I need to reboiler my place. The boiler is at least 45 years old and obviously cannot last forever. I am somewhat older and the same conditions apply.
The supply to existing boiler is 1/2" steel pipe. I'm told that I need to have a 22mm supply for a new condensing boiler. The routing of existing pipework cannot be followed without demolishing about half of the interior of the house. I'm not willing to do that.
Would it be legal to run the majority of the pipework in armoured rubber/flexible pipe?
The last metre or two at each end would be in metal tubing. All above ground at high level (2M) and nothing external to the house.
still down as it includes pressure drop calculations of pipe runs.
If you know the kW of your boiler you would be able to calculate the size of pipe you actually need. In domestic situations with limited pipe runs 22mm copper pipe is a safe bet, plus to save embarrassment to Gas Safe installer Gas Safe have made a blanket requirement to combis where they must be piped in 22mm. Though I would be happy to have the last sectionin 15mm.
There is no need for any mechanical protection. The only exception is using a sheath is through a wall, to ensure that no gas can leak into a cavity and to stop the chemical effect of mortar. Usually a larger sized PVC pipe.
Depending on the pipe runs and if the existing pipe is gas tight then this may be reused. When you say 1/2" steel pipe this normally corresponds to an internal diameter of 18.6mm if 1/2" BSP.
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I believe it is generally said they should not be run in voids. So behind kitchen units is fine, as is outside. Under floorboards is also considered a ventilated space.
Things to consider, if your boiler is on an outside wall, the pipe could be routed externally. Not pretty but would avoid internal disruption.
If your boiler *isn?t* on an outside wall then it?s probably discharging into a chimney. This will be hard to do with a new boiler (as the flue must be accessible for inspection). Consequently you may be looking at boiler relocation and replumbing.
It might be true, or it might be a lazy installer not wanting to do the sums ... British Gas tried that trick when my father had a new boiler fitted, it didn't wash with my Dad who used to work for British Gas* and did the sums for them!
Rubber no, but you could suggest corrugated stainless steel tracpipe
[*] misplaced loyalty means he still expects them to be "good".
I'd say no f***ing way - could you expect rubber hose to be gastight in a fire! You really need to determine the actual gas rate of your proposed CONDENSING (not combi) boiler to discover if the steel pipe is adequate[y sized for the job. It might help if you ask someone who knows what they are doing to measure the current boilers gas rate and the pressure drop from meter to boiler under load. This would give you a good idea of the feasibility of reuse. Don't forget steel pipe corroded so it would also be sensible to do a soundness check while he/she is there. I've seen installations in steel pipe where permitted drop increased year on year until it eventually exceeded that allowable. Then it was a case of having to sort it and rerun the pipe in copper.
I don't want to give false hope to the OP who may well need a new gas pipe.
But I've seen before on some sites that "Gas Safe regulations now state that gas supply pipes from the meter to a combi boiler must be at least
22mm". Smelt to me like a way to get more work and avoid the bother of calculating pressure drops. Gas Safe have no power to make regulations. And while the Gas Safety (Installation and Use) Regulations were amended in 2018 I can't see anything in them about a minimum pipe size. Have I missed something?
When our old gas boiler was replaced at our last house the engineer said he would have to take up the parquet flooring right through the length of our hall to install a new pipe. We objected telling him to find another route.
He then agreed to test the gas flow through the old pipe and guess what? Yes it was more than adequate to feed the new boiler.
Did you mean a new 'COMBI' boiler to replace a heat only?
Combi boiler usually need a larger supply pipe, heat only tend to be OK on the existing, especially if the central heating demand has been reduced over the years, with extra insulation.
We had the very same situation, except the guy wanted to charge us to run an ugly pipe all the way around the outside of the house. I did the calcs for him and proved him wrong/ unecessary.
Our guy (who we have used for years and trust) said he was a bit worried about the flow rate. He measured and calculated, then found that a small part of the run was in 15mm pipe. The rest was in steel pipe.
He changed the 15mm part (which was not disruptive) and it's all fine.
Surely the actual connection at the boiler is always 15mm, and the installation instructions that I have seen say that the last metre or so can be 15mm pipework.
Just because the OP can see 15mm ?iron pipe does not mean it is
15mm all the way from the meter. What size of pipe exits the meter ?.
There is something called tracpipe?? which is flexible stainless steel pipe intended for gas, which has fittings at each end to join up with existing pipework. This could? be wangled through the ceiling void if needed.
Thanks but I was aware of that. And it's a bit of a leap from that to "you *must* use 22mm even if it's a run of 1.5m with one bend to a 24 kW combi". Only makes sense to me if Gas Safe members can no longer be trusted to do sums and measure pressure drops at existing boiler.
That may or may not be true - it depends on the power of the boiler, and the length of the pipe run. Although beware many gas fitters seem reluctant to actually do sums, and just go for rule of thumb answers!
(whether it is condensing or not has no bearing)
You would need to do a calculation on the size of pipe required. The process is described in the wiy wiki, but that is offline at the moment. However watch this space - it should be back soon.
Alternatively if you have access to BS 6891:2005 "Installation of low pressure gas pipework of up to 35 mm (R1 1/4 in) domestic premises (2nd family gas) ?Specification", that also describes the process.
I have put s short extract from that here:
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that covers the basics.
You also need to know the gas rate for the boiler - you can get that by multiplying it power in kW by 0.09, and that will get an approximate figure in m^3/hour.
So a 24kW boiler would be around 2.16 m^3 / hour - allow a bit for
A 15mm / 1/2" pipe can shift that within the 1mBar allowable drop for about 5m maximum. (and that is effective length where elbows count as
0.5m of pipe, bends as 0.3m)
No - although that does depend a bit on what you mean by flexible pipe. While the normal flexible pipe used for say a cooker connection would not be acceptable, products like Trackpipe (a stainless corrugated plastic coated bendable gas pipe) are ok.
You can run normal copper externally, clipped to a wall. That is a common solution to this kind of problem.
My peak hot water requirements are easily met with a mains pressure cylinder allowing me to use a mere 12kw boiler. You need around 50kW to get a decent hot water supply.
I used that for a run through screeded floor from the intake point. In the event the boss chose an induction hob so it was never connected. The gas fitter installing the boiler refused to consider certifying it anyway.
Again, simple rules for simple people. I had huge arguments with the building inspector when I wanted to use single glazing. But a report by a heating engineering consultancy revealed that with enough insulation in the walls and floor it met the regulations, was, in the end enough.
heating engineers of te corgi flavour doi not come equipped with brains sufficient to deal with complex rulesets. 'use 22mm' is as simple rule even a CORGI man can understand....
The important thing is that your cylinder is fed by mains cold water rather than a header tank. Our present house had a cylinder and a conventional (non-combi, non-condensing) gas boiler. It took ages to heat up a tank of water if you wanted more than one bath, and it also took about 5 minutes for the water to run warm due to the length of pipe runs and the very low flow rate, determined by a) 15 mm instead of 22 mm pipe for hot water, b) header tank so only about 3 metres head.
When the cylinder developed a leak, we were originally going to have it replaced, but the heating engineer found that the boiler was badly corroded and wouldn't last much longer. So we had a combi/condensing boiler fitted, giving mains-pressure hot water which runs hot much more quickly and is much easier to mix with cold water in a shower or sink tap: the old one was so low pressure that the cold tap could only be slightly open, otherwise the combined water was virtually cold.
Our previous house had a cylinder (so the same time-to-reheat problem) but at least it was mains-fed.
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