Mixing UFH & rads & HW on a Glow Worm Ultracom2 30sx

[sparkzz]

Hi Guru's,

We are just putting a new system together seeing as my old vented one has gone kaput, (does not help when the overflow into the header tank decided to dip below the water level & use it as part of the system, mmm wondered why the attic had condensation The gunk & sludge in the tank was dire.

Anyway, we have recently fitted our lounge out with water fed UFH, which we will put onto an independent manifold ect. The room next door is also going to be on the manifold, albeit with it's own stat. The rest of the house is good old radiators.

I am about to get a Glow Worm Ultracom2 30SXI & either a Vaillant or Range Tribune unvented cylinder (180l ish)

My question is - we like gadgets, lol, & really like the look of the Glow Worm RF controller, but because the system will be running the HW, UFH & CH seperately, will this controller be any good, or am I better sticking with the ACL one we have to control the rads. I must say I do like the idea that it becomes sort of closed loop & adjusts itself given outside temp etc. hey, we like gimmicks!!

Cheers guys, Shane, (York)

 

[muggles]

Noooo, don't get the Glowworm, it's a cheap and less well built Vaillant. Get the Vaillant ecotec plus 630 with a VRC470, that will do the rads and cylinder, the programmable room thermostats will control the demand for heat for the UFH. I wouldn't touch a Range Tribune with a bargepole, the Vaillant cylinders are good but I'd recommend an OSO Super S over both of them. I assume you've had your incoming mains checked before deciding to go for an unvented cylinder??

 

[sparkzz]

Hiya Muggles,

Thanks for the response young man!!

Yes, pressure has been checked. Not the highest in the world, but will do an unvented system thankfully. I can't cope with our dribble of hot water we get at the moment!!

Right, blimey. Yes from what I have read, the Vaillant boilers are good, but does it really justify the cost. I suppose it does really. Do you think we could get away with the 624? Our existing Potterton is only a 17/18KW and in all honesty has heated all the rads fine. We only have one bathroom at the moment, but will be putting a large ensuite onto one of the rooms, but this will only have a shower. The existing bathroom has a bath & shower. I take it with the VRC740, this could be added at any time with no real impact on the system at the moment?

In terms of the tank, what exactly do you get for paying more money? Sorry if this sounds dumb, but I am trying to research this and not coming up with any decent answers.

Cheers again for your advice

Shane, (York)

 

[Agile]

Over sizing your boiler will just cause inefficiency. You should calculate the whole house heat loss, add 2 kW for water heating and almost certainly an 18 kW boiler will be fine if thats what the old one was.

UFH and rads need to be controlled and particularly timed seperately.

Tony

 

[muggles]

You could add the VRC470 in later but you'll need some sort of control so rather than spend money twice it would be better to go for it straight off. It'll make your boiler more efficient anyway, saving money, so it's worth the expense.

If your current boiler is 18kw the 624 will be more than adequate, you might even get away with the 618, although the 624 would probably be the one I'd spec.

As for cylinders, the OSO, now known as the Super Coil rather than the Super S (I've only just found out they've changed it) has better insulation and faster heatup and reheat times than the Vaillant. Better insulation means cheaper running costs. Faster heatup means less time waiting for it to get warm enough to run a full bath! The OSO 180 litre takes just 18 minutes to heat from completely cold and 13 minutes to reheat after a 75% draw off. Another advantage of the OSO is that it looks much nicer - installed correctly there will be no visible pipework to it at all.

 

[sparkzz]

Hi Guys,

Many thanks for the help here. Some good advice. Bang goes my theory of having more power & throttling it back, rather than something small running nigh on full speed. That's why I don't do plumbing

If we put the VRC470 in the system now, I presume that will control the rads & hot water, then just add diverter valves for the UFH. Where would you mount this, as the main sitting room is one of the rooms that has the UFH, so I don't think this needs to be here. It says it can mount to the boiler face, so presume that is the best place. At the moment we have a wireless Drayton which controls heating & the time clock is switched to always on. the clock then just controls water by time, not heating as the Drayton controls this.

This is the bit I am struggling to get my head round. If the VCR controller is internal to the 624, can it still be wired to be controlled by the UFH thermostat. I was under the impression everything would have to be external to the boiler, so this is literally turned on/off & the UFH, Rad & HW diverter valves control flow etc.

I have sort of sussed out if we were to do my existing boiler, as in pump to 3x diverter valves, each controlling the individual system, but am not sure how the internal system will work, or am I being daft!! Maybe I have not grasped how these boilers work. Is it purely the pump that is internal & the diverters sit external as normal. Does the VCR control the diverters for the HW & rads, if so how do you add the 3rd for the UFH.

Basically my plumber is going to do all the work, but has given me some ideas as to what to go for. I just need to make sure in my head it is all correct.

Thanks again for all your words of wisdom. I think after I have sussed this I better stick with Automotive Electronics, lol. It's a fair bit easier....

Cheers, Shane

 

[Agile]

There is a problem with weather comp when you mix conventional rads and UFH.

Basically rads need flow temps controlled between 30 C to 75 C.

UFH needs 25 C to 45 C.

So quite sophisticated seperate controls are required which are likely to be beyond an average plumber. Also rather over complicated for a normal sized house!

There is also the question of when to start a UFH system. In most cases it would be better for the control to start UFH later but at a higer temp when less heat is needed but then turn it down when it nears the target.

