main combi 30he , hot water not constant

[mrricko]

hi all

can any one shed some light/advice , problem with main combi 30 HE 2 years old which will run domestic hw at correct temp for a few mins then run luke warm , then may run correct temp again for another min or 2 . this pattern continues.

boiler showing no visible faults .

thanks

 

[Billy Bob Bob]

firstly is the diaprahm lifting fully?this is the same boiler as a baxi 105 he and a very good boiler at that

 

[mrricko]

thanks

i have just checked visually the diverter valve assembly . the dwh pressure differential valve appers ok with the pushrod tight against the microswitch.

also i checked the diverter manifold valve the pushrod is not fully lifted on to the microswitch (possible issue).not sure how tight against the microswitch it should be ?

as a quick test i ran a bath with the hot tap only half open reducing the flow and the bath was red hot as expected if this sheds any more light on any thing ?

 

[Billy Bob Bob]

the spindle needs to touch the microswitch you should hear the switch click on contact and thats the pump pressure switch at the back of the divertor valve as well as the large dhw switch at the front,if its the front one you think is not lifting fully more than likely you need a new dhw diaphragm if you are up for changeling this yourself do not allow water to get into the pcb housing and make sure you issolate the electrics al be it 2 years isent long for a diaphragm

 

[mrricko]

hi
i have double checked the micro switch(s) on both valves and they are being made when hw is called for (made sure tested them electrical for switching). so i would have to presume the diaphragms ok? would they appear ok and still move if they had a tear ?

the fact that the hw works fine when the flow is restricted via the tap is bugging me as to why ?

any other ideas

many thanks

 

[Puddle]

check high low flame working correctly and boiler not turning off when hot water running,could be first signs of plate heat exchanger getting blocked up,thus going to low flame for to long

 

[mrricko]

i have just ran the hw on full flow and set the hw temp controls on full and the burners look to on full throttle never dropping and the warm was still luke warm .

 

[Billy Bob Bob]

if the heating is not on run the hot water does the flow pipe get hot?if so the plate heat exchanger is blocked take out and clean itdiverter valves are designed to(dump down)in the event of a blockage on the primary circuit if this is not the case then do you live in a hard water area?

 

[Puddle]

as gas man says check heating flow when running hot water
also could be flow rate if only warm,due to cold water entering building ,close black isolation lever on cold water inlet slightly
Also what size gas pipework to boiler

 

[REDSAW]

main have a 5 year guarentee as apposed to 2 on baxi badge!.

 

[russgas]

hi ive had quite a few like this and it always seems to relate to having to replace the fan and air pressure switch, i know doesnt sound like the fault but ive replaced several and found this cures the fault every time

 

[musicweb]

I have just finished installing a Maui combi gas boiler. When showering, I notice the hot water gets hot, then lukewarm, then hot again in a cycle. Is this characteristic of these units? I have the DHW set at about 140. Also noticed the circulator pump runs when calling for DHW. I thought DHW took priority?

 

[desrob]

I have just finished installing a Maui combi gas boiler. When showering, I notice the hot water gets hot, then lukewarm, then hot again in a cycle. Is this characteristic of these units? I have the DHW set at about 140. Also noticed the circulator pump runs when calling for DHW. I thought DHW took priority?

are you a d.i.y. er.?

 

[musicweb]

yes, I'm a handyman though. I followed the installation manual. It runs fine. Puts out good heat and DHW. Just the shower thing was a little strange. Why? Did I miss something as far as installation?

 

[stevetheplumber]

incoming

 

[musicweb]

incoming?