Central heating not hot enough!!

[Christian and Beccy]

3-Bedroom 1930's Bungalow with cavity walls (not filled), loft reasonably insulated (not great though).

We have a Vaillant Turbomax Pro 837e Combi boiler, fitted in the loft. This boiler is fairly high spec, producing over 105,000BTU's, but we still can't achieve our set temperature of 21.5°c on the room stat.

The radiators are a mixture of 'normal' units and fancy 'designer' units, all of which conform fairly closely to the recommended heat output for each room.

The boiler was fitted by me (except for the final gas connection), and commisioned by a Corgi engineer, who, incidentally, was impressed by my installation. I have also installed all of the rads myself, but didn't totally repipe the bungalow as it is all fairly recent anyway. Alot of it has been altered though during our work and has been lagged as we went.

We have never balanced the system, as I have only recently become aware of a need to. Could this be a likely cause of our systems inadequacy? The first 2 radiators on the system are fantastic, they get nicely hot, resulting in the ability to turn the thermostat's down. However, the rest of the house does seem to struggle.

Also, I do wonder about settings on the boiler. I have set the dial on the front so that it is about 3/4 of the way towards the maximum, which shows 70°C on the display. I increased this tonight, it was previously set lower and have also been round and bled all the rads again. There was a small amount of air in the system. I haven't yet been able to analyse the results of this increase. Are there any other aspects of the boiler that I need to look at?

Additionally to this, last year we had the boiler set very high, almost flat out to achieve our temperature, but we had extortionate gas charges. Almost £70 per month infact. We never really did estalish the cause of this.

We have one or two rooms, which have radiators that are over-sized. Even on their low settings they are plenty hot enough. Is there a way that we can restrict the flow to those rads beyond that of the TRV, so that we can have a range of adjustment, but at a lower level?

Thanks in advance for your help.

 

[Gasguru]

I doubt a 3 bed bungalow will need more than 60,000 Btu's and the boiler if commisioned correctly will have been "range rated" to set the central heating output to suit.

Put the heating temperature on the boiler to max and the room thermostat to max. Turn up all the TRV's and manual valves to maximum.

If the system is balanced you should find all the radiators heat up at the same rate and after say 1/2 hour you should find you can't keep your hand on any part of the radiators.

If the radiators are up to 80-85 degrees and the house isn't warming up then the radiaotrs are too small - install larger rads or improve thermal insulation.

 

[sime10]

Where is the room stat ? In the garage

 

[Christian and Beccy]

Where is the room stat ? In the garage

Thanks for your constructive reply.

It is in the hall, practically in the middle of the bungalow and not in the direct vicinity of a radiator.

 

[kevplumb]

ive got the "old" 242 E " turbomax in a 5 bed house and it's like a sauna on 5

 

[brentwoodheating]

I think the 837's were factory set at about 20KW on the CH side. Vailant say as it modulates so there's no need to range rate downwards (although the outdated requirement to do so is recognised). So if your flow temp is there and your pump is ok, then balancing and then system design would be my main suspects. Then diverter valve as it may be stuck in the middle. How's your hot tap temp and flow?

 

[Christian and Beccy]

Out hot tap temp is quite good. At the moment, it is set about 2/3 of the way towards maximum on the dial and produces hot water that is just about hot enough so that you can't keep your hand under it for long. Not scolding though.

I think the flow is quite good too. Our 1900x800 bath fills in just a few minutes.

I think I will get on and balance the rads, then see where that leaves us.

Any further comments welcome though. Thanks!!

 

[Fluffster]

Was the entire system power flushed/ flushed correctly before connecting new boiler?

As you already mentioned your insulation is lacking so you are adding to global warming get your loft and cavity wall insulated it is very cheap with the grants currently offered.

Even B&Q are offering buy one get one free loft insulation itch free and an a doddle to fit if you can make a bed you can lay a loft.

Pete

 

[AndersonC]

Where is the room stat ? In the garage

Thanks for your constructive reply.

It is in the hall, practically in the middle of the bungalow and not in the direct vicinity of a radiator.

Yes I have noticed Sime10 doesn't half write some pointless rubbish. Perhaps the 10 at the end of his username is his IQ.