fudge factor

Now lets try 15 PSI times 2.31 =34.65 feet kind of high I would think so lets compromise and try 13 PSI as we do not want full feeder pressure and the min. is not quite enough.

13 PSI = 30 FEET which gives us a good positive pressure without over doing it

30 FEET = 13 PSI (do the math)

Now we have these boring facts what is the actual system pressure going to be?

We wont know that until we fire it up and see how much the heated water expands when we get to the SET POINT of the aqua stat on the operating controller.

As long as we do not go into the RED (30 PSI) we are in great shape

We already sized our expansion tank by the BTU input and gallons and height of this system so we know that this tank will take up some of the expansion that the hot water creates.

PLAY by the numbers and all will work out the rest is just plain mechanical junk that can be learned in a few minutes of on the job training.

The real key is punching out this technical stuff that allows plumbers to get a a Mercedes , smoke cigars and tell folks about the joke how plumbers make more then doctors BUT in fact its not a joke.

Have a great one and feel free to E mail me anytime. Sylvan LMP


npknjaoxu

12:02PM | 11/29/12
Member Since: 11/28/12
1 lifetime posts
Click_to_reply_button Inspiration_banner

INSPIRATION GALLERY



Post a reply as Anonymous

Photo must be in JPG, GIF or PNG format and less than 5MB.

Reply_choose_button

captcha
type the code from the image

Anonymous

Post_new_button or Login_button
Register

Follow_banner_a
Newsletter_icon Google_plus Facebook Twitter Pinterest Youtube Rss_icon
 
webapp1