Keeping regular boiler condensing on DWH cylinder

[Friday round]

Hi all,

Been playing around with these toys to measure flow temps on my basic Worcester Ri regular boiler with a single knob. I schedule heating the HW cylinder for an hour a day.

Was able to reduce the flow temp to 62C while satisfying the HW cylinder demand. So far I’ve used about 1.5-2 kWh less gas per day, but what used to take around 25 mins now takes 40 mins. When it runs now, for first 25 mins the return temp is below 55C and then creeps over with the last 10 mins where the flow and return are almost equal at 60-62C. The pump speed is set to the lowest possible at 1 PP. Oh, and it’s a 250L unvented cylinder.
1. In practice, should heating the HW tank remain constant in condensing the whole time? And how?
2. I’m thinking maybe reducing the flow rates by partially closing a pump gate or magnetic filter valve. Should this be done?

 

[JonathanM]

I'd be really interested to know what the percentage saving is.

How many KWh were you using before on DHW, and what was the previous flow temperature?

P.S. What is the cylinder capacity?

 

[Agile]

Only consider reducing the flow rate on a valve on the HW cylinder.

Your boiler should be condensing well when the return is below 55C

 

[Friday round]

I'd be really interested to know what the percentage saving is.

How many KWh were you using before on DHW, and what was the previous flow temperature?

Saw this tip on the heatgeeks youtube. It looks like I was averaging 10.5-11 kWh the last couple of weeks, and early days but going around 9kWh now. Due mainly to being able to measure properly and turning down the flow from 70C to 62C.

 

[Friday round]

Only consider reducing the flow rate on a valve on the HW cylinder.

Your boiler should be condensing well when the return is below 55C

Is it ok to use the pump gate valves to reduce the flow? I’d prefer to use them over the magna filter valves because there’s more turns so finer control. But was also considering which pump gate, before or after the pump, would produce less chance of cavitation.

 

[JonathanM]

Saw this tip on the heatgeeks youtube. It looks like I was averaging 10.5-11 kWh the last couple of weeks, and early days but going around 9kWh now. Due mainly to being able to measure properly and turning down the flow from 70C to 62C.

That's an amazing saving. Anywhere from 14% to 18%.

 

[Friday round]

That's an amazing saving. Anywhere from 14% to 18%.

Ha. I didn’t even compute that as I’ve been thinking about getting that last 10 mins of the return flow into condensing. Maybe it’s the 80-20 rule. Should I even bother.

 

[Razor900]

For the last ten minutes the return temp is basically the stored hot water temp. Looks like you have it as good as it gets with on/off controls