adjusting aquastat
#1
01-04-08, 08:06 AM
adjusting aquastat
Need help adjusting Honeywell aquastat. We have a three zone heating system consisting of three hydroair(First Co.) units, each with a Honeywell aquastat in the supply line to the unit. My understanding is that this keeps the blower from turning on until the supply water temp is at the required minimum temp.We had our boiler replaced in the fall and during the replacement the contractor did some adjustments on the hydroair units. Now after a heat call is satisfied the blower continues to run for appx 10 minutes resulting in blowing cold air for at least part of that time. On contacting him we were told this is normal to some extent to extract any latent heat in the coils. Seems excessive.We would like to at the least shorten this period of time . How is this adjustment made?
#3
01-04-08, 05:55 PM
This may not be adjustable. It is not in the aquastat. This would have to be done with a seperate relay. I believe Taco makes a control for these which have an adjustable fan run time. I know there is a delay fan on but not sure about fan post time.
#4
01-04-08, 07:24 PM
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Makes sense. But since the word "aquastat" was brought up, my first thought was of a Honeywell L6006 [low limit + circulator control] where terminals R and W (circ. cntrl) open on a drop in temperature. Wiring the hot line to the blower in series with this controller it what occured to me was probably the case here.
Anyway, feedback from kmarr will clear the air here.
Anyway, feedback from kmarr will clear the air here.
#6
01-05-08, 11:15 AM
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hummm...
Do you have zone valves? And perhaps also thermostats that would be in charge of opening or closing these valves?
L4006's are high limit aquastats. They have N.C. contacts that open up when the set-point is reached. If they're at all connected to the fans it would be to prevent them from blowing air that is too hot, but I can not see them turning the fans OFF when the call for heat is satisfied...if anything, they'd keep the fans running non-stop after the call for heat is satisfied.
There has to be other control(s) here.
Can you get the model numbers of these HydroAir units?
Now...in your first posting you tell that the contractor indicated is normal for these units to stay running this long (10-min or more) to remove any residual latent heat in the coils...WHAT LATENT HEAT!!!!
There would be latent heat IF these were steam coils. I believe you say these are hot water (not steam) coils.
So...Please clarify.
and don't forget those M/N's
Do you have zone valves? And perhaps also thermostats that would be in charge of opening or closing these valves?
L4006's are high limit aquastats. They have N.C. contacts that open up when the set-point is reached. If they're at all connected to the fans it would be to prevent them from blowing air that is too hot, but I can not see them turning the fans OFF when the call for heat is satisfied...if anything, they'd keep the fans running non-stop after the call for heat is satisfied.
There has to be other control(s) here.
Can you get the model numbers of these HydroAir units?
Now...in your first posting you tell that the contractor indicated is normal for these units to stay running this long (10-min or more) to remove any residual latent heat in the coils...WHAT LATENT HEAT!!!!
There would be latent heat IF these were steam coils. I believe you say these are hot water (not steam) coils.
So...Please clarify.
and don't forget those M/N's
#8
01-07-08, 07:55 AM
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I take it that you meant 36Cdx, not 36Vdx and the "V" was your quick finger on the keyboard.
Is this your unit?
I've got to run now but will be looking forward to your reply for later.
Is this your unit?
I've got to run now but will be looking forward to your reply for later.
#10
01-07-08, 02:57 PM
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Ahhh, that explains.
I take it though, that it's probably similar looking, in other words: a hot water coil (for heating) and a refrigerant coil (for cooling) and a blower. Am I o.k. so far?
And if I understood you correctly, the aquastat appears to control the operation of the blower. Please confirm
I take it though, that it's probably similar looking, in other words: a hot water coil (for heating) and a refrigerant coil (for cooling) and a blower. Am I o.k. so far?
And if I understood you correctly, the aquastat appears to control the operation of the blower. Please confirm
#11
01-07-08, 06:56 PM
It's physical appearance is different, but you are correct in that it has a set of coils, one for heating and one for cooling. My understanding is that the aquastate is being used to prevent the blower from running until the supply water temp hits the set point. This I guess prevents sub-optimal temp air from being sent into the living space. Alas, its being sent after the heat call has been satisfied sometime as long as 10-12 minutes.
#12
01-08-08, 12:38 AM
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I think we've got it covered now!
You do indeed have an L4006 with a N.C. set of contacts that break on a drop in temperature [or make on a temperature rise...two sides of the same coin]. And although originally made for hydronic applications, the ones with remote capillary sensor can be used for air temperature control (see pic below).
The problem you now have is because either (a) the setpoint of these babies has been set too low, or (b) the differential adjustment has been set too high...or both.
Let me know what are the present set-point and differential adjustments.
You do indeed have an L4006 with a N.C. set of contacts that break on a drop in temperature [or make on a temperature rise...two sides of the same coin]. And although originally made for hydronic applications, the ones with remote capillary sensor can be used for air temperature control (see pic below).
The problem you now have is because either (a) the setpoint of these babies has been set too low, or (b) the differential adjustment has been set too high...or both.
Let me know what are the present set-point and differential adjustments.
#13
01-08-08, 04:30 AM
If the controls are in the piping outside of the jacket the coil will cool off a lot faster than the water in the piping. You will get cold air for awhile before the aquastat breaks contacts. A simple fix would be to add a relay to stop the fan when the call for heat ends. I used to use an R845A along with an L4006, or a multi-zone relay with the L4006 control. Therefore the a call for heat started the boiler and circulator. The blower was wired through the L4006, which started the blower when the hot water got through (I put mine on the return side of the coil) the coil and allowed the blower to start. When the call for heat ened everything shut off at once. Than Taco came out with relay for this which gives the blower a short post purge.
#14
01-10-08, 08:48 AM
thanks to all who responded. I think we have the cure in hand. I think if we just add the relay to shut the blower off at the end of the heat call we have solved that part of the equation. The original placement of the aquastat and type possibly of control used is the problem. thanks again
