Hot water but no central heating?

[Simon B]

Hi guys,

Stumbled across this forum and it definitely seems a very useful one.

Basically, me and my partner have recently moved into our first property a couple of months ago and until now haven't required the central heating on.

The boiler in the house is an Ideal Classic HE15P (LPG) with a Heatrae Sadia Megaflo indirect cylinder. Unfortunately, the controls are very minimal and don't tell you of any faults that occur.

From what I understand when the thermostat calls for the central heating, I hear the 2 port valve open, the boiler comes to life and the odd time it will ignite but only stays ignited for 1-2minutes and then goes out, however it sounds like either the pump or the fan for the flue are still running.

I had checked all the radiators for air last night and there seemed to be some in the towel radiators on the 2nd floor (townhouse). Even after bleeding them and topping the pressure back up it is still misbehaving. The water from the radiators seemed clear, no build up of sludge etc.

Are there any other things I could give a try before having to call a plumber out? I am a building services design engineer so know a little about heating systems but I'm electrically biased.

Thanks
Simon

 

[picasso]

Sounds like you have no circulation, make sure all the rad valves are open.

 

[45yearsagasman]

Simon. I assume your hot water is ok so that probably eliminates a pump problem, although it does need checking to see if it's actually spinning. See wiki. The 2 port alive may be suspect, is, switching the boiler on and the valve internals not opening. Do you have rad thermostats?

 

[Simon B]

Thanks for the replies.

Yes, all the radiators but the hallway have TRV's installed and all are fully open.

The 2 port valves seem fine, when the heating has demand, the manual override on the valve moves freely and when the demand for heating is stopped you can hear the valve closing.

 

[picasso]

Could be the valves on the other end of the rads are shut (some people have a strange sense of humour) the pins on the trvs are stuck or the pump is dying.

 

[Simon B]

Ahh okay, I will check them this evening.
If I was to unscrew the TRV from the valve I will be able to inspect the top of the valve won't I?

The pump seems to be okay, it has 3 speed settings and is currently set to 3. Pump being a Grundfoss UPS 15-60.

I'm thinking of getting someone out to have a look at it as I can imagine the boiler needs a service anyway.

 

[Agile]

To check the flow through the boiler you need to measure the flow and return temperatures at the boiler .

Should be a differential of about 11 C and a flow temp of about 80 C.

I suspect the flow is too low and you will find the differential is too low!

So the boiler is just turning off!

Tony

 

[Simon B]

Thanks for that Tony.

Is there a pump which is located within the boiler?

 

[picasso]

So how can he check the differential if the boiler wont run ?

 

[Simon B]

I think the issue may have been an airlock, my boss told me to check the rads on the top floor and the towel rads had quite a lot of air in them. Once bled I topped the system up but it still wasn't happy. However coming home on Thursday evening the system must have sorted itself out as the boiler is firing properly again.

Still I will be getting the boiler serviced; could anyone advise on the typical cost and if there is anyone recommended in the North Yorkshire area on the forum?

 

[Hugh Jaleak]

It would be prudent (and advisable!) to get the Megaflo serviced and checked at the same time, it should be serviced annually anyway to ensure correct and safe operation. You will need to look for someone with a "G3" accreditation which means they are competent to work on unvented hot water cylinders.

 

[Simon B]

Great, thanks for that Hugh!

 

[ianmcd]

unlikely that you have an airlock in a pressurized system but can happen if pipework installed badly, always advisable to have a proper service done when you move into a new property as you dont know the previous history, but please be upfront with whoever you call and tell them of the fault that you had and dont expect them to magically find the fault that they know nothing of while carrying out a routine service, nothing gets an engineers back up more than turning up to service a boiler and getting handed a list of faults or worse finishing the service and getting asked so will that stop the boiler from cutting out all the time or whatever

 

[Simon B]

I shouldn't have held my breath, boiler is back up to its old tricks.

Currently stood opposite with the stat at 30, boilers fan making its usual noise and no pilot light or lit burner.

What are the chances it's a dodgy sensor? Regardless I'll be giving a plumber a call tomorrow.

Do they need any special accreditation to work on LPG as well as an unvented hot water cylinder?

Thanks

 

[45yearsagasman]

Yes and yes. G3 cert for unvented and lpg on his gassafe card.