UFH condensing oil boiler short cycling

[markmorrison1957]

Thanks so much for sharing all your knowledge - I've put Wilo pump at speed 2 and will monitor. I'll likely not get a chance for a few days as working in my retirement job for a large UK retailer selling Percy Pigs!!
Strangely the on and off times when set at 6.0 seemed to vary from 1 on/3 off to 1on/1off. UFH was the only demand on the boiler. Sometimes I can hear faint tapping noise from manifold but I don't know if always there!!

 

[markmorrison1957]

The HW was the only circuit on during summer months and used about 5L of oil a day. It comes on maybe 1 min in 10 but will monitor as well. The upstairs radiators come on in morning when I'm still in bed and come on at night when I'm in bed! They are on for 30 mins each time and heat up we'll all over thought just a fraction cooler at bottom! Hopefully at moment not using excessive amounts of oil (usually 5000L yearly) as no winter fuel allowance!

 

[Johntheo5]

Are you running a Hotel?.
5000L/year, 51,750kwh, seems enormous, my 4 b/room house only consumes 1400L/year, 14,500kwh.
Your HW demand alone, at 5L/day, is more than my total yearly consumption and should produce 840L/day at 60C.
Are you sure, maybe only using 500L/year and 0.5L/day for HW?.

 

[markmorrison1957]

I have kept a spreadsheet over the past 20 years noting oil purchases and how long until next one! Each year over the 20 years ranges
from 4500L to 5500L - your 1400 annual litres would just about last me 3 winter months. I'm on first name terms with oil tanker driver - his quickest delivery after my phone call order was 30 minutes! In depths of winter sometimes daily consumption has topped 29L a day.
I've turned boiler thermostat up. The thermostat just has a thin to thicker line instead of numbers so at a guess its currently 65c (I think the thermostat range us from 55c -75c).
The dhw cylinder is set lower than 65c so powers off once it's temperature is satisfied. Temp at manifold shows flow of 50c (mixer valve maximum).
I'll try to get a chance tomorrow to note cycling times but earlier today was 2 mins on/1 min off thou ufh had only been on for 45 minutes and Wilo pump was setting no 2!
It's not a hotel thou with 4 bathrooms and two daughters who take daily baths and 30 minute showers I thought a daily summer oil consumption of 5L was good! The boiler is in a separate garage with a 20 foot run for boiler flow and return pipes to the house. The pipes are buried and I assume are well lagged about 5 feet deep. TBC.

 

[Johntheo5]

2min on and 1min off = boiler output of 27.3kw.
Don't forget the Wilo power when taking readings.

 

[markmorrison1957]

Okey doke!