Wall thermostat recommendation...

Skyline

My 18 years old wall thermostat from Honeywell did not work with my new boiler. It had been replaced by another Honeywell, Model# RTH2410B, about two month ego. While it is working, I don't like how it does work., mainly keeping the temperature in the zone within 1F to the set temperature.

The requirements for the wall thermostat are:

1. Programmable, battery operation
   
2. Heat only
   
3. User-selectable periods/day
   
4. Adjustable cycle/temperature swing
   
5. Etc...
   

It would be preferable, if the whole week could be programmed with two setting, wake and sleep. We are, like lot of people, working from home 99% of the times and there's really no need for different settings for weekdays and weekends.

Explanation for #4... My old thermostat allowed temperature swing, meaning, that it could be adjusted to kick in the heat, if and when the temperature drops two Fahrenheit below set temperature. For example, if Zone #1 is set to 70F, the thermostat would call for heat at 68F.

Seemingly, the Lux Model #TX9600TS meets these requirement, but I am not familiar with this brand. Does anyone has some experience, good or bad, with this brand? If not...

Do you have a brand/model that would be suitable for my needs?

TIA...

EdTheHeaterMan

I hate thermostats with numbers on them. Do the numbers really matter. I think not.

Try this:

Set the thermostat at a number, any number, then let the heater operate at that number, but don't look at the numbers. if you are comfortable, then don't touch anything, it works.

if you are a little chilly, then raise the number by 1 degree F and wait 2 days before you decide if the room is still chilly or if it is fine. If fine, don't touch it. if you are still chilly then raise it another degree and wait 2 days. Eventually, you will get to a new number that is comfortable. Once you get there, stop fussing and leave it alone.

If you are too warm, then do the same exercise in reverse by lowering the number by 1 degree every two days until you get to comfortable.

Only after you find your new comfort number can you start to use the setback feature as you did with your old thermostat. if only all thermostats worked like this one:



You are assuming the old thermostat was accurate. What if the old thermostat was wrong and the hew thermostat is correct?

FINALLY, if you are experiencing temperature swing in excess of 2 degrees, the Cycles Per Hour (parameter #5 in the setup menu) may be adjusted. This is slightly different than your old thermostat but basically does the same job. The concept is to keep the burner from short cycling, select a higher number if you have deep temperature swing. (more than 3 degrees) choose a lower number if you are experiencing short cycling. the instructions are on page 9 of the manual https://digitalassets.resideo.com/damroot/Original/10011/33-00110EF.pdf

hot_rod

what type of heat emitters? Low mass like fin tube can be setback at night, high mass radiant or large cast radiators may not respond to setback, to your liking.

Skyline

Thanks @hot_rod...

My fin tube/basedboard radiator in Zone #2 already has a thermostat (RobertShaw) that allow adjusting for temperature swings. It's been working well with setback for a decade or so.

Zone #1 is CI radiators and haven't noticed issues with the setback. These are large radiators, 15 and up sections with 3-4 tubes.

The current thermostat cycles too frequently. I don't mind the long cycle to reach the set temperature, the curve is set to ascertain condensing.

On the other hand, after the long cycle finishes, in an hour or so later, the thermostat calls for heat again. Despite showing the set temperature of 70F in my case on the display. Zone #1 is comfortable during these times. Manually shutting off the thermostat does not have any negative impact for 3-4 hours, other than the temperature dropping by 1-2F.

I am just trying to expand the off cycle for at least couple of hours, by setting swing temperature to 2F, or 68F, or something in that neighborhood. Instead of shutting off/turning on manually.

Jamie Hall

And what is the objective here? Running a larger swing will not save any energy, particularly if the thermostat is set for the average temperature of the swing -- say if you are tolerating a swing from 68 to 70, but set the thermostat to hold 69, the total energy used will be the same.

Skyline

Thanks @Jamie Hall

I am open for suggestion...

Maybe my understanding of the on/off cycles is wrong. Isn't better to have longer cycles than short ones? Even if the fuel utilization is the same?

For all practical purposes, I could set the thermostat to 70F for all program choices, or just get a non programmable thermostat in that case.

Maybe the setback doesn't save any energy either. In which case, why most publications recommend the setback?

I am confused...

Jamie Hall

Longer cycles are better than short ones -- up to a point. There is a small efficiency loss while the boiler is coming up to temperature or steam, as the case may be, and one does want to avoid that when one can. However, your fin tube baseboard type system can run moderately long cycles -- say two per hour -- and still give quite even heat. And, in any event, the loss -- particularly with modern small boilers -- is very small.

