boiler reset

Mark J Strawcutter

> I've got this new boiler controller and I find <BR>
> that to protect the boiler from running too cold, <BR>
> I need to set the minimun boiler temp. to 130* or <BR>
> so. When it is set that way the reset feature is <BR>
> completely overridden and it runs the temp to the <BR>
> high limit (180*) then circulator only down to <BR>
> the low limit. I am wondering if in fact that is <BR>
> how it is supposed to be and if so, is a 50* <BR>
> differential good or bad? Also, the control runs <BR>
> the circulator for about 10 seconds after a call <BR>
> for heat is satisfied. My system is zone valves <BR>
> and one pump. Should I put a bypass in so the <BR>
> circulator is not dead heading? Thanks for your <BR>
> input.<BR>
> <BR>
> Larry <BR>
<BR>

Larry (from OSHA)

Honeywell AQ475A

I've got this new boiler controller and I find that to protect the boiler from running too cold, I need to set the minimun boiler temp. to 130* or so. When it is set that way the reset feature is completely overridden and it runs the temp to the high limit (180*) then circulator only down to the low limit. I am wondering if in fact that is how it is supposed to be and if so, is a 50* differential good or bad? Also, the control runs the circulator for about 10 seconds after a call for heat is satisfied. My system is zone valves and one pump. Should I put a bypass in so the circulator is not dead heading? Thanks for your input.

Larry

Mark J Strawcutter

Outdoor Low setting?

What is your outdoor low setting? Is the outdoor sensor connected? Did you get the boiler min and max reversed?

Mark

Larry (from OSHA)

settings

outdoor low setting is about -20. outdoor sensor is connected. did not get the boiler min and max reversed. I think this is just the way this control works. if boiler low is anywhere other than "off", this puppy is just a very adjustable aquatrol. I'm hoping that Bill from Honeywell will weigh in on this sometime soon.

Thanks

Larry

Mark J Strawcutter

my understanding

is that it sets the endpoints of the curve as boiler max at outdoor low, 70degF water at 70degF outdoor. When the computed water temp is less than boiler min, boiler min over-rides. Not sure of the shape of the curve.

Try bringing your outdoor low up to +10 and see if that makes a difference.

Oops - you said it was running up to boiler max, not sitting at min. So taking the outdoor low _down_ should help which sounds like what you've already tried.

Is the 475 controlling the circ? What is controlling the burner - a triple aquastat?

Mark

Larry (from OSHA)

the controller

runs both the circ. and the burner. a simple high limit aquastat is in a well for the upper limit safety. the spec. sheet is enclosed as a pdf attachment. i don't think i've got it hooked up wrong, but the possibility certainly exists. thanks for spending time to think about this.

Larry

Mark J Strawcutter

which limit?

Any idea which limit is shutting the burner down - the 475 or your aquastat?

Any chance you've got voltage applied to the DHW terminals?

I suppose you could have a bad unit, too.

Mark

Rob T

The 475 has a dry

boiler control, do you have it running directly to the boiler or through the existing aquastat?

I asked the very same thing awhile back and was told that the 475 is not to be used as a high limit and that it needs to go through your existing aquastat. I just got mine and am going to use the TT boiler contacts to trigger my existing aquastat (Honeywell 8148E).

Also how is the indoor sensor installed? Maybe it's just not getting the temp correct?

Honeywell also states that you have to set your existing high limit higher than the 475's boiler max to get the unit to operate correctly.


Just some random thoughts from a homeowner...

R

Larry (from OSHA)

a little more detail

by the way, this boiler is a weil mclain HE series 2 with an induced draft. so the 475 is wired to the boiler control which starts the blower etc. the 475 is controlling the upper limit. i have it set at about 175* or so and it is quite consistant. the aquastat high limit is set to about 200 or 210. i haven't checked for voltage at the dhw terminals and don't have the new tank installed yet. my indoor sensor is nicely secured to the supply within 6 inches of the boiler outlet. i even used heat transfer compound and insulated it with pipe insulation (the good stuff). again, when boiler low limit is set to off, this thing works great. it just runs too cold on the low side. i don't want to condense for too long. on the plus side, the system is pretty low water content with 2.7 gal. in the boiler and the total of the 3 zones are less than about 400 feet of 3/4". I don't know what that converts to in gallons... again thanks for any advice.

Larry

[Deleted User]

I wonder?

The sensors don't react as fast as we might want them to. It is possible that the AQ I/D Sensor is still looking for that 130* minimum when the zone valve(s) kill the stat circuit & shut down water movement from the boiler.

It does not take long for that 100 mbh to cause the HE-4 teakettle to go orbital when circulation stops. It heats faster than the sensor can react. Perfect would be a sensor installed in the boiler block. But, the HE doesn't have any left over.

Might be time to drop back & punt.

Larry (from OSHA)

and punt it is

actually, the sensors are quite responsive. I have thermometers at the supply and return and the control shuts off the burners at high limit just fine. I think either this is the way it works or Mr. Strawcutter is correct in that it is a bad unit. In any event, some guidance on where to go from here would be most welcome.
Thanks

Larry

Mark Wolff

Control problems

> actually, the sensors are quite responsive. I

> have thermometers at the supply and return and

> the control shuts off the burners at high limit

> just fine. I think either this is the way it

> works or Mr. Strawcutter is correct in that it is

> a bad unit. In any event, some guidance on where

> to go from here would be most welcome.

> Thanks

>

> Larry



First check to make sure your signals

Mark Wolff

Control Problems

It sounds like one of your heat signals is triggering the domestic water override. The dom. H20 feature will bring system temp up to 175 or 180 like you said, and will run the circ pump in a post purge state for appr. 10 sec. like you described. If that doesn't do it, run through a self-test, verifying that as the control turns each pump and the burner on, that they are running and shutting off appropriately. If all seems correct at that point, an internal control issue is your most likely problem. Install a new one and see if that corrects the problem.