Zoned central heating problem

[doitmyself]

I have checked the motorised valves and I think they are working, based on the return pipe of the zone that is turned off being cold.

Is the return pipe cold on both sides?

It sounds as if there is convection circulation in the zone which is turned off: not surprising with the zone valves on the return!

It might be worth checking that the zone valves are the correct way round (arrow on the side of the brass body, or IN at A, OUT at B).

 

[happyflyer]

 

[happyflyer]

This should help, it may not be exactly like this but this, there is always a chance that gravity circulation can take place even if the valve is shut on one circuit, especially upstairs, there is a way around this the installation of a loaded none return valve, its probably getting a bit too much after all we are in the trade, but the plumber from hell should put it right and stop gabbling about the number of rads on the system

 

[fredfat]

Hi doitmyself, thanks for your reply. the return pipe on the zone that is switched off is cold directly before the valve.The return pipe of the zone that is switched on is hot before valve. After the valve the 2 pipes return into a single pipe going back to the boiler and this pipe is also hot.

The zone valves are both facing in the right direction. many thanks for your help

 

[doitmyself]

there is a way around this the installation of a loaded none return valve,

I know that's the solution for reverse circulation, but would it work for the OP's problem? The valve would have to be fitted to allow circulation when the zone is open; and there could easily be enough pressure from the pump to open the valve.

 

[happyflyer]

zxzzxzxz

 

[fredfat]

cheers happyflyer that drawing is great it helps me understand what you was saying about the auto bypass, and explain what i think could be a problem.If the returns of the upper and lower floors are joined together before they reach the valves would this cause the problem ? I'm pretty sure that 2 of the downstairs radiators are joined to the upstairs return. Anyway cheers for all your advice I will report back as to what waffle I get on Monday.

Can i just ask one question re: the drawing.At the split is the idea that the heated water will only flow to the zone/zones that are switched on due to being pumped/pulled and no heated water should go into the zone that is not switched on ?

 

[happyflyer]

Another version but not showings auto bypass which the system must have, but less chance of cravity circlation when one vavle is open and one valve closed, hope you can understand all of this, you plumber won't.

Tony

 

[happyflyer]

I will do you a few drawing of whats going on in the system give me some time OK

 

[happyflyer]

You will see that if one valve is closed 1st floor and the other is open the flow rate and resistance in the system will change, as the 1st floor valve closes the bypass valve should start to lift causing the excess pressure to be absorbed and more water will go around the bypass loop, you need to understand that plumbers balls are not made out of glass and a lot of this is two hands on the pipe and an ear on a hammer not very assuring but that's how it is, saying all that your system should work, you never did say is there a bypass valve , in your case it must be automatic not just a gate valve

 

[happyflyer]

Automatic bypass valve should look like this

 

[fredfat]

Hi Happyflyer ,

Thanks for all your time and help. Sorry I didn't reply but got called away.

My system looks very much like your first drawing minus the bypass valve part. I cant see that anywhere. However on reading the boiler manual it says there is an automatic bypass inside the boiler, but then goes on to say if the system employs thermostatic radiator valves on all radiators, or two port valves, then a bypass circuit must be fitted with an automatic bypass valve to ensure a flow of water should all valves be in the closed position. Which means you where spot on!

Is there anywhere this could be installed that i would be able to miss it i.e under floor boards or would it be as it appears in your drawing?

One final question does the size of the pipe increase/decrease the pressure? the reason i ask is that it has been installed using a 10mm plastic pipe which seems very narrow compared to the copper pipes coming from and to the boiler.

Many thanks for your help

Fred

 

[jam1979]

why dosent your plumber put the zone valves on the flow and piece the pipes back on the return

 

[happyflyer]

Hi Happyflyer ,

Thanks for all your time and help. Sorry I didn't reply but got called away.

My system looks very much like your first drawing minus the bypass valve part. I cant see that anywhere. However on reading the boiler manual it says there is an automatic bypass inside the boiler, but then goes on to say if the system employs thermostatic radiator valves on all radiators, or two port valves, then a bypass circuit must be fitted with an automatic bypass valve to ensure a flow of water should all valves be in the closed position. Which means you where spot on!

Is there anywhere this could be installed that i would be able to miss it i.e under floor boards or would it be as it appears in your drawing?

One final question does the size of the pipe increase/decrease the pressure? the reason i ask is that it has been installed using a 10mm plastic pipe which seems very narrow compared to the copper pipes coming from and to the boiler.

