Regular boiler advice

[Vip1969]

I have a Worcester Bosch 24Ri regular boiler (open vent) which is 10 years old. It has been pretty reliable with only one fault (the fan unit gave up after 9 years) in last 10 years. It's also had one new burner, rubber seals and electrodes changed in services. I have noted that it's best to keep the temperature dial low (1 keep at the 11:30 clock mark in summer and 12:30 mark in winter), so flow measured temperature is no more than 55C and this has helped to make the boiler reliable. The boiler is fitted under the staircase to an external wall with the flue going out straight to an external wall outside. All the pipes come out at the bottom of the boiler.

I am thinking of replacing the boiler in the next 2 years. Ideally, I would have liked to replace with a Viessman 100 regular (stainless steel HEX), but unfortunately, the flow and return pipes come out at the top of this boiler where I don't have the space. I could always go with another Worcester Ri which would also be cheapest to refit. I know there are better options with system boilers which I have looked into for several years, but I also have limited overall height space and would mean sealing the system which I don't want to do as I consider OV systems to be (most) reliable and a regular boiler to be most simple and reliable (albeit that it does not have good energy saving controls...) and with an external pump that I can adjust...

What other good regular boilers are available with similar external dimensions as a Worcester Ri but where the flow and return pipes come out from the bottom of the boiler?

 

[gmartine]

You should be able to get a stand off frame which mounts the boiler away from wall allowing you to run pipe behind the boiler either upwards or downwards.

 

[Vip1969]

Thank you gmartine. I did speak with Viessman technical support a few years ago and the person did mention this. But then he also said you might get airlock in the HEX on filling up. Also, running 360 bends in very limited side space does not fill me with confidence. I am an engineer and a good DIY plumber and I would not do this.

 

[gmartine]

Pressurise the system and it'll be absolutely fine as well as increase efficiency and reduce oxygen ingress.

 

[Vip1969]

Thank you gmartine. I think I will have to bite the bullet and look at system boilers again which I researched into many years ago. They did attract me then with far better controls including superior modulation. I don't understand why boiler manufacturers make their regular boilers with very basic controls. Understand there are limitations with pump outside, sealed and non sealed option, but they could do far better. Seems to me they are mostly interested in Combination and System boilers where most of the money is today.

Sealing the system may be an issue. Much of the downstairs 22m mm flow and return pipes are under concrete and were laid in the late 70s by the previous owners, with good quality thick copper pipes, much better than what you get today... But the state of the soldering (and some compression joints below floor) is the big question. Much of the upstairs was done by me in the nineties with new copper 22mm and 15mm pipes and my soldering and compression joint work is good. My system water is clean and has been for years and I don't have air ingress issue or corrosion. All my radiators and valves are 10 years old or less.

I don't particularly need the loft space freed up. However, I will be trading simplicity, resiliency and reliability for complexity with the upside being better controls and modulation.

 

[gmartine]

Well as you're familiar with it and it'll cause the least disruption replace with another WB ri, it's still an ok boiler as long as it's properly sized. I say that because unless you live in a very large residence 24kw is a very large heating load.

 

[Vip1969]

The current 24KW boiler was (over) sized by the plumber that fitted the boiler. I have since done the heat loss calculations. The house is old but not too bad. A 18KW boiler would suffice. Thank you for all your guidance.

 

[gmartine]

You're welcome. Well, you can down rate your boiler to 18kw or less by swapping out with a different code plug. It's a simple and cheap procedure which I've done to quite a few of my clients with this boiler if oversized or heat loss has decreased.

Part No: 87144210380

 

[Vip1969]

Appreciate the extra input. Thank you gmartine.

 

[Timmy D]

You seem to have an understanding of what you’re asking, I’m teaching to suck eggs.

The air ingress that was mentioned with regards to open vent systems, was in regards to a continuous supply of oxygenated water entering the system.

In a closed system, correctly dosed with inhibitor, once all the oxygen within the water has been used to make sludge (in essence rust, feo3?), no more is created.

Open vent systems keep providing that oxygen and creating sludge.