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Increase the pump speed up one also to help the ir temp reader use some black insulation tape where your taking the readings
Discuss Real world testing example of Condensing Boiler in older home in the Central Heating Forum area at PlumbersForums.net
The boiler averaged 8.9kw and the rads were producing 85% of rated output.
Choices to reduce return temp for greater boiler efficiency.
Existing: Boiler temp 70C (67C avg) return 61C output 85% of rated output.
1. Leave boiler temp at 70C and throttle the return(s) to give a return temp of 45C (16C reduction) but with a reduced output of 65% of rated output (76% of existing output)
2. Increase boiler temp to 80C and throttle the return(s) to give a return temp of 51C (10C reduction) with the same output (85%) but return temp of 51C (10C reduction)
Increase their impedance, i.e. restrict them by partially closing their lockshield valves.What does "throttle the returns" refer to please?
It means shutting in the rad return valves (a form of balancing) or to get a quick and easy feel of what can be achieved, just throttle the pump suction valve or preferably a common return valve from "all" the rads.
Room thermostats for use with gas boilers are typically limited to a maximum of 6 on-off cycles per hour, for oil boilers this should be changed to 3 per hour. The boilers themselves will usually have their own short-cycle prevention controls built-in.When considering boiler cycling am I correct in thinking this is the total number of times the boiler turns on and off inside an hour of average running? Or how is boiler Cycling assessed in your opinions? For example at present the boiler must be firing up again about 16 times per hour. If a nozzle downsize reduced that to 10 or less then is that an indicator of a more suitable / efficient boiler size?
So the Delta temperature makes perfect sense there. It is a great influence on the heat output of the radiator. The LPM flow is calculated by the delta temp and rad size(?)This is a screenshot of the old spreadsheet that I do the calcs on and contains more info.
View attachment 72777
When downstairs is on again tomorrow I could partially close one of the ball valves on the mag filter at return line would that have same effect? Just to test temporarily. Or better to turn down the gate valve on the pump inlet instead?
I do think the boiler is oversized really. I am interested to take all readings including the hour counter measurements and compare before and after nozzle downsize.
Aka to use 2no hour counters. 0.01 hr accuracy. One connected to the circulator pump which represents the heating flow / duty time and the second to a 240v circuit on the burner. May try to measure actual nozzle firing time VS just when the boiler stat is calling.
When considering boiler cycling am I correct in thinking this is the total number of times the boiler turns on and off inside an hour of average running? Or how is boiler Cycling assessed in your opinions? For example at present the boiler must be firing up again about 16 - 20 times per hour. If a nozzle downsize reduced that to 10 or less then is that an indicator of a more suitable / efficient boiler size?
That's it, the rad size is in Kw, I just used 1kw, the flowrates are then pro rata for other outputs.So the Delta temperature makes perfect sense there. It is a great influence on the heat output of the radiator. The LPM flow is calculated by the delta temp and rad size(?)
That's it, the rad size is in Kw, I just used 1kw, the flowrates are then pro rata for other outputs.
Your pump is definitely oversized, a normal 7M pump would have done the job IMO, the old pump was knackered I'd say.
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Interesting thread. This is the kind of investigative spirit we need to have if we're really to make meaningful improvements to heating systems.
Re the infra-red thermometer, I find they work really well. However, they are usually geared to high-emissivity surfaces (it should normally explain that in the destructions). As such, any reasonably shiny metallic surface can't really be read accurately as it is a low-emissivity surface. However, there is an easy fix in that a piece of masking tape on the pipe can be used as a reliable test point.
I'm not sure re Firebird condensate trap but some traps, to avoid the waste pipe freezing up, fill up the trap with condensate and then blows this down and refills again so on the off chance that this is occuring keep a eye on it but I wouldn't hold my breath as firebird supplied a plastic trap originally which used to melt.
I am going to carry out a test on just one rad soon because as you say, the only sort of fit is if the flow temperature falls as well, see below. I'm quite happy that I had a flow rate of 5LPM both by throttling the 5M pump setting to replicate yours and then at a pump head of ~ 3m unthrottled to give me the same 5LPM. As the boiler output was fairly constant (cycling) at 45 to 50% then the only scenarios that sort of fit are the last two below, ie a flow temp of 64C & return of 35C for 50% output and 45% output at 60C/34C, I didn't see my return going below 42/43C, the only explanation I can give for a apparent low flow temp is that a oil fired boiler acts as a 20/25 litre buffer tank and with the burner off perhaps cold return water flows from the flow side until the burner "catches up" and reheats the buffer??.
View attachment 72892
Carried out the TRV test on one X 1.7kw rad and as expected, the TRV was just copening/closing but keeping fairly tight control of the mean rad temp at ~ 42/44C which gave the required rad output of 0.6kw to maintain a room temperature of 20/22C. The boiler had very long cycling times of around 2.5 mins on and 35 minutes or more off. I then progressively introduced the remaining rads (all TRVd) and their mean rad temps reflected the outputs required, the combined return temp didn't vary hugely ~ 39/45C.
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