Boiler sizing from heatloss calculations

Modern condensing boilers are usually sized at 24kW or above, which will be enough for your needs.

Christian.

The Ideal Icos HE heating boilers come in 12, 15, 18, and 24kW versions. This is the boiler recommended to me by a tank manufacturer. The 24kW version is only about £35 more than the 18kW one. Is there any reason to go for the 18kW version?

Thanks, W

MikeS

No. It is a marketing strategy of theirs. 2 years ago, they only did a 24kW version (which could be "reprogrammed" to 28kW).

However, the "heating" versions should normally be avoided, although they have their uses. It is usually best to upgrade to a sealed pressurised system and use the "system" version, which has the sealed system components internally (and sometimes a pump).

Christian.

I'm not familiar with this boiler, but presumably the lower modulation limit also increases? It's going to end up cycling on and off if you are routinely needing less heat from it than it's lowest level. (If it's like the Keston, there's quite a bit of hysteresis before the boiler will fire up again when this happens.) If you calculated 8.4kW at -3C outdoors, then most of the time your heating is on, you won't need anything like that amount of power.

If your existing gas pipe run was marginal on pressure drop, it might be that you could get away with it on one power rating, but not the next one up without replacing the gas pipework (maybe only some of it).

Most boilers modulate somewhere around 5kW to around 25kW. Glow worm have a

I assume the integrated one withy the heating circuit taken from the store. Make sure the thermal store has two stats to prevent boiler cycling. The bigger the boiler the better with a thermal store

This is a basic. modulating heating boiler and you, or the thermal store maker, supplies the pump. It will re-heat the store pronto. The biz.

The Worcester Bosch Greenstar 28HE is a similar boiler.

The modulation when using a thermal store doesn't matter that much as the store controls the boiler. Set the store to 75C.

Try the Range, which is a heat bank with a plate heat exchanger. Better.

Sorted.

He is going thermal store so the lower level of modulation is not an issue at all.

Like most of them.

This is all irrelevant as you are going thermal store . Get the biggest boiler to your budget as you can. Then a super fast re-heat.

I am interested to know why the heating versions should be avoided. I would have thought they would be more efficient in my situation since the boiler heats the heatbank directly without the need for an additional heat exchanger in the tank or an expansion vessel anywhere.

Cheers, W

According to the specs I have the lower modulation limit is the same for all these boilers.

BTW: I did my calculations at -1C outdoors.

An 18kW boiler would be about the same power as the one I have now so I don't think they'll be a problem with the supply.

W.

What prices have you been quoted?

In your case the basic heating boiler heating they store directly is the one. The system boiler is fine if you want a sealed system as all is inside the case.

Don't forget to put enough inhibitor in the thermals store.

I was tending away from a system boiler because of the additional cost & complexity (which I don't think is necessary in my situation).

Thanks. I'll look into this one.

... and this one.

I've considered a heat bank but I'm not (yet) convinced that they are worth the extra money. Considering that they are about double the price (AFAIK) of a thermal store then they would have to be a _lot_ better to convince me (unless you know different).

Cheers, W

I've been quoted about £700 for a large 250L thermal store. I haven't had a quote for a heat bank but I thought they were around the £1400 mark for a similar size. Maybe I'm wrong though :-)

Use to reheat a direct heat bank is one of the "have their uses" noted above.

Christian.

I Installed one of these to an existing open vented system. The reason was to keep the old cast iron boiler in the garage as a back up. Throw a switch and the old boiler comes in and the new one is out. Full backup of heating and DHW.

Does CORGI know about all this fitting work that you're doing?

Not their business.