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Thermostats (Honeywell and EcoBee)

I currently have a Honeywell FocusPro 6000 thermostat which seems to do regular thermostat things well (schedule, detecting temperature, anticipating when the system should come on, etc.). Although I don't use much of that since I just set the temperature to 67 and hold.

However, the cycles-per-hour setting and determining when to stop the call-for-heat seem to be all wrong.

What a cycle looks like:

T=00 - call for heat

T+18 - system reaches 3oz pressure and vaporstat cuts out. radiators are all ~90% full which is where I would want them to stop getting steam on this vapor/orifice system.

T+18 to T+25 - system pressure reduces to 1oz and vaporstat allows burner to fire again. 30 seconds off then 90 seconds on

T+25 - call for heat satisfied

T+60 - call for heat

What seems odd to me is:

1) the call-for-heat is exactly 25 minutes every time now. earlier in the season (before the cold got COLD) the call for heat was exactly 20 minutes. so is the Honeywell relying on time to kill the call-for-heat instead of the sensed temperature in the room?

2) the second call-for-heat is exactly 60 minutes after the first call for heat. so is the Honeywell using the 1CPH as a rule instead of a maximum? I think the alternate explanation would be that the room loses all of the heat in the 35 minute off time and therefore needs to call-for-heat right when the CPH setting allows it to. In which case, setting CPH=2 might be an interesting test?

I know that the newage 'smart' thermostats aren't really liked around here because none of them (Nest in particular) seem to have a CPH setting. However, I stumbled across the ecobee ( thermostat that looks to be a bit more interesting because it looks as though it is programmable through a software API (Application Programming Interface). Has anyone - specifically any software engineers like myself looked into this ecobee and found anything interesting about it?

What I think I want is a very dumb thermostat along with a control that stops the boiler from firing after being on for 18 minutes and then a control that allows another call for heat after 20 minutes of the radiators giving up heat. I know that MarkS ( has experimented with a time-delay relay after the vaporstat cuts out which might actually be the perfect solution for me.

Anyone else using a similar but different solution?

MarkS, if you're listening, are you still using your time-delay relay and is it successful like you thought it would be?


  • SWEISWEI Member Posts: 7,356
    Pressure Switch

    Was that a Mercoid D, or one of their other models?
  • saikosissaikosis Member Posts: 57

    I'm pretty sure that ecobee's optional ZigBee module is using the ZigBee chip made by my company. If that's true, there's a chance that some software I wrote is running on the thing. And if that's true, I definitely recommend you buy it!

    I started experimenting with building my own thermostat using an Arduino. My house is L-shaped with the boiler near the end of one leg and a bedroom at the end of the other leg. The thermostat is in a room with no radiator and sits almost directly above the boiler. The heat coming off the boiler and the uninsulated mains is enough to artificially keep the thermostat happy on mild days, leaving the other rooms a little cold. On really cold days, the lack of a radiator keeps the thermostat artificially unhappy. I'd like to add temperature sensors in the bedrooms and living spaces and intelligently figure out when to fire the boiler based on time and temperature. For example, during the day, I care about the living areas, but I care about the bedrooms at night. I also had the idea that knowing the temperature of the boiler water would help you know when to fire too. If the water is cold, you'll need to fire for awhile before you start making steam, so the thermostat could be smart and turn on a little earlier than normal. ChrisJ suggested adding outside sensors for temperature and wind speed would give you a lot of useful information for deciding when to fire too. There are a lot of variables. It's definitely an interesting problem.
  • SWEISWEI Member Posts: 7,356

    Nice price...
  • cdmcdm Member Posts: 62
    Time Delay Relay & Pressure Switch Option

    I read the post where a time delay relay and a pressure switch were used in place of a pressuretrol or vaporstat. It seems to me this would be ideal for my set-up, as my system runs at a very low steam pressure (less than 1 oz) and the radiators remain hot for long time after the boiler shuts off. The 20 minute dwell time (or an adjustable dwell time) allows for the radiators to additionally heat the room - This should reduce the short cycling time I see on very cold days. My question is - What is the make and model number for the timer used in this set-up?

    thanks -cd mulford-
  • cdmcdm Member Posts: 62
    Time Delay Relay and Pressure Switch Option

    Thanks for the time delay relay information.

    cd mulford
  • butlermogbutlermog Member Posts: 50
    Programmable Logic Controller

    With a lot of help from another guy from The Wall I am working on a solution using a programmable logic controller from Teco (

    There are many different units. The unit I am using is a bit different from the link above but the one in the link is a better unit because it has a keypad and screen.

    The programming is pretty simple. I am planning on starting with a very simple program that will only allow the burner to be on for X minutes at a time. I will then just use a very simple "dumb" thermostat. This way I will never produce too much steam for my radiators to condense and I will not have to worry about too much overshoot. Those two reasons are what I believe to be causing my boiler to run too long and therefore waste fuel.

    You can find some more posts about this from PMJ on The Wall. His program is much better than mine as it changes the value of X after a few cycles. So he starts out with a 5 minute burn and then waits to see if the thermostat is satisfied. If after a few of those short cycles it still isn't, he bumps it up to 8 minutes (then so on and so on).

    I am pretty excited about putting this solution in place even though I probably will have to wait until the fall since this heating season is mostly over for me. I think that I will make back the cost of the PLC in saved fuel in a few weeks.
  • cdmcdm Member Posts: 62
    Time Delay Relay and Pressure Switch Option

    Thanks for the information on the pressure switch and the time delay relay (both of which I have ordered). Any chance of a wiring diagram so I don't screw-up the installation?

    thanks -cd mulford
  • cdmcdm Member Posts: 62
    Time Delay Relay and Pressure Switch Option

    Thanks for the wiring diagram - This will insure I wire this set-up properly.

    Thanks again -cd mulford-
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