Weird Tstat behavior - slow response time or too much heat?


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Old 02-16-08, 08:16 PM
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Weird Tstat behavior - slow response time or too much heat?

Hi All,

I've done a search and can't find a solution to this. Maybe I'm stuck, not sure. But I'm certainly baffled...

Anyway, we recently finished off a large 550 sq ft space over our 3 car garage. It is baseboard hot water heat (was already roughed with pipes, electric, etc). For a couple of reasons (asthetics, window placement, unknown insulation quality (behind existing drywall), the room has about 40' of baseboard. The plumber (a friend) thought he'd rather oversize than undersize on the amount of baseboard. Basically, along one whole wall. He figured the boiler would just run less as the room would get to temp quickly. Maybe too quickly I've learned...

The Tstat is a RiteTemp 6025 (newer unit), which might be my first mistake. It's located on an inside wall (other side is son's closet) without baseboard below it. About 5' off the ground.

Here's the problem, when the tstat calls for heat, it seems very slow to respond. Say the desired temp is 67, the room will hit 67 and keep on climbing (according to independent thermometers) and get to around 72 73 before the tstat has even moved a degree or two. By the time the tstat gets to the desired temp, the room is about 10 degrees hotter than the desired temp.

I swapped it with the same unit (another 6025) we have in the bedroom, where we don't have these problems, and the same thing happens. So I thought it was too much baseboard, but it seems like it would be fine if the tstat just read quicker. Of course RtieTemp says it sounds like the tstat is defective - go get another one they said. But I'm not convinced.

Any experience with these newer RiteTemps? We have some older ones (8050s) that work fine. Did we put in too much baseboard heat? If so, any solutions that don't require ripping some out? I feel like I'm wasting oil as the boiler is running more than it has to for this zone.

The simple solution is to try another brand, but to be honest, I can't find any that just get great reviews. They all seem to be hit or miss. Any advice is appreciated. I go in the room and it's like a sauna. My wife loves it, but not me.

Thanks a million and sorry for the long post.
 
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Old 02-17-08, 03:14 AM
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Do you know the output of the installed baseboard? I mean, the Bthu/ft it can put out? And how about the aquastat setpoint? at what temperature is the water circulating thru the baseboard?

Let's assume your baseboard there is a not-so-good one and let's assume too that your aquastat is set to 200F (which is typical). Your baseboard may give about 700 Btuh/ft.
You say it's 40-ft long: 40x700=28,000Btuh !!!!!! one can heat an entire 1,200 sq-ft modern home with that.
And if the output of the installed baseboard is larger than that.....we're talking an even larger heat output. You need to find out the specs of the baseboard and the aquastat setpoint in your boiler to know for sure how much heat you're getting there.

How much heat would this room need? Well...that will depend on how well insulated and the quality of windows (if any) installed. A "pessimistic" factor (assuming a lousy job) would be around 50-60 Btuh/sq-ft...only then your installed baseboard length would be justified. But to know for sure you need to run a heat loss calculation. It's the only right way of doing so.
In new construction, factors of 20-30 Btuh/sq-ft are typical, which if applied to your project would mean that you have twice as much baseboard as needed.

Newer thermostats have dip switches that must be set for the type of application at hand. In your case, hydronic heat. I suppose this thermostat of yours is digital. Check the user's manual for input regarding proper set-up procedures. If electromechanical, the anticipator would need to be set to the amp draw of the device being controlled by it. You do not say what does the t-stat controls? or when/when-not the baseboard gets circulating hot water here.

p.s.: you should have posted in the boilers forum, this is for furnaces.
 
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Old 02-17-08, 04:21 AM
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Rtie temp stat use temp swing to turn on and off the equipment, and that is OK, but I'd rather see something like Honeywell.

Honeywell, you can set them to match your heating equipment. YOu can pick up a basic round electronic heat only at Home Depot. Honeywell Learns your home, and cycles as needed.. Where the swing one don't.. So chances of over heat is less with them.
 
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Old 02-18-08, 04:55 AM
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Woops. I saw "Oil heating" and missed the hot air reference on the forum. Any way to move it?

Thanks for the help though.

