Boiler condensing possible with Rads (no UFH)?

[tellme_why]

Hi,

I have an 20yrs heat only potterton 50e boiler with 196x old house - suspended floor - designer radiators, open vent system and hot water cylinder on first floor with two motorised valves and stat.

I want to replace the boiler with minimal cost and max efficiency so thinking of replacing the old boiler with a new condensing boiler.

Currently, the old boiler is set to 70C supply temp to ensure the cylinder gets to 60C to avoid legionella. Also the designer radiators - Milano Aruba - have low BTU output - so the 70C helps getting enough heat out of it.

In order to save money I only heat up the hot water cyl for 30 min before shower.

Question: Can I get a new boiler and new rads that does both 1) provide 70C to the hot water cyl during for 30mins and 2) Operate central heating at low condensing temp?

My solution would be 1) buy a heat only boiler that can normally operates at 50C to feed the rads and changes output temp 70C upon an dry contact signal trigger by cylinder hot water demand and 2) replace designer rads with triple panel radiator and operate them at low temperature.

Finally I don't know whether triple panel radiators can really enable low temp systems, but only underfloor heating can? UFH will cost a fortune I suppose.

 

[cross thread]

You can get boiler with its controls to do as you require ,vaillant, atag, intergas. None of theses are a cheap option ,

 

[vulcancontinental]

Just use an OpenTherm ready heat only boiler and EPH controls to operate two zone valves on DHW priority. An additional feature would be to add weather compensation if the boiler allows. Either or the combination would do what you require. Not sure Atag is heat only or the heat only Vaillant can do what you want, it's certainly not OpenTherm. I'd suggest changing to a system boiler and then using a Vokera Unica Max however it's only fair to mention I work for Vokera.

 

[tellme_why]

Just use an OpenTherm ready heat only boiler and EPH controls to operate two zone valves on DHW priority. An additional feature would be to add weather compensation if the boiler allows. Either or the combination would do what you require. Not sure Atag is heat only or the heat only Vaillant can do what you want, it's certainly not OpenTherm. I'd suggest changing to a system boiler and then using a Vokera Unica Max however it's only fair to mention I work for Vokera.

Hi, why system boiler? What's the advantage? I have an old central heating piping that already experienced a leaks few years back. If I pressurise it there is risk of further leaks and much more expensive upgrade?

 

[vulcancontinental]

Personally I am happy with open vented systems when I installed them as I knew how to do it to avoid air ingress and achieve inert deoxygenated water in the heating system, that is not commonly the case. Take a look at the water in the small feed and expansion cistern in the loft, if clean and not discoloured that's a good start.

If you have pipework below a screed pressurizing is not always a successful conversion as it can cause leaks on occasion, however if you have pipework you are unsure of it will eventually leak anyway, best to find out while there is a plumber in the house.

As for advantages of sealed systems; for guys who do not know how to install OV system boilers are easier and will not permit air ingress, velocities can be faster (not my preference), the system boiler may well be cheaper and there is greater choice.

If your old 50e boiler was installed correctly it will already incorporate a pump overrun so that's OK as most OV boilers need one.

It may be advisable to upgrade your radiator valves if going sealed system as they operate at a higher pressure in most houses but if the install is 20 years old that might be useful anyway.

 

[Mottie]

We had some leaks when we converted to a sealed system. There were three remaining rads left over from the original installation in the 60’s. Two of them were pinholed so all three were changed. The remaining rads were up to 20 years old and they have been fine for the past 6 or 7 years, as have all the pipes.

 

[tellme_why]

how to do it to avoid air ingress and achieve inert deoxygenated water in the heating system, that is not commonly the case. Take a look at the water in the small feed and expansion cistern in the loft, if clean and not discoloured that's a good start.

Hi, this is interesting because my water is murky even after a nice cleanup fernox etc.. how you do this?

 

[vulcancontinental]

Hi, this is interesting because my water is murky even after a nice cleanup fernox etc.. how you do this?

Make sure the water in the system and cistern do not have circulation between them or aeration. Know how to pipe size and position connections and circulator. Sealed systems avoid those issues.