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Real on line help with a no heat problem.

Below is the open dialog between myself and a man named Mike I removed his last name and email address. The first part you see is the the no heat form that I receive when the form is sent. the rest is emails sent back and forth between myself and Mike.
MIKE WROTE I NEED HELP! I am having trouble with my heating system.  My pressure release valve had been blowing off towards the end of last winter.  I shut the system down for the summer and recently made several repairs. I put a new expansion tank on the system, replacing the old one. I replaced the pressure release valve I was even told that the thermostat in the relay must be shot, so I replaced the relay in question with a Honeywell relay. I have 2 zones, and 2 relays.  I replaced the one for the first floor since pressure release seemed to blow off when first floor zone was working. I also replaced the fill valve last year. Thinking that I beat the problem, I replaced the relay today, purged the system and fired her up. The pressure quickly rose to 30 psi, temp to 210f.  I heard the expansion tank making a "BOILING" sound.  I shut the system down before the release valve blew off.  I am pretty handy and can fix most problems, but this one has me a little perplexed. 
One little footnote:  My temp/pressure gauge looks fairly old. Could that be the problem? It seems to work fine! If you could help me, I would greatly appreciate it, and I would love to donate to the site, there should be more like this one on the net.  Thank you

MIKE: Tom, i am not quite sure but I may have found an obstruction.  I felt a little resistance and was able to push right through it.  I got the hanger in all the way until it bottomed out.

TOM: Good go back and forth a little with the hanger, so that if there was a obstruction, you break the rest of it away, and we have more then just the diameter of the hanger. Then put the auto vent back, turn the 2 ball valves above the circulators to the off position, then turn the water back on. you should hear the water going into the boiler and you should hear air coming  out of the auto vent. let me know if you hear the water and the air, and what the pressure is when you no longer hear the air venting and the water filling.

MIKE: I worked the hanger then replaced vent, and filled system with valves closed.  I heard the water and alittle bit of air. once filled the system is at 25psi...(the ball valves are still closed)

TOM: Ok the fill valve is letting too much water into the boiler. But don't worry about that right now. take a hose. and hook it to one of the boiler drains above one of the circulators. run the other end of the hose to a drain or out side. then open the boiler drain. then open the ball valve for about a  minute, (till you get a good flow of water) then turn the ball valve back off, and let the water flow out of the hose till you get a good flow of water, this will take a minimum of 15 minutes, do not turn it off to soon. make sure the boiler pressure does not go below 10 psi when you are doing  this, control the flow by closing the boiler drain some. do the same with  the other. I need to run to the store .I will by back in about 1/2 hour.

MIKE: Ok I let the water run through the hose from both zones for about 15 mins. on the first floor zone and a few minutes longer than that with the second zone. the pressure never went below 12-15 psi while doing this, and when i shut valves off psi went back to 20psi.  both ball valves are still closed.

TOM: Ok  Now turn the water off again. and relieve water till you have 12 psi, open the 2 ball valves and turn the boiler on again. Again. don't leave the boiler.

MIKE: Tom, same result, took a while for pressure to build up this time, but it eventually blew off again.....i have a question about the air vent before the expansion tank. The one I put on there yesterday has a plastic knob on top. Is that knob supposed to be tight or loosened. It is currently tight.

TOM: It is supposed to be loose. Loosen it and let me know if any more air comes out.

MIKE: i loosened it, a lot of air came out, then water.

TOM: Where Does the boiler feed pipe connect to the system? Also what was the temperature when the relief valve blew.

MIKE: The temp I believe was around 200, the boiler feed pipe?  Is it the pipe pushing the water to the baseboard, if so it is on the left side of the boiler, if you are looking for the pipe coming in from the town water, it is located on top of system.

TOM: I'm sorry I meant the pipe from the fill valve.

MIKE: when the system blows off it dumps about 1-2 gal of water and a lot of steam.  as far as the pipe from the fill valve, it goes into the top of the boiler

TOM: Ok, now I think I see the whole picture, sorry it took so long. I made the mistake of assuming the air vent was open all along, this cause me to make extra steps. This is what is going on. The boiler was not full of water, even though we filled the lines, because of the air vent being off very little water got into the body of the boiler. now that you have opened the auto vent. the boiler is full. Keep the air vent loose. bring the pressure back to 12 psi. and fire it up again. you should not have any more problems. but stay with the boiler till the aquastat turns it off. About 180. It went over the 180 make before because the aquastat was not in the water, because the  boiler was not full.

MIKE: should I open the water fill valve to re fill the system?  And after I do, should I shut the valve and bring the psi down to 12

TOM: just open it till you get 12 psi. once we pass this last test we may need to  re purge the lines.

MIKE: pressure valve blew off again, this time at 220 degrees and 35psi, the whole time the system was running, the air valve was blowing steam.

TOM: Ok We may have another problem. Are you sure you left the air vent open? did you do any wiring when you replaced the relay?