Simple UFH controls take a higher CH temp of say 60 C -70 C and reduce it by blending to about 40 C or as manually or automatically set. Automatic controls for this are somewhat over complicated for a small system.

Tony

 

[sparkzz]

Hi,

Right I decided this afternoon that the Vaillant 624 was the way to go. Unbeknown to me, my misses has convinced her poor dear daddy to fund the boiler for her, (struggling self employed graphic designer!!) & they have gone ahead, upgraded & ordered the 630 without consulting me.

This will be running 10 medium & 1 large size rads, two 20mtr sq UFH & the 180l HW tank.

Now I know after chatting to you guys this is too big, but we have plans, (albeit, not in the near future), for an extension so hopefully this wont be too uneconomical in the meantime. I tried to stop the order but they had already shipped it for a delivery tomorrow.

I have decided to forgo the outside sensor after what Young Agile said & just stick with my existing conventional wireless Drayton for the rads, (will this make it much more uneconomical), & separate stats for the UFH, or would I be better getting the VRT392F instead & ditching the Drayton? . Are there any other tricks/toys I can use in the system to make it as economical as possible. Will the boiler still rise & fall in temperature with the Drayton, or does this only work with the Vaillant stats.

I take it this will be fine running along side the UFH manifold & stats. I have been looking for an installation manual for the boiler, just to get an idea on how the system would be wired. I am still unsure if this will work as again, it taps in directly to the boiler so struggling to see how you would call for UFH on this sytem.

Cheers again for all the help guys. it seems as you get older you dont half tend to over-research stuff!! so a thousand apologies for jumping in at the deep end with what must be easy questions for you guys.

Cheers again, Shane, (York)

 

[Agile]

You can have your weather comp with that system and it will work fine on the rads.

For the UFH with the usual simple basic design it will take the WC computed flow temperature and reduce it with the blending valve to that valves set temperature of say 40 C just as it would regardless of the flow value ( as long as its over 40 C ).

The effect of that on warmer days will be the UFH areas will get rather warmer and quicker than needed. The room stat in the UFH area will eventually turn off the UFH but by then it will already be too hot and will remain so for an hour or so with the consequential waste of heat and discomfort.

Such is the problem of UFH !

Tony

 

[muggles]

The 630 will be waaaay too big for your house even with the extension, the 624 was slightly oversized but I said to go for that on the basis that it allowed room to add extra rads later if required. Send the 630 back, it won't be as efficient on your system as the 624 and it might suffer from cycling which will reduce its lifespan, particularly before you have your extension. If you've bought it off the Internet, Distance Selling Regulations mean you have seven days to cancel your order, just refuse the delivery when it turns up and it'll get sent back. If you've ordered it from a merchants they should be happy to change it for you.

The VRC470 will be fine on your system and is the one to go for if you want maximum efficiency. You can put it where your Drayton stat is currently, if that's in a room with a rad in it still. The Drayton won't control the boiler anywhere near as well.

I don't quite see why Tony thinks there will be an issue with the UFH, maybe I've missed something but as far as I can see it should all work perfectly.

 

[Agile]

The basic WC varies the flow temp ( for rads ) from say 30 C bto 75 C.

With a standard UFH system there is a blending valve which reduces the flow temp to about 40 C to supply the UFH.

To vary the UFH from say 20 C to 40 V in response to the WC needs a much more complicated system !

Without it the UFH will always be at maximum power output when teh flow temp is between 40 C and 75 C.

There is also the timing problem with the WC varying the flow temp during the two hour UFH warm up time.

Tony

 

[muggles]

So why is having the UFH at maximum power output a problem? It would be on a system that is all UFH, that works well enough. The programmable room thermostats control the UFH to come on and off as required. One of us is missing the point somewhere, although I get what you're on about with the timing issue.

 

[bell824]

Blah Blah Blah, not going to bore you with all the stuff that has been said before

With regards to the massivley overpowered boiler, Maybe overpowered by about 10kw) big deal you have plans for the future and they may require the extra 10kw.

In the mean time the vaillant ecotecs have a function on them to range rate the heating output of the boiler, so as it's a 30kw you can tell the boiler to produce 20kw, very simple adjustment made by reading the book and adjusting d.o from 30 to whatever you need.

Problem solved

 

[Agile]

Problem not really solved!

Setting the d0 to 18 kW will limit the max power output fine.

But the minimum power output of say 11 kW will still be at 11 kW.

Buy the correct 18 kW boiler and the minimum power will be about 6.2 kW.

The lower the minimum power output the better the boiler can modulate and remain burning and the higher over all efficiency.

Tony

 

[sparkzz]

Hi Guys,

As the say, job jobbed, or problem solved!!

Sorry for starting a "heated" debate, sorry could not resist, but I bet you have never heard that one before!!

Right, 630 cancelled & 624 ordered in it's place. After speaking with Vaillant, we ended up with the VRC430F weather compensator, (wireless) but was told we needed the VR61 wiring centre which allows the 430 to control 2 zones of heating & HW. Because my stat is wireless at the mo, it would have been a nightmare to get wires to where it needed to be so the wireless one it was.

Let the fun commence. once again guys, thanks for the input. I know what it is like to get someone come along who knows a little, but in essence, knows nothing.

Thanks for steering me in the right direction.

Cheers, Shane