Another pathetic T-stat question

Handyman 242

The Taco zone valve has a current draw of .9 amps. A normal thermostat with a standard heat anticpator setting of .4 setting will short cycle the unit the way you describe. The heat from the heat anticapator circuit will actually heat up the thermostat. If the thermostat is old do not try to change the heat anticaptor as all the cooking grease and stuff in the indoor air will have messed the wire slide up inside the thermostat. My advise is to install a new T87F set it at .9 and walk away. If you want to be fancy install a digital stat, set the cycles for 4 or 6 cycles per hour depending on heat responsiness of the system.

Xc8p2dC

One for the HVAC gods >

It is funny, because searching thru the topics, seems like the T-stat question comes up more than anything else, yet isn't descripted in the Hot Tech Topics section>> anyhoo

My on going battle with new construction boiler cycling > Partly related to oversized unit > Now working on control side > A good exapmle of what I am up against was last night>

No prev boiler useage so cold start > T-stat set at 66 deg and calls > TACO takes 90 sec to open >> Burner fires and runs for 2 mins > T-stat satisfy's > Burner shuts down > I run down to the boiler and Temp is still 130 deg so burner did not shut down because of high limit and there was no warm Rads to warm room >>>

So my question is? >> Is there a Digital/programable T-stats the you can control the andticipator or the temp differential between on or off>> again this is a simple, boiler only 2 wire [no heatpump.blower or AC] that works well with Peerless DE-05 and TACO 571 zonevalves?? >> again your help is greatly appreciated>> Rich

Scooter Libby

If your thermostat called for heat and then stopped calling for heat, it must have been due to warmth from the rads. If the rads are cold, why did it stop calling for heat?

Common digital thermostats don't have an anticipator or a temp differential setting, but they allow you to set the number of cycles per hour (or they allow you to choose electric/forced-air/water/steam, which is in decreasing order of number of cycles per hour). Fewer cycles = bigger temp swing.

I believe some of the fancier Totaline thermostats allow you to set a temperature differential.

Big Ed

Some other Problem

Two min run is a problem..You did not metion thermostat that is now on the job. Jump out therm see if it runs steady.. If not problem is with wiring or down stairs.If run steady check voltage make sure thermostat rating and power supply are the same.(Your thermostat is acting like a 24V therm with 110V running through it) If correct replace thermostat make sure it is marked for hydronic use..

Xc8p2dC

Rich> BigEd>Handyman

Thanks for your advice> I had another thread [Boiler Size/ probelms that gave all the details

Home and System is brand NEW in March> Short cycling has been a problem from day 1> T-stats are set a .9 > voltage is 24vac > FHW BB is 2 zone > In March I had cycling that would be every 5 mins and sometimes shutdown after the evac blower came on but before the burner fires [15 secs]> I think my 2 zones are fighting with each other

Are there any Zone valves the are mechanicaly operated [i.e. solenoid]instead of amp'd

Also > My Hi/Low cutoff temp control dial is / min 180 and max 220 > It is currently set for hi cut at 200 and low 185
Much of what I read here always seems to be 160-180
Could I have the wrong control ? or is these temps OK

TIA, again

ttekushan

180 deg min aquastat

I'd love to know the answer to this question as well. I know that with a traditional cast iron boiler that cut out temps that are set too low can cause condensation problems. BUT- isn't this type of control kind of restrictive? Isn't 160 degrees acceptable in this set-up?

Steve_35

You've already got the best zone valves out there

Get a digital stat and be done with it. We use Lux's PSP511 with Taco ZVs by the bucketful. Have very good luck with them and they're very easy to program.

Steve Ebels_2

Two questions

1. What's the BTU input of the boiler?

2. How many feet of active baseboard on each of the two circuits?

Xc8p2dC

Sounds do able

thanks for the info > I'm use to the instant on with oil heat systems and not the 90 sec delay of the TACO's
Rich

Xc8p2dC

Steve

Peerless DE-05 140K btuh in > 115K out >
Heatloss is 24,600 [I can hear ya laughin] > 1300- sq ft ranch >
88' fin tube baseboard both zones, not including poly piping

The loops seem to be proper, starting with the furthest room from the T-stat
Rich

Big Ed

Fighting Each Other

Why do you think they are fighting each other ? Does the system heat the home ? Does the system runs better if you raise both thermostats all the way up ??Try it. Then lower just one all the way down. Let me know if the unit shuts down when you do it...

Steve Ebels_2

Figuring avg btu per ft

That comes to about 57,000 btu output for all the baseboard combined. Can we say oversized? ,,,,,,,,,All together now......OVERSIZED!........ There, that was good.

