Improving central heating performance?

Haggisman

Haggisman

Haggisman

Soldato
Joined
6 Oct 2004
Posts
19,323
Location
Birmingham
It's cold today!

According to my Tado, the central heating has been on since 5:44 this morning, at which point it was 17.7 degrees in the house. The thermostat is set to 21.5, however it is now (almost 5 hrs later) only 18.8 with all radiators set to max!

I realise that the fact it's 1 degrees outside is obviously going to have a huge impact, but surely the house should heat up quicker than that?

Radiators in every room - all with TRVs except for in the hall downstairs (thermostat is at the top of the stairs) - I bled them all a couple of weeks ago (none of them had air in). They feel warm to touch, but not hot - i.e. I can hold my hand on them no problem without it burning, probably about the temperature you'd have a bath at.

Loft insulation all over, not really thick - probably ~3 inches (but still, the temp. difference between the house and the loft is significant).

Double glazing in every window - probably ~10 years old, but none of it appears to be blown.

The boiler is an Ariston Microgenus MFFI 27, and must be going on 8-9 years old (it was in the house when we moved in almost 5 years ago, and the previous owner had it a few years before that). Last serviced ~18 months ago so I realise it's overdue, but that's not going to make a significant difference is it?

One thing I have noticed on the boiler, it has LEDs on it which supposedly show the temperature, and only the lowest one (marked 40) is ever lit, even though I have the temperature dial set to max.

It also never seems to stay on for long - the pump will be running, but the burner seems to cycle 10 seconds on, 20 seconds off.

It also sometimes seems to have trouble maintaining consistent hot water - e.g. when running a bath sometimes it will go cold for 30 seconds or so.

We had the PCB and diaphragm replaced a couple of years ago as it stopped providing hot water at all.

Also just checked - even the pipes coming directly from the boiler aren't hot - they are a bit warmer than the radiators, but I can still comfortably hold them.

Is it new boiler time, should I try a new PCB (can get one for ~£50-100 on ebay) or is it worth getting someone to service/take a proper look at it?

No idea on the BTU of the radiators, but I'm guessing that as they aren't getting "hot", replacing them with higher rated ones won't really make a significant difference?

Edit, a quick google shows they stopped making this boiler in 2007, so unless this was old stock, it's at least 10 years old.

Edit 2: the water pressure in the boiler is fine - right in the middle of the blue section of the dial.
 
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I would get it looked at to be honest, it's obviously not right if it can't maintain its own temperature. Depending on the fault though, with the age of it, depending on cost of repairing it, might be worth considering a new one.
 
Yeah your best option is to get it looked at, it could be something simple like not being rated on the Ch correctly. More seriously could be PCB, or heating blockage causing the boiler to cycle. My own feeling would be to save up to get it replaced, your model is a cheap and cheerful and not worth spending money on if things get expensive.
 
3 inches of loft insulting is circa 75mm, the standard these days is 300mm... If so that might be your problem (Las of diminishing returns with walls in old houses etc)
 
FlyingFish said:
My own feeling would be to save up to get it replaced, your model is a cheap and cheerful and not worth spending money on if things get expensive.
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Yeah, this is kinda what I figured... we're planning on staying here for at least the next 5 years (having just fixed our mortgage for that long), and on the basis that we're most likely going to have to replace it at some point within that time, I'm thinking that really the sooner the better so we get the most benefit from it (rather than spending money to keep it going, finally replacing it in 4 years and whoever buys our house getting a virtually brand new boiler :p)

What would be a reasonable price for getting someone to take a look at it? I'm guessing this time of year is going to be busy so I'd be paying a premium.

Actually, from a bit of research, Aviva do a boiler cover product, as an existing customer it's £15/month with £0 excess, includes an inspection and service, and if it's beyond economical repair it's only a £500 excess - I guess my only concern with that would be whether I get a choice of new boiler or do they pick the cheapest one possible...
 
Could be a number of things. Needs a plumber tbh. Heat exchanger might be scaled up and your getting no transfer. Maybe the temp sens is broken.
Needs a pro to diagnose.
 
If your radiators are only touchable hot despite the boiler being set on maximum and the boiler cycling every few minutes it certainly sounds like a boiler fault. Get it looked at. SSE used to send an engineer to service it when you take their boiler cover. Not sure if they still do mind you.
 
Once you get the boiler issue sorted (which sounds like it's almost certainly the issue), the best way to maximise your central heating performance is to pressurise it if you're running a normal heat only boiler with expansion tank in the loft.
 
panthro said:
Once you get the boiler issue sorted (which sounds like it's almost certainly the issue), the best way to maximise your central heating performance is to pressurise it if you're running a normal heat only boiler with expansion tank in the loft.
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That makes no sense at all m8 ;)

You pressurise a sealed system, which doesn't have a cold feed and expansion tank in the loft.
An open vented system has the tank in the loft, and automatically fills.
A sealed system has an expansion vessel either built into the appliance, or plumbed into pipework nearby. And that system type requires manually charging with water.

The Ariston Boilers I've seen, normally have the expansion vessel built into the boiler. And have a pressure sensor that will stop the boiler if inadequate, so the op would have zero heat.

Mick
 
It's a combi boiler, and the dial on the front shows it is adequately pressurised, so I don't think that's the issue.

I went for the Aviva cover, as it was one of the few which would do anything for a boiler over 7 years old and deemed uneconomical to repair. Worst case scenario they come out to do the initial inspection and diagnose that it's ****ed and I have to pay to repair/replace it as I would done anyway.
 
I've never experienced an easily touchable boiler driven radiator at full settings, should burn you. Don't know anything about boilers in general though. After a quick google, could be a blockage or faulty thermostat.
 
My recommendation is to get it serviced as its due, get it checked out and possibly flush the system through. I get mine checked every year and haven't (touch wood) had an issue with it. The issue could be down to a thermostatic valve sticking on a radiator or trapped air within the system. With the heating on go to the highest point in the house and bleed off any cold water/air in the system whilst with the help of another top up the combi boiler level/pressure. The thermostat is at the top of your stairs, with heating rising you would assume this would be the warmest part of your house so the thermostat would be hardly kicking in the system. With it being a relatively old system it may require the system balancing across the rooms etc, but a good reputable installer/engineer will be able to do this.
 
dark-knight said:
With the heating on go to the highest point in the house and bleed off any cold water/air in the system whilst with the help of another top up the combi boiler level/pressure.
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I've done this - no air in any of the radiators.

dark-knight said:
The thermostat is at the top of your stairs, with heating rising you would assume this would be the warmest part of your house so the thermostat would be hardly kicking in the system. With it being a relatively old system it may require the system balancing across the rooms etc, but a good reputable installer/engineer will be able to do this.
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The thermostat itself is reading the low temperature, so it's not that it's too warm upstairs and turning the boiler off.
 
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