No.
If the flow rate is above 19l/min the boiler will not be able to raise the temperature of the water by 30C or more.
The fact it can raise the water temperature to 60C without really trying suggests that the flow rate is well below 19l/min.
Bugger!
I obviously meant a vented system
Cheers
Dave R
The gas piping had to be upgraded to cope with both the combi and the gas hob, so the appropriate sums have been done.
28mm IIRC.Cheers
Dave R
Ah, I hadn't realised that propane cylinders contain gas at much higher pressure than that of methane in a gas-main feed to a house, and that even after a cylinder-head pressure regulator it's still at a higher pressure than a gas main.
It used to be (may still be) that Butane was regulated down to 28 mBarg and Propane to 37 mBarg - the idea being that the same jets in a camping cooker, blowlamp, etc. would work equally for both.
Gas main pressures vary. I have worked on high pressure transport mains compressors, at 69 Barg. Locally, distribution is typically somewhere around 6 or 7 Barg, with the ones down the street and to your house more like 75 mBarg to 2 Barg, then it is regulated down to 20 to 23 mBarg at the meter.
I have a very high powered blowlamp, which is fed by a variable regulator and to develop full power, it is set to 4 Barg. At that pressure, the flow is so great that a) it must run on Propane and b) if running for any length of time, it must be fed from a 47 kg bottle, or the temperature of the bottle will drop too much and stop the gas flow. It does however, generate 130 kW !!!!
Not much in it for Butane.
The standard supply pressure for Butane is 28 mbar and for Propane it's
37 mbar. Natural gas being 21mbar (I think).
You would not expect a basin tap to deliver 19 lpm usually anyway - so you it would restrict to less than that even if the supply was not restricted.
Yup 30 degree rise over the temp of the incoming cold main - which will normally be in the 5 to 10 degree range in the winter.
Yup it does not need mains cold for CH - only for DHW (or for filling the CH circuit in the first place)
The wiki will accept .doc uploads.
It is possible to use pumps on unvented systems, but it is usually done in different way with a pumped accumulator feeding the unvented cylinder.
A basin tap is probably plumbed in with 15mm pipe and if a flexi used for the last 300mm the bore is likely to be 10mm. A bath tap more probably plumbed in with 22mm pipe but possibly restricted to a 12/13mm bore if a flexi connector is used.
Having lived with gravity cylinder & mains combi, the gravity cylinder was better. Combis tend to not modulate down far enough, making any HW use very wasteful as flow needs to be way up. And you get more flow with a cylinder because you get full mains flow on cold plus whatever the cylinder delivers. A mains only fed combi can't of course exceed the mains flow rate. Of course this can run into problems if your piping is too thin etc, any system badly plumbed can have problems.
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This feeds back into why I don't trust the flow rates at any indoor taps. They are all mixers and so are not guaranteed to allow the full mains flow through.
Bathroom sink, wet room sink, wet room shower, kitchen sink are all mixers. The bath tap is also a mixer - Mira thermostatically controlled with divert to shower head.
I don't have an "old fashioned" cold tap with 22 mm (or even 15 mm) direct from the mains.
The nearest I have is the outdoor tap on 15 mm but still inboard of the pressure restrictor.
I could disconnect the cold feed from the dishwasher or washing machine but this gets back to flexibility and knees for rooting around under worktops.
"Soon" I will get the pressure restrictor checked and potentially removed. I may well have it replaced with a T to allow pressure and flow testing at the point the mains enters the house.
I think the cold feed to the bath is 15mm to match the hot feed at 15 mm. The connections to the combi are 15 mm so I assume that going to 22 mm from the combi to the bath taps will not make a lot of difference.
I recall that all the pipework is plastic not copper so internal diameters may be a bit smaller.
Ta. Will do (soon).
Cheers
Dave R
I would have thought that the rate-limiting step is water arriving at the boiler inlet, so as you say there is no advantage in changing to 22 mm between the boiler and the various hot taps around the house. In fact, changing to 22 mm would be a disadvantage because for the same pipe length,
22 mm will store a greater length of cooled water which has to be shifted when you open a tap before the hot water arrives. Our house has the opposite problem: 15 mm but unnecessarily long pipe runs because they used to supply a hot water cylinder. End result is the same: takes a while for the water to run hot. If the boiler has a pre-heat option, which maintains a small reservoir of water inside the boiler which is kept hot, then this reduces the time for the water to run hot to some extent; but it uses a bit more gas to keep the reservoir warm.There is a pre-heat option but the boiler is on Eco setting because this doesn't seem worth the extra expense.
Cheers
DAve R
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