Configuring RTH7400D

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Old 12-28-06, 09:23 AM
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Configuring RTH7400D

We purchased five new Honeywell RTH7400Ds to replace our thermostats on our 1960s zoned gas boiler/hot water baseboard heating system (we actually have six zones, but we assumed one was to the greenhouse that we don't use). We installed them in the fall, and for awhile all seemed to go reasonably well. But this week we are starting to have doubts. We can't seem to get any room about 65 no matter what we set the thermostats at (even setting up to 90), and we have some some rooms with stone cold baseboards. We are not sure if this is a problem with the thermostats, or with some other part of the system, but since we have recently been monkeying around with the thermostats, we suspect our own handiwork.

First, as I understand it, there could be two issues: wiring and configuring.
Only the heating system is controlled by these thermostats (air is on a completly different thermostat). I had originally assumed this must be a three -wire system, but the heating guy who came to service the boiler for me in the fall said that it was a two-wire system, though they apparently used three-wire to do the wiring, just not hooking up the green wires. Sure enough, when I removed the old thermostats, there were two wires hooked up (R & W), and the green wire was just lying in there unconnected. So we wired the red to R and the white to W (after MUCH research on this and other forums because of course the old thermostat was not marked!). I am not too concerned about this, but I am long-winded in case you want to "check my math" on this.

I am less confident about the configuring.
In the initial setup procedure, one is asked to designate what type of heating system one has(setup #170)--and there are 10 options. I had it narrowed to one of 2: #3 Heat only with no fan (Conventional)--"gas, oil, or electric heating without central air conditioning. No wire on the G terminal on new thermostat." or #5 Hot Water Heat Only (Conventional):"Gas or oil hot water heat with three wires connected to new thermostat or for normally closed hot water values with wires connected to R and Y on new thermostat."
None of the others seemed to match our situation since we don't have air conditioning on this thermostat, nor do we have a heat pump, and I don't think we have multi-stage heating and cooling (drifting out into deep water here.....).
I have tried both options (though I notice that #5 refers to wires at R and _Y_ on the new thermostat--should that white wire I have going to W really be going to Y?). If I choose #3 Heat only with no fan, I am then asked to make a choice at setup #240: Again, there seem to be two options: "5--Gas or Oil furnace (less than 90% efficient)" or "3--gas or oil hot water, Gas 90%+ high-efficiency furnace"

I have tried 3 variations: #3 at Setup #170/#5 at Setup 240, #3 at Setup #170/#3 at Setup 240, and #5 at Setup #170 (which doesn't require a choice at 240). None of them seems to improve the situation. It's not that we don't have heat at all--some of the radiators give off heat, and we can get most of our rooms to 62-65 with it being in the 40s outside--but it almost seems as if the thermostats have no effect on whatever is happening.

Can someone tell me if I have it wired right, and if I've made the right choice in configuring?

If we could rule out a problem with the thermostats, we could then move on to troubleshooting the rest of the system. We have also tried bleeding all the radiators until hot water runs (though some of them never get to hot water, but just lukewarm). We've found no air in any of the radiators.

Thanks!
 
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Old 12-28-06, 09:33 AM
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t-stat

The t-stat is a pretty simple switch. If the measured temp is less than the target temp, it connects the 2 wires (that is how it calls for heat). You can do that manually as well by just connected the two wires together (but it will just keep on heating).

If, with the wires connected, the boiler can't get the house above 65 you have to feel good that it isn't your t-stat wiring skills, it is something wrong elsewhere in your heating system. It might be air-bound, you may have a bad circ... etc.
 
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Old 12-28-06, 09:35 AM
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questions

Does the boiler start when the stat is calling for heat?

What is the system pressure in the boiler (i.e. 12 to 18 psi is normal.)
 
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Old 12-28-06, 11:13 AM
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other issues?

two things: psi was at 12#, but has dropped to below 10# on gauge. Could be because we were bleeding radiators? Do we add more water to system to bring psi back up? And how do we do that? I see a threaded pipe on backside with a valve on it (yellow handled bar)--do we hook up a garden hose to that to add water? And do we need to let furnace cool before we do that?

Second thing is that circulator pump (B&G) is very hot, and while it is clearly doing something, I'm not sure it is doing much. It sounds more like a car starter clicking on and then immediately off rather than actually pumping anything.


