solar combi

[spanker]

Hi all

im looking for a combi boiler that could be used with solar panels in the future. is there anything special i should be looking for or would standard combi boiler do the trick.

 

[JohnD]

Perhaps I'm missing something... but solar panels are particularly handy for heating stored hot water (e.g. in a cylinder) so that you heat it whenever the sun's shining, and use it whenever you feel like turning on a tap.

Combi's aren't (usually) installed like this. System or heat-only boilers usually are.

 

[oilman]

 

[micky p]

there are some combis on the market that will take solar pre heated water. Like Alpha do a system. To be honest it isn't the best way of heating water via solar. You need to store quite a lot of it for it to be worth while. So If you want a combi buy An Alpha condensing combi or if you want to do it the most effective way buy a Solar Cylinder (twin coil) unvented and a system boiler. its more expensive way of doing the solar but its the best.

 

[spanker]

thanks for the replies

im instaling a new central heating system in my house but wanted the option of adding solar at a later date with a heatbank of some sort and using the combi to boost the water temp if needed.

i wasnt sure which boilers can be used this way do they just need to be modulating biolers? would it be worth while doing?

 

[Strachan]

Vaillant are doing something along those lines so the rep tells me. have a butchers on their site. Probably cost an arm and a leg, but without those you`d use less water for bathing, therefore an instant saving!

 

[Biggles..]

Vaillant currently offer mini,medium and large solar packs which are then compatable with their twin coil cylinders or other manufacturers cylinders but the sensors are slightly awkward to fit if not usin a vaillant cylinder.
Their combi's at present do not accept preheated water so you would be better installing a system boiler.Alpha combi and solar valve allow preheated water.
If you use all vaillants materials the solar controller wires directly to cylinder and boiler and works absolutly brilliantly.
Their website will tell you an approved installer in your area or if not try Charlie Lamb at vaillant, he's the solar rep.
Vaillants solar packs are at present non discountable but you should only pay 5% VAT on green energy products.

 

[simond]

Or you could use the Viessman 343 solar hybrid combi?

 

[Paul Barker]

If you can possibly wait the manufacturers will flood this market in the summer, they all recognise that at present it is dormant.

This concept looks interesting to me, one could conceive one's own diy version quite cheaply I recon. Discuss?

http://www.solartwin.com/easy_to_plumb_in.htm

 

[micky p]

If you can possibly wait the manufacturers will flood this market in the summer, they all recognise that at present it is dormant.

This concept looks interesting to me, one could conceive one's own diy version quite cheaply I recon. Discuss?

http://www.solartwin.com/easy_to_plumb_in.htm[/QUOTE]

i can't quite see how that will work.

Looks like to me that the DHW flows through a solar panel and if this is so how come the DHW cold fill tank is lower than the panel.


The Combi that i know od that will accept pre heated DHW from solar is a boiler called Wolf TGB 40 as i have fit one this way.

It had a Ariston unvented indirect cyclinder with the cold mains running through it and the heating coil from the solar panels then the hot outlet from the cylinder went to the cold inlet to the combi. Apparntly the Wolf TGB 40 will raise the temp by just a couple of degrees if need be or just let the water flow throught the boiler.According to the Rep who passed us this job on. We have had no comebacks from it so must bve working fine. Before we fit this Wolf boiler it was running through a Vaillant VCW Sine 18 and that managed well for a few years too.

I'm not sure if all combi boilers will cope with pre heated water. I suppose the combi will need a NTC on the cold inlet to sense the water which quite a few combis have these days. Others have them on the outlet or just on the Primary water.

 

[Paul Barker]

Yes your method sounds good.

I'm trying to get my head round what the average combi will do when presented with water at the temperature which it is set to provide. I imagine the flow switch will trigger it to fire up at 5mbar or so initial start pressure unless it's pre-mix when it'll be lower, then before it fires full rate the ntc will be satisfied, but will it modulate to low rate or will it shut off? I imagine most will modulate to low rate, so will always contribute a little extra heat.

So, what about a tmv with cold inlet connected to the unvented the hot inlet connected to the combi output. If it is satisfied for heat it will not draw anything from the combi, if it is not it will.

A second tmv beyond this could blend the output with cold in case the output of the solar vessel is too high.

 

[spanker]

the alpha solar smart system seems to be what im looking for, has anyone fitted any of these
with the unvented system does this need to be serviced and checked every year or am i thinking of a diferent system?

with condensing boilers is it best to get over sized rads or an under sized boiler i read something about it but cant find it now ive worked out i need about 30,000 btus its for a 3 bed detached does this sound about right.

 

[Paul Barker]

For the band b boilers they only condense properly and only burn gas at a stoichiometric mix of gas and air when they are working flat out. Therefore in the early days of condensing techknowlogy in the UK we were advised to oversize rads and undersize boilers so that a/ the boiler would work flat out and b the rads would dissipate that heat.

With the band a premix burners they run on 10:1 air to gas stoichiometric mix all the time, this is simply because the fan blows the air past a venturi which draws the gas via the gas valve out of the supply pipe at the exact correct ratio. These boilers are efficient the whole time.

However they are most efficient in terms of condensing when the water in the rads is cooler. I don't recall the correct temperatures it's something like 45 degrees celcius return 65 degrees flow. Someone may correct me.

In this case you would need larger rads to heat the house, than on the 80 degrees flow temperature with a 10 degree drop which used to be the case with band d to z boilers.

 

[Paul Barker]

I saw the Alpha solar collector yesterday it looks neat, but I know nothing about it, I am geting trained on it in the new year, they don't anticipate much movement in that market until the summer.

 

[micky p]

For the band b boilers they only condense properly and only burn gas at a stoichiometric mix of gas and air when they are working flat out. Therefore in the early days of condensing techknowlogy in the UK we were advised to oversize rads and undersize boilers so that a/ the boiler would work flat out and b the rads would dissipate that heat.

With the band a premix burners they run on 10:1 air to gas stoichiometric mix all the time, this is simply because the fan blows the air past a venturi which draws the gas via the gas valve out of the supply pipe at the exact correct ratio. These boilers are efficient the whole time.

However they are most efficient in terms of condensing when the water in the rads is cooler. I don't recall the correct temperatures it's something like 45 degrees celcius return 65 degrees flow. Someone may correct me.

In this case you would need larger rads to heat the house, than on the 80 degrees flow temperature with a 10 degree drop which used to be the case with band d to z boilers.

I was understood that if the return temp was below 57 deg C then it would condense. This is what i was told. If the boiler is undersized or rads oversized then it will help the return come back a little cooler but probably not give you enough to heat up sufficiently.