Advice for New Heating System?

[GRN1]

Following the rather unfortunate experience we had with a local heating company that did not manage to fix our Atag boiler after 3-4 visits, we have decided to buy a new heating system from a different manufacturer. We would, therefore, be grateful for any advice members of this forum can provide on a replacement heating system for a large 3 storey Edwardian property.

1. As we need a boiler of at least 58.5 kW output to replace the Atag it seems that we would need to buy 2 x domestic boilers with 30 kW+ output. We absolutely do *not* want a commercial boiler which only appointed 'agents' can service - this was the problem we had with Atag who in my region could only offer only one appointed service agent.

The building currently has 2 heating zones and 1 cylinder which supplies hot water to 3 shower rooms and a kitchen.

2. We have considered the following boiler options:

(a) Baxi Megaflo 32 kW x 2
(b) Worcester Bosh Greenstar 30cdi x 2

Does anyone have any thoughts on the suitability of the above systems?

3. Can either the two Worcester or Baxi boilers be linked together so that the second boiler comes on when demand for heat is high and goes 'on standby' when one zone within the building is not being used?

4. Would the above systems be big enough to send enough hot water for 3 showers to be in use simultaneously?

Finally, I am sorry to ask so many questions but I am keen to put in a replacement system as soon as possible.

Many thanks!


GRN1

 

[studips]

Have you considered having a megaflow system? get a big enough one piped in by someone who knows what they are doing, and it should do what you ask of it.

If you get the same person who knows what they are doing in to spec and quote the new system, they can do the calcs based on room sizes, heat losses and so forth to spec the correct size boiler. too small a boiler is obviously a disaster, but people don't appreciate that going for overkill is not good either...........

 

[GRN1]

"Have you considered having a megaflow system? get a big enough one piped in by someone who knows what they are doing, and it should do what you ask of it."

Do you mean a Baxi Megaflo boiler or the cylinder to store hot water?

"If you get the same person who knows what they are doing in to spec and quote the new system, they can do the calcs based on room sizes, heat losses and so forth to spec the correct size boiler. too small a boiler is obviously a disaster, but people don't appreciate that going for overkill is not good either"

The current boiler installed in 2004 has 60 kW output so I assume that the engineers who put this in did the calcs based on room size, heat loss, etc.

 

[GRN1]

Can anyone answer my query about linking 2 boilers together to increase the output and used on an as and when needed basis? Is this possible?

 

[mehran]

right...

first off I would do a heat loss calculation for your home. 58.5kw is a hell of a heatloss for a house.http://www.idhee.org.uk/calculator.html

next, depending on how it is plumbed you could link one boiler to one zone and the second boiler to the other zone+hot water cylinder...or if you find your heatloss is not 58kw just have one boiler

on the 3 showers front, if you have enough water pressure and flow then no problem. size the unvented tank large enough or have two tanks(maybe have them on different floors). if you dont have enough flow and pressure out your mains then looking to go pumped would be the way to go.

you can have any boiler you like. if it was me I would go for an viessmann 200 or an intergas boiler.

but the person you need to talk to most of all is the installer as he will know better what can be done and what cant.

btw i will give you £50 for your atag

 

[mehran]

Can anyone answer my query about linking 2 boilers together to increase the output and used on an as and when needed basis? Is this possible?

maybe... what you would need to do is have a way to switch them around once in a while to even the wear out. i cant think of any easy way of doing it off the top of my head.

 

[GRN1]

58.5 kW is a large amount of heatloss but this figure was calculated back in 2003/4 by heating engineers when the boiler was first commissioned for the property.

The property is effectively 2 large semi-detached Edwardian houses knocked into one. Including bathrooms there are 24 rooms altogether so I believe the calculation to be accurate.

The zones have already been created so as you said, one boiler for one zone and the second for the other zone. A question, what say one boiler failed (and they do from time to time!!) how could the "good" one continue operating? Would this be seamless or would I have to get a plumber to switch them around?

GRN1

 

[mickyg]

surely the sensible thing to do would be fit 2 boilers on to a low loss header. Then turn off either one as and when. then if one fails the other one will still heat whatever is most important.

 

[mehran]

surely the sensible thing to do would be fit 2 boilers on to a low loss header. Then turn off either one as and when. then if one fails the other one will still heat whatever is most important.

yes that would be the sensible thing you could even have a out side frost stat set at 5 degrees for example, over 5 degrees one boiler, below two boilers

 

[GRN1]

Yes, a good idea regarding frost control stat. Could this be wireless or must it be hard-wired?

How would the 2 boilers (vViessmann, Worcester-Bosch, Baxi, etc.) be connected. In series, or what do you recommend?

Finally, could I ask what is a "low loss header" is? I have seen this term many times but do not really understand what it means. Pls explain. Thanks!

GRN1

 

[mehran]

in your case, you would pipe both boilers to a single large cylinder then pump from that single large cylinder to the zones:

 

[studips]

"Have you considered having a megaflow system? get a big enough one piped in by someone who knows what they are doing, and it should do what you ask of it."

Do you mean a Baxi Megaflo boiler or the cylinder to store hot water?

"If you get the same person who knows what they are doing in to spec and quote the new system, they can do the calcs based on room sizes, heat losses and so forth to spec the correct size boiler. too small a boiler is obviously a disaster, but people don't appreciate that going for overkill is not good either"

The current boiler installed in 2004 has 60 kW output so I assume that the engineers who put this in did the calcs based on room size, heat loss, etc.

i'd guess 60kw is oversize, personally i'd get the calcs done again, it is a lot of btus that thing of yours kicks out, and if you oversize with a condensing boiler then it won't run as efficiently as it is designed to. Also think about any passive insulation you can do to reduce the requirement further - can you get 300mm or rockwool in your loft for instance - if a suspended floor, can you insulate between the joists?

i'm thinking a 210 litre megaflow cylinder - masses of stored hot water ready to flow at the turn of a tap, you could connect the baxi to it or whatever boiler takes your fancy. worcester are probably the best about now, but ask the guys here and they all seem to have their pet hates and faves.

running two boilers is not a cost effective option - servicing, installation cost, running costs, a second set of controls... it adds up.......

 

[D_Hailsham]

58.5 kW is a large amount of heatloss but this figure was calculated back in 2003/4 by heating engineers when the boiler was first commissioned for the property.

The property is effectively 2 large semi-detached Edwardian houses knocked into one. Including bathrooms there are 24 rooms altogether so I believe the calculation to be accurate.

I used to live in an Edwardian 3 storey semi - solid walls, mainly original single glazed wood frame windows. Some loft insulation. It was heated by a 24kW Potterton Kingfisher.

So I can understand why your house might need 58kW.

 

[Agile]

The heat loss still needs to be calculated but I still expect that it will be a lot lower than that.

The presvious calculation may have been an idiot who added the full cylinder heatup input to the boiler powers. You only add 2 kW !

The hot water requirement depends on the number of people who stay and any special useage. If its a guest house then different rules apply but about 50li + 50li per person. So a 210 li would only cater for three people. I would probably still suggest a 300 li as that is little more and covers a sale to a larger family.

Its easy to cascade boilers and select the working/standby order.

Tony