# Anatomy of a HX



## carbonkid85 (Jan 19, 2011)

Trying desperately to upgrade from a single boiler to a HX. I am aware that my machine needs a bit of work, but I think I need to understand the workings of a HX a little better.

As I understand it, when I switch the machine on, the pump draws water into the boiler which is then brought to pressure. The steam arm draws its steam from the top of the boiler and the hot water outlet draws directly from the bottom.

So far so good?

I am less sure of how the water gets to the group head. I know the water from the boiler is cooled with cold water from the tank somewhere a long the way but not sure how/when.

The situation so far is this:

1. Pump filled the boiler

2. Boiler came to pressure and held steady

3. Hot water can be drawn from the boiler

4. Steam can be drawn from the steam arm

5. initially water came from the group head, but this slowed very quickly and almost dried up.

6. When the brew button is pressed, the pump runs but is very loud and seems to be failing to draw from the water tank.

Any ideas what the problem is here? Is it likely to be the 3 way valve?


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## Spazbarista (Dec 6, 2011)

Try messaging this chap:

http://coffeeforums.co.uk/member.php?2386-Coffee-Services

He may know better than anyone else here.


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## MikeHag (Mar 13, 2011)

Could well be the solenoid valve.

Here's some info.

http://www.chriscoffee.com/faq#23

Also, these are 'must read' articles regarding using a HX machine, once you get it going









http://www.home-barista.com/espresso-machines/espresso-machines-101-t368.html

and this

http://www.home-barista.com/hx-love.html


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## jimbow (Oct 13, 2011)

There are basically two separate circuits in a HX machine along which water can travel. One includes the boiler and sources hot water and steam. The other sources the brew water. The brew water circuit is submerged inside the steam boiler so that the brew water is indirectly heated as it travels through the circuit on its way to the group head. Here is a diagram showing the arrangement:










It sounds like your problem is in the brew water circuit. Perhaps the solenoid is blocked/jammed as Mike suggested. If you switch on the machine and leave it a while does the group head get hot?

Sent from my HTC One X using Tapatalk 2


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## MikeHag (Mar 13, 2011)

Great pic. The thing that could be clearer is how the "fresh water in" gets into the brew water circuit (aka the thermosyphon), but as I understand it the inbound cold (fresh) water is pumped in at the bottom of the thermosyphon, mixing with the existing hot water in there as it rises.

Another element is that some groups have an extra cold water input from a mixer valve at the top, which allows the water temperature in the thermosyphon, right at the group head, to be regulated without changing the pressurestat or switching off the machine.


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## carbonkid85 (Jan 19, 2011)

This is all really useful, thanks.

Group head is coming up to temperature nicely, yep.

I have a feeling the pump may have become blocked the first time I switched on. I part emptied the tank through the hot water outlet and the auto fill kicked in. It was making the same loud pump noise and wasn't drawing any water through. I think I have a spare UKLA pump somewhere, but there doesn't seem to be an easy way of getting to the current one!

Looks like a full and slightly terrifying tear down is in order!


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## carbonkid85 (Jan 19, 2011)

Tear down has begun. I took the pump apart last night and it was looking a bit worn. Swapped it for a spare I had lying around and made some progress.

The autofill now kicks in, activates the pump and draws water into the boiler no problem. Hurrah!

The brew circuit is still blocked somewhere though - I'm getting barely a drip from the group head now. BOOOOO!

So all this points to a dodgy 3 way valve, doesn't it? The tear down continues...

As an aside, I drained a pint of water into a glass from the hot water outlet and was really surprised how clean it was. It was perfectly drinkable. Does this bode well for the inside of the boiler? Might I get away with not completely stripping and rebuilding the whole lot?


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## carbonkid85 (Jan 19, 2011)

Awesome set of schematics at http://www.mrcappuccino.com/servicedepot/srancilioparts/s20part.htm for anyone looking to rebuild one of these!


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## MikeHag (Mar 13, 2011)

Are you able to get parts easily enough when you need them? One day I'd love to buy a knackered old machine from an engineer and do a strip & rebuild.


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## carbonkid85 (Jan 19, 2011)

Luckily I haven't found anything that needs replacing yet. I am a little worried about the three way valve - I just can't seem to shift the nut that fixes the pipe which runs to the boiler. I have a blow torch on its way so I'm hoping that will shift it and then it'll just be a case of cleaning it out.

Everything else seems to be in decent enough condition, but it does seem like it would be quite tricky to find a UK supplier of commercial Rancilio parts. I haven't been able to find anyone in London who would service it even...


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## Spazbarista (Dec 6, 2011)

http://www.espressounderground.co.uk/rancilio%20parts.html

There you go. And if he hasn't got it, give him a ring.


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## carbonkid85 (Jan 19, 2011)

Had some time to work on it today. I am starting to think the problem is a lot more basic than I first thought.

The shower screen is absolutely caked in old coffee oils. So much so that I can't shift the screw keeping it in place. I currently have the whole group soaking in its third bath of Puly and there is still more oil coming out from behind that screen.

It really makes me sick to think this machine had been used commercially at one point. The quality of the drinks being served must have been appalling. It's completely filthy...


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## Spazbarista (Dec 6, 2011)

New screen and screw then. They don't cost much.


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## carbonkid85 (Jan 19, 2011)

Yep, I have new ones ready to go on just as soon as the current screw is un-gummed enough to shift. Puly and a wire brush should do it...


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## carbonkid85 (Jan 19, 2011)

This is driving me mad. The shower screen screw just won't budge. I have boiled it with puly, soaked with WD40, bashed with a hammer, heated with a blowtorch and attacked with an impact screwdriver. NOTHING.

I am having a guy drill it out as a last resort. This is literally the only thing stopping me from rebuilding. Incredibly frustrating!


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## carbonkid85 (Jan 19, 2011)

I have admitted defeat and called in some hired help. If the coffee gods are on my side, I'll have this going at the weekend. I plan to stand over the guy and watch everything he does. I find the internals of a machine equally as fascinating as frustrating!

Managed to secure a partial refund from the seller via eBay. He wasn't happy, but it's his own fault for completely mis-selling the machine...


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