No I'm not laughing. It's really too bad for that. Aside from the t-stat problem, that boiler will short cycle forever unless you add some major amount of buffer capacity somewhere in your system. As someone on this post said before. I would take the t-stat off the wall and jump the wires, usually the red and white are your heating circuit. Keep an eye on the boiler and see if it will run up to the limit setting without cycling off. This will tell you if the problem is in the boiler and/or its wiring or in the t-stat. You can also follow the t-stat wires back to where they connect to the boiler, take them off there and jump the terminals that they connect to for the same result. Don't jump the wires on the boiler with the t-stat connected or you'll fry the anticipator in the t-stat.

Xc8p2dC_2

why fight

Big Ed > Not by control circuits or shorts but by zones being close to each other > Once one T-stat ends call the other one calls for heat > your test kept the boiler running with one turned down > If I force test the system it will reach it's cut in/ out temps Ok > It is when the stat is set to a certain temp [ie 68 or 70] over nite > more info below

Xc8p2dC_2

Steve-E

Sadly I bought the new home this way from a builder that is edge of bancrupcy > Most forum advise hear and 1 physical estimate confirm [[[oversized]]] and also suggested buffertank > My problem with that is for every temp change I'm still firing @ 140K btuh [KILLIN MY GAS BILL] and believe me this unit is noisy being right under the master bed.

Here is some of what happens
Tstat at 70 > Boiler cold > stat calls > TACO takes 90sec to open > blower evacs 15 sec > burner fires > boiler reaches cutout 200deg > reaches max temp in 6-7 mins from about 120deg > Burner shuts down > SOUNDS PRETTY NORMAL Eh?

Here is where it gets fun >

Boiler between hi/lo > Zone 1 tsat calls > taco takes 90 sec to open > blower +15 sec > burner fires> runs 1 min > nearing hi cutoff > tstat ends > boiler shuts down > Zone 2 tstat calls > taco 90 sec> burner fires > runs 5 mins > reaches hi cut off > shuts down > tstat still calling> uses all avail heated water > boiler cuts in runs 30 sec > Z2 Tstat satisfied > shuts down > boiler not up to max temp > and NOW ZONE 1 CALLS > this goes on all night long

Sound normal? HVAC who installed said, set the tstats 5 deg different of each other and raised the hi cutoff to 210 >
See what I am up against

Still havent got a good answer on what hi/ low temps it should be ???

Is a buffer still the best option? > Alternatives? >
You know if I could get compensated I would be looking at a Buderus GB142 or a Munchkin

You guys have been a big help and it is greatly appreciated
Rich

S Ebels

Where

Where are the t-stats located in relation to your baseboard? If too close they are maybe sensing the convective air flow from the BB before the room temp is actually satisfied. Try to locate them on walls that are perpendicular to the stat. In other words if the BB is on a North wall, place the stat on the East or West wall. What I have seen happen in rare instances (2 to be exact)is that the convective air current will travel up the wall from the BB, across the ceiling and follow the facing wall downward. By locating the stat 90 degrees to the wall with the BB you eliminate this effect. You can try tru this by pulling the stat, attaching some 18-2 wire to the ones now hanging out of the wall and running them across the room to a "test" location. Just a thought. you're not out anything to try it and I've seen it help.

Xc8p2dC

Interesting observation

In zone 1 [Liv/kitchen} Rads are East and South> tstat is on North wall 16' a way with 10 cathedral ceiling

In Zone 2 Beds/baths > Rads are on West and North walls and tstat is on East > So neither is under Tstat's, but I get the picture about radiating over the top of the room, and

In zone 2, the smaller loop, starts to the furthest bedroom 3 then 2 then master where the tstat is, so I at least got that going for me

My perplexion still goes back to my original topic at the top, where the tstat called > Taco took 90sec plus burner 15 secs burner ran for a couple, did not get to max cutoff and was around 130 deg > rads still cold to touch and tstat terminated > and this was before anyone was awake so no air movement in room >

In March when it was colder there was so much overlapping, I had times where the evac blower would come on and then shut down before the burner would even fire [within 15 sec]

LAst night I put the Z2 @ 68 and anticipator at 1.2 and left zone 1 at 60 deg and seemed to be better as far as cycling with the boiler running for about 6-7 mins every 1/2 hr @ 35deg outside

Xc8p2dC

Pitman9

I looked locally for the LUX's PSP511 > Anywere online or major plum houses that carry them
Rich