Hot water TOO HOT !!

PeeJay · 9 Aug 2006

Ar this time of year as the weather cools, I notice that the temperature of the domestic hot water increases SIGNIFICANTLY.

Over the summer months the hot water was (at times) too cool!!

I have a combi boiler (mains pressure), oil fired central heating. It is controlled by a DCD Heating Controller.

Any ideas where to begin?

Thks

Agile · 9 Aug 2006

When was the boiler serviced?

Was the engineer asked about this?

Tony

PeeJay · 9 Aug 2006

10 months ago. NO he wasn't. Are you suggesting a servicing/ongoing maintenance matter or seeking additional info?

Agile · 9 Aug 2006

There is too little information for me to reach any conclusion or in this case to even risk a guess.

What you seem to be describing is counterintuitive!

The incoming water is about 4 C during the winter rising to about 15 C during the summer. Generally the hot would be hotter during the summer.

Just possibly the temperature control has a negative slope on part of the curve!

Most domestic oil boilers are not modulating and use a simple on/off control although many have a thermal store built in to help smooth out the fluctuations.

Tony

PeeJay · 9 Aug 2006

Tony. I'll try to provide more info..... I appreciate the effort and agree, but maybe I need to be more expansive in the info I provide, so opols if I haven't been clear to date..........

The issue is surely related to the fact that during the summer the heating is off, whilst in the winter (or as the outside temp falls) the heating kicks in. This then leads to a dramatic increase in the temp of the HW, whilst during the summer the HW is heated to the true value that is dictated by the DCD Controller. When the Heating side operates, the temp of the HW goes thru the roof and isn't regulated seemingly by the controller?

Bear in mind that the DCD Controller functions by dictating the temps of HW and/or Heat specifically, not simply firing up either at specific times during the day.

What I don't understand is why and what the relationship between the heating side and the HW side is? To me they "should" be separate. Is this the case?
Whatever the heating is doing, should this effect the temp of the HW? It is clearly doing in my case.

I'll keep providing info if it helps!!!

Paul

Agile · 9 Aug 2006

I would need to know the exact model of boiler and probably spend a little time following it through which I would have no justification in doing except for interest.

You could try calling the manufacturer's technical helpline or just give the problem to a boiler engineer.

Tony

PeeJay · 10 Aug 2006

Hi..........That begs the question "are you interested"?

I'm just seeking ideas!

The boiler is an oil fired condensor, brand new.

Paul

croydoncorgi · 10 Aug 2006

The purpose of the DCD controller is to optimise boiler firing WHEN there is a demand for heat! If there is no demand (ie. the water is hot enough) the boiler should not fire - at all, because in summer there will be no demand for CH either.

But IF you have a combi boiler, the DCD controller should not have any effect on the HW temperature, anyway. How could it?

Or maybe the DCD is incorrectly fitted and does not know the boiler is a combi!

PeeJay · 10 Aug 2006

Hi to you both.

It isn't a Combi boiler!

There is a direct relationship between the hot temp and whether or not the heating is on/off. This does not make sense to me!

Paul

Nige F · 10 Aug 2006

PeeJay said:
a combi boiler
Thks

Was that a typo?...........I`m interested but only as an academic exercise because I`m not qualified to offer help

So, its a brand new condensing oil boiler........manufacturer should help from their website ..........interested to hear outcome

PeeJay · 12 Aug 2006

Sorry Nige F been away for a few days..............

Just realised a very early mistake that only NOW makes me realise I inadvertently led you good folks up the wrong path.

In my first post I should have said CONDENSOR not COMBI.

It is not a combi boiler

Does this move us on?

Paul

Agile · 12 Aug 2006

That means the problem is goint to be a very simple one as the HW temp is controled by a stat on the storage vessel.

You can check that its correctlty attached to measure the temperature and correctly wired to bring the boiler on when the stat temp is raised and turns it off when its reduced.

The stat should be set at about 56 degrees and the boiler output temperature should be set at at least 10 degrees above that.

Tony

PeeJay · 12 Aug 2006

Ah-ha do I see a possible light at the end of the tunnel.....the temp stat has always caused me some uncertainty so it is nice to be pointed in this direction as it is an area I was unhappy about. The reason being is that I use a megaflow and it strikes me as being very difficult to properly mount the supplied (from DCD) stat onto the tank ensuring good contact. The stat is I assume a standardarised surface mounted affair common on all similar arrangements that requires to be butt mounted to the side of the tank. However, the Megaflow is heavily insulated and even if you access the stainless inner tank (i assume the holding vessel itself) via an access panel this is always cold to the touch even when it contains water that scalds the hand-belief me I've just tried it).

So, has anybody succesfully mounted a stat on a Megaflow tank, and if so where, with what etc to ensure good connection?

I apppreciate the help and with the continuing fear of scalding so do the family.

Paul

Agile · 12 Aug 2006

An indirect megaflow comes with a ready installed stat and assuming the stat with your controller is a simple switch then it would be normal to use the built in stat instead.

All unvented cylinders have to use the "probe" type stats which intrude into the cylinder.

Sounds as if thats your problem!

Warning: unvented cylinders have specific safety requirements and should only be installed and wired up by a competent person who has the appropriate Certificate/

Tony

PeeJay · 12 Aug 2006

Thanks...............that is the way I'll go.

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Hot water TOO HOT !!

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