new combi boiler worry

[gogo]

Hello, I've just replaced my old Glowworm Swiftflow 80 with a Worcester Bosh Greenstar 27cdi. All seemed fine but today, I tried to switch it on all the time and I am noe worried that somehow, the desired temperature cannot be reached. I switched the CH to on (no timer) and the room thermostat to 21 degrees. It's been on from 7.30 am and 5 hours later, the temperature reached 19.5 degrees (but only rised 0.5 degrees in the past hour). Looks like it cannot go higher. I checked that the CH demand from the room thermostat is always on and I also checked the temperature cycle on the main display: looks like boiler switch on when Temperature reach 70 degrees and off when it reach 90 degrees (about 1 minute on for

3 minute off). I checked that there is no air in my radiators. Now, 19 degrees is enough for me, but it's relatively mild outside and I am worried that it would not cope in the winter. The old Swiftflow was 17.6 kW max CH output, the new one is 27kW, so in theory, it should be a lot more efficient? I don't remember having difficulties to reach 20 degrees with the old system? I am in a 1 bedroome flat, with double glazing and loft insulation. Obviously, I'm going to call the intaller on monday, but in the meantime, any ideas? I slightly worried that I've spend £2500 for something not quite satisfactory! Thanks Philippe

[John]

Have you now got Thermostatic Radiator valves - and these are turning off at

19 degrees?

[John]

Before you blame your boiler we need to know more:

Are all your radiators getting to the same temperature at the same time (are some slow to heat up?). Is the domestic hot water satisfactory?. It could be a case of the pump not working correctly - or the diverter valve. Try letting the radiators go cold then fire it up and rush around checking that they all heat up in round about the same time. It could be that the installer hasn't balanced the system.

[The Natural Philosopher]

Its been bloody cold and windy actually the last few days.

[Jim Alexander]

In that case I doubt you have 25kW of radiators so the minimum output of 8kW or so should suffice. You have given a lot of detail but nothing about the radiator TRV or lockshield settings. Look over the commissioning paperwork the installer left and see if you can see anything that doesn't make sense.

The temperature cycling doesn't look right but impossible to say from here whether its a boiler or system problem.

Jim A

[gogo]

as far as I'm aware yes

yes, no problem. It could

OK, will try that.

Thanks

[gogo]

Yes, on all radiator but the one in the hall where the thermostat is. The thermostatic valve in my living room where he temperature is also about 19 degrees (although now, after 6h, it's slowy approaching 20) is fully open. My bedroom radiator is off and kitchen and bathrom are set to about 18 degrees.

[gogo]

well, windy yes, but 7-8 degrees, not *that* cold..

[gogo]

Thanks for the reply. I'm not sure I am technically savvy enough to understand what you ask.... I have 5 radiator, all with thermostatic valve, except the one in the hall near the thermostat.

[mick]

Of course, as your hall heats up the thermostat will operate and shut down your heating - whether your other rooms are warm or not. You point out that there is no TRV on that radiator so, effectively, the setting of the lockshield valve on there will control the heating of your whole system. The new combi puts heat out faster than the old one, so maybe your hall is heating much faster than it used to do.

IMHO your thermostat should be in a more central living area (with no TRV on the radiator) and let the hall look after itself (with a TRV). After all, you don't live in the hall, do you? ;-) The thermostat shouldn't be near a radiator anyway.

Try closing the hall rad lockshield just a bit and see what happens. If you are worried about shutting off the flow then turn another radiator's TRV full up.

[Jim Alexander]

what is the setting of the heating control knob on the boiler?

Jim A

[John]

It appears that your thermostatic radiator valves are working perfectly - and cutting off at 19 degrees - how can you expect it to get any warmer?

[gogo]

The thermostatic valve in my living room is open fully. I'm not sure I understand what you mean? Surely it should be possible to reach a temperature higher than 19 degrees with a valve fully open?

[gogo]

I understand what you are saying, but the temperature in my hall is 19 deg and the thermostat in my hall is set to 21, so the thermostat is actually not shutting down my heating. It's been on all the time since the temperature set on the thermostat has never been reached in the hall.

[gogo]

It's set to MAX.

[Jim Alexander]

OK, that rules out a lower temp setting which is desireable with a condensing boiler. How hot do the rads get?

Jim A

[gogo]

well, not sure how to test that properly, but putting a wireless sensor right against the rad in my living room, it goes to 48 degrees.

[Jim Alexander]

Not sure either how useful that is. However, if the 70/90 degree readings are what you think they are, that's a mean temperature of 80 deg. The radiator would be HOT. Maybe only able to touch it for a second or two. If that is not the case there is insufficient flow to the radiator. Could be the lockshield not fully open, faulty TRV, gunged up radiator or faulty pump. Still impossible to say from here. How hot does the boiler flow pipe get? WARNING could be 90deg.

Jim A

[gogo]

well, it IS very hot, but cannot be more precise. Ok, I think I'll call them on Monday to say something is not quite right. At least, it looks like the new boler is working normally. Thanks again for your help.

[gogo]

Hello again, I am slowly progressing. The installer said he could come have a look but is pretty sure it's normal? I said I'll have a closer look to be sure. I will get a IR thermometer which would ease the temperature measurements, but in the mean time, I got one of these clip-on pipe thermometer. Not sur how precise thse are... but CH flow is 72 deg and return flow is 68 deg. But will start again to be sure. In the meantime, I am most intrigued by a pipe linking the CH flow and CH return pipes with a valve in between. I didn't touch this and the valve is fully open. Now, I don't understand the purpose of this, but does it not mean that the cold water flowing back to the boiler is mixed with the hot water coming from it, therefore lowering the output temperature? I may a bit out of my depth here, but here is a phtot showing what I mean (easier like that).

my question: should this valve be fully opened? Thanks Philippe