Furnace partially working, but not quite... let's just say it's not.

Abit2chili

I have a Vaillant hot water boiler (GA92-100 MV) w/ 2 zones that I am having some issues with. The other day we had some family over and one of them turned off the emergency switch for the boiler at the top of the stairs, we didn't notice it until the next morning when it was very cold so I turned the switch back on went downstairs and the boiler was working. It worked for maybe half an hour and then turned off and will not come back on. The pilot light is a continuous pilot light that does not go out and it's working, there's 120 volts coming into the control board and there's also 120 volts going out to the circulation pump. Both of the zones have 24 to 26 volts in that range going to them and both of the thermostats are commanding the two zone valves to turn on but on the two wires coming from the zone valves into the control board which would usually be about a 24 volt signal there's nothing, so I figured maybe there's an issue in the wiring and I wired up a new wire from the zone valves back down to the control board. It had 24 volts coming in for maybe 10 15 seconds and then dropped out and no longer gets 24 volts.

So I think there may be an issue there but I'm not 100%. I have not worked on furnaces before any help would be appreciated as it is a little cold out. I'm pretty handy electronically and don't have any issues testing the system

Jamie Hall

Be sure you run though the electrical logic on this. The zone valves take a signal from the thermostat which asks them to open -- this should be 24 VAC or thereabouts between the center (common) terminal and one of the side terminals when the thermostat is calling. The zone valve should open, and the voltage between the common terminal and the other side terminal should drop to zero (it could be anything with the valve closed); that's the end switch and it's closed when the zone valve is open. That closed circuit should, in its turn, tell the control board relay to fire the burner (assuming that the aquastat is also closed -- which, if the burner has been off for a while it should be, but is worth checking).

Abit2chili

Yes, between pin one and pin 2 on the zone valve on both of them there's about 26 to 27 volts you could feel them getting warm. Then between pin two and pin three on both of them there's continuity which means the zone valve is opened and I'm assuming working. 
Attached picture is where I traced the signal incoming going to and there is no voltage present there.

neilc

do you have your 24v at #3 on the zone actuators?
or is that the power that's breaking?
pull down on the manual levers, they should move freely if the zone is calling,
pull lever all the way down and it should make the end switch for #3,
maybe actuators went bad ?

Abit2chili

neilc said:

do you have your 24v at #3 on the zone actuators? or is that the power that's breaking? pull down on the manual levers, they should move freely if the zone is calling, pull lever all the way down and it should make the end switch for #3, maybe actuators went bad ?

At number 3 on the zone actuators it reads 27v it has continuity between pins two and three with the thermostat calling and the voltage is present on pins one and two or one and three. Both of the levers move freely.

neilc

pull the lever down all the way, firmly,
you should have 24v between 3 and ground,
pg3
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/555-050RP-brochure.pdf

EBEBRATT-Ed

Try putting a jumper across the end switch terminals on the control (where your red arrows show) the boiler should fire.

Also, when the emergency switch was shut off if the boiler was hot it could have tripped a manual reset limit control (if you have one). The circulator would have shut off with a hot boiler residual heat could have caused a limit to trip

Abit2chili

neilc said:

pull the lever down all the way, firmly, you should have 24v between 3 and ground, pg3 https://s3.amazonaws.com/s3.supplyhouse.com/product_files/555-050RP-brochure.pdf

Ok I did this and there is not voltage. I'm assuming ground you mean common or terminal 2. Would this have to be done with the thermostat off and the zone valve not warm because of the temperature contact inside?

Abit2chili

EBEBRATT-Ed said:

Try putting a jumper across the end switch terminals on the control (where your red arrows show) the boiler should fire. 

I've already tried that and with no 24v present there it does nothing.

"Also, when the emergency switch was shut off if the boiler was hot it could have tripped a manual reset limit control (if you have one). The circulator would have shut off with a hot boiler residual heat could have caused a limit to trip"

As for this I think you are talking about this??

There is 120 coming into it still and the circulation pump is getting voltage and running. Red is voltage in and blue is to the pump.

Ironman

What is the switch on the upper right side of the aquastat set to?

Abit2chili

Ironman said:

What is the switch on the upper right side of the aquastat set to?

It is set to Auto

Ironman

Place place the probes from your volt meter across the terminals behind the cardboard flap with the number “A5527” and see what you read.

Jamie Hall

The red and white wires with the arrows in the picture? With the zone valve open, there should be no difference in voltage between them -- 0.00, or very darn close. What they might be to common ground is either 24 VAC or 0; depends on how the system is wored.

Abit2chili

Ironman said:

Place place the probes from your volt meter across the terminals behind the cardboard flap with the number “A5527” and see what you read.

This is the reading.

Ironman

That’s the limit switch in the aquastat and it’s holding the burner off.

There should be a reset button in the hole where it says “Limit Control” but appears to be missing. 

Ed nailed it when he explained how the limit would trip from residual heat.

mattmia2

Is the button mounted in the cover?

Abit2chili

Ironman said:

That’s the limit switch in the aquastat and it’s holding the burner off.

There should be a reset button in the hole where it says “Limit Control” but appears to be missing. 

Ed nailed it when he explained how the limit would trip from residual heat.

I dug out the silicone that was in that hole and appears there is a screw in there and not a button. Is there any way of resetting this or does it have to be replaced?

