New Boiler to replace a old Worcester 35CDi II

[j3oeff]

He hasn’t slightly closed the 2nd in from the right going from right to left has he ?

The pressure switch?

 

[John.g]

Shower set at 50 on tap
6.68 - 35c

Shower set at 45 on tap
6.74 - 35.1c

Shower set at 38 on tap
6.40 - 35.1c

Are you saying I could still achieve hotter water of the boiler was outputting 5/6kwh more. How would I measure the gas readings to investigate further if so?

As before, open the hot bath tap fully, measure its flowrate&temp, then leave it running and monitor the gas meter readings for exactly 2 minutes again.

 

[j3oeff]

As before, open the hot bath tap fully, measure its flowrate&temp, then leave it running and monitor the gas meter readings for exactly 2 minutes again.

Ok. will do tomorrow and come back with findings.

 

[ShaunCorbs]

The pressure switch?

The iso under neath the boiler eg black lever

2nd one in from the right side 15mm

 

[John.g]

Shower calcs attached,

			DHW	Boiler
		Mains	Setpoint	Rated
		Temp	Temp	Output
		DegC	DegC	KW
		7	60	30
		Downstairs
		Bathroom	Measured	Achievable	Required	Actual
		Tap	Temp	Temp	Output	Output
	Bath sink	LPM	DegC	DegC	KW	KW
	7.12 - 52.4c	8.4	52.4	58.0	30.0	23.8
	6.98 - 54.7c	8.6	54.7	57.0	30.0	25.6
		8.5	53.6	57.5	30.0	24.7	Average
		Ensuite
		Sink	Measured	Achievable	Required	Actual
		Tap	Temp	Temp	Output	Output
	Ensuite	LPM	DegC	DegC	KW	KW
	8.39 - 56.4c	7.2	56.4	60.0	26.4	22.2
	9.10 - 53c	6.6	53.0	60.0	24.4	18.9
		6.9	54.7	60.0	25.4	20.5	Average
			Measured	Achievable	Required	Actual
		Kitchen	Temp	Temp	Output	Output
	kitchen	LPM	DegC	DegC	KW	KW
	10.90 - 57.5c	5.5	57.3	60	18.4	17.4
	10.77 - 57c	5.6	57	60	18.7	17.5
		5.5	57.2	60.0	18.5	17.4	Average
		Bath	Measured	Achievable	Required	Actual
		Tap	Temp	Temp	Output	Output
	Bath tap	LPM	DegC	DegC	KW	KW
	6.11 - 53.7c	9.82	53.7	50.8	30.0	28.6
	7.67 - 48.4c	7.82	48.4	62.0	30.0	19.9
		8.82	51.05	55.7	30.0	24.2	Average
			Measured	Required	Required	Actual
		Shower	Temp	Temp	Output	Output
		LPM	DegC	DegC	KW	KW
Shower. SP 50C	6.68 - 35c	8.98	35.0	50.0	26.9	14.4
Shower. SP 45C	6.74 - 35.1c	8.90	35.1	45.0	23.6	14.3
Showr. SP 38C	6.4 - 35.1c	9.38	35.1	38.0	20.3	15.1
		9.09	35.07	44.33	23.61	14.62	Average

 

[John.g]

Corrected calculations (done at 12C) should have been 7C.

Looking a lot better now, so checks tomorrow will verify.

Shower discrepancies probably due to mixing problems, thermostat etc, to be determined.

