Worcester Bosch E7 Alarm and Nest controlled Zone Valves

[joerice50]

The Worcester Bosch boiler can trigger an overheat alarm if a zone valve controlling a cold loop say upstairs bedrooms opens and lets cold water into the boiler supply. Hitherto, the boiler has been pootling along heating the downstairs when it's suddenly hit with a cold event. Its response s to boost the gas into the boiler to boost the temperature and this can result in the boiler temperature shooting up and triggering the over-temperature alarm resulting in an E7 alarm and the boiler shutting down. It depends on the temperature differential as this only tends to happen when the water entering the system is very cold.

One way of countering this is to have all the zone valves turn on at the same time presenting a total system to the boiler and then turning off the circuits that are not required. However, nest only allows control in 1-hour segments so unrequired circuits have to be on for at least an hour.   

Is there a way of exerting a fine time control to nest thermostats to improve this time control?

Thanks for any suggestions

Joe 

[AlexD]

Thanks for reaching out to us @joerice50 and thank you for all the details. I would be happy to try and assist. The heating schedule should be controllable in 15 minute increments while the water heating is controlled in 30 minute ones. Could you clarify to what 1 hour segment you are referring to?  

[joerice50]

Hi Alex

How do I reduce the time length on the 11.5 temp spot sandwiched between the two 19 deg spots in the thermostat's schedule?

All 3 temp spots are adjacent to one another and  I can't crush the 11.5 spot down to make it a smaller time interval. 

Cheers

Joe 

[AlexD]

Thanks for clarifying. When placing a schedule point it can be placed with 15 minute increments. However, temperature points next to each other have to be 1 hour apart to prevent conflicts. This is not something that can be changed currently. 

[george_t]

Hi @joerice50. Did you manage to check the last message from my colleague? Is there anything else that I can help you with right now?

[joerice50]

Hi George

I got the message so its not possible to have temperature spots at less than 1 hour intervals, which is what I suspected.

Thanks

Joe

[DragosC]

You're most welcome. Should anything else come up, we're just a message away. Have a great day ahead and stay safe!