Central heating radiators going cold downstairs when hot water put on.. Help!!

mikeluxy

Hi There :money:

This is my first posting and I wonder if any plumbers out there may be able to help .

We have an open vented central heating system...we had a new boiler fitted about 2 years ago as well as having a full system flush at the same time....I also installed a brand new WILO pump a few days ago in case that was the problem.....

The problem is this....when there is NO hot water selected we get lovely warm radiators both upstairs and downstairs however as soon as we select Hot water AND central heating the radiators start to go cold downstairs. :mad:

I have tried bleeding the radiators to no avail....I was wondering about a blockage but then again why would the radiators upstairs and downstairs get hot when the hot water is off...?

I am wondering about the Zone valve....do any readers think this may be the problem..?..our system has a 3 way valve which I assume is Hot water , Radiators or Both {?}

I am tearing my hair out and to be honest there is not a lot left

Any help and suggestions much appreciated

Cheers

Mike

1984ReturnsForReal_2

Did the same happen last year or is it a new problem?

mikeluxy

Hi M8

This is a new problem which has only started this year

1984ReturnsForReal_2

mikeluxy wrote: »

Hi M8

This is a new problem which has only started this year

If it had been going on for a while ie since it was installed I would of said most likely it is a wiring problem or the boiler/pump can't cope with the demand.


However if your pipework is correct & the pump & valve works & are wired correctly (and DID work properly last year) the only thing it can be is a partial blockage before or at the first rad downstairs.

mikeluxy

Many Thanks for that info....I am a little mystified though why (if there is a blockage) why the water seems to circulate OK upstairs and down when the hot water is off......

Do you think the Zone valve may have some bearing.....?

1984ReturnsForReal_2

mikeluxy wrote: »

Many Thanks for that info....I am a little mystified though why (if there is a blockage) why the water seems to circulate OK upstairs and down when the hot water is off......

Do you think the Zone valve may have some bearing.....?

If it did indeed all work before then you have a flow problem.

So it is either a partial blockage or a port valve not closing/opening fully that would inhibit the flow therefore not as much water circulates & gets colder quicker.

A partial blockage would do the same thing & also a pump that is not set to the right speed to cope with water & heating at the same time.;)

Then you have the thermostat on the boiler. Hopefully you haven't turned down the temperature on that at some point & forgotten about it.

mikeluxy

Thanks

I have the top off the zone valve (standard Honeywell type) and it seems to be removable by 2 screws (the motor mechanism)...If I remove this will it give me access to the flow valve and enable me to move it manually....?

1984ReturnsForReal_2

You are better of waiting for a few more responses before you start playing with it.

There are a couple of good heating engineers that come on here & they know a lot more than me. I am a "beginner".

If it is not a blockage but a mechanical/equipment issue that isn't related to the initial/subsequent installation it more than likely the port valve or pump (including speed).

I think you can take the control unit off of most of them but I know some are different in how they operate to others.

It would be an idea for you to get the model number for them & also that of you boiler, pump & control timer.

mikeluxy

Thanks for your help so far...as you mention ill see if any more ideas come to light on the forum...in the meantime thanks for your help

closed

Are all the pipes going into the 3 way valve hot when both hot water and heating is on - (if so, can't see it being 3 way valve related)? Is there a bleed valve near the 3 way? Is water still circulating downstairs (and upstairs) through every radiator when they aren't heating up? Have you got trv's/room stats anywhere, and if so are they set appropriately? Do any of the downstairs rads stay hot? When the hot water tank gets to temp, do the downstairs rads heat up?

http://www.lovekin.net/honeywell-motorised-valve-faults.html

Canucklehead

Hi.

As said, what's the pump speed?

What was the old one on.

Pump valves fully open?


Is the boiler fitted with a Magnaclean or similar?

Was the pump replaced with the boiler?

GSR