In temperature screen at 49 degrees to back to front t's appear and boiler stops

Question edited for clarity.
Question moved from Kitchen Ranges.

Sounds like the temperature sensor is failing.

https://www.google.com/search?q=rinnai+e110cn+set+back+temperature

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L'errore EA su una caldaia Elm Leblanc indica un problema di accensione della fiamma, che potrebbe essere causato da diversi fattori. Nella tua situazione, sembra che la fiamma si accenda correttamente, ma poi si spenga improvvisamente, portando alla comparsa dell'errore.
Ci? potrebbe essere causato da una variet? di fattori, tra cui:

1. Un sensore di temperatura difettoso o danneggiato, che potrebbe impedire alla caldaia di rilevare la temperatura corretta dell'acqua.
2. Una valvola del gas difettosa o sporca, che potrebbe impedire la corretta alimentazione del gas alla fiamma.
3. Un problema con il tiraggio dell'aria, che potrebbe impedire una combustione adeguata.
4. Un problema con il controllo della fiamma, che potrebbe impedire alla caldaia di mantenere la fiamma accesa per un tempo sufficiente.

Poich? hai gi? sostituito il primario scambiatore, potrebbe essere utile contattare un tecnico specializzato in riparazioni di caldaie per analizzare il tuo problema. Un tecnico esperto potr? eseguire un controllo approfondito della caldaia e identificare il problema specifico.

Don't know your specific unit, but in general, heating systems are two-stage devices:

1: Its too cold: the motorised HW/CH valve moved to the required position, and on achieving it, the circulaion pump starts and the boiler is enabled. (The circ pump may start immediately - its not usually important.) The hot water from the boiler circulates through the heat exchanger and/or radiators until the thermostat thinks its target is warm enough, whereupon it disables the boiler, stops the pump and closes/relaxes the valve(s).

2: The boiler is off while disabled. When enabled, it heats the circulating water to a 'high' temperature and seeks to keep it there. If it reaches that temperature, the boiler will cycle on and off as necessary to maintain the set 'high' temperature. (The circulation pump must run all the time the boiler is enabled.) This may be what you're noticing. Additionally, some boilers will run the circulation pump for a little while after being disabled to reduce the temperature if the water in the pipes and boiler.

Your question doesn't say how the pump running corresponds to thee thermostat settings, but if it were stuck on, I think you'd know!

boiler not getting up to temperature fast enough. If it is an electric boiler, there is a problem with the heating element. If it is oil o rgas fired, you do not have a flame or the boiler temperature is not reaching 180 degrees F.

I have a couple of thoughts. You may have air in the boiler water circuit at the loop that feeds the tank. You'll have to find the vent in the loop to get it out. Second, the automatic valve that opens for hot water may not be opening fully. Have you felt both the boiler water lines that go in and out of the tank? If the water going in is hot and the line out is very cold you have very little boiler water going through the loop. Make sure the isolation valves on the loop are open. Is your boiler full of water? If the boiler loop lines are hot going in and coming out, the tank is full of rust or debris and no water can get to the fins on the internal tubing to pick up heat. If that's the case there is no repair and its time to get a new tank. Hope this helps good luck.

Pressure inside the tank will rise along with the water temperature. As the water inside cools the pressure will wane until the heating element turns on and reheats the water with a subsequent rise in pressure. Running the hot water at the same time will draw heat energy from the boiler and lower the internal temp and pressure as well.

Replace the thermosts,signal not getting thro to boiler.

It sounds like your thermostat could be the problem. Have you noticed the boiler cutting off at all, or does it run continuously until it goes out on low water?

You stated, "when boiler is on", so I am wondering how you get the boiler on. If your boiler is controlled by a thermostat, you need to check it for a cold draft possibly from behind the thermostat in the wall where the wires come through. The thermostat should never be on an outside wall. The thermostat could be defective.

An aquastat can also control your boiler. If you have an aquastat, check the setting, typically 175 - 180 degrees. You should also have a "high limit" which should be set at 210 - 220. Some people run that high side limit higher; not a good idea - defeats the purpose. If the aquastat is set too high, the boiler will operate too hot and the problem you have will occur.

"pressure rises and pressure relief valve opens" This could mean that your pressure switch is prematurely venting. Check boiler temperature to see exactly at what temperature the T&P valve purges. If it blows off below the high side setting, either adjust or replace. The T&P valves are usually not adjustable. That blow off temperature is stamped on the head of the valve. So, if it discharges too soon, replace it.

Have you actually seen evidence thgat the T&P valve is opening? You may have a bad bladder in your expansion tank and your system may have air in it. Your boiler should have 12 psi when cold and 20 - 22 psi when operating. Check your boiler pressure guage.

"this eventually drops below the minimum operating pressure" Technically, there is set point for a NO MINIMUM OPERATING PRESSURE. That is a function of the amount of water in the boiler. If the T&P is blowing off, it will vent water from the boiler and the boiler pressure will go down. There is a minimum operating TEMPERATURE.

Your boiler could be low on water. You will have to manually fill the boiler. Be careful of thermal shock to the boiler. Feel the piping, and fill only when the circulator is running. Make sure the water is not going directly into the boiler. The supply water should go into the circulating supply side which feeds the radiators, radiant floor, or base board circuits.

All this will adversely affect your hot water. The heat exchanger for the potable hot water may have scale build up in it. Using the hot water keeps the boiler running, and a scaled heat exchanger will give you cooler hot water and the boiler keeps running. If this is a problem, you will need to replace the heat exchanger. A better idea is to not use the boiler for your domestic hot water. Why run the boiler in the summer?

We have just had our old system boiler replaced with a vaillant ecotec plus 837 and sounds like a similar working operation to ours. At first I was a little concerned,but I was told by our installer that he was told by vaillant that these very latest boilers size the system on start up for about 10 mins, then take temperature to target flow which you set boiler at. So even by setting target flow temperature very high you still get the initial sizing cycle, which ours was about 30-35c temp. These boilers seem to run biased for efficiency as after a while they modulate the boiler burner down and the radiators run more on the side of warm than really hot like the old type boilers. You also get better efficiency as at lower temperature the boiler condenses better. You will also find you get a more constant temperature in your home rather than over shoots. I was concerned at first, shame there was no info/explanation in user manual as people do need to know that this is normal operation. We are used to ours now, took a month and by the way these boilers can make a creaking noise but was told this normal expansion/ contraction but annoying when sited in bedroom cupboard. Best of luck!

E2 means hot water over shot, make sure to check boiler hot water system to make sure zone valve or control is staying closed when the call for boiler hot water to the water heater is isolated. Sometimes a zone valve will fail open or not close properly causing hot boiler water to constantly feed the water heater.