Radio First Share Discussion Threads

[rhubarbe] 05/2/2011 22:59

Our rad's still a cold 'un. :(

[kokopelli9990] 05/2/2011 19:58

Hi Rhu, picked up a bit of a bug, so not been up to thinking too much (never mind posting)past couple of days. Will hopefully feel better Sun & I'll try and catch you with my e-mail then. Thanks

[steve73] 03/2/2011 13:34

Any of you guys out in the sticks ever considered a CHP (combined heat and power) system?

Basically use a deisel (or gas mains gas if available) generator to produce electricity and then use the hot exhaust to give hot water for space heating. An ex-colleague of mine designed some "home based" systems about a decade ago but I've no idea if they ever went into production. Basically a high upfront cost, but thereafter low running costs if you can match your power/heat requirements, and the other obvious problem was noise - so you can't have close neighbours. I suppose a PV system with the FIT's makes more sense though now...

[rhubarbe] 02/2/2011 23:12

I do agree, and that is why the RHI needs to be properly targetted.

Form my point of view the ASHP gave me the opportunity to swap from an unregulated fuel source: LPG and Coal, with the delights of Oil as the alternative) to be able to use electricity at a cost no higher than mains gas was the no-brainer of all time.

[maxcashflow] 02/2/2011 22:36

Rhu - yes, I agree they do work just fine at -15C, but their efficiency at that temperature is lower. That doesn't matter a jot if your alternative fuel is oil, but if you are on mains gas it makes quite a difference in the comparison.

[rhubarbe] 02/2/2011 22:18

I don't have a generic email - only my main personal one.... do you..?

[kokopelli9990] 02/2/2011 22:02

Just a quick log on to say thanks for info. Will take a look on PV Thread. I'll read/post tomorrow when more time.
Rhu, I probably wont log on again to tomorrow pm , but I wouldn't mind sharing a few 'renewables' tales with you over e-mail ?
I'll post again tomorrow.
By the way, I'm up in Cumbria, edge of Lake district. Plan was to extend up & out on a 50's bungalow , but costs of underpinning, new roof etc when compared to new build (no VAT) weren't going to be that much different. So new plan is to demolish.

[rhubarbe] 02/2/2011 17:16

Let's not forget though, Max, that -15C is still +268K and there is useful heat to be extracted from the air even at those temperatures. From my own experience (we have an ASHP but no mains gas) it is the house's inability to hold onto heat on the coldest days rather than the heat pump's inability to supply heat that causes folk to conclude they don't work well in the coldest weather.

Ours was producing loads of heat even at -15C on the coldest days and nights but clearly 300mm loft insulation isn't enough (even with A Rated double glazed windows) to stop the house losing so much of that heat that a bivalent source was required.

I do agree that without RHI payments ASHP's make little sense if you have mains gas. Maybe the payments should only be targetted at installations where there is no mains gas?

[maxcashflow] 02/2/2011 17:06

koko - PV makes a lot of sense especially if you have space for the full 4KW system and can get it fitted before the tariffs reduce (1yr?). It's essential that you get a good value installation (£16,000 is a good price for a 4KW system and £20k is too much) otherwise they will nick all your profits.

If you are on mains gas then heat pumps make no sense on environmental or energy savings grounds. The RHI, if poorly designed, may create incentives for people to install heat pumps instead of mains gas boilers but I hope it does not. You just end up burning gas in a power station in order to supply electricity to pump heat and this is less efficient than burning gas in your own gas boiler, especially on the coldest days.

[steve73] 02/2/2011 01:49

koko - you may want to ask your PV question on the PV thread - there's a couple of PV users who occasionally post there, and there has been some thoughtful discussions there.

There, there.....

[rhubarbe] 01/2/2011 22:42

Having had a combi for 20 years and now using a pressurised hot water cylinder I would never go back to a combi.

