# Two Thermostats in One Heat Zone. OK?



## yuri (Nov 29, 2008)

If you have one furnace for the 2 floors you would need a zoning system with dampers in the ducts in order to use 2 thermostats. One furnace cannot use 2 thermostats properly as it changes the electrical load on the circuit board etc etc. Impossible if you have A/C as one could call for cooling at the same time as one calls for heating (accidentally).


----------



## fishmanflats (Aug 26, 2008)

*Sorry, this is heat-only baseboard HW system. No AC.*

Sorry, this is heat-only baseboard HW system. No AC.


----------



## kbsparky (Sep 11, 2008)

Hydronic heating systems utilize circulating pumps for the heating cycles.

A 2nd thermostat on the upstairs zone pump makes perfect sense to me.

You may need an additional pump control relay box to make the setup work properly.

This is practical if you have 2 pumps in the first place.


----------



## Clutchcargo (Mar 31, 2007)

You're going to wire this so that either thermostat will trigger the boiler?
That means that downstairs will get warmer at night than the downstairs tstat is set.
I don't see why that wouldn't work. Just wire the two tstats in parallel configuration.


----------



## kbsparky (Sep 11, 2008)

In many cases, the thermostat does not trigger the boiler. The aquastat does that function. The thermostat triggers the circulators. :whistling2:

Wiring them in parallel would defeat the purpose of installing separate zones/circulator pumps. :huh:


----------



## Clutchcargo (Mar 31, 2007)

kbsparky said:


> In many cases, the thermostat does not trigger the boiler. The aquastat does that function. The thermostat triggers the circulators. :whistling2:
> 
> Wiring them in parallel would defeat the purpose of installing separate zones/circulator pumps. :huh:


My boiler only comes on when the t-stat calls for heat otherwise it goes cold. I'm sure someone will correct me if I'm wrong but the only time that you need to maintain boiler temp is when there is a domestic HW loop going to it. 
I thought the OP wasn't interested in adding a zone just a separate t-stat to control the upstairs. Whichever t-stat is colder would be the one that fires the boiler. His t-stat configuration would mean that the downstairs would get warmer than the downstairs t-stat is set for at night. It sounds like whoever installed the baseboard didn't do the heat loss for each room correctly or he's getting solar gain and needs to add insulation.


----------



## fishmanflats (Aug 26, 2008)

*Balancing may be an issue.*

I can turn down the valves on the radiators on the first floor. I have been slowly trying to determine the right valve settings, but it seems very dependent on the outside temperature. I also believe one room's radiator is sized too small. 

Thanks for your replies. I believe that I will install the second thermostat. If I use an electronic one on a timer, I should be able to get enough comfort for the winter. 

-Mike


----------



## beenthere (Oct 11, 2008)

If you have a monoflo system.
DO NOT turn down any rad valves.
That will slow the water flow to all rads.

How high are the second floor rads above the boiler.
What is the boilers water pressure.
Has the circ been changed out in the last several years.


----------



## Mainah (Jan 18, 2008)

kbsparky said:


> In many cases, the thermostat does not trigger the boiler. The aquastat does that function. The thermostat triggers the circulators. :whistling2:
> 
> Wiring them in parallel would defeat the purpose of installing separate zones/circulator pumps. :huh:


 
if wired properly a call for heat should always fire the boiler along with the circ (unless its at the high limit setting)


----------



## fishmanflats (Aug 26, 2008)

*Beenthere*



beenthere said:


> If you have a monoflo system.
> DO NOT turn down any rad valves.
> That will slow the water flow to all rads.
> 
> How high are the second floor rads above the boiler.


 The boiler is in the basement, so I would say about 20 feet.


beenthere said:


> What is the boilers water pressure.


 I turned on the boiler and let it run for a few minutes: pressure seems about 15-20 psi.


beenthere said:


> Has the circ been changed out in the last several years.


 No. I have lived in the house about 8 years and never changed. The circ is a bell and gosset series 100 (h68). There are 8 radiators connected, 4 upstairs and 4 downstairs. 

The ironic part is that the radiators in two of the three rooms delivers too much heat, overheating the rooms. I turned those down to compensate, but overnight the temp is usually 4-5 degrees F cooler upstairs than downstairs. The last room upstairs, the valve is fully open. This radiator is the first off the boiler. This is the coolest temp-wise upstairs, maybe the rad is too small. It has side attics on two sides. I have insulated the walls, joist below and ceilings as best as possible.