Ironman

What’s the model of the control? Look on the cover.

Abit2chili

mattmia2 said:

Is the button mounted in the cover?

No the cover is just a cover held on by a screw no reset button.

Abit2chili

Ironman said:

What’s the model of the control? Look on the cover.

8d42a-704

neilc

I don't think we're looking for a reset,
OP said it ran for a 1/2 hour after switching the EM switch back on,

neilc

0 v across 2 and 3 at the actuators, or across H, H, red and white, at the boiler control suggest the actuator end switches are made,
but,
need to prove 24v to the control case(ground) at T, T, H, H,
check both red and white

Ironman

I can’t find any info on that control other than it’s obsolete.

It’s obviously the the limit switch that’s holding the gas valve off since there’s 24v across its terminals. There’s no need to check anything else.

Abit2chili

Ironman said:

I can’t find any info on that control other than it’s obsolete.

It’s obviously the the limit switch that’s holding the gas valve off since there’s 24v across its terminals. There’s no need to check anything else.

Ok, so my next step would be replacing the combination control unit or are individual parts replaceable? 

neilc

Abit2chili said:

I , , , but on the two wires coming from the zone valves into the control board which would usually be about a 24 volt signal there's nothing,
, , , It had 24 volts coming in for maybe 10 15 seconds and then dropped out and no longer gets 24 volts.

Ironman said:

It’s obviously the the limit switch that’s holding the gas valve off since there’s 24v across its terminals.

@Ironman , respectfully, 24 across terminals where?
and what reset, (that I don't see)

I'm guessing actuator end switch, both,
or lack of 24 at boiler control

OP, could you post picture of that entire label under the cover?
\wire diagram ?

Abit2chili

neilc said:

I , , , but on the two wires coming from the zone valves into the control board which would usually be about a 24 volt signal there's nothing, , , , It had 24 volts coming in for maybe 10 15 seconds and then dropped out and no longer gets 24 volts.

It’s obviously the the limit switch that’s holding the gas valve off since there’s 24v across its terminals.

@Ironman , respectfully, 24 across terminals where? and what reset, (that I don't see) I'm guessing actuator end switch, both, or lack of 24 at boiler control OP, could you post picture of that entire label under the cover? \wire diagram ?

neilc

I'm going back and editing my H H to T T,

Do you have 24v at both TT, to ground/controller case ?

Abit2chili

T2 to case is 5.5vac
T1 to case is 8.16vac

neilc

or,
if you have 24v across T T then your endswitches(therm) is open

Abit2chili

neilc said:

or, if you have 24v across T T then your endswitches(therm) is open

From t1 to t2 there is .087vac

neilc

Abit2chili said:

T2 to case is 5.5vac
T1 to case is 8.16vac

and what about across T T ?

pecmsg

You do not measure voltage to ground except to see if its dead. Measure across the switches.
List it as
1 - 2 is X
2 - 3 is X
3 - 4 is X

Abit2chili

neilc said:

T2 to case is 5.5vac
T1 to case is 8.16vac

and what about across T T ?

From t1 to t2 there is .087vac

Abit2chili

pecmsg said:

You do not measure voltage to ground except to see if its dead. Measure across the switches. List it as 1 - 2 is X 2 - 3 is X 3 - 4 is X

What switches are you referring to?

neilc

ok, well that's not it then,

the circulator is still running, correct?

this is still a power pile gas valve, correct ?
thermopile too weak to open valve?

same tests at V1 V3,
or,
TEMPORARILY jump V1 V3 wires at controller first,
see if she fires,
or then at the gas valve,

neilc

TEMPORARILY, like don't walk away with the jumper still on,

Abit2chili

neilc said:

ok, well that's not it then, the circulator is still running, correct? this is still a power pile gas valve, correct ? thermopile too weak to open valve? same tests at V1 V3, or, TEMPORARILY jump V1 V3 wires at controller first, see if she fires, or then at the gas valve,

Circulator working,it's power pile vs820a
Across v1 to v3 there is .024vac

Abit2chili

neilc said:

TEMPORARILY, like don't walk away with the jumper still on,

This has no effect on it does nothing at v1 and v3 and also at the valve

neilc

post a picture of the gas valve and its label,

pull the wire from V1 and test voltage in series from the wire, to V1,
I'm gonna need help from others on the voltage cuz I don't know what its minimum needs to be.

Abit2chili

neilc said:

post a picture of the gas valve and its label, pull the wire from V1 and test voltage in series from the wire, to V1, I'm gonna need help from others on the voltage cuz I don't know what its minimum needs to be.

.023vac 
Tag is hard to read vs820a

Jamie Hall

Abit2chili said:

neilc said:

or,
if you have 24v across T T then your endswitches(therm) is open

From t1 to t2 there is .087vac

Then your problem isn't with the end switches. 0.087 VAC is indicative of a closed circuit, which is what you want if the end switch is closed. The voltages from those terminals to ground is almost irrelevant -- it's amazing, but little appreciated, how varied the voltages in isolated wires can be in the presence of AC current (didn't used to be a problem, years ago -- you only had the problem with VTVMs with input impedance over 1 megohm -- anyone remember those besides me? Nowadays the big box multimeter has an input impedance that high -- and you can get some really wild results with them).

Problem has to be either the control isn't switching -- or the thermopile or gas valve isn't behaving.