Numerous central heating issues

[coldasfcuk]

First off I am going to apologies as there will be some cross over with other threads, but I seem to have issues which cross on loads of topics so I just want to make sure I am not missing something obvious.

My kit:
Potterton Flamingo 50
Honeywell Mechanical room thermostat
Grundfos UPS 15-50 pump
Generic motorised valve

Issue 1:
Room thermostat is currently a rather ugly piece of modern art. It does bugger all. It’s a Honeywell mechanical job and it does click when you turn the dial and I have had a look at the wiring on the back which all appears to be in order. However it doesn't seem to control anything to do with the heating at the present time.

Issue 2:
The previous owners got round issue 1 by pulling out the hot water tank thermostat (yes I know). This means the boiler is always firing and the hot water is very hot. The radiators lead onto issue 3, but kind of work in the current state.

Issue 3:
If I turn on the upstairs rads and leave the downstairs ones off - upstairs is ok.
If I turn the upstairs rads off and turn on the downstairs ones - the downstairs rads are ok.
If I turn on 1 rad upstairs and 1 rad downstairs everything is ok.
If I turn on all the rads - you'd hardly know there is any heat at all.

At the present time I have just one radiator upstairs on and one downstairs on and both are at what I would consider a normal temperature. This suggests to me that the pump is working (or am I being optimistic?)

I have flushed the system several times and got a lot of sludge out. I have removed all the air (I think) from the system as well. And I can hear the pump working away. I have also added cleanser to give the system a good clean.

The bit I am a bit hazy on is the motorised valve. When the hot water cylinder gets to the desired temperature, does it tell the motorised valve to send all the hot water to the central heating system?

If it does then this may be the answer to all my problems and just getting a working room thermostat may fix the issue.

My only concern is that the thermostat is fine and there is a wiring issue somewhere else causing the thermostat not to work. Or do you believe it’s worth replacing the room thermostat before spending time tracing wires in walls?

Thanks for any replies

 

[GPlumb]

Issue 1: Check the wires behind the roomstat. 1 should be permenant live, 1 will be nuetral and the other will be live when the stat is calling ie: It has clicked on.

Issue 2. Fit a cylinder stat!

Issue 3. Try turning the pump up to max.

Ultimate solution would be to fit new controls. Honeywell and danfoss make up kits that comprise of a roomstat, cylinder stat, MV, timer and a wiring centre.

 

[Agile]

Your system is very old although if in proper working order is capable of good operation.

Its obvious to you what some of the issues are.

The one you may need help with is the flow to the rads. That seems to me as if the pump is either weak or the eye is blocked.

You should isolate the pump and remove the head to check for dirt and to do the "finger test".

Tony

 

[steve32]

refit HW stat when it's up to temp and RS on max motorised valve will go over to heating only if this doesn't happen and the system shuts down the motorised valve may be stuck or motor faulty and may need replacing.
I assume you have a 3 port and not 2 2 ports
New valve Honeywell not sure of wiring on existing may need altering.

 

[coldasfcuk]

Issue 1: Check the wires behind the roomstat. 1 should be permenant live, 1 will be nuetral and the other will be live when the stat is calling ie: It has clicked on.

Issue 2. Fit a cylinder stat!

Issue 3. Try turning the pump up to max.

Wiring is fine, the cylinder stat is there, just pulled out. I have left it out at the moment as its freezing and the pump is at max.

The one you may need help with is the flow to the rads. That seems to me as if the pump is either weak or the eye is blocked.

I was a little concerned about the pump being at fault as that what pushed the hot water round the system.

Given the amount of sludge that was in our central heating system I was wondering if it had blocked the pump and the motorised valve from working properly.

And yep its a 3 port. First step I think will be to replace the room thermostat. Once thats done I will actually be able to test that all the thermostats are working properly. It will also tell me is there is any wiring issues.

Thanks for the replies so far.

 

[Agile]

Thats odd!

I give you advice on what to check and all you want to do is change some stats!

Why do I bother!

