Aquastat Issue??? NEED HELP


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Old 01-29-09, 10:03 AM
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Aquastat Issue??? NEED HELP

How are you guys...

I've been reading through all the posts but have yet to come to a resolution with my honewell l4006b aquastat.
I have a hydro air system installed in my home. The boiler is gas fired and I have two zones, one for the 1st floor and 1 for the second floor. Both zones have their own thermostats and again each zone has their own air handler, one in the basement and one in the attic. I bought the house a year ago so this is my first full winter in the house and I am monitoring the way the system works.

The problem that I seem to be having and narrowed it down to is the aquastats. Both are giving me this problem.
II have them set to MAKE the connection for the air handler to start blowing air at 160F. They both work fine to this point. When there is a call for heat, the boiler fires up (cold start boiler) heats the water circulating through the pipes and triggers the blower on at 160F. The temperature is correct because when look at the thermometer on the boiler itself it reads 160 and the aquastats are set to 160 and thats when they go on.

With this said, the differential was set to 5 by default from the builder which meens that the aquastat will break the connection when the temp goes 5 degrees below 160.

My problem is, that when i set the differential to a higher number, lets say 15 or 20, this should let the blower run until the water cools to 145 or 140 depending on the differential setting. This does not happen. The blower still shuts off when the water temp drops 5 degrees below setpoint or in this case 155. This is leeding to a very frequent short cycle because its only allowing my blower 5 degrees of working time to heat my home. Does anyone know of a solution? Both aquastats are doing the same exact thing. Is it possible that they are both defective? Any troubleshooting solution would be highly appreciated.

As an FYI, My boiler is a Weil-McClain Gold CGI with an Amana air handler.
 
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Old 01-29-09, 01:27 PM
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http://customer.honeywell.com/techli...0s/60-0915.pdf

It's possible both differentials are set wrong, I doubt if both are snafu. Try setting them at 30* diff.
 
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Old 01-29-09, 01:30 PM
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Im going to try that as soon as i get home tonight. Is there any chance it could be a thermostat issue? Just throwing it out.
 
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Old 01-29-09, 02:36 PM
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No. With a circ. relay, the anticipator on the stat is usually set at .4a, this only affects overshoot or undershoot from your setpoint on the stat.
It would be easiest to break the control wiring to the circ. relay with the L4006B, less wiring work than breaking the line voltage.
I assume there's a flocheck on the boiler to prevent gravity flow, or zone valves?
Tom Beer 4U2
 
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Old 01-29-09, 02:51 PM
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When I troubleshooted it, I had broken the connection of the aquastat and the fan immediately would go on when there was a call for heat resulting in the boiler taking a very very long time to heat up the water. This is why Im confused and still narrowing it down to my aquastat.
 
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Old 01-29-09, 02:55 PM
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A few points that may need clarification...

The aquastat on the air handler is only running the BLOWER and does not communicate with the BOILER.

The boiler is under control of it's own aquastat and differential setting, and the differential on your boiler is likely FIXED, non-adjustable, and the high limit should probably be set to 180.

The air handler a'stats are reacting to the water temperature AT the air handler, not at the boiler. Increasing the diff on those a'stats will result in a slightly longer run time of the blower AFTER the heat call is ended, and the boiler stops firing.

Check the specs on your air handlers, there's a very good chance that you can turn the setting on them back to 140 or so and still get good hot air out... what you want to watch for if you do this is that the temperature of the water RETURNING to the boiler does not get so cool as to cause flue gas condensation in the boiler or flue. The 160 setting MAY be correct.

The reason the boiler takes longer to heat up when the blower is running is because the water returning to the boiler is COOLER and placing more LOAD on the boiler.
 
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Old 01-29-09, 03:03 PM
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How many BTU is your boiler?

What are the specs on your air handler? (model #, etc?)
 
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Old 01-29-09, 03:08 PM
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You are absolutely correct NJ Trooper... The boiler has its own aqustat and is actually set to 180 like you said. The aqustats on the blowers ONLY control the blower and have no communication with the boiler itself.
I do understand that if i turn them down to 140, I should still get good air. BUT even when I do that and lets say its VERY cold out, like its been the past couple of weeks, if the water temperature drops to 135 and below, the blower stops. Isnt this suppose to be controlled by the differential setting on the aquastat on the blower? If it were to be set at 15 differential for example, shouldnt the water have to actually cool to 125 in order for the blower to stop? This is where Im having trhe problem.
 
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Old 01-29-09, 03:12 PM
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Dont know how many BTU's my boiler is, how can I check? The house is brand new ( a year old ) built from scratch... can there be a possibility that the builder or person who installed the entire system didnt put the correct size in?
 