We are still trying to figure out if system is responding in any way to the thermostats. We've tried moving white wire to Y terminal on two of them (one controlling zone with some working radiators and one controlling zone with some stonecold radiators) and changed Setup #170 to 5--doesn't seem to have made much difference at all. Radiators that were working are still working, though there is some improvement in temps after a half-hour, but radiators that were stone cold are still stone cold.

There are just so many variables, it's giving us a headache!
 
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Old 12-28-06, 11:54 AM
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water

There should be some sort of fill valve. 10 psig should do for a 1 story house. Is there a pipe coming into the boiler through a valve from a domestic water feed? There should be a fill valve and pressure reducing valve to fill the boiler. The spigot is the boiler drain. DO NOT use it to refill the boiler--you could contaminate your drinking water, and you could crack the hot boiler by adding cold water directly into it!!! Post photos of the system, someone here can help. You're circulator could be shot or airlocked.
 
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Old 12-28-06, 01:48 PM
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pictures

OK--I've got pictures--such as they are. If you need me to go and try to retake some (I could try lighting them with something other than the flash on the camera, I'll be glad to try).
I dropped them into photobucket: http://s122.photobucket.com/albums/o241/GoMuskies/

BTW--thanks for all your comments!
 
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Old 12-28-06, 02:06 PM
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circulator

If you were at 12 PSI and it worked before, I'd guess 10 psi should as well. Bleeding air will cause the pressure to drop.

I'm wondering if the coupling in that old Bell&Gossett circulator has given up the ghost! It's possible the motor is turning, but the pump impeller isn't moving. I'm not that familiar with the B&Gs to advise if pulling the little plate will let see what is going between the motor and pump.

I suspect that red object in jpg 0038 might be your pressure reducing valve for filling the boiler, there looks to be a valve next to it that's a cutoff. Does that device go back to your domestic water system?

I'm just a homeowner, but Grady, Who, Ed or one of the regular experts will probably chime in and offer better advice that I can when they get home.

Pete
 
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Old 12-28-06, 04:43 PM
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Originally Posted by radioconnection View Post
I suspect that red object in jpg 0038 might be your pressure reducing valve for filling the boiler, there looks to be a valve next to it that's a cutoff. Does that device go back to your domestic water system?
Yer suspicion is correct PeTe, if that valve to the right is closed, opening it should let water in... you won't need much to go from 10 to 12 .

Looks like you've got a leaker just to the left of the reducing valve... see all that green crud ? maybe oughter have that taken care of.

You may not see any liquid water leaking there... but I almost garontee it's leakin'

I'm down with the circulator problem diagnosis... especially since it's been working with the new t'stats, and this seems to be a problem that cropped up alla sudden last week. You should be able to see the coupling if you look in them holes between the pump and the motor.
 

Last edited by NJT; 12-28-06 at 04:54 PM.
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Old 12-29-06, 01:18 PM
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We have heat!

We called in the pros, and we were all right--it was the circulator. It was bound up and not turning, and just required a whole lot of oil--though this was the same guy who serviced it in the fall and he says he knows he oiled it then. But he worked with it and freed it up. He had to work a little with the pressure reducing valve too to add water to the system. Then we had an extensive chat about the thermostats--he found them as mystifying as we did! The work he did got heat to all the radiators except the livingroom, and we discovered that problem there was due to the thermostat signal not being received at the flow valve, but he monkeyed with it for awhile and finally got that to work (by moving the white wire from the W to the Y). I then asked if we should do the same thing to all the others, and he said "Don't mess with them--they work!" So, near as I can tell, we have 5 thermostats wired/programmed in three different ways--but they seem to work right now. I just hope they turn off when we want them to! Still after several hours, thermostats are all holding at 70. Beats me why we worried so much about configuring them when it doesn't seem to matter what we do!

If anyone has any idea how they SHOULD be wired/configured, I'd be glad to hear it!
Anyway--thank you all for your help. I was able to have a pretty intelligent conversation with my professional, instead of feeling clueless and helpless.
 
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Old 12-29-06, 01:30 PM
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stat

They should be all wired the same. Make sure they are all set for heating, not cooling! It might be wise to plan having that old B&G replaced next spring. It will bind up again.

Pete
 
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Old 12-29-06, 02:10 PM
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Hey!

What kind of circulator is this?

I'm guessing B&G Series 100... was I close?

Okay so he got it going. Big deal. He can come and do that again next time as well. What a miracle worker. That circ takes 1.75amps, not .75 amps like a 007 or similar gpm newer cheaper b&g design, grundfos, armstrong etc.

