URGENT worcester bosch greenstar 28i combi not hot water but radiators are fine

[doffcocker]

having a few issues with my boiler. worcester bosch greenstar 28i. has been serviced every year. last serviced in jan. i moved into this property in feb. been experiencing these issues since feb but in the past month has gotten much worse.

so radiators work fine they all heat up. the combi boiler came with its own control panel receiver plus thermostat.
its the waters for the sinks baths and showers. since feb, the water sometimes would go lukewarm instead of hot. the boiler pressure meter would be in the green zone, usually the middle but still the water from the taps and showers would stay lukewarm. the boiler would be turning on and the green light that indicates that the fire is on would also be on. but still lukewarm. the radiators would still work. the water would still be lukewarm even if the radiators were on or off. the only thing that would solve this issue and increase the temperature of the water is I would have to turn the valves under the boiler so that i could increase the pressure from green to borderline green/red.

but this would solve the issue for a few days to a week. eventually the pressure would normalize back to bang on the middle of the green area.

about a month ago, i bought several HIVE smart TRV's and a HIVE receiver and thermostat. the hive system has been installed for about a month and works well. but i have definitely noticed that in the past month this issue with the water has become more frequent and i have to turn the valves under the boiler right to the top of the red area. and even that doesnt give hot water it just gives lukewarm. the radiators still work perfectly.

can anyone give me any advice?

 

[cjg]

1st you have over pressured your boiler and the prv will have tripped.
2nd sounds like the diverter has failed or stepper motor .
you need a engineer to look into it to be sure.
hope that helps.

 

[doffcocker]

1st you have over pressured your boiler and the prv will have tripped.
2nd sounds like the diverter has failed or stepper motor .
you need a engineer to look into it to be sure.
hope that helps.

hi thanks for the reply.
with regards to the pressure, the guage still returns to the green after a while. i turn the valves to increase the pressure but it doesnt go beyond the green/red borderline. just stays at the max green point. so its still not in the red but i know im pushing it to go into the red.

does this mean that the prv would've still tripped?

 

[cjg]

most prv trip at approx 3bar or weep just before ,as you push it up passed what is norm, heat it, = water expans pressure up! = prv , cools pressure drops back to safe green.

 

[doffcocker]

most prv trip at approx 3bar or weep just before ,as you push it up passed what is norm, heat it, = water expans pressure up! = prv , cools pressure drops back to safe green.

yeh i know what you're saying. so its going to be the diverter or stepper motor that needs fixing. do you know how much i would be looking out to get this fixed? just so i make sure im not drastically ripped off

 

[Chuck]

yeh i know what you're saying. so its going to be the diverter or stepper motor that needs fixing. do you know how much i would be looking out to get this fixed? just so i make sure im not drastically ripped off

You'll need to ask the person who is going to do the work how much they will charge and what they'll cover. If you want certainty, Worcester Bosch have a fixed price repair scheme which you can book via their website. Unless you have an existing relationship with a heating engineer, e.g. the one who services your system, I'd recommend the fixed price option.

 

[ShaunCorbs]

Is it all taps that have the hot water problem?

 

[doffcocker]

Is it all taps that have the hot water problem?

yes thats correct

 

[GeorgeHunt]

Experiencing the same type of problem here. Have the Bosch 42-3 Combi boiler. Installed fall 2014. In floor heating system works fine. Since last fall 2020 we have been experiencing fluctuating hot water temperatures at all faucets & showers. Tech support advised our technician that it was the plate exchanger on the hot water side. We order a new one (took over 2 months) and had it installed. Worked great for about 1 week and then back to the same problem again although not as severe....no sudden cold water during your shower only hot to warm to tepid.
Spoke with Tech support again and checked all settings on the boiler. Boiler seems to be running fine and settings are good. They are unable to assist anymore and just stated to monitor the system.
Now what?