No hot water - Indirect System


Postby markwt » Thu May 01, 2008 8:27 am

Hi everyone,

We have an indirect boiler system thats about 30 years old.

For a few months we could only get HW when the CH was on.

Now the HW has gone off completely.

The boiler still fires up when we turn the HW only on. The CH system itself is fine, the radiators get hot very quickly.

I'd like to know what the possible causes of this could be.

Is it likely to be something that can be fixed without requiring new parts? If we do need new parts, will they be hard to find, and will that mean we'll need a whole new system?

Thanks in advance.
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Postby rosebery » Thu May 01, 2008 9:43 am

Superficially it sounds like a failed actuator on a three port valve. If that's the case they are not difficult to replace and no, a complete new system will not be required.

Also after 30 years it's more than possible that the valve itself is just so gummed up with crud that the actuator has difficulty operating it. Difficult to tell without actually seeing it.

It sounds to me as though you would be well advised to get a plumber in to have a look at it for you and provide on site advice.

Cheers
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Postby htg engineer » Thu May 01, 2008 3:28 pm

As rosebery says - it could be the actuator or the three port valve at fault.

Is it a fully pumped system, not a gravity HW system ?
(can you have central heating on by itself, or does the water have to be on too ?)

Will watch for further posts.
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Postby markwt » Fri May 02, 2008 1:00 am

Hi guys,

Thanks for the quick replies.

I'm not sure if its a fully pumped system or a gravity HW system.

When its working normally you can have the CH on by itself though.
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Postby markwt » Fri May 02, 2008 2:27 am

Sorry htg, I think I misunderstood your question in my last post.

When its working properly you have to have the HW on when you want CH on.

Does this mean its a gravity HW system?
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Postby htg engineer » Fri May 02, 2008 10:37 am

Yes it is a gravity system, I thought that would be the case when you said it was 30 years old.

It'll probably be a blockage of some sort in the primaries, coil in the tank or heat exchanger, will probably work when the heating is on because the pump is running and it will force it through.

There could be a build of of sludge or limescale, you could drain down and check the condiiton of the primaries, if you're a competent DIYer, if not get a heating engineer out to repair or offer advice.

Hope this helps
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