I can ask my plumber about the output. I know it's not high output board though. The aquastat, I believe, it set to about 185. We have an indirect hot water heater too. So because of expected hot loss. side attics, etc, we did use a bit more than probably needed, but that was planned. It doesn't seem like he was far off. Even at 35btuh/sqft, that's about 19250.

I'm not really worried about that, but just have a tstat that reads the temp changes a bit quicker and responds. Then all will be well.

Since the room was roughed with piping to the boiler, we didn't change the layout that was required by it. If we reduced the baseboard amount, the whole back 30% of the room would have had no board, and 2 windows. We were worried that back end would feel cooler. Probably some rookie decisions, but at least I'm not worried we don't have enough heat!

So if Honeywells are in fact better, and "learn" better than RiteTemps (the 6025 is digital and does use a Swing feature), which once would you recommend, for either a 5-2 programmable minimum feature set. Can you guys help with that?

And if possible, can I get his moved? Thanks a million.
 
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Old 02-18-08, 05:30 AM
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I own a honeywell now, and I don't feel the temp swing like I used to have with the Lux and RiteTemp that I've owned in the past.
 
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Old 02-18-08, 05:37 AM
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Do you have the installation manual handy?
You have to set some jumpers in this thermostat that must correspond to the type of fuel, type(s) of system(s) hooked up to it and type of controlled device. If you don't have the manual, take a look at the weblink below.

All that may be necessary for this baby to behanve is perhaps proper set-up.

http://www.ritetemp-thermostats.com/6025.html
 
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Old 02-18-08, 01:15 PM
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[dupe post by accident]
 

Last edited by StevenG; 02-18-08 at 01:18 PM. Reason: duplicate post
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Old 02-18-08, 01:17 PM
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I do have the manual, but it comes out of the box ready for oil or gas heat. No jumpers needed. The odd thing is, if you take it off the wall, it quickly adjusts, but when mounted, it's SLOW to adjust. Either in this room or the bedroom (another room). It's less of a problem in the bedroom though, as the baseboard isn't as much.

But today I bought a Honeywell 5-2 Programmable Tstat. I put it up in place of the RiteTemp, and raised it a degree from the then current room temp. It kicked on in a few seconds, the heat ran until the unit registered the additional degree (a few min run time) and shut right down. PERFECT! The RiteTemp would have run an additional 10 min or so, and raised the temps about 10 degrees over the desired.

So the answer - junk unit. I'm replacing the other with a Honeywell 5-2 as well (the bedroom) and the two main floor zones with Honeywell 7 day programmables. A $60 5-2 unit is way better than a $38 7 day programmable. You get what you pay for.

Thanks guys - your advice helped me out, by questioning the quality of the unit.
 
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Old 02-18-08, 01:22 PM
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Glad to hear that the Honeywell is working out for you.. I am guessing you followed the set up menu #240 to 3 for hot water heat?

Also give the stat a few days to learn the home, and it will work out perfect!
 
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Old 02-18-08, 01:25 PM
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Wink

Lets go back to how much base board. Did you do a heat loss for the room??? Slant/Fin Baseboard should give you a heat output at 200o water , 4 G.p.m flow is 720 BTU/hr Per foot.
 
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Old 02-18-08, 01:57 PM
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Yes, I did do the setup options. I only have 3 menus come up

1. Heat only
2. Hot water/Gas furnace over 90% effic
3. Farenheit

(note, not the right menu numbers, just a list)

I was pretty on the "hot water heat". I used to call a boiler a furnace, so I made sure I read "gas or oil furnace" as just that, a furnace (hot air system) vs hot water which is what I have.

As for a heat loss test, I believe the plumber did all this. He too a bunch of measurements, looked around, wrote down notes about the room being exposed on 3 sides (all exterior walls), side attics, etc, and then had the guy at the plumbing supply house run the numbers. The room has 9 foot ceilings too.
 
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Old 02-18-08, 04:04 PM
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I deal with quite a few rentals that have hot water heat and never have had this stat over-run business, no matter what type of stat. I see the theory in all that is said, but we have never had that. I am wondering something that has not been mentioned, I don't think: Is the circulator shutting off when the stat shuts off, or not?
 