I think that he really should have replaced it. If that circ is in continuous day 200 days a year and you have average electric rates, then the new circ would pay itself off in two seasons... after that it is saving YOU money. Instead he bumped a pump that he should have dumped. Okay that was bad...

Anyway, a new 007 or 15-58 and you would have been good to go for longer than it will likely be until the next service call on your oil circ. These newer circs will fail. Everything does and in the case of one it is disposable, and in the case of another it can be restarted but it has become a near-routine maintenance item.

In the meantime the customer would have had a quieter circ, especially in the case of the 15-58 on anything but hi, as well as lower the electrical bill enough to pay for the circ (oh yeah and add the serviceman in and even if it is a multiple like 5 that circ will still pay for itself. I think for either type of circ the mean time before first failure would be the same. By then the newest circs will be yet that more efficient by motor design variable speed super low wattage hopefully.

You can keep these old pumps running forever but at some point it becomes a bit like owning George Washington's axe even though the handles been replaced 12 times and the head only twice.

I'd ask his manager or the owner of the business why they wouldn't put it a new pump that would be more reliable? Reliability should be first and foremost in this regard.

Wait... better yet, now is your chance to feel at home here. Go buy a B&G 15-58. It has 3 speeds. Medium will easily be best, but you get to try different speeds out... different delta... no. If you can twist a big adjustable wrench with one hand and hold a wrench in the other, do simple wring to disconnect it properly from one to the other and also how to shot down, drain the system --- wait, if it has isolating flanges, just **** down , don't drain, just isolate the circ by valves, grab a pail and unbolt the bottom flange. If instead you have to drain it, then you have to wonder about moving on to stage 2 which would be replacing those simple rusty flanges with some nice brass flanges to better mate against you new 3speed circ. But as you imagine how simple it could been and also how much you'll regret not doing it if you start it up with air by accident... then yet another drain, add the isoflanges once and for all and make sure my pipe wrenches are big enough to do it. You'll need piping dope and teflon tape. One roll more than you think you'll need and you are going to wrap that pipe four or more times over. And not with the cheap white tape. Pink or orange. The toughest part will be figuring out just how much to shorten the pipe for the new iso-flanges and what pipe lengths you'll need or perhaps get many lengths all just in case. And afterwards you can give it to your next serviceman (he'll use them) if you didn't enjoy it, otherwise you can start a new milk crate for piping parts in your workshop area. Now you're set! ;-)
 
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Old 12-29-06, 04:28 PM
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Who....

Dude, what's going on? Something about this strike a nerve? I see the humor here, though.

GoMuskies: Who makes a very valid point: the circulator should have been replaced. It's not a big deal and would have been the best option, short and long term. When it seizes up again (and it will) ask for a Taco 007 or a Grundfos 15-58.

If the thermostats are talking to the zone valves, and everything is working ok, then I wouldn't mess with it until you see or observe something demonstrably wrong. A pro, however, is welcome to correct me. This is somewhat out of my element. You should at least make up a simple wiring diagram to trace out everything so it is at least written down.
 
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Old 12-29-06, 07:20 PM
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Originally Posted by GoMuskies View Post
So, near as I can tell, we have 5 thermostats wired/programmed in three different ways--but they seem to work right now. I just hope they turn off when we want them to! Still after several hours, thermostats are all holding at 70. Beats me why we worried so much about configuring them when it doesn't seem to matter what we do!
Bottom line is that the thermostat is just an on/off switch. BUT:

Those different settings control when, and for how long, the thermostat is ON, and similarly how long it stays off... The newer t'stats LEARN the response of your house to whatever form of heat input it has. They adjust themselves after operating for a while. They measure the amount of time it takes for the rooms to reach setpoint, the measure the amount of temp overshoot, etc etc ... you need to tell the stat the type of equipment you have so it can make the best artificially intelligent decisions. Program them properly and they will make your house more comfortable by limiting the temp swings, and save you money while they are doing that.

Unless you know what to look for, you may not notice any difference, but I know for a fact that they do work. Mine does. If set on 70* as an example, my old stat would let the room cool to 68-69, kick on, overshoot to 72 . The new stat holds rock steady at 70 . It didn't do this right away, took about a week or so for it to learn. Works especially well for recovery from night time setback.

Long story short... settem up right...
 