MIKE: the only wiring I did was removing the old relay and replacing it, I marked all wires to make sure that the wiring was done the same, to the same terminals on the new relay..could the problem lie in the Aquastat?  I cant figure this damn problem out!

TOM: Yes it can be the aquastat in the jacket. but first I have to be absolutely  sure the boiler is full of water before we move on. Just so that you understand sometimes there are more then one thing causing the problem. Next step. open the auto vent all the way. turn the fill valve on, and leave it on. then on the gas control valve, the one with the pilot tubing attached to  it. turn the knob to the pilot setting. then turn the power on and tell me  if you can hear water circulating through the
baseboard pipes.

MIKE: I opened the auto vent completely, opened water fill valve, turned gas to pilot and turned system on.  I did not hear water circulating, the only thing I heard was water filling the system when I opened fill valve but that only lasted a few seconds

TOM: Did the circulators come on? do you have the thermostats up all he way?

MIKE: i didnt hear the circulators come on and the thermostats in the house are way up

TOM: Ok we have to address this too. remove all the control covers and send me pictures.

MIKE: the older box is a white Rogers relay and the new box is a Honeywell, that replaced a white Rogers.  I got it at supply house that said it was same specs as the white Rogers.

TOM: Try turning the aquastate down as far as it goes And turn the gas valve on again. and run the boiler. if it gets to 180 turn it off.

MIKE: it took a few minutes to get there but it got 180+ degrees and didn't shut down.

TOM: Ok Last test. remove one wire from the aquastat then turn the power bask on. the boiler should not fire.

MIKE: removed a wire, did not ignite

TOM: Ok. the aquastat is no good. did you hear a click when you turned it all the way down? and are toy sure you turned it the right way?

MIKE: i turned it the right way, and didnt hear a click?  I can replace that asap.  But what about the amount of pressure in the system? Should I replace the fill valve or the check valve that is located before it?

TOM: Yes you will need to replace the fill valve, please send a picture of that, so that I am sure we are talking about the same thing. also you should get a strap on aquastate as well as the replacement aquastate. the strap on one should be strapped to the lowest point of the pipe coming out of the top of  the boiler going to the baseboards. follow this link to see an image.
 the strap on should be set about 5 above the main aquastat. this will be an important safety setup. if the main one fails again the secondary one will turn the boiler off. Earlier you said the circulators were not working, I noticed 3 switches by the boiler. I assume 1 is for the boiler and the other  2 work the 2 circulators. Did you have all the switches on?

MIKE: i had all the switches in the on position earlier.  I will take your recommendation with the strap on aquastat.  Should I replace the fill valve and the check valve

TOM: you may not need to replace the back flow preventer. just the watts fill valve. it should be fairly easy. another note. you may want to get the type of strap on aquastat that has a manual reset switch. this will let you know  if there is a problem with the primary aquastat. You should also clean the burners on the boiler. they look very dirty. And if you do not have a carbon  monoxide detectors in your home, you should get them. I recommend you get  the ones that have a digital display. Do you want to try to figure out why  the pumps were not working?

MIKE: i will clean the burners, replace the valve and get the strap on aquastat...i am heading to store right now to get these things.  I will update you when I get them in place

TOM: Where will you get them on a Sunday evening?

MIKE: Tom, I tried home depot, yesterday I was surprised at the selection of parts they had...tonight was a different story.  I did not find anything.  I will be heading to supply house in the am.  I will get in touch with you tomorrow evening to update you on the progress.  Thank you for your help today, it is a fascinating service that you provide.  I look forward to talking to you tomorrow

TOM: Thanks I'm glad you don't feel we wasted a lot of time today. I should be home most of the day tomorrow, so if you have a problem, let me know. One thing you should do tonight is, remove the old aquastat, the reason is sometimes you can not get the probe out of the well, if this is the case, it's better to know before you go to the supply house, so that you can get a  new aquastat well at the same time. and If you do have to replace the well. you will need a good pipe wrench at least 14", It is unlikely you will be able to remove the well with channel locks

MIKE: Tom, I think we are now alright.  I replaced the backflow valve, fill valve and aquastat.  I asked about the strap on aquastat and the supply house did not have one in stock but they are having one shipped from another location to their store tomorrow. 
I filled the system, lowered the pressure to 12 psi and turned the boiler on.  I let it run a while and
when temp got to 180+ degrees, the boiler turned off. I felt the taco circulators and felt each of them moving water.
Should I now purge the system.  If so, should I purge by opening the fill valve, run the water, open the ball valves for a minute until good flow, close ball valves then run the water until I see a good stream. Once this is done should I close fill valve, and lower the system to 12psi, or just stay at the psi that the fill valve fills the system to..(20-25psi)...MIKE

TOM: If you replaced the fill valve the pressure should not go that high, maybe the gauge is off a little. leave it on and see what happens. but as far as the purge goes you have the right order. Do it with the power off.

MIKE: i have one question.  The first floor does not seem to be warming up.  the pipes heading to the first floor are cool and it doesnt seem like the taco circulator is sending water around.  last night it worked fine during the tests?

