Where and How to Tie in Time Delay Relay

FYI: I made some edits to my earlier post.

So the euro-thermostat can get a signal from the radiators in the rooms and signal the thermostat to call for heat. Interesting.

Your concept to time delay the gas valve in order for more of the radiators to call for heat before relighting is an interesting idea. I can see how that will work and there may be some savings in that design. Similar to purging heat from a system after the call for heat is over, so you don't leave unused heat in a water boiler. By waiting 10 minutes before restarting the gas valve, you are removing one of the causes of short cycling, (oversized boiler in relationship to the few radiators that are calling for heat) and also giving that longer run cycle for the boiler to reach the cutoff pressure.

Let us know how this works our for you. I can see an @ethicalpaul video of this in the future. As long as the Netatmo system isn't too expensive.

It is only 10 minutes, and that is not a lot of time for a steam boiler. Worst case scenerio is 20 minutes if the call for heat reestablishes and then the gas valve fires up for a few seconds, then the CycleGard opens the circuit and you need to wait another 10 minutes. The recovery will just take a few more minutes. I think it will be an acceptable amount of off cycle.

If not, you can always reduce the time to 8 minutes.

You could probably size the boiler close to the heat loss with that much zoning. the radiators are only consuming steam if the boiler is producing it. The radiators may still be hot when the boiler isn't firing but they aren't getting additional heat for more than a very short period after the boiler stops firing. It produces pressure because the radiators are consuming les steam than the boiler is producing, not that they "are full of steam".

That being said, i think that littlefuse time delay powers a timer circuit inside when it is energized by flowing some current through the load then closing its contacts when the timer expires. If the load is high impedance it won't work, it needs to control a relay coil or gas valve or something. If it is in the wrong place it could cause an ignition control to lock out because it is expecting flame to be proven in a certain timeframe.

The steam condenses in the radiator and shrinks in volume something like 1700 times and pulls more steam in. if the radiators are condensing as much steam as the boiler is producing it builds no pressure, the pressure only builds if the boiler produces more steam than the system can condense.

are you comparing the output of the total radiation to the heat loss of the structure? i bet it is still way more than the heat loss even if the connected edr is close to the output of the boiler. with your zone valves if the boiler can't quite fill the whole system some zones will be satisfied and close then the zones that were starved of steam can heat. as long as the connected edr is greater than the heat loss a smaller boiler would work. i'm not saying you should change it, just pointing out that a significantly smaller boiler could probably work with the control system.

Hello KarlW,

Why didn't the ICM203 work, the one I have works fine with an open circuit. In your case I would have inserted it in series with the Dwyer Capsu-Photohelic relay contacts, although other places may work too. Looks like your Dwyer Capsu-Photohelic is set to open the circuit at 18 inches WC, then the delay of the ICM203 would start and not re-close the circuit until the delay expires (0.03 to 10 Minutes later). By then the pressure would have diminished and possibly the thermostat satisfied.

I have a ICM203F, just to play with, and I have played with it. My EDR is larger than my boiler so I have no actual need for it in my system. Its an interesting timer (since the delay continues totally un-powered, I will re-verify this). Also I wanted to reverse engineer it, so far it looks like a TRIAC is the AC switch.

With Ed's placement of the ICM203 at the gas valve, if the thermostat or your "smart valves and TRV" system is calling for heat during the 'Off Delay' of the ICM203 the damper won't close. Benefit, less wear and tear on the Damper, disadvantage $$$ going up the chimney.

Assuming the 2nd timer is a HRDB223 that should work to, however the way it is integrated into the existing circuit would be much more critical. Was the transformer that powered the HRDB223 the same as the transformer for the boiler's control circuit ?

EDIT: Looked into it deeper, my second opinion is it will not work for this application, see text below.

I would say this relay (the HRDB223) would not work for this application. The problem is the relay does not change state at the trigger event.

If you have not, please re-read my last two posts I kept editing them after the initial post, I never refreshed the page so I did not know you had probably read them already.

I would have wired the HRDB223 this way to make the normal trigger operation correct (terminal 6). However there is two issues with using that device, no initial closure of the 'initiate switch' function and the relay is in the wrong state during the time delay interval as stated in a previous post.

Once triggered the timing of the ICM 203 is fine with no power connected to the unit.

I suspect the ICM 203 did not work in your original setup due to the load current of the Damper trigger circuit is below the 0.040 Amp (40 mA) minimum load specification (Holding Current). The gas valve current should be easily above that, so it worked there. For me I would want the Damper working correctly (issue explained above). If it is determined that the Damper trigger circuit current is too low an appropriate resistor could be added as a slight additional load.

" When you say $$$ going up the chimney, is this just heat escaping? If it's just that, I can afford it somewhat as I have a dedicated overheated boiler room. "

Yes, heat you are paying for. For the cost of a 620 Ohm, 2 Watt resistor I think I would want my Damper to work as intended.

If your boiler duty cycle is reduced the boiler room should not be as hot. I would run the timer with the longest delay your comfort will tolerate. Same with the Dwyer pressure settings as low a pressure your comfort will tolerate.