Troubleshooting Honeywell aquastat relay L8148A

Reply

  #1  
Old 01-12-14, 10:03 AM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Troubleshooting Honeywell aquastat relay L8148A

Hi All,

I have a Weil Mclain boiler that uses a L8148A. I am getting no heat when any thermostat calls for it. My system is a 4 zone system that uses the typical Taco valves. I tried to measure 24VAC on pins 1 and 2 of my valves and found nothing there.

I have been reading all of the posts related to the aquastat to see if I can figure out if there is an issue with the valves/thermostat/aquastat... and I had some questions.

There seems to be a button on the aquastat that is part of a switching relay? If I manually push that, should the circulator pump turn on? (I push it and it doesn't seem to do anything.. is that correct, do I need to hold it down longer?)Also, if I try to measure across the TT terminals, should I be getting 24VAC? I do not read anything there, but I did not disconnect the wires to see if something in the external wiring is shorting.

Thanks in advance for any help.
Seth
 
Sponsored Links
  #2  
Old 01-12-14, 11:27 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Hi Seth,

Back up and stop pushing on stuff inside the aquastat.

You should measure ZERO volts between 1 and 2 on the zone valves when NO zones are calling for heat. When a thermostat calls, you should measure 24 VAC (nominal) between 1 and 2 on the zone that is being called for heat.

If you do NOT, it means that your 24VAC transformer may have gone bad, do you know where that is? Look on the wall or the ceiling around the zone valves. Probably mounted on a 4" utility box. There will be 120VAC INSIDE THAT BOX, DON'T KILL YOURSELF!

If your transformer is OK, the next thing to check is the voltage between terminals 2 and 3 of the zone valves.

When there is NO call for heat, you should measure 24 VAC (nominal), and when ANY zone calls for heat you should measure ZERO volts.

Do this and let us know what you find and we'll go farther if necessary.
 
  #3  
Old 01-12-14, 11:30 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
You have checked the circuit breaker to see if you have power to the system, is that correct?
 
  #4  
Old 01-12-14, 12:05 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Thanks.

Sorry, I take back what I said before, I can measure 24 VAC on the TT terminals.

I found the transformer, it measures 25 VAC. I measured all four zone values and each has 24 VAC on pins 2 and 3. Turning the thermostat for demand (heat on) did not change the voltage. ( I checked all valves for any change)

The furnace produces hot water, so that is powered.
 
  #5  
Old 01-12-14, 12:47 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Sorry, my last reply wasn't complete.

On pins 1 and 2, I do get 24 VAC when demanded and 0 when not. I can feel the heat on the head from the wax heating on the inside too.

Let me revisit the pin 2-3 measurements again.
 

Last edited by huskerdooo; 01-12-14 at 01:22 PM.
  #6  
Old 01-12-14, 01:35 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Turning the thermostat for demand (heat on) did not change the voltage. ( I checked all valves for any change)

Let me revisit the pin 2-3 measurements again.
It won't be immediate... those valves can take a couple minutes to open.

But if you measure nothing at 2 and 3, then go to the aquastat and with NO HEAT CALL, measure across the " T T " terminals in the aquastat. You should measure 24 VAC (nominal) there. When any one of the valves open, the T T terminals should measure ZERO.

Be aware that there is exposed 120VAC inside the aquastat as well.. so BE CAREFUL! DON'T GET KILLED!

If you measure nothing at the T T terminals, then measure the L1 and L2 (may be labeled 1 and 2 ) for the presence of 120VAC --- again, BE CAREFUL!

If you have no 120 VAC at L1 and L2, it means that something is wrong with the AC line coming in... those terminals are where the power connects to the aquastat to run the boiler.

You did check the breaker in the panel, correct? I know it's a dumb question, but I have to ask.
 
  #7  
Old 01-12-14, 01:56 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Thanks,

Ok, I had some confusion because my wife had changed one of the other thermostats.. the 2-3 output is in parallel and having another thermostat calling for heat messed up my pin 2-3 measurements. Ugh, I thought I was going insane.

So, the voltages on the Taco seem correct with and without demand. On demand after the warmup, pins 2-3 go to zero... then back to 24 when cool. Pins 1-2 at 24 VAC with demand, 0 without.

Same goes with TT.. this looks ok too. With demand zero, no demand 24 VAC.

I have 115 VAC across L1 and L2.

Where next?
 
  #8  
Old 01-12-14, 02:19 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
OK, so zone valves seem to be working properly, and you have power to the aquastat.

So far so good...

When any zone calls for heat, does the relay switch in the aquastat case "click" closed?

If it does click, do you hear the circulator pump start... and the oil burner does not?

Tell us exactly what happens at the boiler when you call for heat.
 
  #9  
Old 01-12-14, 02:23 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
If the relay switch DOES click closed, CAREFULLY measure for 120VAC at the C1 and C2 terminals, and also measure for 120VAC at the B1 and B2 terminals. You should have voltage at both when there is a call for heat, AND the boiler is cool (below the high limit setting of the temp dial inside the aquastat).