			DHW​	Boiler​
		Mains​	Setpoint​	Rated​			​
		Temp​	Temp​	Output​			​
		DegC​	DegC​	KW​			​
		7​	60​	30​			​
		Downstairs​					​
		Bathroom​	Measured​	Achievable​	Required​	Actual​	​
		Tap​	Temp​	Temp​	Output​	Output​	​
	Bath sink​	LPM​	DegC​	DegC​	KW​	KW​	​
	7.12 - 52.4c​	8.4​	52.4​	58.0​	30.0​	26.7​	​
	6.98 - 54.7c​	8.6​	54.7​	57.0​	30.0​	28.6​	​
		8.5​	53.6​	57.5​	30.0​	27.6​	Average​
		Ensuite​
		Sink​	Measured​	Achievable​	Required​	Actual​
		Tap​	Temp​	Temp​	Output​	Output​
	Ensuite​	LPM​	DegC​	DegC​	KW​	KW​
	8.39 - 56.4c​	7.2​	56.4​	60.0​	26.4​	24.6​
	9.10 - 53c​	6.6​	53.0​	60.0​	24.4​	21.2​
		6.9​	54.7​	60.0​	25.4​	22.9​	Average​
		​	Measured​	Achievable​	Required​	Actual​	​
		Kitchen​	Temp​	Temp​	Output​	Output​	​
	kitchen​	LPM​	DegC​	DegC​	KW​	KW​	​
	10.90 - 57.5c	5.5​	57.3​	60.0​	20.4​	19.3​	​
	10.77 - 57c	5.6​	57​	60​	20.6​	19.4​	​
		5.5​	57.2​	60.0​	20.5​	19.4​	Average​
		Bath​	Measured​	Achievable​	Required​	Actual​
		Tap​	Temp​	Temp​	Output​	Output​
	Bath tap​	LPM​	DegC​	DegC​	KW​	KW​
	6.11 - 53.7c​	9.82​	53.7​	50.8​	30.0​	32.0​	​
	7.67 - 48.4c​	7.82​	48.4​	62.0​	30.0​	22.6​	​
		8.82​	51.05​	55.7​	30.0​	27.3​	Average​
		​	Measured​	Achievable​	Required​	Actual​
		Shower​	Temp​	Temp​	Output​	Output​
		LPM​	DegC​	DegC​	KW​	KW​
Shower. SP 50C​	6.68 - 35c​	8.98​	35.0​	54.9​	30.0​	17.5​	​
Shower. SP 45C​	6.74 - 35.1c​	8.90​	35.1​	55.3​	30.0​	17.5​	​
Showr. SP 38C​	6.4 - 35.1c​	9.38​	35.1​	52.9​	30.0​	18.4​	​
		9.09​	35.07​	54.35​	30.00​	17.79​	Average​

 

[j3oeff]

Bath tap run today

6.45 - 48c
6.36 - 48.5c
6.11 - 48.6c

Full 2 minute tap run

Gas reading start - 456.228
Gas reading finish - 456.372

 

[j3oeff]

The iso under neath the boiler eg black lever

2nd one in from the right side 15mm

Nothing looks closer to me?

 

[John.g]

4 min gas readings, 456.372-456.228 = 0.144 = 2.16M3/hr = 2.16*11.3. 24.41Kwh
Assume boiler efficiency at 90% = boiler output of 24.41*0.9 = 21.97kwh (22kw output boiler)
but your retested bath tap calculations show a calculated requirement of 27.5Kw so something not adding up here, you were able to get flow rates of ~ 14LPM from the bath tap a few days ago, so why not now?.

Bath tap

4.12 - 31.7c

4.27 - 34.6c

60/4.12 = 14.56LPM. 60/14.05LPM.
We have to be absolutely sure that the HW demand is well > than the boiler output and then do the gas meter check again
SO, either get a set of readings from the bath tap full open but if you cannot get more than the 8.9LPM at todays test, just open another hot tap, take the readings from both taps, let both taps open and do your 2 minute gas meter test again and that will finally prove the boiler output.
Also for accuracy, have a look at one of your gas bills and note the gas usage in M3, the gas usage is also converted to Kwh so divide the Kwh by the M3 used and that will give the Kwh/M3. I am using 11.3kwh/M3 from some user on another thread here.