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Old 01-29-09, 04:07 PM
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Billy, I thought ya mighta known that, just wanted to make sure everyone on the same page... good.

Yes, if you increase the diff then you are correct that the blower shouldn't go off until the temp at it's 'sensing' point drops below the diff.

Let me ask you this... are you saying that the blower will actually cool off and STOP _during_ a call for heat? WHILE the burner is still firing? and the circulator is still running?

You should be able to find BTU on the spec plate on the boiler, same for the model # on the air handlers.
 
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Old 01-29-09, 04:14 PM
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Originally Posted by Billy K View Post
can there be a possibility that the builder or person who installed the entire system didnt put the correct size in?
Anything is possible!

The tendency is usually to install some fuel guzzling behemoth that's twice (or 3 or 4 X) the size it needs to be ... and I would tend to applaud any builder who attempted to install a properly sized unit...

If that blower is cutting out DURING a heat call, and WHILE the burner is still firing, that means that either:

1. The air handler is extracting more BTU from the boiler than it can replace.

2. The flow to the air handler is too lazy to get the BTUs into the coil fast enough.

3. There is air trapped in the coil which is slowing down the flow through it.
 
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Old 01-30-09, 08:53 AM
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Ok, what i did last night was increase the differential on the aquastat to 30*. Didnt do anything. The only thing i noticed that the aqustat DID do was when the call for heat ENDED and the boiler shut dow along with the circulator, the blower kept working until it reached the sensing point of the differential. When I adjusted the differential and re-cycled everything it worked perfectly fine ONLY when the call for heat stopped.

This is all leading for me to believe that there is a wiring mistake somewhere along the line between the aquastat and the blower because when the call for heat is active the differential of the aquastat is basically ignored and the blower shuts off when temperature falls more than 5* but when the call for heat ends, the aquastat keeps the blower on to the differential set point and then cuts off.

Im not a plumber by trade, nor an electrician, but I am pretty savvy and do try and read, as well as understand how the concept of different things work. This is why Im drawing this conclusion from what I was able to observe last night.

Any Thoughts?
 
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Old 01-30-09, 08:56 AM
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And to answer a previous question......


Yes, the blower does stop while the circulator and boiler are still working during a call for heat... This was my original observation which led for me to post in the thread.
 
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Old 01-30-09, 02:48 PM
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Billy, I'm not doubting that something is wrong... a few points though...

How are you measuring the temperature at the sensing point of the aquastat? Laser thermometer? Something else? If you use a laser job on copper pipe, you must paint a spot on the pipe flat black or you will not get accurate readings.

If the blower is shutting down while the boiler is still firing and the heat call continuuing, it means that the system can't keep up with the load, due to one of the factors I mentioned, or possibly even something I haven't thought of...

What is the BTU rating on the boiler?

What is the model # of the air handlers?
 
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Old 01-30-09, 02:50 PM
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Is the aquastat sensing the SUPPLY or the RETURN to the air handler?
 
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Old 01-30-09, 02:57 PM
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The aquastat is sensing the return to the air handler.

I did measure it with a laser thermometer and painted a black spot. Im getting an accurate reading because when i manually shut the blower off and let the system run and measure the temp... it is in syc on my thermometer with the temp reading of the water in the boiler (boiler thermometer).

Also, another note. The actual water temperature does not drop enough to shut off the blower when 1 zone is working at a time. This usually happens when both zones are calling for heat at the same time.

I know NJ Trooper, I need to get you the btu ratings and blower model info.. But any other info or troubleshooting will be helpful.
 
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Old 01-30-09, 03:56 PM
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You anticipated my next question about whether or not the blower shuts down with only one running! You are perceptive!

Here's what I'm thinking... it really doesn't matter that the differential may or may not be accurate or working as you want it to... the bigger picture is the fact that it seems as though you may not have enough flow through the air handlers or boiler capacity to keep the water hot enough... it could be as simple as air in the pipes partially blocking the flow, or as serious as a design issue.

In other words, you may be looking at a SYMPTOM, rather than a CAUSE.

Have you measured the return water AT THE BOILER? I think that would be a good step to take because you want to make sure it doesn't get too cool. You don't want that return water to spend much time below 135F or you will have problems in time...

Also, measure the water temp at the INLET to the air handler to get an idea of the delta-T ACROSS the coil in the handler. That's an important design consideration and may give clues as to the flow issue.

Are the blowers multi-speed? And you are seeing this problem only on HIGH?

I would like to see the info on the boiler and the air handlers so I can take a look and see if the system is properly sized, that's why I'm asking for that...
 
 

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