I thought having the second thermostat might help regulate this issue.

Thanks


----------



## beenthere (Oct 11, 2008)

Second stat will do as others said, cause the first floor to over heat while making the second floor warmer.

The rad you said is first off the boiler. Is it the hottest rad?
If not, its actually the last off the boiler, but looks to be first because of the piping.

The B&G 100 series, is not always the best circ for monflo's.
I've seen more then one place that a tech didn't use the right bearing assmbly when replacing one, on a monoflo.


----------



## fishmanflats (Aug 26, 2008)

*beenthere*

I believe it's the first. It is the first to get heat, I am not sure about being the hottest, but it is the smallest of the bedroom rads, about 1/2 size of the other bedrooms.

I have thought about using TRVs and perhaps putting a larger rad in the small room.

Thanks for your input.


----------



## beenthere (Oct 11, 2008)

Monoflo systems are very flow rate specific.
Too little can cause what your experiencing. Because the mono tee isn't restrictive enough.

Do a temp rise on your boiler, post it, and what size boiler(BTU) you have. 

Another thing you can do. Is put a top on the rads that are in rooms that get too warm. This will reduce the amount of convection you get from them.


----------



## buletbob (May 9, 2008)

Here is a suggestion!! You could be able to separate the two floors to make two zones from the basement below. that would be the best bet! with a monoflow system, there's usually is a 1" loop with two tee's cut into it. then 1/2" coming from the tee to the rad.. find the monoflow tee that brings the hot water to the second floor and remove it and install a standard coupling on the feed side and the same for the return side. then run a new loop for your zone to the four pipes leading upstairs.don't forget to install the monoflow tee's.
And also check and see if the system was repaired at some point. I have seen Mono flow tee's installed backwards which will make the system not work properly. there should be and arrow on the tee to show the direction of the water flow. BOB.


----------



## fishmanflats (Aug 26, 2008)

*@beenthere*

It's a 105K BTU Utica NG boiler.

What are you looking for on the temp rise? It looks to be running about 180F before it cycles off. (It will run constant for about 30-40 minutes when calling for heat, not short cycling.)


----------



## fishmanflats (Aug 26, 2008)

*@bulebob*



buletbob said:


> Here is a suggestion!! You could be able to separate the two floors to make two zones from the basement below. that would be the best bet! with a monoflow system, there's usually is a 1" loop with two tee's cut into it. then 1/2" coming from the tee to the rad.. find the monoflow tee that brings the hot water to the second floor and remove it and install a standard coupling on the feed side and the same for the return side. then run a new loop for your zone to the four pipes leading upstairs.don't forget to install the monoflow tee's.
> And also check and see if the system was repaired at some point. I have seen Mono flow tee's installed backwards which will make the system not work properly. there should be and arrow on the tee to show the direction of the water flow. BOB.


I looked into doing this last summer. Both plumbers that i had come out never called back. I was guessing about $2500-3000 for the job. The loop is 1 1/2" copper and I'd need about 110 feet (about $1000 for the pipping alone). My basement is partially finished, so I'd need to have some ceiling removed. I figured 30 ft of wire and a new thermostat would be less than $50 and a little easier to get done.


----------



## beenthere (Oct 11, 2008)

Temp rise, is the difference between return water temp, and discharge water temp.
What is it on your system.


----------



## buletbob (May 9, 2008)

fishmanflats said:


> I looked into doing this last summer. Both plumbers that i had come out never called back. I was guessing about $2500-3000 for the job. The loop is 1 1/2" copper and I'd need about 110 feet (about $1000 for the pipping alone). My basement is partially finished, so I'd need to have some ceiling removed. I figured 30 ft of wire and a new thermostat would be less than $50 and a little easier to get done.


if I remember correctly that there is just two rads on the second floor, which i would guess you should be able to use 3/4". and you could switch from copper to pex. just another thought. BOB


----------



## fishmanflats (Aug 26, 2008)

*inlet outlet temp*

I don't have a way of measuring this. The boiler is too old to have these controls. There's only the analog reading on the side.

-Mike


----------



## fishmanflats (Aug 26, 2008)

*radiators*

I actually have four radiators on the second floor, three in bedrooms and on in a bathroom.


----------



## buletbob (May 9, 2008)

then the bigger pipe will be needed.


----------

