Heatmaker Boiler Firing Intermittently

DanR132

I have a 1992 Heatmaker H.   The boiler is firing intermittently.  The house gets cold, check the unit.  The blower is running, but not the boiler.  Turn off the A/C power, turn it back on.  The unit goes through the normal startup and the boiler fires.  It runs and cycles OK for a couple days and then back to the mode where the blower is running but the boiler didn't fire.  Repeat power cycling and its OK again for a couple days.  Its done this 3 time so far.  Not sure if it as simple as a bad ignitor (current one is at least 5 years old) or if there is something else wrong that causes it not to fire all the time.

Steve Whitbeck

flow switch

more than likely a bad flow switch. It is the object left of the pump with the small copper tubes going into the top and bottom. They are a weak link with this boiler.

The blower and pump are running but until the flow switch closes the ignition wont start. next time the boiler acts up - carefully remove the cover on the front of the flow switch ( it is 24 volts under there ) be careful the idea is to NOT jostle the switch, Then with the cover off you will see a micro switch with I believe a red plunger. with a small tool push the red plunger in and the boiler should fire. This is not a fix it is a way to determine that the switch is the problem. It could also be a pump problem but those Grundfos pumps don't usually work on and off.

DO NOT JUMPER THE FLOW SWITCH - IT MUST BE REPLACED.

DanR132

No Flow Switch

My unit (H 130) doesn't appear to have a flow switch.  I looked up the part # and I don't have anything like that anywhere and the manual doesn't list a flow switch or that part # for my model.  Water lines goes through the pump.  Nothing else but wiring connected to the pump or inlet.  

Slimpickins

Heatmaker

It could be a lot of things. A bad stack switch, operating limit, safety limit, clogged coil, cross contamination, control. I would guess a clogged heat exchanger if its never been cleaned in over 20 years. Its not hard to clean, you might need a new ignitor gasket. The blower and flame trap gaskets will probably be ok to reuse. But really, you've gotten your money's worth at 21 years old and I would consider upgrading and I'd recommend the Triangle Tube Excellence.

Steve Whitbeck

Pressure differential switch ( pressure switch )

Both the H and the HW have the pressure switch.

Both wiring diagrams show the switch.

What you are describing is a pressure switch problem.

Slimpickins

press switch

Pressure switch problem = clogged heat exchanger

Steve Whitbeck

Pressure switch

A bad pressure switch does NOT always mean a plugged heat exchanger.

Those switches were a very bad design and just go bad. I have replaced many of them and the heat exchanger was clean inside and outside.