Tekmar 260 OTR Loooonnnng Recovery

shoudabeenaplumba

I have a Tekmar 260 w priority for hot water.  No indoor sensor.  My design temp is -7F and my max boiler temp is 180f.  Some days there's no one home so I manually lower the thermostat to about 60F.  I know setback thremostats will increase the recovery time for a zone, but how much is too much?  8 hours?  10 hours?  After measuring the baseboard there's more than enough. 

Is there a way to boost the temp of the water?  I'm guessing raising the design temp would work.

R Mannino

Why Not

just let the ODR do it's job and not setback the t-stat?

kcopp

ditto.

I have a Tekmar 260 and I do not set it back usually.  Sometimes I do it if I am away for days.... And yes... 4+ hours to come up to temp. kpc

shoudabeenaplumba

I adjusted the design temp

I don't typically use the setback feature of my thermostats, which are all learning thermsostats (learn how long it takes to heat up). My parents have a seperate zone just for them, and keep it 70f all the time.   I keep our side of the house at 60-62 and use a wood stove insert for supplemental heat when we're home/awake.  It works great save for that all importaint moment of getting out of bed! I harvest my own wood and don't think its worth it to stoke the stove the night before just for a moderately warmer house in the morning.  I finally gave in and started fooling around with the thermostat, but found it taking too long.  4+ hours to get from 62 to 66 degrees.

I had the Tekmar set for 170f with 180f max temp, and a low temp of -7 degrees.  I changed the low temp to +5 degrees, and raised the design temp to 175f.  This is working great for the past 2 days.  We don't see -7 that often.  My one pet peeve with these setbacks are the simple fact they don't take wind/convection into account, and anyone who works outside knows its not the cold, its the WIND that freezes you. 

Charlie from wmass

These controls are made to do this.

The point is to have a long slow climb this is how the beast works to save fuel. It is like driving with a governor instead of a throttle. By moving the curve you can make it so your folks side they keep at 70 is using more fuel than before. put the thermostat at 64 and return to the older settings is my best advice for conserving fuel. or go back to old settings on the tekmar and have the t stat bring it up 4 hours before you wake.

Mark Eatherton

The problem is...

The thermostat and the ODR don't speak the same language.



When the ODR gets a message from the T'stat, all it hears is "CIRCUIT CLOSED"



It needs to hear "CIRCUIT CLOSED ADN THE ROOM TEMP IS 10 DEGREES AWAY FROM ITS TARGET TEMP. BOOST THE WATER TEMP TO SATISFY THIS CALL FOR HEAT"



The t'stat assumes that when it calls for heat that the heating system is sitting there, over full of extremely hot BTU's, just waiting for the thermostat to call, so it can POWER VOMIT heat into the space.



In reality, the thermostat will NEVER learn how early it needs to turn on before it can hit the "target" temp and time, because the boiler keeps on changing the rules of the game.



Can the set backs.



The source of energy is more important to control than is the point of use. If your room temps are really dropping that much heat, your money would be better spent on insulation and caulking or new windows.



I agree with you and have told every major control logic manufacturer that they should include the following into their control strings, to no avail.



1. Wind (simple pressure differential transducer if nothing else)



2. Solar gain (AM, Noon and PM using a 4 sided square sensor with 4 sensors on it facing North, East, South and West)



3. Clear night sky re-radiation. (Add a fifth sensor to the top of the previously explained 4 sided sensor, fifth sensor facing straight up but only referenced when the first four sensors read the same)



I don't know how much easier we can make it for these guys....



ME

CC.Rob

it's in there....

Why do all that fancy sensing when just a simple temperature measurement at a key location or two in the conditioned space integrates those three things and more, like cooking, occupancy, etc.?



For a balanced, zoned system controlled with a 260, one indoor sensor can work wonders. You can also ladder indoor sensors with a 260 to derive an average.



Or get into the fancier feedback controls from tekmar, H-well, or whoever.



And of course do the insulation and air sealing thing.....

shoudabeenaplumba

how do you ladder the indoor sensors?

Do you need different sensors?

CC.Rob

look

http://www.tekmarcontrols.com/sb/sb018.pdf

shoudabeenaplumba

Would you believe

I drew this in my head?  I figured they were doing parallel/series to get back to 10k. 

How does the Tekmar heat curve compare to say a WM/Buderus/Viessman OTDR?  It used to be more linear, but I guess the newer controls are more on a curve to prevent over-heating.

Randy Baerg

tekmar 260 with setback

Not sure if you are aware of the option to add an indoor sensor and setback to the 260 control. If you added the indoor sensor and then wired in a switch to the unoccupied Switch terminals the 260 control could do setback with indoor feedback. This can work really well to help eliminate the longer recovery times when trying to do outdoor reset.

The unoccupied switch could be a simple manual device or a timer. You just need a dry contact. When closed the control starts using a Room Unoccupied setting.

Now when the switch is opened in the morning the control goes from Unoccupied to Occupied. It would be seeing that the Indoor Sensor (room temp) was now  further away from the desired Room Occupied temperature. This causes the heating curve to shift up and the result is that the target temperature is boosted until the room temperature reaches the setting. Voila you have a faster recovery time.

The thermostats would be operating independently of this.