TOM: Did you purge it yet?

MIKE: yes

TOM: is the thermostat still turned all the way up, and did you open the ball valve?

MIKE: ball valve open, thermostat up...circulator feels like it is running, and feels hot but pipe above it is not.

TOM: Did you purge for 15 minutes with the ball valve closed?

MIKE: purged for app. 10-15 mins

TOM: Are you sure you got all the air out.

MIKE: i will purge again...should i purge just first floor

TOM: Yes be sure to turn power off, and do the 1 minute with the valve open then with the ball valve closed for a minimum of 10 minutes then till there is no more air. If you raise the flag on top of the new fill valve the water will flow faster, but make sure to put it back down before you turn the boiler drain off.
MIKE: tom, i purged the lines for about 25 mins. I then started the system back up.  boiler is working great, but water is not circulating throughout first floor. I don't feel hot water beyond the taco valve.
TOM: Ok the taco valve you are talking about, it's not a zone valve right? it's a  flow valve? is the pump still getting hot? If the line is full of water, and the pump is hot, and water flows good with the ball valve open or closed. and the water is not moving, the pump is bad also. if the pump is not hot  you need to make sure there is power going to the circulator. and that the  heat you feel is not just from the hot water.
MIKE: I think I know what the problem is now. I believe that I have the wrong relay.  The new one that i have on the system has a full load current of 7 amps and a locked rotor current of 44 amps, the old one had a full load current of 12 amps and a working current of 72 amps...could this be my problem...there was power at the circulator but it was not working good, I realize now that it was moving water very slowly...
TOM: The taco pumps only pull 1 amp. it is more likely the impellers on the pump are shot. you should replace the pump.
MIKE: After replacing the aquastat and a Taco circulator, I purged the system and fired it up.  It took some time for the first floor to heat up, but now everything seems fine. The system pressure is still pretty high between 24-30psi. but I think that the gauge is not right. I really appreciate the help.


TOM: I would be glad to help you, Can you send me pictures of the boiler and all the controls.
MIKE: Here are some pictures, if you need more I can send some.
TOM: Good morning Mike. There should be another aquastate in the jacket of the boiler. can you remove the front door and send pictures of the controls in side the door. The one in the door is the one that controls boiler temperature. Let me know if you would like me to call you, and what would be  a good time.
MIKE: Tom here are the pictures that you requested.  I really appreciate the help, it is cold as hell here this morning.  I will be heading out to breakfast with my family and I will be back in an hour. Thanks again.
TOM: Hi Again Mike. The Aquastate is set too high. turn it down to about 180 then  start the boiler. and see how hot it gets before it shuts down. This is just one possible reason for the problem you are having. stay with the boiler till you see it turn off. and be sure, it turned off because of the aquastate and not the thermostat. also tell me what the pressure is before you turn it on and what it is when it turns it's self off.  
MIKE: Tom, I turned temp on aquastate down to 180 then turned system on.  The starting pressure was 25psi. It quickly rose to 30+psi. At that time, the expansion tank started making the boiling sound.  I turned the system off because it is at this point where the pressure release valve had been blowing off.  I also checked the baseboards on the first level and noticed that they were not heating up.  I know that the system was only running for 5-7 mins, but shouldn't the baseboards begin heating by then...Thanks 
TOM: Ok the pressure is too high to begin with. I don't see the boiler fill valve  in any of the pictures you sent me. Find the fill valve. ant turn the water to the boiler off, then drain some water out of the boiler till you only have 12 psi. then start running the boiler again. and again note the  starting pressure and what it rises to when it is heated. And Very important do not leave the boiler till you see it shut off by way of the aquastat.
MIKE: tom i am now down to 12psi, before i turn the boiler on do i re-open the fill valve or keep it closed?
TOM: For now keep it closed. we will open it after the test.
MIKE: Tom I started it at 12 psi. it ran above 30psi before release valve blew off.  I then shut down boiler MIKE.
TOM: Ok Mike. Now we are on to something. Remove enough water, so that the  pressure is 0 psi. do not drain the whole system at this time, then with the pressure at 0 psi, use a tire gauge and test the pressure in the expansion tank, It should be 12. Also tap on the expansion tank, it should sound hallow at the top.
MIKE: Tom expansion tank at 12psi., and sounds hollow. I only let out a little bit of water to get boiler pressure was at 0psi, and it does not appear that there is much water left in the system.
TOM: Ok, So far everything has happened as I expected. Be patient. and we will get this solved. Please send me a picture of the pipe that comes out of the  boiler and goes to the expansion tank, including the auto air vent.
MIKE: Tom, here are the pictures, the auto air valve is also new, replaced it yesterday.
TOM: Get a metal clothes hanger, remove the auto vent, and push the hanger down the pipe that the  auto vent was on. push it all the way down, about 20" If you feel an obstruction stab at it, it should break up. Let me know if  it goes straight through or if you felt an obstruction, and if you were able to pass through it.