Two Boilers in one house good idea?

[Sharpie43]

Hi
I am thinking of installing two boilers in my house one upstairs to run the upstairs rads, bath, bedroom sinks & mains shower & another boiler downstairs to run the downstairs rads, mains shower washing m/c etc.
the pipe work is conveiniently split to allow this happen. I guess the main reason for doing this is that the hot water pipe run is quite long & takes for ever to get to the taps & if another tap is used then you either get scalded in shower or water pressure drops.
Do you think this is a good idea?
can you recommend a reliable boiler i could use.

Any advice would be most welcome thankyou

 

[Rob]

Seems a bit OTT.

I assume were talking combis here? Sounds like you'd be better off with a conventional system with secondary circulation to over come dead legs.

What do you mean 'mains shower'. Is that mains fed electric shower?

 

[Sharpie43]

Hi Rob
Thanks for the response, I figured that the cost of two boilers £2k ish would be the same as installing a new convensional system. at the moment I have a combi boiler which feeds everything, so I would need loft tanks, copper cylinder and a larger combi boiler which would cost about the same. so I though smallish boilers working independantly would do the trick.
It is too late put put in a return loop for the hot water.

 

[megawatt]

No problem doing what you suggest and you would have redundancy in the case of a boiler failure. Two boilers to program though (which would drive my wife nuts) and I'd check that your gas supply is sufficient first also

 

[Sharpie43]

Thanks Megawatt
Would the gas supply check be via British Gas or approved Heating & Plumbing Eng.?

 

[Doctor Drivel]

I would recommend using two Atmos Intercombi
combi boilers (RR quality and very simple with few components), one doing one CH zone and one the other. One doing one bathroom and shower, one the other.

Combine the DHW outlets for the baths only for very fast fills. The bath is the only outlet that needs fast fills. To combine the DHW outlets use two check valves and a shock arrestor after the check valves.

One shower does not affect the other when the two are on. Very fast re-heat of the house too, with over 50kW of heat being pumped in.

Two combis is the most cost effective route and saves lots of space too. Easy to fit. Simple wiring and piping and DHW. A back up if one is down very rare with an Atmos). Enter Dan.

Make sure each combis has its own dedicated 22m cold feed supply from the stoptap with tee off from these. The only tee off should be the cold to the showers teed off from just before the combi - pressure drops on that combi with be applied to hot and cols on the shower

The Intercombis can be got for ~£800 each. Now price up a quality boiler (£1,000 plus) and unvented cylinder (Megaflow at £1,200), and then the zone valves and control stuff, etc. On cost alone the two combis wins hands down, as nearly all is in the box.

There are other makes of combi. Those with small tanks inside to stop nuisance firing are good.

I have come across and implemented a number of two combi setups - they work very well. Backup if one is down too. Lots of space saved.

According to Dan, Atmos man, the Atmos boilers can have a smart pump fitted (Wilo Smart or Grundfos Alpha) and have TRVs on each rad and no wall room stat. The Atmos boilers don't need an auto by-pass.

 

[Doctor Drivel]

No problem doing what you suggest and you would have redundancy in the case of a boiler failure. Two boilers to program though (which would drive my wife nuts) and I'd check that your gas supply is sufficient first also

A gas meter can take 6 cu metres of gas/hr which is 212 cu/foot hr. That is 62kW of boiler. Two 28ish kW combis will run off a U6 gas meter. Have a dedicated gas supply for each boiler back to the meter.

You can store energy in a cylinder using little of the energy available down your gas pipe - most do for some strange reason. Most only use 1/4 of available energy down that gas pipe. Using two combis divides and rules, and you use most of the energy available to you down the gas pipe.

It comes down to storing energy in a cylinder or using it immediately.

 

[Agile]

The meter is rated at 6 m³ but that does not mean that the supply pipe from the street will allow that flow rate.

I know an installer who got into difficulty when he fitted a 32 kW boiler to replace a 24 kW boiler.

Customer was blaming him and gas supplier wanted paying to upgrade supply to house.

Tony

 

[Doctor Drivel]

The meter is rated at 6 m³ but that does not mean that the supply pipe from the street will allow that flow rate.

I know an installer who got into difficulty when he fitted a 32 kW boiler to replace a 24 kW boiler.

Customer was blaming him and gas supplier wanted paying to upgrade supply to house.

Tony

They have to supply 6 cu metres/hr by law. The gas people upgrade the pipe at their own expense. The gas people will try it on. In any cases their regulators are crap and the flexible inlet is undersized as is the maintap.

In the past I have had trouble with crap Trancco meter fitting and they argued. I just ordered the parts from BES, better quality, and fitted them myself. Cheaper than playing around with those clowns and the customer then a had a working system the next day. Voila!! all worked no problem.

In one I put a large bore hose on the maintap and opened it up to outside (realistically this needs flame trap). The amount of rust and crap that came out was amazing. Connected all back up with no kinks in the flexible connections and all was fine.


Transco may charge if the gas supply is off a riser to flats.

 

[Softus]

Do you think this is a good idea?

Yes.

can you recommend a reliable boiler i could use.

http://www.diynot.com/forums/viewtopic.php?t=93975
http://www.diynot.com/forums/viewtopic.php?p=323463
http://www.diynot.com/forums/viewtopic.php?p=670899

 

[Agile]

[
They have to supply 6 cu metres/hr by law.

Its easy you you to say that!

But can you quote any actual law ???

Tony

 

[megawatt]

Dr Dribble, have you ever actually installed anything?

The reason for asking the OP to check supply was to ensure that both the piping to the boilers would be adequate and also to take into account other gas appliances already installed ... Cooker, fires etc.

Presumably, if the supply wasn't adequate you'd simply hire a JCB, dig up the road and replace the gas main yourself ... The more I read your posts the more concerned I get for your state of mind

Sharpie43 wrote:

Would the gas supply check be via British Gas or approved Heating & Plumbing Eng.?

Your Corgi approved installer would carry out the survey as part of the quote for the job.

MW

 

[Doctor Drivel]

[
They have to supply 6 cu metres/hr by law.

Its easy you you to say that!

But can you quote any actual law ???

Tony

The old Gas Boards had to and would. The new privateers have to as a part of their licence. They will fob you off no end as the old service focused Gas Boards would do what they to do. The service depts of the old Boards were designed to draw even on cost, not make money. Money was made on the sale of gas.

 

[megawatt]

And you would spend years arguing the toss and still not get an improvement in supply.

Sometimes you need to accept things as they are and move on.

 

[Doctor Drivel]

Dr Dribble, have you ever actually installed anything?

Far too much to remember.

The reason for asking the OP to check supply was to ensure that both the piping to the boilers would be adequate and also to take into account other gas appliances already installed ... Cooker, fires etc.

Very good.

Presumably, if the supply wasn't adequate you'd simply hire a JCB, dig up the road and replace the gas main yourself

I have actually done something similar. I replaced about 3 metres of 3/4" iron service pipe with 1" pipe. It was in a flat and the riser could be isolated by a gas cock in a cupboard at the bottom of the block. I was considering using 28mm copper pipe, which is all legal.

... The more I read your posts the more concerned I get for your state of mind

I find it amazing that many of the people here are let loose on the general public. The systems they fit in, the poor naive customer is being short changed. Most have little engineering imagination (most are not engineers anyway) and are 20 generally years out of date. Most have only just accepted combis.