heating and Boiler problem

[JMaartenW]

I am hoping someone can help me diagnose the actual problem here. I'v had 3 plumbers in and each one gave a different diagnoses, and rather then spend loads of money on replacement parts I may not need I thought I'd try the forum for advise.

a few weeks ago we noticed that thr radiators are not getting hot, or when they do they don't stay hot for very long even if the controller CH is set to "on"

futhermore whilst I've been trying to investigate this i've noticed that the pump is running continuesly even when CH and HW are "off" at the controller. I can manually move the 3 way switch from auto to Manual but most of the time my radiators do not get hot.
I've noticed the pipes to the pump and to the boiler are generally hot when the system has been on for a short while, it seems the boiler Termostat reaches temerature very quickly ( moving the dial from 3 to MAX it does not click anymore unless the boiler has been off for a while )
so it seems the boiler gets hot quickly causing it to stop heating the water. the pump runs 24/7 but my radiators stay cold.- yet it seems i do have HW. today I let the system cool down, by truning it off at the wall for a few hours, then turning it on ( the boiler was cold) the pump kicked in straight away. the 3 ways switch was in mid position. my radiators got hot/warm for about 15 minutes and the cooled down again, and my boiler stopped heating the water but the pump just carries on

I have a standard pumped open vented system with a potterton boiler, and room thermostat and 3 way valve switch with 10mm Microbore themostat controlled radiators

current diagnoses have been:
faulty boiler PCB
faulty pump
faulty 3 way switch
pipes clogged needing powerflush


I have a spare pump which I could swap out but it occured to me the water in the tank is getting hot so the pump must be working

very confused, any help greatly appreciated

 

[Dan Robinson]

a potterton boiler, and room thermostat and 3 way valve switch with 10mm Microbore themostat controlled radiators

Any chance of narrowing it down a little?

 

[JMaartenW]

all I know is that its a Potterton profile 60 Boiler.

I've just had the system off (At the wall) for a few hours s0 pipes and boiler are cold. I turned the room thermostat to 0 and the boiler thermo to 0. then turned it on at the wall and moved the dial to 4 on the boiler and the pump stays off until i turn on the room thermostat to max. the pump kicks in to life as does the boiler, the radiators start to warm up until the boiler thermo reaches maximum temp. then the boiler stops heating the water and the radiators get cold again even though the room has not reached anywhere near the right temperature.

 

[Dan Robinson]

Sounds like a tired pump/ sludge issue to me.

 

[JMaartenW]

by Tired pump you mean wearing out? needing replacement?

 

[Dan Robinson]

Yup.

Take the the head off, see if there is any gunge in the impeller,

If you already have a spare it will cost you nothing to try it and see. The hot water circuit needs a lot less oomph from the pump; and with microbore, you could have a combination of issues. I have just replaced my 10mm/156,,/22mm mixed abortion in my own house.

The rad in my living room which never heated all the way across (a ponsy 1800mm high thing that looks like a lot of Tolberone bars) is now tip top because the rads and pump are working off a central manifold rather than some peenarse's idea of a heating system layout.

I assume your three way switch is a mid position valve? (see the FAQ).

 

[JMaartenW]

yeh tried to swap the pump out today but it looks Like I'm going to have to drain the whole system to remove the top Isloator valve as it is absolutely seized onto the pump. I'm going to have to put the pump in a vice to get the isolator off - such a pain.

Yes I think its a midway valve, but not sure. it seems the midway position is the default postition of the leaver, I've never seen it in any other position unless I've moved it myself, when I move it to manual there is quite a lot of resitance which suggest the valvel is openeing and cosing ok

 

[dcawkwell]

Pump not working or a blockage.

I would check the pump is spinning as a start.

Since you have a replacement pump easy to swap out.

As it is small piping a blockage is very possible

Although you are wasting 3 plumbers time get suggestions about what
is wrong and then going to do it yourself. The guy who said pcb was an idiot
though.

 

[Agile]

If you just remove the pump head then you can see the FAQ and do the finger test on the pump.

If you have the same kind of pump then you can change just the head.

Calling three plumbers to come out free to diagnose the fault is not going to get the best result. Most people who know what they are doing will not do that anyway. I always charge to diagnose a fault!

Tony

 

[JMaartenW]

thanks for all the feedback
I called the plumbers out to get it fixed but none were able to due to time reatrictions. so once I had had 3 different diagnosis I decided to have a go myself. good job too else by now I would have paid for a new PCB and a power flush, neither of which may be the cause of the problem.

will have a look at the pump head first

 

[Agile]

You should never have to pay for a part provided by an engineer which does not fix the fault!

Unfortunately calling people who will come free will not usually result in a correct diagnosis for free.

It makes me wonder why all three came at all if they were not prepared to complete the repair as you say. Makes me wonder if they had any confidence in their diagnosis!

Or just possibly they sussed that you really were only trying to get a free diagnosis so you could do the repair yourself ???

Tony

 

[JMaartenW]

I never said the diagnosis was free

 

[Dan Robinson]

Don't worry, Tony loves his generalisations...

Some of us do come out FOC to diagnose. Some of us even get the diagnosis right when those with diagnostic fees's don't .

 

[JMaartenW]

and some even provide free diagnosis in online forums Dan

just one last question this, I've drained the system today and removed the pump and currently powerflushing the system. the question is that none of the downstairs radiators drained down as the drain plug is above the wall mounted boiler in the utility room. how am I supposed to drain the downstairs radiators seeing as these are below the drain plug?

 

[Dan Robinson]

That is why we get paid lots of hard currency.

You might well have a lower DOC somewhere.

Otherwise it is a case of carefully doing each one from the valve unions.