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Old 02-19-08, 07:13 AM
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Originally Posted by ecman51` View Post
I deal with quite a few rentals that have hot water heat and never have had this stat over-run business, no matter what type of stat. I see the theory in all that is said, but we have never had that. I am wondering something that has not been mentioned, I don't think: Is the circulator shutting off when the stat shuts off, or not?
The problem was that the tstat wasn't shutting off. By the time to temp reading on the tstat hit the desired temp, the actual temp was about 9-10 degrees higher in the room. I think the RiteTemp 6025 has a design flaw in this. When it's mounted, it seems to respond very slowly to temp changes in the ambient air. This happened with 2 units not one. If the temp change is very slow in the room, it works ok I guess.

The new Honeywells 6300s solved the problems wonderfully though. The room was very comfortable and seems to hold the temp very well now.

I'm now going to swap out the two main floor tstats (older ritetemps) with Honeywell 7 day programmables, just for good measure now.

Thanks for all the help.
 
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Old 02-25-08, 07:48 PM
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temperature overshoot with your ritetemp 6025

Your temperature overshoot may be due to the units lack of an anticipator setting. That little wirewound variable resistor in most typical old thermostats artificially added heat to the thermostat when it was turned on to "anticipate" the heat soon to arrive in the room. This was specifically to preclude overshoot. The variable resistor is actually the heater itself, and you select more of it as you set for lower operating current, and less of it if your control draws more current. You can always cheat either directon to make it shut off faster or slower depending on your room and the thermal time constants of the heating system to room equipment. Blown hot air probably won't overshoot much, but a monster good old cast iron radiator (TOTALLY UNDER APPRECIATED BY THE FOOLS THAT HAVE BEEN "SOLD" RADIATOR COVERS OR ALUMINUM FINNED BASEBOARD...) may well take some time to get heat over to the thermostat, and without an anticipator you may well have a lot of overshoot.

You can have a smart-ass thermostat that "learns" over a few days of watching what happens in the room, but remember who makes ritetemp. It is a house brand for home despot, and doesn't even have real wiring diagrams of whatever is happening inside cuz they assume you are too dumb to be able to read them.

I think I have been warned by your post and just called their support line and she would not fess up to any learning capability in the thermostat, so with my big old wonderful cast iron radiators with cats napping on top, this new toy thermostat is going back unopened.

No "C" terminal on the boiler's triple aquastat, so to get constant power without the AAA cells, they say I need a seperate transformer. I just bet someone who cared could make a ckt that taking microamps could keep a pair of 1.2VDC rechargables charged and yet not fire the boiler while charging.

After the corporate media press that normally protects their advertisers was so jolted by the golden parachute of the departing top dog at hd that they actually reported his $250 million get lost package, I've been drawn to Lowes, but sadly they are a lot farther away, so for little projects I still suffer bad staff moral (when you can even find them) at hd.
 
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Old 02-26-08, 04:20 AM
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Thanks for your helpful post. Very interesting. The Honeywells from HD are performing much better. My only concern with them is that you can't set a temp swing, so I'm worried that my boiler is cycling more now. Hard to tell though to be sure. I need to place a call to them to ask. I have another thread going on that question.

Thanks for your help.
 
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Old 02-26-08, 06:00 AM
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The Honeywell stat will not see the swing.. it cycles on the 10th of degree.. example 68.5˚. as long you have it set up to your heating equipment #240-3, you are fine.. it's not going to short cycle.
 
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Old 02-27-08, 06:36 AM
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#240-3? Not sure what you mean by that.

I programmed it to "Hot water system/high efficiency gas" or something like that.
 

Last edited by StevenG; 02-28-08 at 06:35 AM.
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Old 02-27-08, 08:01 AM
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That is what I meant by.... "Hot water/High Eff."
 
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Old 02-28-08, 06:35 AM
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Oh I see. Thanks! Yes, "Heating Cycle Rate" (Function 5) is set to "Hot Water or High Eff Furnace."

I wondered what that did. I guess I didn't read the function title closely enough - Heating C Y C L E Rate. Dunce cap for me.

Thanks!
 
 

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