Heating and Hot Water - Have I Understood correctly?

[mikebakke]

I've done a lot of research on web sites and forums, but I want to be absolutlely sure I've understood before throwing my toys out with my builders...

I have a new build with an ICOS condensing boiler and independent timer controls for HW and CH. 1st 5 months just used hot water - all ok. In November I switched the heating on and found it less than great. I did a lot of looking around and found that this system was using twice the gas I'd done in my old house which given relative sizes and occupancy didn't make sense.

It turns out that the heating will only work, ie send hot water to the rads if the stat on the storage tank is set high enough. As soon as it clicks off when (I assume) the water's reached temp, a valve turns and the radiators don't get any more heat. I assume therefore that I'm wasting gas heating water which doesn't need to be heated just so I can get the CH working. To do this the boiler stat has to be low, and the tank stat high... I've checked as much as I can and everything seems set right(ish). The room stat controls feed to the rads correctly if the condition above is met.

I've had the builder in (twice) and last time they took off the second valve which never seems to move (I assume this is actually where the problem is) and changed temps on all the stats. As far as I can see however, it is still broke.

My question is - am I correct in assuming that a modern system like this should be able to provide CH to the rads even when the HW is set to off on the timer?

I need to know this, because this is the simplest way to prove that there is a problem with no need to wait for various interactions.

Any replies much appreciated - this is driving me crazy

 

[chrishutt]

am I correct in assuming that a modern system like this should be able to provide CH to the rads even when the HW is set to off on the timer?

Yes, of course you're right. My guess is that there's a wiring fault in the control system - quite likely on new build where the least competent operatives find a living. Your "builder" won't have a clue, but an experienced heating engineer should be able to sort it out.

 

[scatmanjohn]

Its not right.
I've never heard of a system that will only allow heating whilst the hot water is on.

 

[mikebakke]

I "know" I'm right of course, but after being told "it's fine now" several times I started to doubt myself.

Thanks gents - toys away!

 

[meldrew's_mate]

Just wanted to add to Chrishutt's message.

Do you have a large house (>150 sq. m area)? If so the heating will be split into two zones, with (probably) two heating valves and one hot water valve.

It could be that you have a single 3-port valve if the house is not this large; so what do you have? The three-port holds most hope for matching your symptoms with probable causes.

Anyhow the bottom line is that your builder should have the responsibility and oportunity to fix it, suggest solutions by all means, but start with accurate symptoms and he'll stand a better chance.

 

[Paul Barker]

You're not alone half the country hasn't got a properly wired Y plan system. The cylinder stat should have three wires in it, one of them must go to the part of the main junction box where hot water off from the programmer goes and the grey leed from the mid position valve.


This is the only way your boiler will come on when heating is demanded but not hot water, so if it is missing then the boiler will never come on unless hot water is also demanded.

http://content.honeywell.com/uk/homes/systems.htm#Y Plan

Not likely that general builders get this right, not many electricians seem to either. It ios so commonly wrongly wired around here a mate and I have been wondering if it was just sheer lazyness not wanting to run the extra wire from the controller and from the cylinder stat.

 

[mikebakke]

As far as I can see (the installation is incedibly cramped with half the pipework inaccessible), I have 2 seperate valves - not a Y type arrangement.

The tank stat directly controls one of them ie, when that clicks on or off the valve opens or closes. As I write this I do start to wonder if they've just wired the valve to the wrong stats...

The other valve never moves, which I assume is wrong - that's a silver Honeywell item with a lever pointing down.

Thanks

 

[Paul Barker]

with hot water stat turned down, move the flat metal lever at the end of the zone valve for the heating over and up into the notch. Does the boiler and pump now come on?

If so, now youy have to check that the live feed is getting from the heating on part of the programmer to the roomstat and finally to the zone/two port valve, and if so then you have to consider that either the sincronous motor or the microswitch inside that metal cover is capoot. You can buy the parts or buy a new head or a whole valve.

My guess is it's the microswitch because if you get heating when the hot water is on the sincronous motor must work as these valves rest in the off position. Or else the orange leed from the heating zone valve has come adrift inside the connection box. Or the whole valve is stuck partially open but unlikely in a 7 year old system.

 

[scatmanjohn]

Paul Barker wrote:

with hot water stat turned down, move the flat metal lever at the end of the zone valve for the heating over and up into the notch. Does the boiler and pump now come on?

When the lever is at rest on the notch, the microswitch is not made (honeywell) is it?

 

[mikebakke]

The Honeywell valve does work - I can just never see it because the room stat is upstairs so by the time I get down it's done it.

The Honeywell is controlled by the room stat. When the stat is off the lever is over to the left and if I push right springs back slowly like it has a flywheel. When the stat is on, the pump runs and the lever has no resistance when I push right so I assume it's open. However the pipes above and below it turn cold when it is open so I assume it's pumping cold water. The boiler does not fire hence no heat.

That continues until the tank stat is set high so it clicks. At that point the other valve opens and the boiler fires. I also note there is a connecting pipe between the two valve's pipes.

The tank valve goes from "main coil" on the tank to the valve to the pump and up into the ceiling. Between the valve and the pump is the spur which feeds the Honeywell valve which then goes up into the ceiling.

Not sure what it all means, but it sure isn't right...... Thanks for all your replies so far - I will discuss with the builder again tomorrow.

 

[fitz1]

is ur system a pressurised system with unvented cylinder or a vented system with tanks in loft.

 

[scatmanjohn]

Someone has got their wires crossed, Have'nt worked out how that can happen yet.

 

[mikebakke]

Not sure what the correct term is. There is no gauge on the boiler, and (I believe) a small header? tank in the loft. I'm assuming it's sealed, not pressurised?

 

[fitz1]

programmer may be set at 10 position and not 16 position

 

[fitz1]

heting will only work with hot water on 10 position . works independant on 16 position. just a thought.