DIY Doctor

Heating system

Postby GARYF » Thu May 10, 2007 11:30 pm

I am doing some work on a friends system. The boiler is a Baxi. It has a bottom gas feed and a flow and return at the top. The pump is mounted directly to the flow pipe on top of the boiler. Beneath the boiler is a Horstman electro/mechanical programmer. In the loft is a header tank for the DHW and a feed & expansion tank for the central heating. There is an immersion fitted as well as having a indirect heating coil. My query is:

1) I cannot see a 3 way valve! Is it possible that there isnt one?

2) I cannot see a thermostat on the copper cylinder and there is no room thermostat. How does the boiler know when to switch off the heating because there are no TRV'S fitted either. How does the boiler know when the DHW is up to temperature?

Any help will be greatly appreciated.

Thanks in advance,

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Simply Build It

Postby Arnak » Sat May 12, 2007 10:49 am


With plumbing anything is possible. :cry:

There may well not be a 3 way valve although there should be one especially as there is a timer.

Is the valve somewhere else in the system, perhaps under the floor?

The boiler probably has thermostat to control the HW temperature, have a look at the boiler controls and see if it is there.

Alternatively is the stat in the immersion heater, usually a removable rod cabled in at the top of the heater?

I have also seen an external thermostat held onto the tank by a metal strap around the cylinder.

Hope that helps.

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