Ideal Icos Boiler - Central heating but no hot water

Hello I would like some advice if possible. I currently own a flat which is rented out. I have just got some new tennants that have moved in on the weekend and there are normally some moving issues but i have no idea on this.

The contacted me saying that the central heating is working but the hot water isnt.
I went down to the flat and looked at the boiler. (ideal, icos, he12,he15,he18,he24) unsure which of these it is, this is on user guide

The guy explained to me that when he turns the tape on he gets some hot water but then it goes seconds later and become cold.

I thought that the old tennants or i have turned off something off while there was a change over. I have gone round and made sure all the water tapes are on and all power switches.

I control the boiler by a honeywell st6400c programer (the box that i change to turn hot water on/central heating and what times etc)

When i turn the central heating on to contineous the boiler fires up and the burner light comes on stating that it is working. I have no issues with this as the radiators are hot. and the symbol shows a C when means its working

When i turn the hot water onto contineous the burner doesnt fire and no light comes on. There is no symbols that come up like fl or lr like it says in the manual to say there is an issue.

I have turned the switch on in the cupboard which i thought was the key but later worked out this is just the immersion. therefore the boiler isnt working still but they at least got some hot water why i figure this out. :S

Has anyone got any ideas? If the central heating is firing up why isnt the hot water? I have read some things on the condesnate drain and about cleaning it. I will try that tomorrow but if the central heating is firing i cant see this is the issue.
IS there a communication issue with my honeywell programmer and the boiler? meaning it cant work out it is meant to turn on?

im hitting my head against a wall now as i ran out of ideas and really need some help. sorry for the long entry but thought i try cover everything.
hope someone can help me
thank you
rob

these crates have serious issues i would recommend getting an RGI familiar with the problems of these heaps of crud.

it is most likely a diverter valve jamming or the plate heat exchanger is blocking up.

i to would recomend a rgi to take a look at it but it wont be any of the above! its not a combi for a start!

i to would recomend a rgi to take a look at it but it wont be any of the above! its not a combi for a start!

kevindgas said:

these crates have serious issues i would recommend getting an RGI familiar with the problems of these heaps of crud.

it is most likely a diverter valve jamming or the plate heat exchanger is blocking up.

Click to expand...

If its an Icos it wont have a diverter or plate.

kevindgas said:

these crates have serious issues i would recommend getting an RGI familiar with the problems of these heaps of crud.

it is most likely a diverter valve jamming or the plate heat exchanger is blocking up.

Click to expand...

Heat only boiler

Oh dear!! these are heat only boilers.No hot water but heating ok suggests external control fault. No mention of any cylinder or motorised valves.A better system description would help.

i have further. i went back to the flat and had another look. there is a double honeywell value. when i played with this it turned on the central heating and fired up. this is not a 3 way valve so the hot water is not on this.

I found another double value. sunvic, synchronous motor, model hs100-23-cc01ta. when i turned on the hot water it is done nothing. i took it off the pipe work and had it in my hand. when i slightly pushed the rotating mechanism it did a rotation on electricity. which would therefore turn the valve and open the pipe for hot water to move i guess.
i made sure the valve moved smoothly and the sunvic wasnt stuck but when i turned the hot water on at the programmer it still didnt do anything and the boiler didnt fire up.
so is sunvic not working correctly, so it doesnt have enough power to turn the valve open? or do you think its the boiler? even though this fires up on command with central heating?
any advice would be good.
thank you

It should work kind sorta like this:


I should have put a comma in :"the valve motors open, and closes... "

SO either the valve motor/head isn't turning (new head required) or it's switch is faulty ( new head , really). Or the thermostat has failed ...
In situ, a stiff valve can stop the head moving.

You can latch open the water valve manually, so the hw gets hot when the ch is on, temporarily.