Many thanks for your help

Fred

Fred,

If there is no bypass valve on the system then when say the 1st flr valve is closed and the GF open the system pressure will be higher and there will be a tendency for the pressure to try to push against the sparing in the valve that is closed, hydraulics are not simple, I did ask you what the pump is set at and its probably in the boiler case so you can't get at it. He needs to fit a proper bypass valve, I will have a look at the boiler instructions did you tells what the boiler was

 

[happyflyer]

Fred page 9 of Installation Instruction


Boiler Control Interlocks
Central heating systems controls should be installed to ensure
the boiler is switched off when there is no demand for heating, in
compliance with Building Regulations.
Heating systems utilising full thermostatic radiator valve control
of temperature in individual rooms should also be fitted with a
room thermostat controlling the temperature in a space served by
radiators not fitted with such a valve.
When thermostatic radiator valves are used, the space heating
temperature control over a living / dining area or hallway having
a heating requirement of at least 10% of the minimum boiler heat
output should be achieved using a room thermostat, whilst other
rooms are individually controlled by thermostatic radiator valves.
However, if the system employs thermostatic radiator valves on all
radiators, or two port valves, then a bypass circuit must be fitted
with an automatic bypass valve to ensure a flow of water should
all valves be in the closed position.



Fred,

My English is poor but this is what they should have said

or two port valves, then a bypass circuit must be fitted
with an automatic bypass valve to ensure a flow of water is maintained within the boiler, should
all valves be in the closed position.

Tony

PS I have noted the pump is in the boiler case to stop people adjusting it, how sad is that, its not a hanging offence to adjust the pump, never mind the buzzcocks unk:

 

[leethegasman]

Hi,



I was told that it was a dual zone system and it was installed only 3 months ago, but there is a problem. When I switch a zone off i.e. upstairs ,the rads still get warm in that zone, once the other zone (downstairs) comes on and vice versa.


Fred.

Can I just ask when you have one room stat on and one off do both upstairs and downstairs radiators get hot.if this is the case take no notice of my post.but if when you turn on your downstairs room stat your upstairs radiators come on.and when you turn on your upstairs room stat your downstairs radiators come on
The reason I am asking I can not tell from your post.if this Is the case the room stats are controlling the wrong zone and is a simple fix.

 

[fredfat]

Hi Tony,

I will be speak to installer tomorrow and will be requesting that he comes back and fits a bypass circuit with an automatic bypass valve as it seems he should of done in the first place !

As you have mentioned about the pump being inside the case I'm i right in thinking that i'm not allowed to remove the case?

Once again many thanks for your time and help with this

Fred

 

[fredfat]

Hi leethgasman, thanks for your reply, the room stats are controlling the correct zone valves it is just that all the rads are getting heated instead of just the zone that is requesting heat. I think with the help of Tony and Croppie the problem has been found to be the lack of a bypass valve on the system and potentially the pump being set to fast.

Fred

 

[fredfat]

Hi jam1979, thanks for your reply as you may see from other post's it seems as thought the problem has been identified cheers

Fred

 

[fredfat]

Your boiler has something called pump overrun which protects the boiler. An automatic bypass provides a route for the water to flow when the zone valves are closed.

You've definitely a combi yes? And a hot water cylinder?

Your house doesn't sound huge! Two bedroom?

Hi Croppie,

Thanks for your help looks like you where spot on, will be speaking to the installer tomorrow and getting him back to install an autobypass as per yours and Tony's and installation manuals advice. Cheers

Fred

 

[Nostrum]

Zones valves on flow, bypass fitted. Jobs a good un. Sounds like its not necessarily caused by circulation. Heat rising into a few of the radiators upstairs. Do they get roasting hot, or warm on top? How long do they take to warm up if only downstairs zone is on?

 

[fredfat]

Hi Nostrum ,

thanks for your reply, my system and problem is Ideal combi boiler 30, 3 rads upstairs 3 rads downstairs. Controlled with wireless enabled 2 zone programmer and 2 wireless room thermos. There are 2 x 2 port motorised valves on the RETURN pipes.

When I switch a zone off i.e. upstairs ,the rads still get warm in that zone, once the other zone (downstairs) comes on and vice versa.

The rads upstairs don't get as hot as down stairs but they get warm fairly quickly. I don't think the water is being circulated as such in the zone thats switched off as the return pipe remains cold. The same thing happens if upstairs on and down stairs off with the exception of 1 rad that i think is the last in the system

Fred

 

[fredfat]

Hi,

Just quick update spoke to Engineer this morning and he is going to come out and look at the problem. No mention of not enough rads ! so fingers crossed he has forgot about using that as an excuse. I will let you know how it goes. cheers

Fred

 

[rob2048]

Hi your zone valves are on the flow not return pipes if they have used one return pipe and not two separate returnes the hot can creep up the one that is turns off we have had this now we always run two seperate returns and link in just before boiler hope this helps

 

[fredfat]

Hi Rob, thanks for your reply, the valves are defiantly on the returns and there are 2 returns 1 for each zone. Cheers

Fred