If the boiler is HOT (which we know it is not at this point, but for reference purposes) the burner may not run. It should turn off when the water reaches the limit setting.

As long as a heat call continues, you should have power to the C1 and C2 terminals (this is where the circulator pump is wired).
 
  #10  
Old 01-12-14, 02:50 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
No click, no pump action (in the past I have been able to feel it vibrate slightly when running, nothing now). Nothing seems to happen at all on the boiler.
 
  #11  
Old 01-12-14, 02:59 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
That's odd...

Here's why:

You have power to the aquastat, and by measuring 24 VAC at T T terminals when there is NO heat call, you have proven that the internal transformer in the aquastat is good. You have also proven that the relay coil is intact and by all rights, there is no reason for the relay NOT to click in.

When a zone valve calls for heat and you see the voltage at T T go to zero, that relay must pull in.

I don't see any reason for it NOT to at this point.

You also said earlier that you pushed on something? Was that the top of the relay? When you push that in manually (which is for testing purposes only, technically you shouldn't really do that...) the burner and pumps should come on.

In other words, what you are saying is happening (or not happening) is not possible...

If you had said that the relay DOES click and nothing happens, that I can grok... if you had said that there was no 24VAC, again, understandable... but to have the 24VAC and NOT pull in... doesn't make sense... and pushing the relay manually closed and nothing happening doesn't make sense either.

I dunno man, ya got me!
 
  #12  
Old 01-12-14, 03:07 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
As a last resort:

CAREFULLY place a wire jumper between the T T terminals. Just short them together without getting across the 120VAC and hurting yourself (or the boiler).

Relay should click and boiler start.
 
  #13  
Old 01-12-14, 03:36 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
I am very confused on how the system works. I have been battling the boiler all day today because it happens to go on for the hot water...it will cycle I believe to keep the hot water coil hot? The relay does click in for that.

Does the circulator pump get used for making hot water and heat? Or just heat? My current suspicion (not knowing how this thing really works) is that the pump is not working. If this is the case, my theory would be that the coil temp/furnace temp is happy and when commanded it doesn't go on because it is already up to temperature (E.g., with the pump not circulating cool water into the furnace, it wouldn't go on?)

I had actually jumpered TT early in the day with noting happening.
 
  #14  
Old 01-12-14, 03:54 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
it happens to go on for the hot water...it will cycle I believe to keep the hot water coil hot? The relay does click in for that.
Say what?

Are you sure you have an L8148A ?

It's not an L8124 ?

It IS an oil burner, right?
 
  #15  
Old 01-12-14, 04:02 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
I think it's time for you to take some pictures so I can see what you're working on.

Once I know what you've really got there, I can probably get this straightened out.

Does the circulator pump get used for making hot water and heat? Or just heat?
If you've got a coil inside the boiler for hot water, then the pump will run only for a HEAT call.

My current suspicion (not knowing how this thing really works) is that the pump is not working.
You should still get a 'click' when there is a heat call, whether the boiler is up to temp or not.

I need to know exactly which aquastat you have before commenting on the pump action because it's quite different if you have an 8124 and not an 8148.

Are there any OTHER temperature controls on the boiler in addition to the 81xx ?

Is there a wire on terminal 3 to another control? and if there is, the internal 'jumper' between L1 and terminal 3 will be removed.
 
  #16  
Old 01-12-14, 04:06 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Oh God. I am not sure. The cover on it is gone and the label on the back is worn too much to read. I tried to look up the PN from using the type of furnace... maybe I messed that up. I'm so sorry if this confused all of the posts. It is an oil burner Weil Mclain.
 
  #17  
Old 01-12-14, 04:09 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Hold on, I will check this out. Our two posts crossed... I will see if I can get a pic.
 
  #18  
Old 01-12-14, 04:35 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
Images

Name:  photo2.jpg
Views: 8220
Size:  40.0 KBName:  photo1.jpg
Views: 12368
Size:  42.8 KBName:  photo.jpg
Views: 7010
Size:  32.1 KB

Here are some photos of the setup.
 
  #19  
Old 01-12-14, 04:42 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
OK, that's an L8124A.

Let me regroup for a minute.
 
  #20  
Old 01-12-14, 04:48 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
In the meantime while I'm thinking...

What is all the drippage on the burner swing door? If that's leaking from behind the coil plate, you need to get that fixed. Let that go and it won't be fixable from all the rust around the coil plate. It needs a new gasket installed. Fairly big job.
 
  #21  
Old 01-12-14, 04:52 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
It still does not make any sense that with the 24 VAC at the T T terminals that the relay is not pulling in when you short those together...

But I'm gonna say that whether it makes sense or not, you are probably looking at a new aquastat.

In ANY case, that relay should be pulling in when there's a heat call.

I just don't have that 'warm fuzzy AHA!' feeling about declaring this aquastat bad... the diagnosis just doesn't make any sense.

