reset curve

Robert_15

brad the senser had 14 gauge wire attached to it the instruction call for 18 or larger , one would think thinker gauge but it is higher number on the gauge 22, works better. now we will see when the warmer weather comes
thanks

Robert_15

adjusting that reset curve

Hello now that i put he supply senser in a Honeywell Immersion Well utilizing an 1-1/4" x 1/2" x 1-1/4" c-fip-c tee the odr is accurate.also what i did was pipe a system bypass works alot better then the boiler bypass. on a cold start then boiler return went up to 140f just before the burner went off on one cycle. when i had the boiler bypass in operation it would take two cycles to achive this.now the temps are 52f outside my odr is shutting down around 160f. my question is when i adjust the curve i can lower the outdoor low temp (design is 8f)to say 0 f or lower to achive the lower burn temp or lower the high now set at 170f? now this is on a c.i. boiler the min setting is set to 135f works wonderful with the senser inside big difference
Thanks

Brad White_19

Scott

> Hello now that i put he supply senser in a

> Honeywell Immersion Well utilizing an 1-1/4" x

> 1/2" x 1-1/4" c-fip-c tee the odr is

> accurate.also what i did was pipe a system bypass

> works alot better then the boiler bypass. on a

> cold start then boiler return went up to 140f

> just before the burner went off on one cycle.

> when i had the boiler bypass in operation it

> would take two cycles to achive this.now the

> temps are 52f outside my odr is shutting down

> around 160f. my question is when i adjust the

> curve i can lower the outdoor low temp (design is

> 8f)to say 0 f or lower to achive the lower burn

> temp or lower the high now set at 170f? now this

> is on a c.i. boiler the min setting is set to

> 135f works wonderful with the senser inside big

> difference Thanks

Brad White_19

Scott

Thanks for getting back to us on this.

If I gather your posting correctly, you are using 160F water on a day like today? (unseasonably in the 50's). Seems like you should be closer to your 135F low limit unless I am missing something.

As for playing with the curve, yes, try it. Risk of dropping your design OA temperature (your bottom out to maximum temperature) you could over-heat at what used to be the higher design. I say try it, no harm if you monitor it versus comfort. But unless you have experienced it first at 8 degrees, not sure why you would want to change it.

Robert_15

Hi Brad that is something i am still confused about now i am basing this temp on the boiler termastat. the boiler on cold start (one firing i think 24 hours or so)goes to 160 then shuts off & satsifies the thermastat. so that is making me think to lower the outside to a lower valve? the high end probably should stay around 170, no?
Also maybe adjusting the system bypass for a higher degree temp? what do think of not using the boiler bypass?

Robert_15

brad

Hey Brad Thanks for the response what i did is turn down the outside low to -8f now it seems to have a long cycle of the circulator. now the temps are 21 feels like 5 with the wind chill.i think that is what the odr is suppose to do?with the system bypass it is doing a better job.but your point about the 50 degree weather & my burn of 160 is still confusing. also with the return temp haw long should the water be below 135f after the burn starts
Thanks

Brad White_20

Wire Gauge

Hi-
Away from the wall for a couple of days. Will get back to your other questions later.

14 GA is larger than 18 GA for sure. Smaller the number the thicker the wire.

Sort of like sizing a shotgun. For example, how many lead spheres of bore diameter make up a pound? 16-gauge shotgun balls weigh an ounce apiece, hence 16 GA. 12 GA uses 12 such balls. A one-gauge elephant gun? One pound in one ball. Damn.

Robert_15

it was misleading that the instructions state 18 awg or(larger).anyway thanks

Brad White_9

Let me see here....

Normally if I have OD reset on a conventional CI boiler, the span goes between high operating limit of 180 degrees corresponding to my outdoor design (8 degrees in your case). The low limit would be about 135 or 140 in a gas-oil boiler. Up or down if you push the limit and fully understand your CO2 levels and dewpoints from that.

Assuming you are going direct to the radiators with supply off the boiler, that is about it.

IF you are de-coupling the boiler circuit from the radiator circuit (by a 3-way or 4-way mixing valve, P/S hydronic bridge, injection, etc.) you would get more efficiency by tailoring your radiation loop to the wider range of outdoor temperatures and use constant circulation as well.

In other words, instead of having a total HW temperature range of 140 to 180 for OD temps of 8 to 65 F., you could have a radiation temperature range of 70 to 180 over the same OD temperature span. Your boiler would still fluctuate over its 140 to 180 range but the temperatures would be governed by a control valve, not a manual bypass and based on temperature. Also the boiler temperature is maintained several degrees warmer than the loop temperature to keep things under control.

As you have it described now and do not use the boiler bypass all you will do is give one temperature water and cycle your pump. No savings there.

Brad White_9

My point about the 160F

supply is that it is too high for warm weather, more fuel cost than you need to spend. You could and should be lower in mild weather.

You can have 135F return for a few minutes maybe 15 or so during warm-up. This is normal for you often have a cold start. The bypass tempers this of course and lessens the time below 135. The danger is when you fire the pump after your boiler reaches high limit and you force a slug of cold return water into a hot boiler. I usually have the circulator running first and gradually warm things up. A short amount of condensation that burns off (evaporates) is a small risk compared to cracking a section.

Robert_15

Hi Brad so your saying to put in a varable speed injection. what i understood was if i adusted the bypass (boiler & system) to get a return temp at a stable dergree of 140 in a reasonable amount of time on a warmer day that would be ok. so by using the combination of the system & boiler bypass to achive this dergree of 140 would that be ok?

Brad White_9

Variable Speed Injection

is but one method of achieving de-coupled control (separate temperatures, higher in the boiler loop and more widely variable in the radiation loop) in order to achieve higher efficiency. Control valves are another way. The use of 3 and especially 4-way valves allows you do have all the features using only one circulator.

I mention these more "exotic" methods (pretty common ones, really) because what you are doing now, manually diverting hot water from your supply to protect the boiler, does not adjust automatically in response to always-changing variables. Only automatic controls do that and can both respond to boiler return water temperature and best of all index your radiation loop temperature to the outside air temperature. Saves money and that is the name of the game is it not?

What you have now "works" more or less (better than not having it) but does not track changes. Your parasitic use of boiler hot water to protect the boiler is still a mark in the "Debit Column" of energy expenditure. Automatic controls adjusts to what is needed at a given time.

Also, Scott, it gets you out of the basement and back to enjoying life! (But I will confess to hours watching my 4-way mixing valve modulate knowing that it was saving me money.)




Brad

Robert_15

so off the supply bypass i would put a three way mixing valve. how would the mixing valve sence the return? by it self or through a aqaustat? and what kind do you suggest? the aq 475 does not have that option so is there another means?
if i use the three way then i would not have to use the boiler bypass?

Brad White_9

Scott,

I would have to see a diagram and exchange sketches with you to describe it. For starters though, I would browse the Tekmar web site for ideas. For any point you want to control, be it supply temperature, return temperature, outdoor temperature, you do understand that there will be a sensor. The key is, what the "Brains" of the control will do with that information. If return water control is warranted the valve will over-ride supply for a period, things like that. Generally though, I have found 4-way valves to be the best of all worlds. What it does is sip hot water from the boiler such that what returns to the boiler is equal to what leaves the boiler. Likewise the radiation loop; recirculates what is warm enough (has more work to do) and draws in HWS to maintain supply loop temperature. Boiler protection generally is not a problem in a dry-base atmospheric boiler but for oil-fired/wet base a return sensor will balance the needs of both.

A dozen ways to do the same thing, so I do not want your head to spin too much!