Which Type of Boiler / System?

[Deryck Tintagel]

I have been having problems with cold rads (https://www.diynot.com/diy/threads/number-of-cold-radiators.652613/#post-6150056) so have been getting quotes for a flush as nothing has cured the problem.

A couple of plumbers have suggested changing the boiler as the current one is 25 years old and we could get more problems once the system is flushed.

We currently have a conventional boiler with HW tank with immersion heater. The HW feeds one bath and one shower. It has been suggested that we can keep the HW tank as it is in good condition and convert to a pressurised system.

Woiuld a pressurised system give us any benefits?

 

[Mottie]

I’d say get your flow problem sorted first. If some rads are getting hot but not others, thar would rule out a faulty boiler in my mind.

When you say pressurised, do you mean the heating system or hot water (which is called unvented)?

 

[Harry Bloomfield]

Woiuld a pressurised system give us any benefits?

No real benefits, but a potential for more leaks due to extra pressure. The only real benefit, being both loft tanks will be no longer needed.

 

[dal5band]

It is possible to have a system boiler. You could call this a hybrid system. The system boiler is pressurised so the radiators are pressurised and the heating coil in the HW tank is pressurised. The CH small tank in the loft is no longer needed. But the HW side is not pressurised so still runs off the main storage tank. So this is not a combi system. Need someone with experience to confirm this. I agree there may be leaks on the radiators.

 

[Deryck Tintagel]

I’d say get your flow problem sorted first. If some rads are getting hot but not others, thar would rule out a faulty boiler in my mind.

When you say pressurised, do you mean the heating system or hot water (which is called unvented)?

That was my thinking to be honest. Get to a known good position before changing anything. A full clean should be part of the changeover, and this could uncover other issues but we deal with those if the arise. I think the boiler is OK - it runs and we get heat where the pipes are not blocked, just not is all areas


Yes, pressurised heating system, with gravity fed HW

 

[Deryck Tintagel]

It is possible to have a system boiler. You could call this a hybrid system. The system boiler is pressurised so the radiators are pressurised and the heating coil in the HW tank is pressurised. The CH small tank in the loft is no longer needed. But the HW side is not pressurised so still runs off the main storage tank. So this is not a combi system. Need someone with experience to confirm this. I agree there may be leaks on the radiators.

MIght be worth a think.

I briefly considered a combi, but we had a breakdown a few years ago and were left without heating for about 5 days. The immersion heater at least gave us hot water. Also, getting the HW from the combi boiler to the tank location to connect to the existing would mean considerable upheaval of floor sheets (not boards)

 

[stem]

The only real benefit, being both loft tanks will be no longer needed.

I have heard a couple of reports from people living in Kent that have been without water for days / weeks who now have heating now as their boiler pressure has dropped and they are unable to repressurise it from the mains. Water stored in a header tank in the loft would have prevented that.

Others who have water for a few hours at a time will also appreciate a 25 gallon cistern supplying their hot water cylinder as it will be topped up when water is available and can be used any time. Combis and unvented cylinders can only provide hot water when the mains supply is available.

On the other hand, anyone who has had a frozen pipe burst in their loft would be glad to see them gone forever.