Another seasonal heating question

[Alex.]

Must be the time of year..

We have a combi boiler system, a Ravenheat LS80T, and while it does the radiators OK it is not satisfactory at heating water. For example it takes 30 mins to fill a bath!

Is there likely to be an adjustment I can make, or is the thing on the way out? Seems queer it can heat radiators but not water? Could it be simply that the water coming in is so cold right now?

TIA

Alex.

 

[KTMMICK]

Must be the time of year..

We have a combi boiler system, a Ravenheat LS80T, and while it does the radiators OK it is not satisfactory at heating water. For example it takes 30 mins to fill a bath!

Is there likely to be an adjustment I can make, or is the thing on the way out? Seems queer it can heat radiators but not water? Could it be simply that the water coming in is so cold right now?

TIA

Alex.

Sounds like the heat exchanger is playing up........

 

[Sam]

Could it not be the anti-scald valve which now has to be fitted to all new systems. My tank can be full of hot water but will take an age to fill a bath as when you turn the tap full on too much water is passing through the valve and it kicks in mixing it with cold. i think thats how it works!

 

[Debs.]

If you live in a hard water area; the heat-exchanger may be calcified.........or the flow-sensor (or diaphragm) may be sticky or faulty.

If the 'throughput' of water seems restricted or at least; 'less than usual': is there an inlet filter mesh/screen that may be partially blocked?

 

[Shox Dr]

Does it fill a bath in summertime in a reasonable time scale? If the answer is yes, then it is more likely down to the incoming water temp. A Combi boiler will heat the incoming water by a set number of degrees.
So when the water supply is colder than usual, it cannot raise the temp as high. So to counter act this, you throttle the tap, thus increasing the time the water is in the boiler, heating it more, the down side is it takes longer to run the bath.

 

[Mig-Phil]

Assuming it is not the temperature thermostat on the boiler it is very likely to be the heat exchanger, they can scale-up quite easily.

Next time you fill the bath try doing so as slowly as you can and watch the boiler, I suspect you will see it fire up and then switch off in cycles which normally means the heat exchanger.

 

[pidgeon chit welder]

Try looking on the boiler control panel to see if there is a control that allows you to turn up the heat of the boiler to compensate for a colder incoming water. I have a 10 month old oil combi Firebird by Envoromax & had to turn mine up this morning to almost 2/3 of full, the house is now like a sauna at 21oC
Older boilers some times had this facility but not all ,they slowed down the incoming water instead so it sits in the heat exchanger longer.

 

[Tigman]

How old is the boiler ? did you have a lime fighter or equivilent fitted from new ? sounds like scale to me !
Also the flow rate of your mains supply must be taken into consideration , if your on an old lead supply the flow rate is reduced , we used to put in a new poly main supply to give the maximum flow to the house , nice !

 

[Mig-Phil]

Tigaman, what limefighter would you recommend?

I live in a hard water area which effects the heat exchanger on and have been thinking of fitting some sort of device which 'apparently' helps by reducing the effects of lime scale.

I have just done a quick search and there appears to be two types. one is fitted into the pipework and the other wraps around the pipe work. Does anyone know if one works better than the other or if they even work?

 

[Shox Dr]

I fitted a mains magnetic limefighter, with alot of scepticism. However after 8 yrs it has been a total success. Descaling the kettle, was a 4-6 monthly job now maybe once a yr

 

[Tigman]

The last one I fitted was a Liff Wrappa , does the whole house ! you wrap the wires around the incoming main leaving the required gap ( instructions included ) and plug in ! press the button in the middle , I think once for 15mm pipe , twice for 22mm pipe , and away you go , I to was scepticle but they work well ( Aunty Pat dont phone once a month anymore for a descale )

 

[Shox Dr]

That's the jobby (though maybe not that make). Good bit of kit

 

[pidgeon chit welder]

Tigaman, what limefighter would you recommend?

I live in a hard water area which effects the heat exchanger on and have been thinking of fitting some sort of device which 'apparently' helps by reducing the effects of lime scale.

I have just done a quick search and there appears to be two types. one is fitted into the pipework and the other wraps around the pipe work. Does anyone know if one works better than the other or if they even work?

Phil,
I have an Aquamate magnetic flux molecule aligining water softener going for for £17 inc P&P if you want it .

I think they top £45 new nowadays

It is a mains plug in unit, I ran a protected spur to under the sink where my incoming water cock was and fitted it there.

The one I have offered you , I took it off our washing machines incoming water pipe ( It lived out in the garage /office ).
It was 7 months old when we moved from East Anglia hard water area here to a soft water area in South Wales and has been sitting in a filing cabinet unused in my garage ever since

This one wraps wire around the pipe work cant remember if it has to be copper to give the best magnetic circuit effect .. Ithink I still have the destructions ...if not they are online somewhere.

 

[Alex.]

Thanks for all the input.

I'm not sure how old the boiler is,but it's in Aberdeen which is not a noted hard-water area! So I doubt it's scaled up, but there was some work on the street mains last summer, maybe some crud got stirred up by that?

There is a thermostat-style knob on the control panel but it doesn't give the impression of being connected to anything inside the boiler. Maybe I'll summon up my courage and pull the cover off..

 

[the snooper]

probably the diaphragm that operates the gas flow when the hot water tap is turned on
look here £14.00 to replace they perish over time reducing the gas flow until there is no gas to ignite

 

[hunter27]

As already mentioned a combi boiler can only heat so much hot water depending on it's output. The one you have appears to be a 24KW one which is quite small. Your boiler should give you 9.9 litres/min raised by 35 degrees C and as the water is coming into your house very cool at the moment the only way you can get really hot water is to throttle the water down at the outlet tap giving the boiler more time to heat a smaller flow.
The reason the central heating is ok is that most average 3 bed houses require around 10 to 18KW for the radiators and your boiler gives you 26KW.
This why it always pays to size combis on hot water requirements.
pete

 

[busa]

I have a Firebird combi system. Like you Alex, I was having trouble with the domestic hot water, slow to run a bath, low temperature etc. A couple of weeks ago on the anual service I asked the fitter to check it over, he replaced the heat exchanger and we can now fill a bath with the hot tap fully open and water is really hot.

 

[Alex.]

Snooper

Tried to PM you today but it doesn't seem to have worked (from my end anyway) I will get an engineer in I think.

Thanks for all the advice lads

Alex.

 

[the snooper]

yes got it.
if you are unable to diagnose it for definate it may be cheaper in the long run

 

[Wozzaaah]

Snooper

Tried to PM you today but it doesn't seem to have worked (from my end anyway) I will get an engineer in I think.

Thanks for all the advice lads

Alex.

I'd advise that Alex, too many conflicting ideas on here though my guess is also heat exchanger scaled up.
You might be better off asking over on Ultimate Handyman, there's some CORGI guys on there.

That diaphragm is nothing to do with the gas flow btw, it's operated by water pressure and the pin actuates a flow switch when DHW is called for.
If it's perished then the pin won't protrude far enough to actuate the micro switch and there will be no DHW at all.
Having a slightly temperamental old boiler myself (the one on the wall ) I'm starting to know my way around one.