Pressure Testing Rads and Keston air intake

[Andrew]

The 'new' heating system is progressing slowly :-( - I have taken all the radiators outside and flushed them out with the hose pipe but I hope to install a Keston with their sealed system kit. There was a fair amount of black sludge in the rads (I don't remember BG putting inhibitor in when they rebuilt the original BAxi Bermuda with a new case and heat exchanger in 1991 !! - house built 1976) and a few crusty flakes as well.

Rather than dump them and buy new rads I would like to pressure test them and re-use - if all possible (with an inline muck filter as well). However, having searched Google, no-one seems to sell or hire the sort of device that is used to pressure test under floor piping, which is what I intended to use. Does anyone know of a source or work-around ?

[IMM]

At that age and not protected, they will probably be in a high state of corrosion. I would replace them all. rads are not that expensive.

[Andrew]

In article , Andrew writes

Forgot to mention the Keston air-intake. The keston manual says in section 2.8.4 "the air terminal must be located outside the building", and also "drawing of combustion air directly from a ventilated boiler room invalidates the heat exchanger warranty". What about drawing air from a well ventilated loft ?, is this not the same as outside air ?.

[IMM]

That is "inside" the building. You don't want to drag in dust from insulation into the unit. Best take in clear fresh air from a high position. There is far to much dust lower down. You have to take the exhaust to outside, so take the air intake out at the same position. If you are having the two at very different locations then check that they have to both be on the same side of the building. Most makers insist on this.

[Andrew Gabriel]

I used a bicycle pump (not a little hand one) and a pressure test adaptor which consists of a push-fit fitting with a pressure guage on it and a tyre valve. They are available from plumbers merchants and screwfix. Pressure testing pipework is easy, but you'll need to be very fit to pump up a circuit which includes 2 or more raditors to 2 bar. Also beware you end up storing one hell of a lot of energy in the radiators when you do this -- don't be tempted to just let the pressure fire off a push-fit stop-end unless there's nothing breakable within 50 feet and you are wearing ear defenders (just don't ask how I happen to know this;-)

Use gas leak detector spray to find small leaks. It can take a long time for the pressure to drop if the volume includes a radiator.

[Tony Bryer]

Blank off one end of the heating loop, and temporarily connect the filling loop, expansion vessel and pressure gauge at the other. Pressurise the system to 2-2.5 bar and see what happens. You can also use the same setup to really flush the system if you attach a drain hose instead of a blanking cap at the other end: turn off all the rads, then open each one in turn so that the full flow goes through it.

[IMM]

Pressure relief valve are usually 3-3.5 bar. I would charge them up to over this pressure. If they are only good for 3 bar then you may end up with gooky water all over your carpets if the pressure vessel fails and pressure rises right up.

[Andrew]

In article , Andrew Gabriel writes

Thanks - How silly of me for not thinking of that - I presume you mean the sort of pump that has two flaps that you stand on then pump like mad with both hands. I shall investigate a cycle shop that specialises in racing cyclists tomorrow. There's a good one on Grays Inn road, next to a useful but expensive plumbing supplier. One of the reasons why I was looking for the proper kit is because pressure testing vessels with water is less eventful than using compressed air. They sort of make a thud if they fail when full of water rather than attempt to launch themselves if full of air.

Another idea that just occurred to me is to test then individually by filling with water and using a pressure washer to supply the effort via a check-valve. This assumes that the blow off pressure can be reduced to say 10 bar, when I think they normally go up to 100 bar.

[Andrew]

While on the subject of heating, do you know what the u-value is of a cavity wall with standard brick outer skin (LBC Tudor), 75mm cavity filled with rockwool and block inner. The reason I ask is that the blocks are not 'breeze' blocks (about half the weight of concrete blocks) nor are they 'thermal' (1976 built). Each block has oblong holes going right through them vertically. I am using a U value of 0.5 on the Myson calculator, but else where I have seen 0.83.