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Old 12-29-06, 07:30 PM
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Talking Stat problem

Five identical stats in a heat only system. Basic two wire hookup operating zone valves for all of the stats. Before switching over all of the older mechanical stats worked fine.

Four of the five stats are wired to the red and white terminals, which is correct for a heating system.

To get the fifth stat to work they had to move the wire from the white to the yellow terminal (i.e. Compressor!!!). That suggests to me that the stat is set for Cooling, and not Heating.

That's my story and I'm sticking to it!!!!
 
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Old 12-29-06, 07:54 PM
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Originally Posted by radioconnection View Post
That's my story and I'm sticking to it!!!!

Once again, I'm with PeTe ... (great minds ya know!)

I just looked at the PDF file again.

Red to R (with the jumper in from R to Rc)
White to W

170=3
240=3

and just to be sure you are using the artificial intelligence feature...

530=1
 
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Old 12-30-06, 07:40 AM
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Thanks!

First, I know you are right about replacing the circulator. I should have asked why he didn't replace it. But I can now plan to replace it (and budget for it), and if it doesn't bind up again this winter, I'll have them do it at our next servicing next fall. You've given me some ideas of what to ask for. I'd seen another post about switching to the newer wet rotor types (and actually priced a Taco 007 which is surprisingly inexpensive) so I'll have some basis for an informed discussion. I can also warn them ahead of time when I make the appointment so they can bring it with them when they come (in an ideal world).

Thanks to those who pointed out that some of the thermostat's value lies beyond it's simple "on-off" switch. We got them precisely for their ability to "learn" and we won't be taking full advantage of them if we don't set them up right. I'm not sure about how the one t-stat could be set for cooling--the configuration is at the 170-3/240-3.

I wanted to watch them today to see if they follow the programmed schedule, but it just bugs my orderly mind to have five identical t-stats wired/programmed three different ways to five identical zone valves.

Finally--thanks to NJTrooper for finally giving me a concrete answer to how I should wire/program the stats.

And one more "finally" (I promise!)--There are limits to what I trust myself to do myself. This forum has helped me (long before I actually posted with this problem) understand the system better, figure out what I can do, and be reasonably intelligent in dealing with service man when I can't do something. I probably screwed up when I didn't just tell him to replace the pump, but I was less clueless than I would have been. Thanks to all of you, and.....
HAPPY NEW YEAR!
 
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Old 12-30-06, 11:59 AM
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stats

"I'm not sure about how the one t-stat could be set for cooling--the configuration is at the 170-3/240-3."

Not to belabor the point, but for two wire heating the W and R contacts should have worked. The Yellow is normally used for a compressor, which would be either for airconditioning or heat pump operation. I'd be tempted to try one of the working stats in place of the one that is different since it would drive me nuts, being a techy type <VBG>. But, if everything is working as it should be, leave it alone. No use looking for problems, especially during heating season.

It's good to do a quick heat call every month or so in the
summer for 10 or 20 seconds, that'll exercise the circulator and keep it from freezing up from non use! Have a good New Year, at least it will be a warm one!!!

Pete
 
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Old 12-30-06, 01:32 PM
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Red face PB Blaster would have worked!

I reccomend you pick up a can of PB Blaster. If the circulator does this again before spring, spray a bunch in the oil cup on the pipe side. Basically the B&G 100 circulators have a snap disc thermal switch built into them so that if the shaft stops moving, the motor will try to turn the coupling, which will just move back and forth a little, making a loud noise, till the high amp draw heats up the thermal switch in the motor and it stops the motor till it cools down enough and starts again. I wish I had gotten on this thread before you called the tech. Now, being a tech, I understand why he didn't want to replace the circulator at this time. It's friday before new years, and I'm sure he didn't want to work late. Your water feeder and air vent both look very sketchy (i'm guessing they either don't work, or work at a very limited capacity), and with no isolation valve on the bottom of the circulator (isolation flanges would be nice), he would have to drain the whole boiler to change the circulator. Sometimes looking at old valves/components the wrong way will make them leak. I'm sure he would probbably be willing to do a better job making it right if you told him that you anticipate having to replace these parts if they fail, and he is able to schedule the time to do it. I had three tune-ups scheduled for friday. I was able to only do two of them because everything went wrong on my second call. A tune-up and check of the LWCO turned into a $400+ service call. The last guys that serviced the oil fired steam boiler apparently just did a "quickie".
 
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