			DHW​	Boiler​
		Mains​	Setpoint​	Rated​			​
		Temp​	Temp​	Output​			​
		DegC​	DegC​	KW​			​
		7​	60​	30​			​
		Downstairs​					​
		Bathroom​	Measured​	Achievable​	Required​	Calcul​	​
		Tap​	Temp​	Temp​	Output​	Output​	​
	Bath sink​	LPM​	DegC​	DegC​	KW​	KW​	​
	7.12 - 52.4c​	8.4​	52.4​	58.0​	30.0​	26.7​	​
	6.98 - 54.7c​	8.6​	54.7​	57.0​	30.0​	28.6​	​
		8.5​	53.6​	57.5​	30.0​	27.6​	Average​
		Ensuite​
		Sink​	Measured​	Achievable​	Required​	Calcul​
		Tap​	Temp​	Temp​	Output​	Output​
	Ensuite​	LPM​	DegC​	DegC​	KW​	KW​
	8.39 - 56.4c​	7.2​	56.4​	60.0​	26.4​	24.6​
	9.10 - 53c​	6.6​	53.0​	60.0​	24.4​	21.2​
		6.9​	54.7​	60.0​	25.4​	22.9​	Average​
		​	Measured​	Achievable​	Required​	Calcul​	​
		Kitchen​	Temp​	Temp​	Output​	Output​	​
	kitchen​	LPM​	DegC​	DegC​	KW​	KW​	​
	10.90 - 57.5c	5.5​	57.3​	60.0​	20.4​	19.3​	​
	10.77 - 57c	5.6​	57​	60​	20.6​	19.4​	​
		5.5​	57.2​	60.0​	20.5​	19.4​	Average​
		Bath​	Measured​	Achievable​	Required​	Calcul​
		Tap​	Temp​	Temp​	Output​	Output​
	Bath tap​	LPM​	DegC​	DegC​	KW​	KW​
	6.11 - 53.7c​	9.82​	53.7​	50.8​	30.0​	32.0​	​
	7.67 - 48.4c​	7.82​	48.4​	62.0​	30.0​	22.6​	​
		8.82​	51.05​	55.7​	30.0​	27.3​	Average​
		Bath​	Measured​	Achievable​	Required​	Calcul​
	Retest​	Tap​	Temp​	Temp​	Output​	Output​
	bath tap​	LPM​	DegC​	DegC​	KW​	KW​
	6.45 48c​	9.30​	48​	53.2​	30.0​	26.6​	​
	6.36 48.5​	9.43​	48.5​	52.6​	30.0​	27.3​	​
	6.11 48.6c​	9.82​	48.5​	50.8​	30.0​	28.4​	​
		9.52​	48.3​	52.2​	30.0​	27.5​	Average​
		​	Measured​	Achievable​	Required​	Calcul​
		Shower​	Temp​	Temp​	Output​	Output​
Shower. SP 50C​	6.68 - 35c​	LPM​	DegC​	DegC​	KW​	KW​
Shower. SP 45C​	6.74 - 35.1c​	8.98​	35.0​	54.9​	30.0​	17.5​	​
Showr. SP 38C​	6.4 - 35.1c​	8.90​	35.1​	55.3​	30.0​	17.5​	​
		9.38​	35.1​	52.9​	30.0​	18.4​	​
		9.09​	35.07​	54.35​	30.00​	17.79​	Average​

 

[j3oeff]

With regards to previous flows,I have no idea why it is now slightly slower. I don't know if the engineer changed something or adjusted something. Like I mentioned above, I now have the noise inuse to have with the old boiler when switching hot water taps on which disappeared initially upon new install.

I've ran both hot water taps in the bathroom and the readings are below.

Gas start readings 456.977m3

Gas reading finish - 457.064m3

What am I looking for on gas bill usage btw?

 

[John.g]

Something like this, you might see about 5 lines down from the top left corner " consumption (110.9) M3 and energy used directly below it, (1257.3) kwh.

Presume below is a 2 Minute reading??
2 min gas readings, 457.064-456.977 = 0.087= 2.61M3/hr = 2.61*11.3 = 29.49Kwh. Boiler efficiency of 90% = 29.49*0.9 = 26.5kwh, short fall of 3.5kw so I suppose nearly there??.

The bath flow rate is IMO drastically reduced for whatever reason, if you were getting 14.5LPM at say a mains pressure of 4 bar, the pressure (mains or otherwise) is now only around 1.54 bar to give a flow rate of 9LPM.

 

[j3oeff]

Sorry yes,those are 2 minute tap runs.

I honestly don't know why the flow rate has dropped off, its only since the engineer visit.

Attached screenshots

 

[John.g]

Your gas usage was 152.1M3 which was converted to 1719.1Kwh = 11.302kwh/M3 which was the number I used in the calculations. (11.3)
If the engineer you are referring to was the Gas Engineer then he must have throttled the mains flow to the boiler, I don't think that's a good practice, the end user, IMO can do his own throttling at his own taps/shower etc, it may also play havoc with your shower mixer if the hot water pressure is now way lower than the cold pressure.
Can you do a quick check on your bath cold water flow, just the flow with the tap opened fully for say 2 minutes, this might tell you something.