It seems that there are MULTIPLE problems. It's not your typical 'one or the other' problem.

Even if the relay isn't pulling in on a heat call, the boiler SHOULD fire up when you manually close the relay.

I would recommend this as a replacement :

48-3250 - Hydrolevel 48-3250 - Model 3250 Fuel Smart Hydrostat (Temperature Limit, LWCO, & Boiler Reset Control) for Oil Boilers
 
  #22  
Old 01-12-14, 04:59 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
That was a leak from the mixer valve input that has been corrected since that happened.

I believe the furnace might be coming on with the heat demand. I just tried and 1.5 minutes after turning on the thermostat and it sis come on for about one minute and then turned off. As I said, I've been battling the hot water use all day and things get sketchy. Wife and kids keep using water.
 
  #23  
Old 01-12-14, 05:48 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Whether or not hot water is being used, you should still ALWAYS hear (and see if you are watching) the relay in the aquastat pull in when there is a heat call.
 
  #24  
Old 01-12-14, 05:57 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
If the pump is dead, should the relay kick in and stay on as long as there is demand from the Taco valve? Or could the boiler come on, run and then shut off?
 
  #25  
Old 01-12-14, 07:03 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Whether or not the pump is dead, the relay in the aquastat must pull in when there is a heat call.

should the relay kick in and stay on as long as there is demand from the Taco valve?
YES, from ANY ONE OF THE VALVES.

Or could the boiler [you mean BURNER] come on, run and then shut off?
Neither the BURNER nor the PUMP will come on during a HEAT CALL -- IF THE RELAY DOES NOT PULL IN

We keep going back to this, I think what you are missing is this basic fact:

If ANY ONE of the zone valves opens, and the voltage at the T T terminals goes to ZERO, and the relay does NOT pull in, then there is a problem with the aquastat.

The relay MUST PULL IN when there is a heat call, REGARDLESS of the boiler temperature.
 
  #26  
Old 01-12-14, 07:07 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
You need to understand what distinguishes a HEAT CALL from a DOMESTIC HOT WATER DEMAND.

When HOT WATER is needed, and there is NOT a heat call, the relay will NOT pull in.

When there is a HEAT CALL, the relay will ALWAYS PULL IN, even if there is a demand for HOT WATER at the same time.
 
  #27  
Old 01-13-14, 04:20 AM
Member
Thread Starter
Join Date: Jun 2005
Posts: 15
Received 0 Votes on 0 Posts
I think I understand it now. And I believe from what you are saying, that my aquastat might be the issue because I have definitely seen TT go to zero without a pull in. I will do some more checks when the house isn't so full with people.

In the mean time, I'll keep the pellet stove humming away.

Thank you so much for you time and patience with me.
 
  #28  
Old 01-13-14, 05:41 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
Need to be careful with the pellet stove (or any type of supplemental heat that keeps a boiler from operating regularly)... with these super cold spells we've had, it's very possible that the outer extremities of a home can get cold enough to freeze heat (or domestic water) pipes because the heat from a stove is not 'distributed' evenly.

Let us know what you find...
 
  #29  
Old 01-13-14, 10:57 AM
Member
Join Date: Oct 2013
Location: United States
Posts: 2,698
Received 11 Votes on 11 Posts
Husk,
If you're comfortable around electricity, WITH THE POWER OFF remove the circulator wire from C1 in your control and put it on to L1.

By doing this, you are bypassing the circulator relay part of the control and running on a separate 110v. This should start the pump.
With the power turned back on the pump should continuously irreguardless if the tstats call for heat or not so this is only a test.

Turn your tstats up to call for heat. When they open the pump will send hot water to the zones and cool the boiler water down. When this happens the boiler will fire back up to heat the water as it does for your domestic water. The tstats will work normally but the pump will continue to run until you disconnect it from L1.

This will tell you if the pump is bad or the zone valves or tstats aren't working. If you get heat to all zones by this method it eliminates everything but the aquastat.

A word of caution. You don't want to leave the pump running without at least 1 zone calling. It must be able to circulate and not pump against closed circuits.
You will ruin the pump.

If this works for you you can wire the circulator to an independent 110v source and control it with a switch until you get the part.

This is just a thought. As Trooper said pellet stoves are nice but they won't keep the pipes from freezing.
My cousin found out the hard way when they came home to a flood when a pipe burst.
 
  #30  
Old 01-13-14, 11:21 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 2 Votes on 2 Posts
But...

The relay in the aquastat we are told does NOT PULL IN when the T T are shorted.

Yes, your test could tell if the pump is functional, but no matter what else, if the relay doesn't pull in when the T T contacts are closed, either by a direct short, or by the zone valve(s) opening, the aquastat has a problem.
 
  #31  
Old 01-13-14, 03:01 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 2,698
Received 11 Votes on 11 Posts
I agree 100% . I don't know why it's still there. It sounds like he still needs more validation. Thought this might help.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: