House Cold with Outdoor Reset

Neil_5

HW gas fired heating system, new Burnham Series 2 boiler. Had the contracter install a Tekmar 256 outdoor reset. I read the documentation and undertand how the system works. Based on my convectors the water temperature range is 140 to 180, so now being around 49-55 outside, the Tekmar is using the lower limit for the water temp. However using this lower water temperature is only heating the house to 69. I have the thermostat (Honewell Prog.) set to 71. The recovery feature on the thermostat even calls for the heat earlier but still I cant get the house pass 69. I have the following setting on the Tekmar:

ROOM: 72
Outdoor Min: 25 (checked some stats and seems to be the AVG for my area)
Boil Design: 180
Boil min: 140 (I changed this to 145)
Indoor Desgn temp: 72

The house temp is nice and even, I like that, i just need to have the AM temp be a little higher that 69.

Thanks,
Neil

Alan(CaliforniaRadiant)Forbes

You can either

bump up the boiler minimum to 150° or increase the reset ratio. Read the tekmar instructions.

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Mike T., Swampeast MO

Have you verified that the Tekmar is set for the proper type of heat emitter?

Are you using both night and day setback? e.g. setting back a few degrees at night and another setback after you leave in the morning?

If so, with a very well balanced curve your supply temp in the morning might not be high enough to get "over the hump" before the next setback period begins. Have you left the thermostat at a constant setting to see if you have the same problem?

Does your Tekmar controller have the "recovery boost" feature? If so, I'd use that. If not you might consider using a bit less setback. You could also flatten the reset slope a bit so your supply temp is a few degrees warmer in moderate weather. If the problem reappears as the weather cools, then go back to your original slope and introduce a parallel shift (raise supply temp a few degrees at all outside conditions).

Neil_5

Verified

Mike:

I have the emitter set for #4 which is the fin/convector. I am using setback with the Themostat and not with the Tekmar which have the switch feature to allow the unit to go into night mode (Tekmar), so as far as the Tekmar is concern it is operating in the day mode. At nights I have the thermostat go from 72 to 67, and at 630am have the thermostat come up to 72.

In the evenings, I have the thermostat at 72, from 430pm to 930pm and the highest temp attained is 69 or 70 as well. Havent left the themostat at a fix 72 24hr, cox sleeping at nights will be uncomfortable.

No recovery boost feature as far as I know of with the Tekmar, its model 256 which is single stage unit.

How do you flatten the reset curve a bit?

Thanks,
Neil

Jay_12

Increase ROOM setting

Hello Neil,

I recommend increasing the ROOM setting until the house feels comfortable.

You imply that the Honeywell thermostat has a programable setback schedule. I would recommend two things:

1) Descrease the setback amount.
2) Come out of setback earlier.

Since outdoor reset is trying to match the heat loss of the building, a large setback in temperature may result in the room taking a long time to recouver in temperature (in some cases the room never recovers since the rate of heat lost is greater or equal to the heat in).

FYI: Some tekmar controls have a Boost feature in order to allow quick temperature recovery when coming out of setback.

Jay www.tekmarcontrols.com 250-545-7749

Mike T., Swampeast MO

I haven't used Tekmar controls--have only studied their operational essays--not the specific operation.

Neil_5

Thanks for all the Inputs

Mike ... thanks again, I also spoke with Jay @ Tekmar and have some tweeking to perform. Will keep you guys uptodate.

Neil

Neil_5

Increased ROOM

Jay:

From 70 to 75 to 78, still house at 69 max, should I go higher on the ROOM to say 80? Is this normal?

Neil

Chuckles_2

something else is wrong

The OP is being advised to "flatten the curve", or that the water may be too cold to bring the house out of setback, but if 140 (the minimum limit) is too cold in pleasant fall weather, how will it heat the house when it is actually cold outside? This does not compute. There is something wrong with this new boiler, and just readjusting the Tekmar probably won't help.

Questions for the OP: do you know that the water is heating to 140? There may be a dial thermometer near your boiler in addition to maybe a digital readout on the Tekmar. Do you know that your circulator is running? When the thermostat calls for heat, does the boiler go on and stay on for long periods or does it soon shut off? How long is the thermostat calling for heat per day? (The stat may have a feature that records this.) You seem to be technically competent, sniff aound and look for a problem that is not just the Tekmar or the thermostat.

Neil_5

Checked Water Temp

Before the Tekmar was installed, the system was setup to cut off at 180 and at 180 the house would heat up to 72, maybe a bit on the warm side given the outside temp was around 48-55.

Now with the Tekmar, its limiting the water temp to around 145 now and the house STat is reading 69, 70 the most when I have it set at 72. I should also note that at 69/70 on the Stat it is comfy, not too hot. Maybe my 72 is too high. Without the Tekmar I measured the supply line with a digital thermocouple (a calibarted one from my lab) and the water temp is 180. Now the watter temp being set by the Tekmar is 145 and indeed 145 is leaving the boiler.

The circulator is running; verfified, the entire system was vented for air on each convector and each is circulating the hot water (monflo system).

Boiler does not stay on for a long time, actual it fires up per the Tekmar and let say the boiler traget is 145 and the watter is at 120, it would heat the water pretty fast to 145 and turn off, leaving the circulator running.

I noted some #s this morning, the Stat came on at 5am with house @65 and by 615am house was at 69. By 7am house was at 70 and even though the Stat was still calling for heat; house did not go pass 70, water temp supplied by Tekmar was 145, outside was 52.

Thanks for all the inputs,
Neil

Chuckles_2

I'm out of ideas then. I would think that with 145F water, you can heat your house to 85 in this weather if that's what you want.

Jay_12

Re: Increased Room

If you have adjusted the ROOM setting and there has been no change then there may be other issues at work here.

Please call us at tekmar 250-545-7749.

Jay

Mike T., Swampeast MO

Something sure seems strange.

Aren't you using a "smart" setback thermostat? Nighttime AND daytime setback? When is your daytime setback period set to begin? Remember that a smart thermostat will attempt to achieve the room temperature you want at the time you program.

It almost sounds as if your daytime setback is in a fight with the early morning boost.

Did you have the smart stat installed before you added reset? If so you should clear the thermostat memory as the heatup characteristics will be MUCH different with reset but the cooldown characteristics will be nearly unchanged. Some have a command to clear the memory, others must have their batteries removed for quite a long period of time. Check your manual.

Unknown

Anticipator?

Just for grins, to rule out any interferance from an anticipator, crank up the thermostat 5 degrees, and see if you can hit 71 or 72.

It might be a simple thing like this.

Noel

Neil_5

Am using a smart setback thermostat, Honeywell Unit. Yea I also think the dayset back is fighting the early moorning temp. Day begins at 6am, so the smart feature starts to kick in around 430ish.

But think about this, the unit is firing from 430ish to 8am and cant get pass 69. Tonight I will check to make sure the 145 water temp that is leaving the boiler is actaully getting to the convectors, of course I do expect some loss, but how much.

Neil

Neil_5

Hey hey

Noel:
e
you may be onto something, will crank the Stat higher to say 75 and see if it can bring the house pass 69.

Mike T., Swampeast MO

Have you tried using the boost feature of your Tekmar to allow significantly higher (say 180°) supply temp in the hour or so BEFORE you want it warm?

Also, verify your t-stat programming to ensure that you've set your daytime setback period AT LEAST an hour after your wakeup temp. If your periods are too close or too short that poor "smart" stat won't know if it's coming or going!

Neil_5

No BOOST Feature

On the Model 256 that I have.

I have the following set on the STAT.
Mon-Friday
6am turn on to 72 and at 830am go back to 67
4pm turn on to 72 and at 9pm go back to 67

Fri-Sat
9am turn on to 72 stay at 11am go to 70
at 10pm go to 67

Mike T., Swampeast MO

Sorry--thought you mentioned a while back that your Tekmar had the boost but you weren't using it.

Am running out of ideas. Anticipator as Noel suggested? Clear the t-stat memory in case it's been corrupted for some reason? Possibly a bad stat?

Mike T., Swampeast MO

Sorry--thought you mentioned a while back that your Tekmar had the boost but you weren't using it.

Am running out of ideas. Anticipator as Noel suggested? Clear the t-stat memory in case it's been corrupted for some reason? Possibly a bad stat?

One last idea... If the new programmable stat has only been used in recent (warmer) weather and your home is reasonably insulated, the stat may have a false impression of how long the house holds the heat and thus shuts down the heat much earlier than you would expect. If so, the situation will get better as the the weather gets colder and the stat learns more. To test the idea now, change your daytime setback time to noon or so for a few days.

Neil_5

I dont think thats the case, I say this because I keep an eye on the Stat, the flame signal (on indicator) is on ALL the time, so I dont think the stat is turning off the heat in anticipation that the house will remain warm.

Two things I plan on tonight, first is to reset the Stat and set the temp to 75 to see if the boiler/tekmar can bring the house pass 69.

Next I spoke to Jay @ Tekmar, and I would be increasing the boiler design temp from 180 to 190 and increasing the low end from 140 to 145.

This is a new system as mentioned in my first post with a new stat, see link for info on stat:

http://www.homedepot.com/prel80HDUS/EN_US/diy_main/pg_diy.jsp?CNTTYPE=PROD_META&MID=9876&com.broadvision.session.new=Yes&CNTKEY=misc/searchResults.jsp

Weezbo

by pass the thermostat . jump it out ...

take note of the time, every hour on the hour four the first 4 hours...tell me where the room temp is tomorrow,and what was happening by the hour and the time period you let it run jumped out ...I will be able to give you a real quick synopsis of what is really going on.....*~/:)

Neil_5

Evening or AM?

you want the 4 hr run in the morning or the evening?
I have time in the evening to do so.