Tony

 

[coldasfcuk]

Thats odd!

I give you advice on what to check and all you want to do is change some stats!

Why do I bother!

Tony

Sorry.

I am going to check the pump, but that will not be as easy as replacing a room thermonstat which I know is already broken. And when I say know, I know the function isn't working, but I am not sure if its the thermostat itself.

Isolating the pump will be a lot of work for me as I am not an expert so it would be one of those weekend jobs.

I did have one question for you though, the finger test?

 

[Agile]

Should only take 15 minutes if you have gate valves on the pump.

Search on this site and you might find:-

//www.diynot.com/forums/viewtopic.php?t=41182

Tony

 

[sambotc]

How are you getting heating if the room stat is faulty?

Sounds like a faulty motorised valve to me.

 

[MANDATE]

sounds like the room stat has been linked across and does not control anything, ( boiler is always firing)
Hey I removed a pump head and the input and output holes were almost closed off, down to about 6 mm. So with kind of resistance you can understand a reduced flow.

 

[coldasfcuk]

How are you getting heating if the room stat is faulty?

Sounds like a faulty motorised valve to me.

We're getting heating because the tank stat has been removed and because of that the boiler always fires as it has no idea how hot anything is.

Agile - I will try the finger technique at the weekend when I have time to fix what I break, so thanks for that. I am kinda putting off pulling out the pump and the motorised valve as the cupboard they are in are tiny and with the cylinder as well, they are very hard to do anything with. The pump, valve and cylinder are all only at most 6 to 8 inches apart.

Plan of action:
1: Replace room stat and hope for the best. It doesn't work at the moment so it can only get better.
2: If the stat doesn't work, the 'finger' test on the pump and see if there is anything else clogging it up.
3: Replace the motorised valve / check it out. My dad has a spare valve so I may just replace it rather than trying to figure out if its broken.
4: Replace the pump maybe. I guess at this point I will take stock and see if the thermostats are working as they should be, if not, then there is a bigger issue than just the pump.

Thanks for your help guys! Its much appreciated!

 

[MANDATE]

I agree the boiler will not know how hot the rooms are or how hot the hot water is in the cylinder, but it will know how hot the water is in the boiler.

I think there has been a problem with the heating, most likely due to the motorised valve not moving beyond the mid position or a faulty microswitch. You can understand the 'room stat' being considered as the culprit, so its taken out of the circuit. But it makes no difference to the problem.
So with valve in mid position there is some heating but only until HW is satisfied. The valve attempts to move to CH and either can't or if it does then the boiler can't light (microswitch)
By removing the cylinder stat HW will never be satisfied, so valve will stay at or return to mid position where you get HW and CH, but with no control of either.
The only control is the boiler stat, which is why the hot water is very hot.
Also with the valve in mid position, the CH port is only half open and that will reduce the flow to the radiators.
Based on this it would appear the motorised valve is the problem, but it's still worth while checking the pump.

 

[coldasfcuk]

OK stat changed.
Motorised valve changed.
Finger test done.

Problem still there. Looks like there is a wiring issue somewhere. I had a very quick look at the wires and have decided that the only choice is to call in a professional at this point.

Thanks for your help guys, I will let you know what gets found out. If there is anything to tell that is...

 

[Agile]

Is the motor valve closing off the port supplying the cylinder when its satisfied? And is it getting satisfied?

Turning down the cylinder stat should cause the valve to close the port to the cylinder causing the heatoing coil to cool after a short time and thus giving the full boiler output to the heating and heating all the rads.

My first thought is that you need to fit a gate valve in the supply to the cylinder coil as when thats on there is little flow available to the heating circuit as the cyklinder is taking all the flow.

Others on this forum pretend its not needed but I have fixed many similar alleged problems that way.

Tony

 

[coldasfcuk]

Thanks for the info. I will bear that in mind and mention it when I get the pro in.

It would be beyond my ability to add new parts that require piping or electrics. Changing parts that are already there though is another thing as they are usually quite interchangable.