Ideal ISAR combi HE24 problems

[conservatory4me]

hi guys,

I have an Ideal ISAR combi HE24 which was fitted approx 3yrs ago. The boiler has been working fine, but has over the last week developed a strange issue. When we open the hot water tap, we get reasonably warm water, which then becomes luke warm within about 5-10 secs and then goes pretty much cold within 15-20secs. No error messages are shown on the boiler. Normal messages kick in such as T and D.

Missus is doing my head in as she can't have a warm bath

Any ideas what this could be?

FYI, the central heating works fine.

Thank You

EDIT:

I would like to add that i have just found this topic:-

//www.diynot.com/forums/viewtopic.php?t=215026

As Garfeild suggests, i checked the pipes and the one that he mentions "CH Flow" never gets hot. The actual pipe that gets hot is the one next to it, i.e "DHW OUTLET", but it cools down within approx 30 secs.

 

[conservatory4me]

anyone?

 

[45yearsagasman]

Possibly you plate heat exchanger is restricted causing the boiler to give hot water in short bursts.There are other causes but I always suspect the plate and providing you have enough access below boiler they are fairly easy to remove.Bit beyond DIY unless you are confident and feel lucky!

 

[conservatory4me]

ok thankyou mate.

I've been doing a bit of a 10 min test myself and the following is what i have observed:-

1. The first time when i open the tap, boiler burner light kicks in for about 20 secs and warms the water up quite a bit, but then goes off (cooling the water) and after a while comes back on again and warms the water up.

2. If i reduce the water flow, the water stays pretty hot throughout and also the burner light stays on.

3. The boiler finds it difficult to warm up faster flow, although once the burner light kicks in for the 2nd time, the water does warm up again. Also the burner light stays on.

I'm no expert, but is there some sort of dirt stuck in one of the parts???

Also how do u clean the plate?

 

[45yearsagasman]

The plate heat exch must be removed and the primary side cleaned by flushing and tapping gently to remove debris.Better bet is to fit new one with new rubber seals.If the clean side is scaled then that is more difficult and the use of strong descaling chemicals is not recommended.Make sure that the ports on the boiler are cleaned berfore refitting the plate.

 

[conservatory4me]

thank u gasman. The dilemma i have is that what if its not the HE plate and i end up replacing it for nothing.

From what you've read in my last post which explained what happens when i run the tap, does it definately sound like the HE plate?

 

[45yearsagasman]

Try cleaning the HE 1st and refit it. If that does not solve the problem then you have spent nothing but your time.Your symptoms do indicate a blocked plate.

 

[conservatory4me]

Thank you and sorry Gasman if this sounds like i'm repeating like a broken record but do you mean Clean the Heat Exchanger and not the plate?

 

[45yearsagasman]

They are the same thing.The water to water heat exch is called a plated heat exchanger due to its construction.

 

[conservatory4me]

I thought the HE is the big tank with a burner and the Plate HE is the one just above/behind the pipes or am i wrong?

 

[45yearsagasman]

The plate heat exch is the one at the bottom behind all the pipes and is made of stainless steel.Don't you have the instruction book to refer to?They are both called heat exchangers.

 

[conservatory4me]

yes i do mate. The plate is behind the pipe, and the HE is the tank itself right?

 

[45yearsagasman]

yes i do mate. The plate is behind the pipe, and the HE is the tank itself right?

The main heat exch is aluminium.

 

[conservatory4me]

right brilliant! Thank You.

I will try to clean the HE first and then the plate HE behind the pipes.

One thing though...do i need any accessories such as gasket, sealer or anything else?

 

[45yearsagasman]

At no time have I suggested cleaning the main heat exch so don't touch it as it requires RGI.The plated heat exch is all that requires attention.You don't seem to have understood any advice and to save you a lot of grief call in an experienced engineer.