New combi fitted...help!

jenks · 3 Mar 2004

Just had a bosch worc 28i combi fitted. I'm hoping to eventually run a shower from it. Tech info tells me that I should get hw flow of 11.5 l/min.@ 38 DEG.
My cw inlet pressure is 3 bar.
CH is working fine, but I need to really throttle down the inlet cw supply to the boiler to get the water anything like hot.
38 Deg isn't really hot is it?...
max is pre set to 55deg but to get that I have to open my taps to allow only 2 l/p/min.
Realistically, i want hw that I can just about get my hands under, with a flow rate of about 6 or 7 l/p/min...does this sound achievable...or have i bought something not upto my requirements!
Any comments appreciated.

breezer · 3 Mar 2004

38 Deg isn't really hot is it?... a washing m/c heats up to 40, think its safe to say that 38 is very hot, you wouldn't want to put your hand in it

ollski · 3 Mar 2004

The 28i should give you a temperature rise of 40 degrees celsius from your incoming water temperature. At that you should have a flow rate of 9.8 litres a minute maximum....do you have something else?

The 38 degrees they quote you is the temperature rise of the water not the temperature at the tap, so in summer when you have a warmer incoming water feed the boiler will not have to work so hard to raise the temperature to how you like it so will allow better flow rates.

jenks · 3 Mar 2004

If I set my kitchen tap to run at a constant 8 lpm for example...the hw will run at a very luke warm temp.
Tried measuring the temp...but broke the bl**dy thermometer shaking it!
Cheers!

jenks · 3 Mar 2004

My washing has settings for 40 60 and 90 deg.
40 degrees is low.
The max my boiler is factory set at is 55 deg.
I would want the temp about 45 to 50 for my mixer shower i would have thought.
cheers!

breezer · 3 Mar 2004

when you next try a 40 degree wash, touch the door (but dont let the kids see you doing it)

ollski · 3 Mar 2004

Yep it will max out at 55c but it still only has a temp rise of 40c....if the water in your mains is 15c you will get your 55c, but in this weather I would say your mains is about 3c giving you a max water temp of 43c....the joys of combis.

Most hot water cylinders are set at 60c, that is the recommended figure.

Also bear in mind that temperature of the combi is based on an immediate draw off... if you have long pipe runs you may lose another degree or 2.

jenks · 3 Mar 2004

think i was getting my deg c and f confused...anyway...

i've just done some flow rates at the kitchen sink....
9 lpm flowrate... temp is only 32 deg.
5 lpm flowrate....temp is 42 deg.
tech info says i should be getting temp rises as follows:
7 lpm 56 deg
8 lpm 49 deg
9 lpm 44 deg
10 lpm 39 deg.

what can be the problem??.........

ChrisR · 4 Mar 2004

Breezer is out with his temps - 38-40C is showering temperature. 45 is washing up. 60 is full thickness burns for a child in 2 seconds or so....
Could be your installer has used gas pipes which are too small. Check your manual for gas rate. At a guess something like 3.2 cubic metres per hour.
Put your hot taps on and measure the gas being used, at the meter. You'll need a calculator!

For a combi this size I only use 28mm pipe if the run is more than a few metres. If he's used 15mm he's a dork.
If the pipe IS too small, your appliance is technically "at risk" so should be turned off! Corgi would ******* him and make him repair.

breezer · 4 Mar 2004

i will get a thermometer

(i also never said it will scald, just that its hot)

jenks · 4 Mar 2004

Thanks all for your input.

The problem was with the gas valve...it was only allowing 8 mb through...all sorted now, flowrate of 9 lpm is giving me temp of 50 deg cccccc!!
Well happy chappie

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New combi fitted...help!

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