Another problem is that the 'builders' who assembled this house dropped so much mortar down the cavity (and the gas flue blocks) that it is actually a solid wall up to about 6-8 inches ABOVE the dpc. Strangely enough there is no obvious sign of water penetration, The bridging of the cavity means I have a nasty cold radiator around the entire perimeter of the ground floor - what sort of correction should I allow for the actual boiler output needed. (Its actually less than 20Kw so the Keston won't have any problems).

[Ed Sirett]

Because air can get out through small leaks much easier than water a small pressure drop over 30-60 minutes might still count as a pass for the circuit.

I have converted a number of old systems to pressurized and I would say that unless there is obvious signs of a lot of corrosion [1] then you would be fine to go for a water pressure test.

I pulled the end cap of of a 4 rad circuit at 0.3 bar of air which got some installation debris out of the pipes!

[1] Where the sludge is brown rather than black, perhaps one or 2 radiators have been eaten through and replaced, the boiler died by corrosion etc.

[Ed Sirett]

'Fraid not. The idea is to make a sealed combustion system. Perhaps you might be able to drill a suitable hole in the soffit ?

[Andy Hall]

Although presumably it would not be appropriate to make the flue exit in the same place, since the fumes would likely be drawn into the loft. I know that Keston allows for inlet and outlet to be separated, but since the outlet is probably going to leave through a wall anyway, then wouldn't siting the inlet and outlet adjacently make sense? I suppose there are always ridge and other roof terminals, though, in which case inlet at the soffit is a nice soution.

.andy

To email, substitute .nospam with .gl

[John Stumbles]

You sure Ed? IIRC it's permissible for b/fs as long as the attic is ventilated to modern standards.

-- John Stumbles

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-+ If a job's worth doing, it'll still be worth doing tomorrow.

[John Stumbles]

I've also used a bike pump and can vouch that it's hard work to get any significant pressure into the system. I use a pressure gauge from BES at about a fiver, but it has a 1/4" thread so a certain amount of ingenuity is necessary to get it onto a 15mm or other suitable fitting. I've toyed with the idea of connecting a cheap electric motorised car tyre inflator to one of my cordless batteries and using that to pump it up. For testing CH systems though I just fill 'em up from the mains to about 2 or 3 bar.

Leaks show up [too?] easily with water.

-- John Stumbles

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-+ a town is never big enough to support one lawyer, but it can always support two

[IMM]

It would also drag into the loft very cold air cooling down the loft and making the house colder. Not a good idea.

[The Natural Philosopher]

Well I hired a pressure tester for not very much..OK I had to fake the connectors up, but a pressure tester is a pump, some water in a trough and a pressure gauge. Can't see your problem...

[Andrew Gabriel]

Actually, I worded that badly. What I meant to say was check all joints with gas leak detector spray, as that's the way you find if you have any small leaks (rather than waiting for pressure drop). However, since I've never done a bad soldered joint (except when the pipework was wet), I no longer bother checking those on new/dry pipework.

I much prefer testing with pressurised air... When it leaks, it doesn't damage anything; Easy to 'drain down' if you need to dissassemble part of the pipework; Pipework remains easy to solder as it doesn't get wet; Being very much less viscous than water, air leaks much faster, so you can be sure that if you're air tight, you will certainly be water tight. Easy to test sections of pipework (useful if you put heating in over a long period of time, and some of the sections will become rather inaccessible long before they get any water in them).

[Tony Bryer]

If it's a cold roof (i.e. insulation at ceiling level) and insulated to something approaching current Parrt L standards the loft space is/should be ventilated anyway and will be not very different in temperature to the outside.

[IMM]

In a normal loft the outside cold air floats through the vents. When you force cols air through the vents it will be much colder.

[Christian McArdle]

A non-thermal concrete block isn't likely to have much insulative capacity when compared with the 75mm of rockwool in the cavity, so it won't make much practical difference exactly what type of uninsulated block it is.

Using 75mm rockwool, unplastered, I get:

(100mm Topcrete): 0.40 (concrete blocks) (100mm TopLite7): 0.35 (insulated blocks)

To calculate around the bridged zone, just treat the bridged area as a solid brick wall for heat loss calculations. The U-value will be around 2.1 for this area. No wonder it feels cold!

Christian.