1960s crane boiler aquastat temp set?

Jsmith94

I have a 1960s Gas crane boiler that has 1 zone and 1 circulator, just for hot water baseboards. I don’t get my domestic water from here. I was wondering what should I set my low circ temp and high temp on aquastat

EBEBRATT-Ed

Set high at 180-190. The low limit should be 135-140.

You shouldn't need a low limit if you don't get domestic hot water off it. Did it have a tankless coil at one time?

Jsmith94

I’m not sure about the tankless coil but if I 0 out low temp it will take a lot of gas to get temp back to 180 no? Higher lowtemp pops more 140 to 180 but doesn’t take as much gas? Compared to going on a cold start every time thermo is calling for heat . Does it even need to be as hot as 180 in 30 degree outside temp?

mattmia2

You will use gas in increments to keep it at a higher low temp or all at once to bring it from cold up to temp. if you keep it hot, that heat will have more opportunity to escape from the basement rather than be circulated in the system.

The upper temp will depend on what your emitters can output at that temp. You also need the supply hot enough to keep the return hot enough to keep the boiler from condensing.

Jsmith94

Well when I go from a colder start my pressure builds

STEVEusaPA

Do you have a triple aquastat, or separate high limit and low limit (reverse)?
Is your boiler maintaining temperature?

mattmia2

Jsmith94 said:

Well when I go from a colder start my pressure builds

What do you mean by this? as the water heats it expands and the air in the expansion tank should compress to allow for that expansion. The pressure should go up some, maybe from 12 psig with the system cold to 15-20 psig or so with the system hot but it should stay well below the relief valve setting which is typically 30 psig. If it rises to the point where it discharges water from the relief valve either the expansion tank has lost its air charge or is defective.

Jsmith94

Here’s the system. pilot keeps going out if there’s a low circ temp set. could it be a breeze Cutting of pilot? when I installed the thermocouple is it possible I slid it in to high?the thermocouple is maybe a inch above pilot piece. Expansion tank has a good amount of water in it but won’t drain easily

Jsmith94

Bump

Grallert

That boiler did at one time produce your domestic hot water. That's the reason for that low limit. It looks like you have the control set right for heating only.The boiler will never really get cold at that setting. Or I should say it's not likely to cool off much. Of course it depends on the size and type of emitters you have.
he airtrol on the tank there has a little bleeder valve on the bottom. if you open the boiler drain on the other end of the tank water will glug out slowly but if you then open the bleed valve on the bottom of the airtrol it will allow air in to replace the water as it come out. Assuming everything else is working properly that should restore the air cushion in the tank.

Jsmith94

When I loosen the airtrol a stream of water poors out no room for air to go in

mattmia2

Look at where the thermocouple is in the pilot flame. The flame should pretty well envelope the thermocouple. If the pilot flame is low or the thermoucouple isn't in the right distance or oriented right it won't make enough current to reliably keep the safety valve open. It also needs to be tight in to the valve body.

ch4man

Jsmith94 said:

When I loosen the airtrol a stream of water poors out no room for air to go in

good!, keep it open to drain off the extra water. once it spits air stop. that part of the valve has an inverted dip tube to 1/2 way in the tank to set the level

neilc

wait a minute,
do you have a way to isolate the compression tank from the rest of the system ?
or valve the boiler from the rest of the house?
couldn't see if so in the pictures,
otherwise you're draining down the whole house here, right?

Grallert

Jsmith94 said:

When I loosen the airtrol a stream of water poors out no room for air to go in

I think your expansion tanks is full. If you put a hose on the boiler drain, open it and then open the airtrol, the airtrol should at some point and relatively quickly start to pull air. Do this with the boiler off. The level of water in the tank could be higher than the top of the tube and under some pressure. Your boiler gauge should tell you what's happening with the pressure.