Long versus short really doesn't make any significant difference to the boiler itself.

Whether setbacks save energy, and to what degree, depends very much on the type of heating system. With steam or hot water running massive radiators, there seems to be a general consensus that up to 3 degrees setbacks, for the overnight hours, at least doesn't use more energy than constant temperature, and may use slightly less. Less massive hot water systems may tolerate a larger setback -- say to 5 degrees. In any case, on/off setbacks such as warm in the morning, cool during the day when folks are away, warm in the evening and cool at night just doesn't save. Some radiant floor type systems won't tolerate a setback at all, as they often take as much as 24 hours to change temperature by a degree or two. Now if you are looking at forced hot air, it's a different situation: setbacks, even fairly large ones -- say 10 degrees -- and for shorter periods do make sense, as you are not trying to heat the building, but just the air, and even though the furniture and walls and all are cold, you will feel warm enough if you can find a warm breeze. This is where the politicians come in, as they assume that everybody nowadays has forced hot air. Which of course isn't true -- but that's politics.

Skyline

Thanks @Jamie Hall...

My heating system is CI radiators, as stated earlier. For my 70+ years old house, the heat loss, rather the overall insulation's "R" value is constant. There had been changes to siding, windows, doors, insulation, etc., so, it's really not like a 70+ years old house. Other than the maintenance of it...

AFAIK...

The heat loss also depends on the temperature difference between indoor and outdoor, or ΔT. The thermostat has no control of the outdoor temperature, but it can control the indoor temperature.

Wouldn't having the setback of 8F decrease the ΔT at given outdoor temperature and subsequently reduce the actual heatloss? Strictly by numbers, this would be true for any temperature ranges for a given infrastructure. Conversely, keeping the temperature constant with no setback would have more heat loss, due to the greater ΔT value.

Is there really a difference between the amount of energy utlized between the two? Well, it seems that the answer depends on the person who is answering the question:



The other aspect of the setback is preference. I personally like to sleep in lower temperatures, even 62F don't bother me. During the day, there's no setback in my house, only at night. This is not related to the pandemic, it's been that way for years.

Jamie Hall

The factor which is overlooked in considering setback is the energy it takes to warm the house and the contents of the house. Not the air -- that's trivial. Air has very little heat capacity. The contents, however, are not trivial. It's the structure of the house -- the walls, the floors, etc. -- and the contents -- furniture and the like. And, clearly, this factor depends enormously on the nature of the house and the contents. A modern house, let's say, with plaster board walls, modern minimalist furniture, and so on, may take relatively little energy to warm (and, conversely, cool very quickly if the heat is off). An older house, with plaster walls, thick hardwood floors, and a good deal of heavier furniture will take more energy to reheat (and, conversely, will cool much less quickly). The extreme, of course, would be a stone or concrete house -- such as it might be an adobe in the southwest, or a castle in Scotland. These may literally take days to change as little as 10 degrees!

This is why any discussion of how much setback is useful is bound to be hazy at best. That modern house, with forced air heat, may do very well with really deep setbacks, for instance.

Is there a rule of thumb? Not really. Are there any hard measurements available to say this is good, that wastes energy? Again, not really, at least not that I know of. My own feeling -- and I have little to back it up in the way of hard engineering -- is that a setback which takes more than an hour to an hour and a half to recover from is probably the maximum that structure can handle.

The route which I have found quite satisfactory for myself -- like you, I prefer to sleep in a cooler space -- is rather simple-minded: my sleeping room, which is rarely used for anything else during the day, is simply kept at a lower temperature all the time.

All of which doesn't help much, I'm afraid.

Skyline

Thanks @Jamie Hall

Oh yes, you helped me a lot and it's much appreciated...

We may disagre on certain subject, but generally, we are pretty much on the same page. Including my bedroom with baseboard heat, temperature set to low, where the thermostat seldom calls for heat. It does help, that this room is adjacent to Zone #2 and gets some of the heat from there.

I am still learning how my new boiler behaves with different settings and the results to the indoor temperature. I do monitor both the NG and power utilization. This will be going on for awhile, until settings are finalized.

I did state 8F setback, but that's just the starting point and yet to have the 62F temperature reached overnight. Even when the outdoor temperature was 28F, the indoor temperature dropped to 64F from the 70F. The wake cycle kicked in and Zone #1 heated up pretty much like any other times, probably thanks to the outdoor temperature reset.

The chance are that this will change in the winter month, but at the current time, it remains to be seen.

Jamie Hall

Sounds good to me!

SuperTech

@Skyline The Honeywell T4 has all those capabilities that you require.