New boiler advice, standard or combi

[Elkato531]

you can have that with a mains-pressure HW cylinder

I wasn't going to come back either as this is just going round in circles but you are correct and its why unvented is now the preferred option in new build family houses. Don't forget though that unvented has the same potential drawbacks as a combi when it comes to mains supply and feeding multiple outlets.

Go on then - the negatives???

What some people see as negatives will be of no concern to others with different priorities
I can't say why your friends are unhappy but I am sure that there are aspects that have improved. If not, I come back to my point that they got bad advice and made a poor decision. That is their fault and not the combi boiler's.

 

[bernardgreen]

just want to add that you can have that with a mains-pressure HW cylinder

and that is also possible with a vented cylinder with a shower coil. Removes the need for pressure reduction / limiting valves and the necessary safety devices that an unvented cylinder requires.

This works for me.

The 16 kW heat only boiler runs for about 20 minutes in the morning to heat the water in the cylinder.

 

[bernardgreen]

That is their fault and not the combi boiler's.

Quite often the installer convinces the home owner that a combi is the best option when the reality is the combi is the best option for the installer's bank account.

 

[Elkato531]

Quite often the installer convinces the home owner that a combi is the best option when the reality is the combi is the best option for the installer's bank account.

You know, that is probably a bit of a myth. A straight swap of a heat only is likely to involve a very healthy profit margin for considerably less effort than a combi conversion. But I refer you back to my earlier post. Get proper advice and bin off anyone who is trying to push either option without properly getting to grips with what the customer wants.

 

[Harry Bloomfield]

You know, that is probably a bit of a myth. A straight swap of a heat only is likely to involve a very healthy profit margin for considerably less effort than a combi conversion.

More effort, much longer job = potential for more profit, plus added potential for extra profits later due to leaks as the system then runs under greater pressure.

Heat only, means a straight forward job, half a day, minimal changes to existing pipework.

 

[Elkato531]

Quite often the installer convinces the home owner that a combi is the best option when the reality is the combi is the best option for the installer's bank account.

Actually, this comment deserves a stronger response.
As an installer, I strive to give my customers the best solution I can depending on their circumstances. I also want to keep those customers into the future for ongoing service and maintenance work. I am not in the business of fleecing as much as I can and then disappearing. I expect the majority of installers, especially the independents, to operate in the same way.
There are undoubtedly dodgy dealers out there and if you come across one and don't spot them before they rip you off, I feel sorry for you. But do not tar us all with the same brush.
I will not be adding any more to this post as now that it has got to the slagging off the plumber stage, rational discussion is out of the window.

 

[camerart]

What system do you have?

Hi F,
Housewarmer 45 back boiler. It has a safety cut out, but the gas fire in front of it doesn't so I have a gas alarm.
C.

 

[camerart]

I would suggest, you have been very lucky then

My system is perhaps a couple of years older than your own. On it's third heat only boiler - first had nowt wrong with it, just convinced to swap it for a more efficient one. The 'more efficient one' caused constant issues, and faults, a year or two back I became fed up of it and swapped it for a new one.

A new pump, 3-port valve, and controls, were fitted as part of the package of the second boiler.

Over the years, we have had numerous 3-port, spring return actuators fail, but never a single valve.

I have now swapped out the spring actuator, for a MOMO type, as I liked the less mechanically stressful design, of no spring.

At the last boiler swap, I upgraded the controls to a fancy electronic system, taking into account outdoor temperatures, and setting the boiler output to match the heating demand, which it always has. perfectly.

So generally, the most frequent point of failure, is the 3-port actuator. An easy fix for me - I always keep a spare to hand. Heating is never off for longer than 30 minutes.

Hi H,
Yes, I've been lucky, but DIY and not racing to change has helped.
I've seen that 3 port actuators and simillar have problems. Could it be due to the water hardness? My thermostastic radiator valves sometimes stick, so I tap the internal brass rod with a bit of wood to clear them. I have inhibitor in the tank!
C

 

[fixitflav]

Hi F,
Housewarmer 45 back boiler. It has a safety cut out, but the gas fire in front of it doesn't so I have a gas alarm.
C.

That sounds pretty basic. Do you have any motorised valves? Is it gravity hot water, pumped rads? In that case it's probably not all that efficient, but not much to go wrong!

 

[Madrab]

Oh my 4 pages later and the OP still hasn't replied

 

[Harry Bloomfield]

I've seen that 3 port actuators and simillar have problems. Could it be due to the water hardness?

No, not the valve - the actuator, the box on top, which operates the valve. The valve will survive several replacement actuators.

'My thermostastic radiator valves sometimes stick, so I tap the internal brass rod with a bit of wood to clear them. I have inhibitor in the tank!'

They usually stick, simply due to being left closed for such a long time.

 

[camerart]

That sounds pretty basic. Do you have any motorised valves? Is it gravity hot water, pumped rads? In that case it's probably not all that efficient, but not much to go wrong!

Hi F,
No auto valves, a motorised pump, which occassionally needs a cap, but basic and working.

How inefficient do you think it is compared to the cost of a new one, and possible repairs, in not too long?

I've debated a new one, also heat pumps, but I leave well alone for now.
C

 

[diy_fun_uk]

I've not read the small print re t's & c's, however if you get a boiler with a decent warranty that surely mitigates a bit re any potential reliability issues? I have Ideal's in my BTLs, 10 year parts & labour warranty.

Before you all start shouting at me, I'm not interested in hearing how good/bad Ideal boilers are, I'm simply stating the fact a decent warranty can help.

 

[fixitflav]

Hi F,
No auto valves, a motorised pump, which occassionally needs a cap, but basic and working.

How inefficient do you think it is compared to the cost of a new one, and possible repairs, in not too long?

I've debated a new one, also heat pumps, but I leave well alone for now.
C

Found it on the web, and efficiency about 79%, whereas modern boilers are more like 95%. But it would take a long while to get into profit if only changing it for that reason.
Another thing is, with no motorised valves, can only work in HW only mode (power to boiler but not pump), or HW + CH mode (power to both). In HW mode, even when the cylinder is hot, the boiler goes On/Off on its control-stat, using gas, and it soon loses heat up the flue between cycles. So if you want HW always available, to avoid too much waste, need to set the HW time right, manually or by timer (if you have one).
You could improve efficiency by converting to Honeywell C-plan, by addition of a motorised valve and a cylinder stat, without great expense. There's information on the web.
Edit - I suppose you have a roomstat?

 

[Harry Bloomfield]

I've not read the small print re t's & c's, however if you get a boiler with a decent warranty that surely mitigates a bit re any potential reliability issues? I have Ideal's in my BTLs, 10 year parts & labour warranty.

We've only had three boilers here, one of which was an Ideal, all heat only. The Ideal was the most unreliable of the three by far. Once out of warranty, it had three pcb's, and one fan. The last straw was the loom running up the back of the boiler melting, and taking out the pcb..