New heat exchanger left me with no hot water

H

Howard123

Joined
12 Jun 2021
Messages
25
Reaction score
4
Country
United Kingdom
Hi,
Due to my old heat exchanger getting clogged up and giving me a hot cold hot cold hot shower I have today replaced the heat exchanger - something which has worked well in the past to resolve the same problem.
After fitting the new part today though, I am left with no hot water. The CH works fine but when I open the hot tap - nothing. Interestingly if I turn the CH on and then the DHW, the boiler cuts out.
The LED on the DHW flow switch lights up so I suspect that is working ok.
The diaphragm which pushes the spindle into the flow switch works fine for CH but doesn't move for DHW.
If I manually override the flow switch and press the microswitch, with the tap open the boiler fires into life and I get hot water.
So it seems to me something is stopping the diaphragm from doing it's thing. And it only started after I replaced the HE.
Can anyone help? I know it's hot today but I don't really want a freezing cold bath tonight!!
Thank you.

Edit: I'm not sure how I left this off - it's an Ideal mini HE C28.
 
Sponsored Links
on the DHW flow switch, is the LED solid red or does it flicker or flash ?
 
Hi Howard , the diagphragm you refer to is the primary flow switch, basically it tells the boiler that the pump is running and the boiler has enough water in it, it should prove on both HW and CH demands, does the pump run on DHW demand ?
 
Sponsored Links
Yes, the pump runs on both CH and DHW. The only difference is the primary flow switch turns on for CH but not for DHW
 
Hi Chris,
The primary flow switch works fine for CH but nothing for DHW
 
Howard123 said:
Yes, the pump runs on both CH and DHW. The only difference is the primary flow switch turns on for CH but not for DHW
Click to expand...
then you have a blockage somewhere, as soon as the pump starts the primary flow switch should activate, switch the \CH off run a tap and make the primary flow switch manually see if you can force the blockage to clear, hold it closed for a good 10 mins and see if it moves it
 
  • Thanks
Reactions: CBW
Good morning, I tried running the DHW for 15 minutes last night but no luck on shifting the blockage. I'll try it again this morning and update shortly.
 
Did you fit the heat exchanger the right way?
 
D

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
You must log in or register to reply here.
Sponsored Links

Similar threads

T
biasi riva advance 110b.32s/c no hot water
Replies
3
Views
1K
tonysp
T
R
How can I test my DHW Heat exchanger?
2
Replies
18
Views
2K
RogB
R
G
Intermittent Hot Water Alpha CB28
Replies
3
Views
2K
Gruffalodad
G
S
No hot water - Heatline C28
2
Replies
15
Views
21K
jayjay252525
jayjay252525
P
Alpha CB28 DHW micro switch/diaphragm problem?
Replies
4
Views
2K
snb
S
Back
Top