cold radiators - inconsistent

[mms1]

We have a condenser system. After the heating has been off overnight the radiator in the kitchen (where the boiler is)is usually stone cold while the other rads are hot.Going around the house switching them all off and then on again cures the problem but only temporarily. Sometimes we have a different problem: the rad in the kitchen comes on and the rest of the rads don\\\'t. At present the kitchen one is on as are other rads except one (my office, which is upstairs). If I switch off and on all the rads yet again I will probably solve the problem, but again only temporarily. Bleeding some rads is often necessary. I wonder if the boiler just isn\\\'t up to the job. It is no more than about 5-6 years old.

 

[ChrisR]

Maybe the kitchen rad is plumbed to come on with the HW?

Turniong rads off and on again wouldn't normally do anything - perhaps the valves stick ?

 

[mms1]

Thanks, but I don't think so because the kitchen radiator, like all the others in the house, goes off when there is 'domestic hot-water demand'. Then when the hot water has finished heating up, the kitchen rad may come on again (or may not, depending on its mood at the time! ).

 

[brumylad]

sounds like the pump is not up to the job.

Is the pump in the airing cupboard.
Is there a small expansion cistern in the loft.
or
is it a combi (combination) boiler

does the pump have 3 speed settings on it, if so what number is yours set on.

 

[mms1]

Thank you for getting me thinking! The boiler is an ecohometec EC38H condensing boiler. It seems to have an expansion talk attached to it. The pump is described as 'variable speed integral circulating pump'.
At the moment rads in the kitchen and my office are hot, but another (in the room between kitchen and office) is cold at present. There also seems to be an intermittent small leak from the kitchen rad; bleeding does seem to help, so could there be a leak in the system?

 

[ChrisR]

Er,

There also seems to be an intermittent small leak from the kitchen rad;

so could there be a leak in the system

Eh?

 

[mms1]

I'm obviously not a plumber so please forgive my ignorance! Does the fact that there is a small amount of water very occasionally from one side of the radiator mean that the whole system is affected so that sometimes some rads a long way from the one that seems to leak will be stone cold? Also does it mean that the sometimes 'leaky' rad is cold at some times and at other times just as hot as the rest of the system? I'm sure you plumbers understand (though not the one who has looked at the system!), but why is the fault so inconsistent?

 

[brumylad]

I think the leak is a red herring. However,

yes, a leak in one radiator will mean the total volume of water which is shared by the whole system will slowly reduce. Yes this will be a problem if it never replaced.

Is there a pressure guage on or near the boiler

what colour is the

expansion talk attached to it

do you / how often do you --- have to top-up the water in the system (which is leaking out)

 

[mms1]

Thank you very much for your patience. Yes, there is a pressure gauge on the boiler. The expansion tank is blue. We have not topped up the water in the system, and would have no idea how to do so (nothing in the instruction manual!). The leak so far has been very slight, and not evident every day. Today a few ml only have leaked out (sticky/oily rather than watery).

 

[brumylad]

what is the pressure on the guage ? should be about 1 to 2 bar

 

[mms1]

We keep the pressure at 1. (From time to time it falls below, and then we turn it up again.)

 

[brumylad]

when you increase the pressure you are actually introducing water into the system in exactly the same way you would to fill the system.

can't find much about your boiler but it seems it is designed to be used with underfloor heating. These systems generally operate at a lower temperature than boilers designed to run conventional radiator systems.

I am considering using the EC38H LPG modulating condensing boiler from Eco Hometec Ltd. This boiler is specifically designed for underfloor heating systems. It has the advantage of having two circuits one for heating the underfloor heating at the temp it requires but then can switch to the domestic hot water circuit and heat this to the different temp this requires.

If this the case you might just be stuck with what you have unless you change the boiler.

 

[mms1]

Thank you very much for all your help. Even though we haven't found a solution you've helped to clarify things. For the time being I guess we will just have to put up with regular rounds of the house switching radiators off and then on again.

Thank you again for your patience.