New Boiler (Heat only) for use with a Thermal Store (Kingspan Flowmax)

[catflap2]

I need to replace our 20+ year old Myson Orion 50B with something a little new more efficient.

I've been trawling through the forum and the web for current thoughts on what the best heat only boilers are at the moment and come up with about 8 different manufacturers, most I've heard of and a few new ones.

However our heating is slightly different to the norm so it might very well lend it's self to one or two models more than any others.

Basically we have a Kingspan Flowmax thermal store that the Myson currently heats.

Looking through the Kingspan info it recommends the following in regard to a suitable boiler:

Due to high operating temperature of thermal Storage Systems condensing boilers may not be cost effective - ?? What does this mean as I assume my only choice these days is a condensing boiler?

A boiler with a cast iron heat exchanger is far more tolerant of a system design when compared with one incorporating a "low water content" heat exchanger - again most are Aluminium aren't they?

When a boiler requires any form of pump overrun then the existing pump overrun device must be disconnected and our timed pump overrun device used in its place. The boiler pump overrun will be solely under the control of our timed pump overrun to ensure maximum efficiency. We don't have their overrun device so I guess it would be easier to get a new boiler that doesn't need pump overrun? If so then what's the best option?

The current out of our boiler is 15KW, was looking at 18KW boilers as we have added a radiator to the system since it was originally put in.

We have a 4 bed detached house with 12 rads. In terms of sizing kingspan state Calculate space heating as per BS5449 then add 3KW for hot water. The Flowmax and all pumps etc. was replaced by BG under their service care about 5/6 years ago so that side is much newer than the boiler.

Boiler makes I've looked at so far

Worcester Bosch - Greenstar 18si
Vailliant

Glow Worm as I read they don't need a pump overrun and are based on the Vailliants

Think I also read that Baxi boilers don't need the overrun either but not looked at them yet.

Then looked briefly at the following as they get good reviews on here
Veissmann
Intergas
Atag

So given the parameters of our current set up what should I be looking at? Once I have a few options then I'd like to see who the approved installers are close to me for each manufacturer.

Thanks

 

[hertsboilers]

If you want a heat only boiler which doesn't pump over run, it must be one of the followings:

1. Viessmann

2. Ideal Logic

3. Vaillant ecoTEC 4xx series

4. Baxi EcoBlue.

As the first three all need a permanent live alone with a switched live, so only Baxi EcoBlue is suitable for your existing Orion B wiring.

I just installed a Baxi EcoBlue advanced heat only boiler yesterday, and noticed its highest temperature setting is 90C on the dial.

 

[hertsboilers]

For Kingspan Range thermal store, if it is a twin pump pack, you need to check how many cores on the cable between the boiler and thermal store. If it has 5 or more, you can use whatever boiler you wish.

If you only have 4 cores, you will be okay with 1. 2. and 3.

If it is only 3 cores, then Baxi EcoBlue only.

 

[catflap2]

For Kingspan Range thermal store, if it is a twin pump pack, you need to check how many cores on the cable between the boiler and thermal store. If it has 5 or more, you can use whatever boiler you wish.

If you only have 4 cores, you will be okay with 1. 2. and 3.

If it is only 3 cores, then Baxi EcoBlue only.

Thanks for the info. Would the fact the cabling was put in around 25 years ago mean it's likely to be 3 core rather than 4 or 5? Also we have Hive fitted would that signify anything in particular about the wiring? Guess I need to take a look or wait for someone who knows what they're doing to take a look.

 

[Agile]

The number of cores in the cabling depends on how the controls were wired. Needs to be looked at! Not Googled!

 

[Dan Robinson]

Intergas can have pump overrun disabled in software.

However, the installer should be advising you on this as there is no way you're going to get accurate information on this kind of job from a forum.

 

[Hugh Jaleak]

Surely the worst case scenario is you'd need to run an additional cable between Thermal store and boiler. Not the end of the world?

 

[hertsboilers]

The worst case is, the installer didn’t survey the exiting wiring promptly, and chose a boiler model which requires pump over run, like Vaillant and Worcester. After he installed the new boiler, he didn’t connect the pump over run, so the boiler will run, but often get over heat cutouts. If you call boiler's manufacturer to do warranty repair, their engineer will point out the installation error, and refuse to proceed.

 

[catflap2]

I'm struggling to see why they want the flowmax to control the pump over (timed) run rather than the boiler as surely it's just going to run for a few minutes in either case? Am I missing something here?
Anyway, had our local Vaillant approved installer around to give us a quote this evening and running the extra cabling if it is needed was a complete non issue, he would just do it. Just waiting for the quote now.
So if we process on the basis of having a boiler with or without overrun and live feed are there any particular makes / models that would suit heating the thermal store better than any other given we should always run with the boiler thermostat on max? Just wondering as they mention low water content Heat Exchanges can be noisy, does every modern boiler have these nowadays?

So the WB Greenstar 18ri is back in contention I guess now along with just about every other regular boiler out there.

 

[Dan Robinson]

Wooshitter back in contention? Blimey.

If you have to have a well known boiler then Vaillant is as good as any other.

Want something built to last - Intergas is the way and the light.

 

[Agile]

Do you know the actual measured flow temperature that the old boiler was working at?

Thermal stores rely for their capacity on being run at a much higher temperature than is used for radiators now.

Normally that would mean the boiler would be controlled to run at two different temperatures. But there are two different ways to use thermal stores.

Tony

 

[Dan Robinson]

Please explain....?

 

[catflap2]

Do you know the actual measured flow temperature that the old boiler was working at?

Thermal stores rely for their capacity on being run at a much higher temperature than is used for radiators now.

Normally that would mean the boiler would be controlled to run at two different temperatures. But there are two different ways to use thermal stores.

Tony

Sorry don't know the measured flow temp.

The store is maintained at 75c and the advice is to always run with the boiler set to max. Think it's pretty simple and just calls for (max) heat when the store temp drops to a certain point. In terms of the pump overrun when the Store controls it then it's timed somewhere between 4-6 minutes - is this pretty much what a boiler would do?

If we need to run the boiler on max then would a boiler with a higher max temp be better or will it make little difference? Looks like some are 80, some 82 and some 90? (and probably a whole load in the middle of these as well).

If there's no particular brand / model that is better suited to heating the store then I'll get a few more quotes from local engineers and see what's offered. If there's anything in particular anybody thinks would be a bad idea for our system then that would be good to know as well so I can avoid that mistake.

Thanks.

 

[hertsboilers]

If we need to run the boiler on max then would a boiler with a higher max temp be better or will it make little difference? Looks like some are 80, some 82 and some 90? (and probably a whole load in the middle of these as well).

Baxi EcoBlue heat only has a temperature setting dial up to 90C, but on checking its technical specifications, it is still 80C max flow temperature. Are you sure you have found any particular models which have 90C output?

Kingspan Flowmax is bitter strange, somewhere said it maintains 82C but another 75C.

If it is 75C, all boiler models will be okay with their 80C output max.

 

[catflap2]

Baxi EcoBlue heat only has a temperature setting dial up to 90C, but on checking its technical specifications, it is still 80C max flow temperature. Are you sure you have found any particular models which have 90C output?



Kingspan Flowmax is bitter strange, somewhere said it maintains 82C but another 75C.

If it is 75C, all boiler models will be okay with their 80C output max.

Flowmax state the store should be maintained between 70 & 80 with a typical boiler installation set to 75.

The Intergas states 90c max water temp. I've not looked at all the options out there just what I've seen recomended so there could be more. The greenstar appears to be 82c not sure about the Vailiant yet, looks like it is restricted out of the box to 75 but can be set higher by the installer.