Boiler supplies hot water but no baseboard heat (pics attached)

KpR7

Hi there,
Hoping someone can provide some advice.
We have a Weil Mclain p-468-w boiler with one zone.
Right now, we have hot water in sinks, shower etc. but no baseboard heat.

When the thermostat is turned on, the boiler kicks on. The outflow pipe gets hot up until the flo control valve where the outflow splits into two separate baseboard lines. After this control valve, there is no heat in the pipes. (see picture)
The return pipe is also hot on the boiler side of the circulator pump, and there is some warmth in the return pipe just above the circulator pump but not too far up.

We've had some issues with air in the system in the past and the bleeder valves are attached to the baseboards (9 bleeders in total).
Just wondering what you think: an air bound circulator pump, bad flo control valve, something else entirely?

Any help will be much appreciated.

Thanks,
Kevin

STEVEusaPA

Sounds like your circulator isn't working, maybe in combination with not enough water in the system, air bound, stuck flow check. If you gauge is working, pressure looks a little low, can't really get a good look at it.
Are all the shut-off's open?
I assume column radiators. If you go to the highest radiation and open the bleeder, do you get water or air?

BDR529

Monoflow? Boiler feed stuck? Expansion tank is where? what's the pressure? Low limit set to high? New circ installed because of no heat? and everything Steve said.

Think you might have to call the guy.

Kickstand55

Hi Kevin,
Need more information.
Pipe above the circulator may be hot due to convection within the return pipe.
Should check what the others listed above.
If you're a homeowner, please only check the obvious things and don't get yourself hurt, scalded or electrocuted.
If you had a LICENSED tradesman there before and got less than satisfactory results, ask around. Who do your neighbors use? Are they pleased with their techs?
Stop by the supply house and ask the sales staff who they would use to service their systems.
It's worth paying good money to get a good job done than little or no money and have a disaster on your hands. Stay away from Handy Men unless you need a screen replaced or the dog house re-roofed.

SuperTech

I don't see any type of air elimination device on that boiler,  or the expansion tank. It may have a compression tank.  My first thought is that the zone is not circulating due to air in the system but I would need to be able to see more than whats shown in the picture. 

EdTheHeaterMan

I can see what appears to be a 3/4" supply pipe for the DHW tank coming from a Tee fitting from the boiler's internal air scoop tapping. the other side of the tee (straight up) most likely goes to a compression tank for expansion. The air in the system may go to the tank since it is connected to the air scoop fitting. Or the air in the tank may migrate by way of Henry's Law and Boyle's Law to a place where it will cause problems.

The return pipe from the DHW tank appears to be connected to a tee fitting at the boiler drain location.

This is unfortunate since the piping was all 3/4". Can't get all the capacity of the DHW system with feeding only a 3/4" pipe. I would have used 1" copper minimum. I would file that under "If it ain't broke don't fix it" for now. If you find you are not getting enough hot water in the future you can address that later.

I would like to see what is inside the Aquastat Relay. That is the gray cover box on the top right of the boiler with all the wires going to it. I'm guessing it has an L8148 control and was not equipped with a tankless coil. The boiler model number would have a T in it if it has a tankless coil. But if it has the L8124 control there could be an adjustment issue as mentioned by @BDR529.

I'm betting on a defective circulator or a defective electrical circuit to the circulator. (could be a loose wire or burnt relay contact)
This is indicated by the fact that no heated water is flowing past the flow control valve. If there was air in the loop, the circulator would move some water past the flow valve then stop moving water once the air pressure in the radiator loop reached the maximum head the pump could develop, the water flow would stop. So the supply pipe would be hot for a foot or two past the flow valve, then cold after that.

Circulator pump not moving at all is indicated by the lack of heated water on the discharge side of the flow valve.

But I could be wrong.

Merry Christmas
Ed

Limey68

Might be a separate issue but isn’t it a no no to have a shutoff valve in the hot feed line?
Thought that is a safety issue?

mattmia2

Limey68 said:

Might be a separate issue but isn’t it a no no to have a shutoff valve in the hot feed line?
Thought that is a safety issue?

There can not be a valve between the heated vessel and the relief valve, but isolation valves on DHW or DH supply are fine (and in many cases are required on DH).

EdTheHeaterMan

@Limey68

What @mattmia2 said!

Limey68

Thanks for the clarification