eco TEC plus 615

[jessica09]

Hi! I need some advice before I call the engineer out.

I had the above boiler installed last year november. About 3 months later I noticed the boiler was taking too long to fire up when the temp had dropped. There's no problem when you switch the heating on for the first 2 hours or so, rads are hot to touch. When the room temperature is reached the boiler switches off and it should fire up again when the temperature drops. But I noticed it was getting very cold before it fired up, I waited about 55 mins before it came back on again by that time the house was cold again. The room thermostat is located in the hallway and is set at 20 degrees. I think the thermostat is working as I can turn of the heating when I turn it and make the boiler fire up sooner when I increase the temp but I don't want to increase the temp because I want to save on fuel. Appreciate some advice, thanks!

 

[Hugh Jaleak]

Boiler seems to be working as it should when it gets the call for heat from the stat. It may be you require a new stat in the hallway, if its not measuring the temperature accurately then the boiler will not fire until the stat tells it to.

 

[jessica09]

thank you will tell engineer to check stat. Also I have a few other Q's


1. when I had boiler installed the engineer removed the smaller tank from the attic, can you tell me why I don't need it.

2. cannot turn down two radiators using TRV. Is it because its stuck!

 

[Hugh Jaleak]

1. The small tank on a conventional system (which is likely what you had) provides room for the water to expand when its heated, and the vent pipe over the top is a pressure relief/safety valve in the event of the system getting to hot and the water boiling. It all works at atmospheric pressure.

The Vaillant works on what is known as a 'sealed' system, which is what you have now. With a sealed system then the tank is unnecessary, the boiler incorporates an expansion vessel and a Pressure Relief Valve that will discharge any excess pressure outside should a fault develop. Normal system pressure when its cold should be 1-1.5 bar on the gauge, this will rise a bit when the system is working.

2. Unusual for a TRV to stick open I think. Remove the head, does the pin move freely? If so the valve is working ok. If stuck, a GENTLE tapping with a small hammer may free it off. If the pin is free then I would think the bellows in the head are not working to open/close the valve with the temperature fluctuations, probably need new valves. Have a word with your engineer, freeing stuck TRV's is a fairly quick job while he's there if you are unsure. Also it may be possible with some TRV's that they're fitted the wrong way round. The water should flow in the direction of the arrow stamped on the valve body, if its wrong then it wont work....

 

[jessica09]

hey! Hugh thanks for the helpful info. I have a traditional central heating system with a hot water storage tank, so its still fine to do without the small tank.

I don't have numbers on the gauge just a light grey, dark grey and red area on gauge, was told its ok if needle stayed in the dark grey area.

The TRV's are the original ones that came with the radiators which were installed approx. 20 yrs ago.

Also do I need an inhibitor and where would they put this??

 

[Hugh Jaleak]

Ah, you have a system boiler. Basically the boiler and heating side are on a sealed system, hence no requirement for a Feed and Expansion (small!) tank.

If the TRV's are that old it may be they are not working properly. Hallway radiator (where roomstat is) should really have 'normal' valves on it anyway. If a thermostatic valve is fitted then it may shut the rad down too early, thus preventing the rest of the house from getting to temp. Does the roomstat date from then or was it replaced with the boiler?

Any sensible installer should have flushed the system before installing the new boiler, and added inhibitor on completion. The installer should have filled in the 'Benchmark' book with his, yours and details of the work undertaken fitting the new boiler, including flushing system and a record of chemicals used.

 

[jessica09]

roomstat is the original one from back then. No thermostat valve fitted on radiator in the hallway. I'm a bit confused, the roomstat is fitted in the hallway right opposite the front door which is the coldest part of the house. shouldn't the boiler be firing up quite frequently. The hallway never feels warm cos we've got one of them doors with top and bottom panes of large glass.

 

[Hugh Jaleak]

You saying that does make me think the roomstat is dodgy. They are basically an on/off switch, when temp drops below that set on the stat it should switch the heating on, then switch it off again when set temp is reached. Just, in your case it doesnt appear to be doing so as it should!

Id be minded to replace it, (I cant really think of anything else that could be wrong, its simply not reacting when the temperature drops).

Depending how technically minded you are, it shouldnt be difficult to change, new stats start from £7.49 at Screwfix. Some of the current Honeywells are a direct swap wiring wise for their ancestors, depending on what you have currently. The digital versions are more expensive but I believe the higher price is reflected in greater accuracy in operation, basically choice is yours there!

Hallway rad sounds correct BTW!

 

[jessica09]

hi! Hugh thanks for answering my Q's. I am definately not technical, not in plumbing and heating but ok in putting together flat packs

I was deciding on having a digital one but was told it needed to be connected to the boiler as well so will cost me over £150+, or did the engineer misunderstood me ?!?! a digital thermostat ???

 

[Hugh Jaleak]

All stats need to be connected to the boiler! Either directly or indirectly, depending on system type. The stat detects temperature and give the boiler the signal to fire when heat is required, so not sure what your engineer is on!

The wiring is already there, the existing stat is using it! Although some new stats may require 3 wires and if yours only has 2, then you may need a new cable from stat to boiler. Im not sure if there is a digistat that would work on a 2 wire connection, might look into that.

Alternatively however, wireless stats are available. The base unit would be wired to the boiler in place of existing stat connections. Sender unit can be placed in hallway or living room, provided it is able to 'talk' to the reciever then it only needs batteries now and again and you have your control. Something such as this: http://www.screwfix.com/prods/87377...ing-Controls/Honeywell-CMT921-Room-Thermostat
Although there is a price premium attached.....

 

[jessica09]

My original roomstat is over 20 yrs old knowing my luck its probably a 2 wire one. Does new cable mean making a big hole in the wall? is it a straight forward job? I'm looking at the Honeywell DT200 roomstat, a nice simple one.

http://www.screwfix.com/prods/40819...ting-Controls/Honeywell-DT200-Room-Thermostat

the one you suggested is toooooo expensive plus installation and it'll cost me over £150+

 

[kevindgas]

hugh seems to have given you a lot of good advice already.

just a little tip that hasnt been given on the 600 series boilers you can see the exact pressure by pressing the - button it will then say 1.4 or similar if it say 0.8 or less then it needs topping up by using the grey taps under the boiler.

the old tank in the loft would only be used on a 400 series vaillant as they can be open vented
the 600's & 800 combi's have to be pressurised

 

[kevindgas]

Im not sure if there is a digistat that would work on a 2 wire connection, might look into that.

yes you can get a drayton one, ask in any merchants for the voltage free version

 

[jessica09]

hugh seems to have given you a lot of good advice already.

just a little tip that hasnt been given on the 600 series boilers you can see the exact pressure by pressing the - button it will then say 1.4 or similar if it say 0.8 or less then it needs topping up by using the grey taps under the boiler.

the old tank in the loft would only be used on a 400 series vaillant as they can be open vented
the 600's & 800 combi's have to be pressurised

Thank you kevindgas for the extra tip, I pressed the - button and its reads 2.1 bar, is that ok? The tap for increasing the pressure is in the airing cupboard next to water cylinder.

 

[kevindgas]

Thank you kevindgas for the extra tip, I pressed the - button and its reads 2.1 bar, is that ok?

yes thats fine

The tap for increasing the pressure is in the airing cupboard next to water cylinder.

well it shouldn't be - the old filling loop should have been capped off.