It does, but Vaillants, in particular can be a right pain to get to refire due their "stupid" requirement to maintain ~ 65% of max rating for 60 seconds after cycling, their minimum output though is now improving.
What size heat-only boiler?
- Thread starter gerbils
- Start date
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Pick one that does then.(Who are they?)
With heat only boilers, Ideal Logic and Worcester Bosch Ri series cannot be range rated. At least not from the control panel. I would guess a gas engineer could open the boiler and range rate that way.
Doesn’t the Worcester have an adjustment knob on the front panel?
My Vaillant heat only boiler is adjustable through the menu.
Yes. But that just adjusts the flow temperature.
Yes, Vaillants can be. As can several other brands or models, The Worcester Bosch 8000 can but the Worcester Bosch Ri can't. I can't remember the full list anymore. I don't know about Baxi/Main. Assume Glow Worm can as part of Vaillant but not 100% certain. VIessmann, Intergas, Alpha can. Only talking about open vent heat only boilers here.
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It's a Glowworm Space Saver MKII - I believe it's Max output is 14.65KW looking at the Manual. And Max input 19KW
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14KW I believe (Glow Worm 50BR MKII - 1977).
It's fine I guess, the house can get to temp when desired but can sometimes feel like it takes a while (usually wake up at around 15/16 degrees in winter and get it to 18/19 in a couple of hours). We tend to just boost for a few hours a day when cold.
If it was me, I’d go for a modulating 18Kw boiler then, to give you a faster warm up and a faster hot water heat up. You could look at a more efficient hot water cylinder. Maybe think about making it a sealed system and unvented hot water too if you have the water pressure/flow for it. I’m happy with my Vaillant 418 Ecotec plus.
Unfortunately our flow is 12L/Min which rules out an unvented system unless we pay for accumulators etc which is almost doubling our quotes.
So we can either stick with unvented and get a new standard boiler + cylinder + shower pumps or switch to a combi....
Well, my experience is limited but as far as I understand it, if you don’t have enough flow for unvented hot water, you won’t have enough for a combi.
Minimum is 20L/Min for unvented and 10L/Min for combi. May not be ideal though, I agree.
We can get a 418 Eco Fit pure. Is yours an open system?
No, mine is sealed. The 'Pure' is a lesser model. I think some on here have said its just another make of boiler badged up as a Vaillant so check it out . You can have it as open vent or sealed.
Here you go:
Is there any reason it must be a heat only boiler rather than a system boiler? That would open up more options. If you plan to pressurise (seal) an open vent (heat only) boiler you might as well have a system boiler.
If you use controls to make the system HW priority you don't have to add the HW load to the heating load. The HW load will be dependant on the size of the coil in the cylinder.
I know Vaillant so can't comment on other brands. With Vaillant controls you can set the power output and flow temperature independently so can have a cylinder with a large coil for fast reheating and a high flow temperature, while having the heating output matched to the heat loss with weather compensation.
If you use on/off controls you have one flow temperature for all situations.
My house came with a 24KW boiler, undersized radiators and a cylinder with a 3KW coil. Noting worked well.
I now have a boiler set to 12KW for heating, 18KW for HW and it works very well. I will be able to reduce the output further as I improve the insulation.
An Ecotec plus 610 (10KW rated) Can modulate down to 2.8Kw in heating mode while having 19.6Kw available when in HW mode when fitted with Vaillant controls.
If you use controls to make the system HW priority you don't have to add the HW load to the heating load. The HW load will be dependant on the size of the coil in the cylinder.
I know Vaillant so can't comment on other brands. With Vaillant controls you can set the power output and flow temperature independently so can have a cylinder with a large coil for fast reheating and a high flow temperature, while having the heating output matched to the heat loss with weather compensation.
If you use on/off controls you have one flow temperature for all situations.
My house came with a 24KW boiler, undersized radiators and a cylinder with a 3KW coil. Noting worked well.
I now have a boiler set to 12KW for heating, 18KW for HW and it works very well. I will be able to reduce the output further as I improve the insulation.
An Ecotec plus 610 (10KW rated) Can modulate down to 2.8Kw in heating mode while having 19.6Kw available when in HW mode when fitted with Vaillant controls.
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@gerbils
I believe both the Plus 418 and the Pure 418 have the same aluminium heat exchanger these days. I think the only heat only boilers currently with a stainless steel heat exchanger are Viessmann and Alpha. The stainless steel Alpha heat exchanger seems identical to the one Vaillant used to use (and still use in some of their other boilers). It's used by other manufacturers as well. Intergas gets a good reputation. Their heat exchanger is totally different to anybody else's.
Our water flow is 12L/Min & 2 Bar - not enough for a vented system I have been told and borderline for a combi.
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