 

[j3oeff]

Your gas usage was 152.1M3 which was converted to 1719.1Kwh = 11.302kwh/M3 which was the number I used in the calculations. (11.3)
If the engineer you are referring to was the Gas Engineer then he must have throttled the mains flow to the boiler, I don't think that's a good practice, the end user, IMO can do his own throttling at his own taps/shower etc, it may also play havoc with your shower mixer if the hot water pressure is now way lower than the cold pressure.
Can you do a quick check on your bath cold water flow, just the flow with the tap opened fully for say 2 minutes, this might tell you something.

Will do. I'm not measuring anything am I or looking for something?

 

[John.g]

If the hot & cold taps are the same size/type then one might expect the flowrates to be similar when fully opened so if you find the cold tap flowing 12 to 14 LPM (the hot is presently ~ 9LPM) then obvious throttling going on somewhere.
Some combi boilers have restrictors installed to limit the flowrate to give a dT of 35C through the boiler, a 30kw boiler will give a flowrate of 30*860/60/35,12.3LPM. with a temperature rise (dT) of 35C.

 

[ShaunCorbs]

All looks good to me maybe there was a fault flow regulator inside the boiler as well causing too much flow through the plate compounded by the fault hw thermistor

Glad your happy and have a working boiler to correct spec 👍

 

[j3oeff]

If the hot & cold taps are the same size/type then one might expect the flowrates to be similar when fully opened so if you find the cold tap flowing 12 to 14 LPM (the hot is presently ~ 9LPM) then obvious throttling going on somewhere.
Some combi boilers have restrictors installed to limit the flowrate to give a dT of 35C through the boiler, a 30kw boiler will give a flowrate of 30*860/60/35,12.3LPM. with a temperature rise (dT) of 35C.

Cold water from bath tip is filling a 1 litre jug in around 2.10 seconds and it was consistent on about 6 fills.

 

[j3oeff]

All looks good to me maybe there was a fault flow regulator inside the boiler as well causing too much flow through the plate compounded by the fault hw thermistor

Glad your happy and have a working boiler to correct spec 👍

I am happy now yes. Just glad to finally have hot water and be able to take baths and also keeps the wife happy.

I will however have to investigate the shower further as there is an issue with that and the temperature not being correct .

 

[John.g]

That's some flow through the cold tap at 28.5LPM, the hot and cold pressures to any mixer should be more or less the same, I think within a 0.5 to 1bar of each other to get satisfactory mixing so possibly some problem with a PRV on the cold supply to the shower or whereever. . Probably have to get a plumber to investigate this.

 

[ShaunCorbs]

I am happy now yes. Just glad to finally have hot water and be able to take baths and also keeps the wife happy.

I will however have to investigate the shower further as there is an issue with that and the temperature not being correct .

Have you tried cleaning the filters/ strainer in the shower ?

 

[j3oeff]

Have you tried cleaning the filters/ strainer in the shower ?

It's a new shower head so shouldn't be the issue. The issue started with the old boiler where it was boiling hot even on 38c. Had to turn it right down to 25c and then it was ice cold so that's why I was thinking an issue with the tap itself?

 

[j3oeff]

That's some flow through the cold tap at 28.5LPM, the hot and cold pressures to any mixer should be more or less the same, I think within a 0.5 to 1bar of each other to get satisfactory mixing so possibly some problem with a PRV on the cold supply to the shower or whereever. . Probably have to get a plumber to investigate this.

It is abit odd. It was previously working fine months ago but as the old boiler deteriorated the shower temps started playing up and have continued with the new boiler.

 

[ShaunCorbs]

It's a new shower head so shouldn't be the issue. The issue started with the old boiler where it was boiling hot even on 38c. Had to turn it right down to 25c and then it was ice cold so that's why I was thinking an issue with the tap itself?

Yes sounds like the shower cartridge has gone

 

[John.g]

Shaun was referring to filters which may be installed where the mixer bar connects to the pipework but would require hot and cold water isolation somewhere.

Not sure, what this will prove, if anything, but maybe turn the shower temperature setting to max then reduce the Boiler DHW temp setting to 40Cish and monitor flow/temp.

 

[j3oeff]

Shaun was referring to filters which may be installed where the mixer bar connects to the pipework but would require hot and cold water isolation somewhere.

Not sure, what this will prove, if anything, but maybe turn the shower temperature setting to max then reduce the Boiler DHW temp setting to 40Cish and monitor flow/temp.

Will give that a go.

I assume I can isolate the water upstairs and then take the mixer tap apart to check filters etc and give it a clean/descale or replace.