Better Thermostat Recomendation - or should I just install an Outdoor Reset Controller

[oconnor]

We are intending to use our new wood insert as much as possible this winter, but our "main" heat source is a 24Kw Slant Fin electric boiler. Our 26x26 two storey home uses 6 cast iron rads on three loops, two rads in parallel on each loop, and with the electric boiler I have been able to run quite low water temps and still stay comfortable this fall.

In years past (last year we ran a 1950's American Standard Oil waster), we had problems with temperature overshoot, given high water temps needed by the oil boiler. So far, the overshoot isn't as bad this year,as I'm running the water at 110F, but I know I'll need to turn the aquastat up as the outside temps drop.

So here is the question - are there any good electric programmable thermostats that have a heat anticipator circuit? Most I come across have nothing more than a programmable cycle rate, and I haven't had any luck altering the cycle rate and avoiding the temp swings.

Given the cost of such a thermostat, am I better off spending the $500 or so on an Outdoor Reset Controller (like a Tekmar 260/261)?
While my boiler is electric, I imagine the issue is similar for those with wood boilers, as it is mostly a problem with the type of radiator and water temperature. Thanks in advance.

 

[Jersey Bill]

Assuming that there is only 1 zone, one way to control the boiler would be to get a proportional room thermostat. The way that this will work is the controller output will increase based on the deviation from set point. Given a particular heat load the controller output (and boiler supply temp) will settle in.

If there are more than 1 zone, then the only way to do it is outdoor reset.
I have found that the best way to tune the controller ts to set all the t-stats to max, and then adjust the settings so that the coolest room will just barely satisfy. It will take a few days to dial in the coolest room. This will be your lowest and most efficient setting.

 

[oconnor]

There is only one zone - I balance the system by adjusting rad valves to increase/decrease flow rate.

So the proportional room Tstat is going to alter the circirculated water temp based on room temp delta from desired - cool. How customisable are these units, and any recommendations? Our overshoots are minimal so far (1 degree C when a call for heat comes to raise from 19 to 21), but I fear that they will increase once I bring water temps up mid winter.

Any other thoughts?

 

[ISeeDeadBTUs]

I can only base my opinion on under-floor radiant . . .

Programable stats are a waste of money.

I'm not sure that outside control is all that important when I'm actually using wood, not oil. Also, the 'European' conventions seems to be constant circulation. We generally don't do things that way here in the States. But I figure it saves on oil when I do use it for any extended period of time.

I've always assumed that with Hot air heat, programable stats could save substantial fuel. But the the stat still needs info about current outdoor conditions (not just temp - wind speed, direction, humidity, etc) AND FUTURE weather conditions! When you find a programable that does all that, go for it!

 

[Jersey Bill]

Grainger has them. The key is to figure out how the boiler control works.
If its on/off with a mechanical contactor you have to change it.
if its on/off with an electronic contactor you need a PWM (pulse width modulated) output on the stat
if its 4-20 ma then you need a 4-20 stat
if its 0-10 volts then you need a 0-10 v stat.

some of the stats have multiple output configurations.

This stat might seem odd to some, but its a standard in industry. there usually are some tuning settings on the stat.