I am having a couple of issues with my hot water boiler. The first is the pressure is rising to 30 psi as the temp rises to 220. The relief valve starts to drip when it gets this high.The aquastat is set to a high of 170. Does this (the aquastat) need to be changed?
The second problem i am having is occasionally my baseboard heat CRANKS with the thermostat as low as it can be set. (50) There are two zones on the boiler and the other zone does not do this. Could this be the thermostat? And would these two problems be related?

 

Welcome to the forum.
For your first issue, replace your pressure/temp gauge. They are reasonbly inexpensive and will give you a proper reading of what you are working with.

For your second issue, what type of t-stat do you have? If digital, have you replaced the batteries?
The issue could be many things, but that would be the first thing to look at.

 

The gauge was recently replaced along with the relief valve and the fill valve. The thermostat looks like original equipment from 1972.

 

I guess that takes the battery issue off the table.
Are your zones using control valves or a circulation pump per zone?
What does the t-stat of the affected zone connect to (relay box, directly to the aquastat, etc)?

 

There is a circulation pump per zone and i believe there is a relay box from the t-stats

 

What is the make/model of the boiler, and the fuel type?

What is the make/model of the installed aquastat?

When the boiler temp is at 180°, what is the pressure at that point?

What type of expansion tank do you have, and has it been 'serviced' recently?

You don't want to repair stuff just by throwing parts at it...

Have you checked that the sensing bulb is fully inserted into the 'well'?

When this is occurring have you noticed if the associated pump is also running?

It could. Troubleshoot by disconnecting it.

If it shuts down, it's likely the thermostat or a shorted thermostat wire.

If it keeps cranking, it's likely the associated relay sticking closed.

I wouldn't think so. The burner should cut off close to the high limit setting of the aquastat even if a zone keeps calling and calling.

 

The boiler is oil fired, Thermo Dynamics Model NYV100. Expansion tank is an Extrol Model # 15 12 psi. As far as I know it has'nt been serviced recently. Aquastat is a Honeywell not sure of the model #. It hasn't been touched recently so I don't think the bulb would be unseated. I just went down to check when it came on again. The pump was running at this point and the pressure was 10 with the temp being 190. I ran upstairs and disconnected the t-sat and the boiler kept running. When it finally shut off the temp was 200 with 25psi and it is now 78 degrees in my house.

 

10 PSI is way too low for 190°

The fact that when the water got 10 hotter the pressure rose to 25 tells us that one of the things you need to do is check the air charge in the expansion tank.

The #15 tank is probably marginally sized for the system. Might be OK as long as everything else is in perfect shape, but when the water gets too hot or the air charge is lost from the tank it starts to become a problem. I feel that a #30 is probably a better choice.

I'm willing to bet that the gauge is toast too...

Sounds like you have a number of items that need service all at once...

Read these two threads:

http://www.doityourself.com/forum/bo...ure-gauge.html

http://www.doityourself.com/forum/bo...sion-tank.html