Need help! - No heating or hot water!

[nathanj]

Hi,

I hope someone can help me with my problem. I just moved into my first house and my heating system has gone wrong.

The problem is that the boiler will run but I don't get any hot water or heating. The system has been working fine for the first three weeks of me being in the property but before I moved in it was vacant for about 6 months.

The timer is not the problem because the boiler fires up when the timer kicks in. I have tried bleeding the radiators and they were fine. I have tried bleeding the pump but very little came out of it. I even took the bleed screw right out and there was no more than the odd drip coming out. The pump is running because I can see it moving when the bleed screw is out.

Above the pump is a motorised 3-way valve. I have taken the motor off but when I try to turn the valve manually, it won't move more than about 5 degrees. When I do this with the boiler (and pump) running it clonks and all the pipes rattle.

At the moment I am using the immersion heater to heat the water.

System details:
Potterton netaheat gas fired boiler
6 radiators (3 upstairs 3 down). The downstairs radiators are on inverted loops (I think thats what its called when the pipes come down from the ceiling to each radiator).
Hot water cylinder in airing cupboard upstairs.
Pump next to hot water cylinder, below 3-way motorised valve.

If you need anymore info to be able to help, I'll do my best to answer any questions.

Sorry this has been a bit long winded!

 

[croydoncorgi]

Check the (smaller) F&E tank in the loft,to makesure it's got water in it. (You didn't actually say whether 'bleeding' the rads actually produced any water.)
If the pump's turning and the boiler fires up, with a 3-port valve it's very hard for the system NOT to produce warm rads, hot water, or both.
(The spindle on a 3-port valve only moves through a short arc - but more than 5 degrees.)

 

[nathanj]

Thanks for the response.

I'll have a look in the small tank in the loft tonight.

When bleeding the radiatiors, water came straight out. There was no air in them.

The 3-port valve may have moved a bit more than 5 degrees but it really didn't move much.

 

[Softus]

Faulty/worn pump.

 

[nathanj]

I'm fairly sure that the pump is ok.

When I remove the bleed screw, I can see the impeller spinning. I can hear it changing speed when I switch the speed of the pump. I have tried leaving it on the highest speed setting for a while and it doesn't improve the problem.

 

[Softus]

I'm fairly sure that the pump is ok.

Oh. OK. Over to you then.

 

[Soggy_weetabix]

I'm fairly sure that the pump is ok.

But you are not certain

The impellor could have become detached, thus spinning freely but unable to circulate the water.
Can it be removed & checked?

David[/b]

 

[nathanj]

Sorry, I don't mean to say that I know better, I just want to be sure that it is the pump that is the problem before I replace it.

The reason I'm trying to fix it myself is because I can't afford to spend more on it than I need to.

Is there any way I can be sure that the pump is the problem?

Thanks for the responses so far.

 

[Soggy_weetabix]

You can remove the pump head on most models.

Once removed, if there is no resistence when manually spinning the impellor, its knacked. Could be sludged aswell.

David

 

[nathanj]

OK, Here's an update.

The system definately has water in it.

I have now fitted a new 3-port valve (head and body) and pump but the problem is still there, but at least I have a new pump and valve for the price of a call out fee

BTW There was no sludge and very little scale/corrosion.

I now think that the problem is that the boiler is not firing up completely. I think it is just lighting the pilot light but nothing else.

When I turn the thermostat knob on the boiler it doesn't seem to affect the flame. Niether of the water pipes to the boiler get warm and the boiler doesn't overheat and cut out so it seems like it's not producing any heat.

A friend who is a heating engineer (commercial not domestic) thinks that it's either the boiler thermostat, the air pressure switch or the gas valve.

I've ordered a new thermostat because it's cheap. I'll fit that and hopefully that will solve it, otherwise I'll get someone in to look at it.

 

[gas4you]

Potterton netaheat have known issues with pcb. I have had to replace loads of them.

Does the fan spin when there is a call for heat, if not forget pressure switch and gas valve. You need somebody with electrical/multimeter diagnostics to check all the connections to the boiler and PCB etc. I take it you have checked that basic live feed to boiler is live???!!!

 

[nathanj]

Yes the fan starts when the boiler switches on.

When I switch the boiler on (from the thermostat knob at the front), the fan starts, then it clicks a few times and the pilot light ignites. The same thing happens if the thermostat is switched on and the timer switches the boiler on.

According to some notes written on the user manual, it had a new electrical unit (I assume they mean the PCB) in early 1999, then a new fan later in the same year.

 

[gas4you]

If the pilot is lighting then the APS is working. This leaves the PCB or the gas valve. Againyou need to check voltages with a multimeter to see iff there is voltage coming off pcb terminals to gas valve or you can check voltage at gas valve terminals. If you are unsure of tesing with live current then please leave it to an expert!

 

[Soggy_weetabix]

What about the earthing bracket?

Sounds like its worn, thus not allowing the boiler to rectify.

Could even be reverse polarity. Have you or any sparks been tampering with any wiring of late?

David

 

[nathanj]

Thanks for the suggestions.

I've just noticed that there is a fault finding flow chart in the manual.

There are two flow charts and one suggests that I check for 240v across two terminals on the electronic control unit. I assume that these terminals connect to the solenoid on the gas valve. I'll check tonight. I'm an engineer (but not a heating engineer) so I know my way around a multimeter.

The other flow chart suggests changing the thermostat so that won't hurt.

Earthing bracket? Is that the earth electrode? Can I get to that without having to dismantle anything that would need a corgi engineer? Wouldn't that effect the pilot light though?