Weezbo

go for a trial in the morning and that way you will be ...

around to see whats happening...by afternoon it should have risen 16¡ãF or so .....if not, then you need to look at the valve you have on the injection return for help,it may also be the indication that the system like the tekmar guy says is not high enough at the boiler...however that doesnt bode well if that is the case.

marc

how about the

baseboard, is there enough footage to heat the space with lower water temps. 550 btu/ft. at 180 approx. marc

Chuckles_2

If there's enough baseboard to heat the house with 180F in January, I suspect there is enough to heat the house with 140F now. The OP didn't say, but I'm guessing that the boiler is new but the radiation has been there for a while, and has been used successfully with 180F in past years. I could be wrong, of course.

Nron_9

tekmar

take the room setting down to 68 or 70 on the tekmar control it will raise the temp , it moves the reset curve the other direction

Weezbo

that might be a possibilty also....

and the boiler return bypass could be keeping the boiler plenty warm and it is satisfied that is being met ,other possibilities exist though from the logic it is being fed here is more what i find "other" or different...some heat is making its way through the system...is it an air lock? could it be two returns are connected to two supplys on the same header? And it has air? if the supplys and returns are Hot that doesnt mean that forsure there is circulation through all zones,only that there is circulation through the header and possibly some ghost flow....it sounds more like the control is telling the system pump everythings Hokie Dohkie...on new systems air or crossed supply and returns are easy enough to diagnose and fix controls that are telling the boiler one thing when your sure its supposedly telling it the full meal deal seems sorta common too. broken sensor wires or t stat wires, a run of bad zone valve actuators,pumps turned around Backwards that seems to happen from time to time also .How? to much hurry up, too much slow down.

Weezbo

someone have a link to clarify Partial Reset and full reset

i think that is not really my favorit subject as i Hate full reset. and unless this place warms up dueto global warming, by at least....100¡ãF every winter i really hate it. i hate cold start boiler controls... and i hate full reset on boilers ...its not that i cant be reasoned with or understand the Principal...I just flat out have no liking whatsoever for them...furthermore the words 76 below zero and full reset dont belong in the same sentence.how ever i just recalled that from looking at the weilMclain ultra pdfs not that it was chirping up full reset just that i saw it there and my dislike for cold start full reset reared its ugly head and ruined my web surfing experience...:) how ever it always sounds so good whenever someone explains it to me:)))))and as much as I hate it it is something worth considering in more favorable environments.

kevin coppinger_4

ditch the programmable...

t-stat...outdoor reset does not work well with it.... find a temp and leave it there always...I have a tekmar 260 and went through a similar thing for the first 2 days....went to the std. t-stat problem went away...kpc

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Jason_13

Bypass piping

Does this boiler have a boiler bypass pipe installed? It is required according to the installation instructions. A boiler bypass will take cooler return water and add it to the warmer supply water. You would have to sense water temperature from Tekmar above the bypass to get a true system temperature reading. A boiler bypass will send less water volume through the boiler and max flow through the system. By reducing the flow through the boiler the temperature exiting the boiler get hotter and does boiler protection. The hotter supply water will mix with the cooler return water and reduce the supply water temperature. With large water volume systems and no boiler bypass the volume and velocity of water going through the boiler is too great to add enough btu's to get the system temperature up fast enough.
When the system operates in colder weather it will climb faster as the outdoor temperature gets colder the average system temp and boiler temperature stays higher between cycles, due to cycling more often. This time of year it does not run often enough due to warmer outdoor temperature's and night setback.

Neil_5

Update

Thanks for all the suggestions:

First up, Jay @ Tekmar recommended increasing the boiler design from 180 to 190 and the low end from 140 to 145. With 50 deg outside this morning, the boiler target was at 150 and the house came up from 68 to 72 this morning at 415 and by 445 was at 72. Looks like the 140 may be a bit on the low side for me.

This is a new Burnham Series 2 HW gas boiler (175KBTU) that was installed fater I moved in (replaced an oil system). Teh house consist of 5 large convectors, 5 small convectors and one 5 feet base board and 2- 3 feet baseboard. No air in system, a monoflo system.

What I did notice from the boiler, the supply line connects to one convector and one baseboard right off the boiler and then there is a 18 feet run of the supply line that is expose (1 inch copper). There is a 15 deg drop within this 18 feet supply line, the line is in the basement laundry room that is not insulated and was at 70 deg at the time I measured the temp on the pipe. Should I insulate the line?

The system is piped with the circulator on the return line and as far as I can tell the water circulates into the boiler and then leaves the boiler where the Teknar sensor is mounted on the supply line. There is a watchdog low water sensor, air vent on the boiler, backflow valve and water fill that is set at 12PSI. All convectors and baseboards are heating up OK.

Now this morning the poor Stat went into its recovery mode and within 45 mins as I mentioned above the house was up to temp. I think for now I will turn off the recovery mode until I fine tune the system.

Someone mention to reduce the ROOM temp to 68 to shift the curve, this quite opposite from the recommendation of Tekmar.

Thanks again, with time and patience I will tweek the beast

Neil