T3 thermostat

Silverbird65

Hi I have Honeywell T3. What is cycle rate it is on 6 do I need to change it to get best economy?
Thanks

[Deleted User]

Yes, you could save energy but at the cost of reduced heat exchanger life. Read this Honeywell link:

https://ensupport.getconnected.honeywellhome.com/s/article/What-cycle-rates-do-you-set-for-different-applications?language=en_US

The Cycle Rate specifies how often the boiler will switch on and off in any given hour, measured as Cycles per hour. A typical Cycle rate is 6 cycles per hour giving a 10 minute Cycle length. A minimum boiler on time for the heat source to dissipate from the system before shutting off.

MWT

Most modern boilers protect themselves with cycle rate limits and pump-overrun timers so the cycle rate on the thermostat is more important when used on older boilers.

Silverbird65

Ok so could I change it 1 instead of 6. Does that mean the boiler goes on and off less?👍

MWT

That doesn't necessarily equal better economy...

Dropping the temperature slightly and leaving the cycle limit where it is would save more.

How old is the boiler?

Silverbird65

The boiler has just been put in Worcester bosch 30i .they didn't explain the thermostat.

MWT

Then leave the thermostat alone, it will do a great job set at 6 cycles.

Your boiler will modulate the burn so just because it is on doesn't mean it is running at full throttle so to speak.

Tallerdave

Silverbird65 said:

Ok so could I change it 1 instead of 6. Does that mean the boiler goes on and off less?👍

1 would be insane, but the minimum setting is 3. I'd leave it on 6.

[Deleted User]

Most gas boilers are oversized for the property that they are in. Why because installers believe that homeowners want rapid heating and hot water at the expense of efficiency.  All modern boilers have a modulation ratio which reduces the output from, say, 24kWs to 7kWs - but 7kWs is far too much heat for an average home in Spring and Autumn. In this situation, the boiler will then cycle to maintain a set temperature within the home. Each time the boiler goes off, the pump will continue to run to protect the heat exchanger. 

When I had full heat loss calculations carried out on my previous large 5 bedroomed home, the installer calculated that I only needed a 18kW boiler which modulated down to 4kWs. You may be surprised to know that most UK boilers rarely ever condense because they were oversized to start with,  and fitted to old radiators etc which cannot output sufficient heat with lower temperature flows. 

MWT

Same here, replaced a 28kW boiler with a 19kW on a similar sized property to yours.

Silverbird65

So really my boiler is grossly oversized. Great that's good to know☹️