[kokopelli9990] 01/2/2011 22:26

Hi Rhu,
posted a couple of times on your XEL thread (are we allowed to mention XEL on the RAD thread !)
Anyway, was wondering if anyone has ground source heat pumps & photovoltaics installed and what they have found re running costs compared to mains gas combi ?
We are thinking of a new build (especially if XEL takeover comes soon) and have just started looking at renewables. I've sent for some manufacturers lierature. Plan on underfloor heating. The RHI stuff doesn't come into June (i think) so don't know what up front incentives will be

Off to bed now, so will pick up any kind replies tomorrow.
thanks

[steve73] 01/2/2011 14:04

RD,
Yes, thinking about it you could be correct - I'm a little out of date recently, and codes could have changed since I last fitted a system. As I recall Wikes did a really good guide to installing CH systems.

[steve73] 01/2/2011 09:17

osi - the system should be set up so that a contact in either of the motorised valves powers the pump. i.e. at least one valve must be open to provide power to the pump. THERE SHOULD NOT BE A BYPASS.!!! (only needed on the CH circuit if you have TRV's on EVERY rad)

The boiler should be independant of the pump, and have its own temperature cut out.

I.e timer comes on and powers the boiler and one or both of the MV's. When one MV opens the pump runs. If the boiler gets too hot it should shut off for a short while with the pump still running through either (or both) the HW or CH systems.

[riggerdigger] 01/2/2011 08:34

sorry for the multiple posts.

[riggerdigger] 01/2/2011 08:34

Osi is this a new problem? a lot of boilers have a pump over-run, the pump stays on after the boiler switches off to get rid of excess heat in the heat exchanger. this can be operated either by a timer in the boiler or a thermostat. S plans should have a bypass built in so the pump does not pump against a closed valve

[osirisra] 01/2/2011 04:15

Help,,, my pump keeps running and running some times?????? I have what I believe is referred to as as an "S" type system ie one pump and two motorised valves (CH & hot water). I've tried changing the tank stat and that didn't do it. I have a wierd 80v on a couple of connections in the terminal box when the pump is running on?????
Stray current from somewhere? When the pump runs on I can turn down the tank and room stats, deselect heating and hot water on the digital controller and the pump will still run, blasting away at the two closed valves! The only way I can stop it is to turn the whole system off at the wall and just hope it works OK when I turn it back on the next day.

HELP, please.
Osi'.

[steve73] 01/2/2011 03:53

First house I owned had the CH system piped up with the overflow to the expansion (header) tank coming off after the pump, but the feed in from the header tanks in before the pump.

Worked OK until I fitted TRV's to all (except one) radiators, then as the TRV's closed down the flow of hot water got directed up into the overflow tank with the same problems as Rhu mentioned of steam condensing in the roof space and dripping on the ceilings. Easy enough to fix though once I went up into the roof space and saw what was happenning, although a local plumber (with a small "p") that I called out had no idea, by repiping the overflow and return to the same side of the pump.

I've since fitted 4 hot water CH systems (except the final gas connection - leave that for a CORGI) with no problems.

Rhu - your problem sounds as if that one radiator has been fitted in series to a parrellel system. i.e. the errant rad is piped with both inlet and outlet to the supply (or return) pipework, rather than between them.

And if anyone wants to knowmy credentials - I'm an ex-Process Engineer so very experienced in piping up complete refineries, petrochem, platforms, etc.

GL.

[aj the red] 31/1/2011 23:55

Reading back through the various posts i can only think that its piped wrongly.

Every other rad works
2 pipe system (flow and return)
15mm rarly blocks
Rad clear
Flow and return flow well(like our xel :)

Its also not getting hot when everything else is off its got to be piped wrongly or the rad is partially blocked somehow(longshot)If you flow both sides 1 at a time out of the drainoff on the radvalve into a bowl it will prove the the water is flowing through the rad ( you should be able to tell by how well it flows)

As you know its difficult to diagnose over a forum if i come up with anything else i will post

cheers

[rhubarbe] 31/1/2011 23:50

Mm, yes, we had to take them out here.

[barongboy] 31/1/2011 23:49

Well,we used lead pipes for a starter...very healthy!!